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Objectives Welding is a physically demanding job that entails exposure to metal fume and particles. There is little information on the effect of welding exposures on the outcome of a pregnancy conceived during a period when a woman was employed as a welder. Methods Women welders recruited to the Workers Health in Apprenticeship Trades—Metal and Electrical (WHAT-ME) study were followed-up every 6 months for up to 5 years (January 2011–August 2018), and every pregnancy recorded. At the first 6-month follow-up, a detailed questionnaire was completed for the most recent day in welding, and this information was collected again at each follow-up and also from questionnaires completed during pregnancy. The date of conception was estimated for each pregnancy and the job at that date identified. Exposures to ergonomic factors, work schedule and perceptions of noise, heat and cold were extracted for the job at conception. Exposures to metals (aluminum, chromium, manganese, and nickel) and particles in welding fume were estimated from previously validated exposure algorithms reflecting the welding process, base metal and consumables of the job at the conception date. The effects of exposures were estimated in multilevel multivariable models allowing for confounding. Results There were 242 pregnancies conceived by a welder working in her trade, 87 were before the first follow-up, 3 were after first follow-up but detailed information was not collected, 22 of those potentially included in the assessment group were in-trade but not welding leaving 122 pregnancies in 90 welders for analysis. Of these 91 resulted in a live birth and 31 in a fetal loss (27 miscarriages and 4 stillbirths). Mean birth weight for live births was 3365 g and gestation 39.4 weeks. Final models showed that risk of fetal loss increased with manipulating heavy objects [odds ratio (OR) = 5.13, 95% confidence interval (CI) 2.04–12.92], whole-body vibration (OR = 5.86, 95% CI 1.81–18.92), a higher rating for noise exposure intensity (OR = 1.52, 95% CI 1.24–1.85), and decreased with use of local exhaust ventilation (OR = 0.20, 95% CI 0.03–1.18). Gestation decreased with perceived heat intensity (β = −0.15, 95% CI −0.29 to −0.02) and number of previous pregnancies (β = −0.35, 95% CI −0.65 to −0.05). Birth weight was lower in those reporting whole-body vibration (β = −596 g, 95% CI −924 to −267) and increased with the welder’s body mass index (β = 36 g, 95% CI 12–61). Estimates of exposure to metals and particles were unrelated to gestation or birth weight. In a bivariate analysis, allowing for the same welder reporting >1 pregnancy, estimated airborne aluminum exposure (and to a lesser degree exposure to nickel and particles) was related to greater risk of fetal loss (OR = 1.52, 95% CI 1.04–2.24) but neither aluminum nor the other estimated elements of welding fume added to the final model. Conclusions In this group of women actively engaged in welding during the time surrounding conception, the outcome of pregnancy was strongly related to work exposures, particularly vibration (reported in grinding tasks), manipulation of heavy objects, and perceived intensity of noise and heat. The study was unable to show an independent effect of exposure to metal fume constituents.

To determine the relationship between ergonomic demands of the job at conception and fetal loss (miscarriage or stillbirth).Women with a welding or electrical trade apprenticeship were identified across Canada for the Women's Health in Apprenticeship Trades-Metal and Electrical study. They completed a reproductive and employment history at recruitment and every 6 months for up to 5 years to provide details on pregnancies and work demands. Job at conception was identified and fetal loss examined in relation to ergonomic exposures/demands, allowing for potential confounders.A total of 885 women were recruited; 447 in welding and 438 in electrical trades. Of these, 574 reported at least one pregnancy. Analysis of 756 pregnancies since the woman started in her trade suggested no increased risk of fetal loss in those choosing welding rather than electrical work. Among 506 pregnancies conceived during a period working in a trade, 148 (29.2%) ended in fetal loss: 31.2% (73/234) in welding, and 27.6% (75/272) in electrical work. Detailed exposure information was available for 59% (299/506) of these pregnancies. In welders, the risk of fetal loss was increased with whole-body vibration (prevalence ratio [PR] = 2.14; 95% confidence interval [CI] 1.39-3.31) and hand-arm vibration for 1 hour/day (PR = 2.15; 95% CI 1.33-3.49). In electrical workers risk increased with more than 8 days working without a rest day (PR = 2.29; 95% CI 1.25-4.17). Local exhaust ventilation reduced risk in welders.There was no significant increase in fetal loss in welding trades compared to electrical work. Vibration, largely from grinding, and extended work rotations appear to be potentially modifiable factors of some importance.

Objectives Men and women working in the welding trades undergo the same apprenticeship training but it is unknown whether, once in the trade, their exposures differ. Comparison of urinary metal concentrations, having adjusted for estimated airborne exposure, may provide an answer. Methods Men and women were recruited to a cohort study of workers in the welding and electrical trades (the Workers Health in Apprenticeship Trades-Metal working and Electrical [WHAT-ME study]). They completed a recruitment questionnaire and further questionnaires every 6 months for up to 5 years. At each follow-up, they gave details on employment and, if welding, answered trade-specific questionnaires. Urine samples were collected by mail. Welding exposure matrices were developed to estimate metal exposures from welding process, base metal, and consumables. Urinary metal concentrations, determined by ICP-MS, were compared by trade (welding or electrical). Within welding, the relation of urinary concentrations to estimated airborne exposure was examined, with adjustment for potential confounders including sex, use of respiratory protective equipment (RPE), and time spent outdoors. Natural logarithms were taken of exposure estimates and urinary concentrations, to reduce skew. All regression analyses included creatinine concentration. Results Urinary metal concentrations were analysed for 12 metals in 794 samples. Antimony, arsenic, lead, and mercury had a high proportion of samples with no metal detected and were not considered further. The urinary concentrations of aluminum, cadmium, chromium, cobalt, copper, manganese, nickel, and zinc were compared for welders (434 samples) and electrical workers (360). After adjustment for potential confounders, welders had higher urinary concentrations for aluminum (β = 0.13 95%CI 0.03–0.24) and chromium (β = 0.66 95%CI 0.55–0.77). Of 434 welder urines, 334 could be matched securely to detailed information about the most recent day welding. For these, an estimate of airborne exposure was made for aluminum, chromium, manganese, and nickel. Male welders were estimated to have higher airborne exposure to chromium and nickel than women welders. No difference was seen in the estimated exposures for aluminum or manganese (or total dust). Regression analyses of the relation of urinary metals to estimated exposure showed a good concordance for aluminum (β = 0.09 95%CI 0.04–0.15 (P < 0.001) and chromium (β = 0.11 95%CI 0.05–0.17 P < 0.001). The concordance for manganese and nickel was positive, but much weaker. Urinary concentrations of aluminum and nickel were somewhat lower with increasing time wearing RPE and, for chromium and nickel, with time working outdoors. Having adjusted for estimated exposure, creatinine and other confounders, male welders had lower urine concentrations of aluminum (β = −0.35 95%CI −0.51 to −0.19 P < 0.001) chromium (β = −0.38 95%CI −0.57 to −0.19 P < 0.001) and manganese (β = −0.36 95%CI −0.49 to −0.23 P < 0.001) than female welders. Conclusion Welders had higher urinary concentrations of aluminum and chromium than electrical workers. Exposure estimates of aluminum and chromium for welders were a valid representation of the airborne exposures to these metals. Although male welders were estimated to have higher exposures of chrome and nickel than female welders, the higher urinary metal concentrations in women welders is of concern, particularly for women who may conceive while in the trade.

PurposeHealth care workers (HCWs) were recruited early in 2020 to chart effects on their health as the COVID-19 pandemic evolved. The aim was to identify modifiable workplace risk factors for infection and mental ill-health.ParticipantsParticipants were recruited from four Canadian provinces, physicians (MDs) in Alberta, British Columbia, Ontario and Quebec, registered nurses (RNs), licensed practical nurses (LPNs) and health care aides (HCAs) in Alberta and personal support workers (PSWs) in Ontario. Volunteers gave blood for serology testing before and after vaccination. Cases with COVID-19 were matched with up to 4 referents in a nested case-referent study.Findings to Date4964/5130 (97%) of those recruited joined the longitudinal cohort: 1442 MDs, 3136 RNs, 71 LPNs, 235 PSWs, 80 HCAs. Overall, 3812 (77%) were from Alberta. Pre-pandemic risk factors for mental ill-health and respiratory illness differed markedly by occupation. Participants completed questionnaires at recruitment, fall 2020, spring 2021, and spring 2022. By the 4thcontact, 127 had retired, moved away or died, for a response rate of 89% (4299/4837). 4567/4864 (92%) received at least one vaccine shot: 2752/4567 (60%) gave post-vaccine blood samples. Ease of accessing blood collection sites was a strong determinant of participation. Among 533 cases and 1697 referents recruited to the nested case-referent study, risk of infection at work decreased with widespread vaccination.Future PlansSerology results (concentration of immunoglobulin G (IgG)) together with demographic data will be entered into the publicly accessible database compiled by the Canadian Immunology Task Force. Linkage with provincial administrative health databases will permit case validation, investigation of longer-term sequalae of infection and comparison with community controls. Analysis of the existing dataset will concentrate on effects on IgG of medical condition, medications and stage of pregnancy, and the role of occupational exposures and supports on mental health during the pandemic.Strengths and limitationsRecruitment of a broad spectrum of health care workers close to the start of the COVID-19 pandemic through their professional organizationsConsent to link to records held by public health departments allows for validation of self-reports of vaccinations and episodes of COVID-19 infectionRepeated contacts permit charting the evolution of anxiety, depression and sources of stress through the course of the pandemicThe inclusion of a nested case-referent study allows exposure reporting in near real timeThe absence of good denominator data limits the ability to examine recruitment biasN=4216

We examined whether discretionary use of an N95 mask reduced symptom reporting in wildland firefighters. The study collected data from two Canadian provinces during the 2021 fire season, with each firefighter followed for up to 4 rotations. Participants completed questionnaires on symptoms at the start and end of each rotation, when they reported also on mask use (if any) and completed a task checklist. Eighty firefighters contributed data. Nineteen firefighters were successfully fit-tested for N95 masks to wear whenever they felt conditions justified. Start-of-rotation symptoms reflected total hours firefighting in 2021. Symptoms of eye, nose and throat irritation and cough were more bothersome at the end of rotation. Cough, throat and nose (but not eye) symptoms were reported as significantly less bothersome at the end of rotation by those allocated masks, having allowed for crew type and start-of-rotation symptoms. Among those allocated a mask, use was most frequent during initial attack and least during driving and patrol. Reasons for not wearing included high work difficulty and low comfort. It is concluded that symptoms in wildland firefighters increased with hours of exposure. While provision of an N95 mask reduced symptoms, work is needed to overcome barriers to respiratory protection

OBJECTIVE Determine effects on respiratory health of firefighters attending a catastrophic wildfire. METHODS Within the Alberta Administrative Health Database, we identified five community-based controls for each firefighter in a cohort of 1234 deployed to the 2016 Fort McMurray fire. Spirometry records were identified and a stratified sample assessed clinically. We estimated PM2.5 particles exposure. RESULTS Firefighters had an increased risk of asthma consultation post-fire (OR new onset asthma = 2.56; 95%CI 1.75 to 3.74). Spirometry showed decreased FEV1 and FVC with increasing exposure. In the clinical assessment, 20% had a positive MCT and 21% BWT. Those with ongoing fire-related symptoms had a higher concurrence of positive MCT and BWT (OR = 4.35; 95%CI 1.11 to 17.12). Lower diffusion capacity related to higher exposure. CONCLUSIONS Massive exposures during a wildfire are associated with non-resolving airways damage.

Introduction Little is known about the effectiveness of ongoing mental health support in reducing the mental health impacts of a traumatic deployment. Methods A cohort of firefighters was established among those deployed to a devastating wildfire in Alberta, Canada in May 2016. Firefighters completed three questionnaires: at recruitment giving details of exposures, a first follow‐up reporting mental health supports before, during, and after the fire and a second follow‐up, at least 30 months after the fire, with screening questionnaires for anxiety, depression, and posttraumatic stress disorder (PTSD). Fire chiefs were interviewed about mental health provisions. The impact of supports on mental ill health was estimated, adjusting for clustering within fire service and potential confounders. Results Of 1234 firefighters in the cohort, 840 completed the questionnaire on mental health supports. In total, 78 of 82 fire chiefs were interviewed. Analysis of the impact of supports on mental ill health included 745 firefighters from 67 fire services. Only 45.8% of reports of peer support were concordant between firefighters and fire chiefs. After adjusting for confounding, the odds ratios (OR) for peer support reported by both fire chief and firefighter were depressive disorder: OR = 0.22, 95% confidence interval (CI), 0.08–0.61; anxiety disorder: OR = 0.45, 95% CI, 0.24–0.82; PTSD: OR = 0.62, 95% CI, 0.37–1.02. Symptoms of anxiety and depression but not PTSD were reduced by resiliency training before the fire and by support offered within 48 h of return from deployment. Conclusion The results suggest peer support in firefighters is protective but its availability is poorly recognized. PTSD was somewhat less responsive, perhaps reflecting the cumulative effects of previous exposures.

Objectives The Fort McMurray fire in Alberta, Canada, devastated the townsite in May 2016. First responders were heavily exposed to smoke particles. Blood samples taken from firefighters in May and August/September 2016 were used to measure concentrations of inflammatory markers in plasma and the relation of these markers to exposures and respiratory ill-health. Methods Blood samples were drawn from firefighters from two fire services, who also completed questionnaires about tasks and exposures during their deployment to the fire and about respiratory symptoms. Plasma was analysed for 42 inflammatory markers in a multiplex assay. At Service A, samples were collected twice, within 19 days of the start of the fire (early sample) and again 14–18 weeks later (late sample). At Service B, only late samples were collected, at 16–20 weeks. Principal component (PC) scores were extracted from markers in plasma from the early and late samples and, at both time periods, the first two components retained. PC scores were examined against estimated cumulative exposures to PM2.5 particles, self-rated physical stressors during the fire, and time since the last deployment to an active fire. The relation of component scores and exposure estimates to respiratory health were examined, using self-ratings at the time of the blood draw, a validated respiratory screening questionnaire (the European Community Respiratory Health Survey [ECRHS]) some 30 months after the fire, and clinical assessments in 2019–2020. Results Repeat blood samples were available for 68 non-smoking first responders from Service A and late samples from 160 non-smokers from both services. In the 68 with two samples, marker concentrations decreased from early to late samples for all but 3 of the 42 markers, significantly so (P < 0.05) for 25. The first component extracted from the early samples (C1E) was unrelated to respiratory symptoms but the second (C2E) was weakly related to increased cough (P = 0.079) and breathlessness (P = 0.068) and a lower forced expiratory volume in one second/forced expiratory capacity (FEV1/FVC)(β = –1.63, 95% CI –3.11 to –0.14) P = 0.032. The first PC at 14–20 weeks (C1L) was unrelated to exposure or respiratory health but the second PC (C2L) from these late samples, drawn from both fire services, related to cumulative PM2.5 exposure. In a multivariate model, clustered within fire service, cumulative exposure (β = 0.19, 95% CI 0.09–0.30), dehydration (β = 0.65, 95% CI 0.04–1.27) and time since last deployed to a fire (β = –0.04, 95% CI –0.06 to –0.01) were all related to the C2L score. This score was also associated with respiratory symptoms of wheezing, chest tightness, and breathlessness at the time of the blood draw but not to symptoms at later follow-up. However, apart from the lower FEV1/FVC at 15–19 days, the marker scores did not add to regression models that also included estimated cumulative PM2.5 exposure. Conclusions Concentrations of persisting inflammatory markers in the plasma of firefighters deployed to a devastating fire decreased with time and were related to estimates of exposure. Although not a powerful independent predictor of later respiratory ill-health, they may serve as an indicator of previous high exposure in the absence of contemporary exposure estimates.

Objectives We aimed to characterize polycyclic aromatic hydrocarbons (PAHs) in the breathing zone and on the skin of wildland firefighters and to assess their contribution to urinary 1-hydroxypyrene (1-HP) over repeated firefighting rotations. We asked if improved skin hygiene or discretionary use of an N95 mask would reduce absorption. Methods In collaboration with wildfire services of two Canadian provinces, Alberta and British Columbia (BC), we recruited wildland firefighters from crews willing to be followed up over successive rotations and to be randomly assigned to normal practice, enhanced skin hygiene (ESH), or ESH plus discretionary use of an N95 mask. We collected spot urine samples at the beginning and end of up to four rotations/firefighter. On designated fire days, as close as possible to the end of rotation, we collected skin wipes from the hands, throat, and chest at the beginning and end of the fire day and, in BC, start of fire-day urine samples. Volunteers carried air monitoring pumps. Participants completed questionnaires at the beginning and end of rotations. Exposure since the start of the fire season was estimated from fire service records. Urinary 1-HP was analyzed by LC-MS-MS. Analysis of 21 PAHs on skin wipes and 27 PAHs from air sampling was done by GC-MS-MS. Statistical analysis used a linear mixed effects model. Results Firefighters in Alberta were recruited from five helitack crews and two unit crews, and in BC from two unit crews with 80 firefighters providing data overall. The fire season in BC was very active with five monitored fire days. In Alberta, with more crews, there were only seven fire days. Overall, log 1-HP/creatinine (ng/g) increased significantly from the start (N = 145) to end of rotation (N = 136). Only three PAHs (naphthalene, phenanthrene, and pyrene) were found on >20% of skin wipes. PAHs from 40 air monitoring pumps included 10 PAHs detected on cassette filters (particles) and 5 on sorbent tubes (vapor phase). A principal component extracted from air monitoring data represented respiratory exposure and total PAH from skin wipes summarized skin exposure. Both routes contributed to the end of rotation urinary 1-HP. The ESH intervention was not demonstrated to effect absorption. Allocation of an N95 mask was associated with lower 1-HP when modeling respiratory exposure (β = −0.62, 95% CI −1.15 to −0.10: P = 0.021). End of rotation 1-HP was related to 1-HP at the start of the next rotation (β = 0.25, 95% CI 0.12 to 0.39: P < 0.001). Conclusions Exposures to PAHs during firefighting were significant, with samples exceeding the American Conference of Governmental Industrial Hygienists Biological Exposure Index for 1-HP suggesting a need for control of exposure. PAH exposure accumulated during the rotation and was not fully eliminated during the break between rotations. Both respiratory and skin exposures contributed to 1-HP. While improved skin hygiene may potentially reduce dermal absorption, that was not demonstrated here. In contrast, those allocated to discretionary use of an N95 mask had reduced 1-HP excretion. Wildland firefighters in North America do not use respiratory protection, but the results of this study support more effective interventions to reduce respiratory exposure.

Objectives: The study was designed to estimate the prevalence of mental disorders in a cohort of firefighters who had been deployed to a devastating fire in Fort McMurray, Alberta, in 2016. Methods: A cohort of firefighters was established and followed up by online questionnaires. The contact in October 2018 to March 2019 included the PCL-5 questionnaire screening for post-traumatic stress disorder (PTSD) and the Hospital Anxiety and Depression Scale (HADS) screening for anxiety and depression. A sample was selected comprising all scoring ≥31 on the PCL-5 or ≥12 on either scale of the HADS, 30% of those scoring 8 to 11 on the HADS, and 10% of those with lower scores on all scales. This sample was assessed through a structured clinical interview to categorize disorders as defined in Diagnostic and Statistical Manual for Mental Disorders, fifth edition ( DSM-5). Interviews were carried out face-to-face or by telephone between August 2019 and February 2020. Diagnoses in the interview sample were reweighted to obtain prevalence estimates for the whole cohort. In an analysis of receiver operating characteristics (ROC), possible cut points for scores from each screening questionnaire were examined. Results: In 2018 to 2019, 1,000 of the cohort of 1,234 firefighters completed the HADS and 998 completed the PCL-5. Of these, 282 were identified for structured clinical interviews for DSM-5 (SCID) assessment. Interviews were carried out with 192. Among those assessed, 40.6% met the criteria for PTSD, 30.7% for an anxiety disorder, and 28.5% for a depressive disorder. When reweighted to allow for sampling and losses to assessment, cohort prevalence estimates were as follows: PTSD 21.4% (15.7% to 29.1%), anxiety disorders 15.8% (11.0% to 22.5%), and depressive disorders 14.3% (9.9% to 20.8%). Lower prevalence estimates were obtained when using the cut point with least misclassification in the ROC analysis. Conclusion: Using the gold-standard SCID assessment, high rates of mental disorders were found in this cohort of firefighters who had experienced a devastating fire. Fewer cases would have been identified by screening questionnaire alone.

Objectives There is limited knowledge of exposure to polycyclic aromatic hydrocarbons (PAHs) in wildland firefighters, or of the effectiveness of interventions to reduce this. This study of wildland firefighters assessed whether PAHs were present and considered respiratory protection and enhanced skin hygiene as possible interventions. Methods 1-Hydroxypyrene (1-HP) was measured in urine samples collected pre-shift, post-shift, and next morning from wildland firefighters in Alberta and British Columbia. Skin wipes, collected pre- and post-shift, were analysed for eight PAHs. Breathing zone air samples were analysed for 11 PAHs. As pilot interventions, participants were randomized to either normal or enhanced skin hygiene. A sample of volunteers was assigned to a disposable N95 mask or a half facepiece mask with P100 organic vapour cartridge. Participants completed a brief questionnaire on activities post-shift and respiratory symptoms. Results Non-smoking firefighters (66 male and 20 female) were recruited from 11 fire crews. Air sampling pumps were carried for the full shift by 28 firefighters, 25 firefighters wore masks (14 N95 and 11 P100); 42 were assigned to the enhanced skin hygiene intervention. Sixty had hot spotting as their main task. Air monitoring identified PAHs (benzo(b,j,k)fluoranthene in particulates, phenanthrene in the gaseous phase) for 6 of the 11 crews. PAHs (largely naphthalene) were found post-shift on 40/84 skin wipes from the hand and 38/84 from jaw/throat. The mean increase in 1-HP in urine samples collected after the shift (compared with samples collected before the shift) was 66 ng g−1 creatinine (P < 0.001) with an increase over the shift found for 76% of participants. 1-HP in next morning urine samples was significantly lower than at the end of shift (a reduction of 39.3 ng g−1: P < 0.001). The amount of naphthalene on skin wipes was greater at the end of the shift (post) than at the start (pre). The mean post–pre weight difference of naphthalene on skin wipes taken from the hand was 0.96 ng wipe−1 (P = 0.01) and from the jaw/throat 1.28 ng wipe−1 (P = 0.002). The enhanced skin hygiene intervention lead to a larger reduction in 1-HP between end of shift and next morning urine samples but only for those with naphthalene on skin wipes at the end of shift. The difference in 1-HP concentration in urine samples collected before and after the shift was reduced for those wearing a mask (linear tend P = 0.063, one-sided). In multivariable models, 1-HP at end of shift was related to gaseous phase phenanthrene, estimated from air sampling [β = 318.2, 95% confidence interval (CI) 67.1–569.2]. Naphthalene on hand skin wipes reflected work in hot spotting during the shift (β = 0.53, 95% CI 0.22–0.86). Conclusions This study provided evidence of PAHs in the air and on the skin of many, but not all, fire crew. Absorbed PAHs, reflected in 1-HP in urine, increased over the shift. Results from the pilot interventions suggest that enhanced skin hygiene would reduce absorption post fire where PAHs had been accumulated on the skin, and that masks could be effective in reducing PAH inhalation exposure. Interventions to reduce PAH absorption are supported by the pilot work reported here and warrant further evaluation across a full fire season.

Objectives Women are reported to have higher rates of nickel sensitization than men, but there have been few studies of sex-related differences in dermatitis associated with occupational nickel exposure. This analysis examines dermatitis in a large cohort of women and men in welding and electrical occupations and considers how far differences in rates of dermatitis may be accounted for by nickel exposure. Methods Women and men were recruited to cohorts of workers who had entered welding and electrical apprenticeships (the WHAT-ME and WHAT-MEN studies). Participants completed questionnaires at baseline and every 6 months for up to 5 years. At each contact, cohort members were asked about current dermatitis and whether it was made worse by work. From the first follow-up after recruitment, those working in their trade completed detailed subroutines about tasks in their trade including, for welders, the process, base metal, and consumables. Exposures were considered by trade and, within welding, by stainless or high alloy steel (SOHAS) as the base metal. Urinary nickel concentration was also examined. Using only report of dermatitis that began after entry to the trade, new-onset dermatitis, all episodes of dermatitis, and dermatitis made worse by work were examined against exposure by multilevel, multivariable logistic regression, allowing for potential confounding. Results Among 1885 participants (welders; 447 women, 554 men: electrical trades; 438 women, 446 men), 200 reported dermatitis that started before they entered the trade, leaving 1685 for analysis. Women, but not men, who had entered the welding trades were more at risk of new onset [odds ratio (OR) = 1.54; 95% confidence interval (CI) 1.02–2.32] or dermatitis episodes (OR = 1.75; 95% CI 1.10–2.77) than those entering the electrical trades. Within welding, women were more at risk than men of new-onset dermatitis (OR = 1.85; 95% CI 1.15–2.96) and dermatitis episodes (2.14; 95% CI 1.24–3.68) but were not more likely to report these were made worse by work. Use of SOHAS as the base metal was associated with reports that dermatitis was made worse by work (3.54; 95% CI 1.04–12.03), but having adjusted for SOHAS use, women still remained at greater risk. A final analysis considered the effect on risk estimates of removing those welding SOHAS from the analysis. The risk for women of episodes of dermatitis was essentially unchanged, whether the comparison group was male welders or women in the electrical trades. Conclusions Welding is associated with risk of dermatitis in women. Although welding of SOHAS was associated with dermatitis that was made worse by work, it does not importantly explain the higher female rates in welding and other causes must be examined to support preventive measures.

Aims Pelvic floor and mobility exercises were shown to be effective in managing incontinence in a cluster-randomized trial (CRT) of village women aged 60 to 75 years in Bangladesh. The present analysis examines continence 12 months after the CRT and exercise program implementation with village paramedics as preceptors. Methods Women from nine villages in the exercise arm of the CRT were followed-up 12 months after the 6-month intervention. They provided information about exercise since the CRT and a 3-day continence record (3DCR). Posttrial, a further 6-month exercise intervention led by village paramedics was initiated in 20 villages. Women completed the two-item Sandvik severity questionnaire before and after the intervention. Paramedics kept a record of each woman's attendance at the 48 exercise sessions RESULTS: A total of 130 of 150 women from the CRT completed the 12-month follow-up; 61.5% were dry on the 3DCR at follow-up. Total continence was related to the continuation of exercises carried out in the home and absence of urinary tract infection at follow-up. Those exercising at follow-up had an odds ratio (OR) of 3.49 (95% confidence interval [CI], 1.86-6.58) of being continent at follow-up. Higher end-of-CRT body mass index was associated with greater follow-up leakage. In the 20-village roll-out, with 316 incontinent women, improvement in both severity and total continence on the Sandvik questionnaire were related to a total number of sessions attended (OR = 1.09; 95% CI, 1.05-1.13). At roll-out, 38.6% achieved continence, comparable to 43.0% in the CRT using physiotherapy preceptors CONCLUSIONS: Group exercise classes led by paramedics resulted in a marked improvement in continence but maintenance requires exercise postintervention.

Introduction Healthcare workers (HCW) working through the pandemic are in the front line for infection, psychological pressure and overwork. Objectives To identify modifiable work factors associated with COVID-19 infection and mental distress, and to assess the effectiveness of provisions to mitigate their impact. Methods A cohort study of HCWs was set up in the first weeks of the pandemic in Canada. HCWs from British Columbia, Alberta, Ontario, and Quebec completed an online questionnaire in the spring/summer of 2020, and a Phase 2 questionnaire from October 2020. They also provided a blood sample to assess SARS-CoV-2 antibodies. HCWs reporting a COVID-19 infection after the Phase 2 questionnaire were matched on job-type and province to 4 referents for a nested case-referent (C-R) study concentrating on exposures immediately prior to infection. Phase 3 is underway, with a final contact planned for March 2022. Results 5135 HCWs completed the Phase 1 questionnaire with 93% (4539/4857) of those eligible completing Phase 2. By March 1st 2021, 157 cases had been confirmed by PCR and a further 10 found positive only on antibody testing (an overall rate of 3.3%). The odds of infection doubled for working one-on-one with known COVID-19 patients. Rates were lower in physicians and nurses, compared to personal support workers, health care aides, and licensed practical nurses. HCWs in a hospital setting had lower rates than those working in the community, where shortages of personal protective equipment were more widespread. High rates of anxiety (on the Hospital Anxiety and Depression Scale) were recorded in both Phase 1 and 2. Only 1 in 4 HCW had used available mental health supports. By May 2021, 100 cases with 389 referents had been recruited to the on-going C-R study. Conclusion Information collected prospectively has the potential to improve HCWs protection during this and future epidemics.

Introduction Workers moving between states or provinces to find employment are reported to take longer to return to work after the injury. Methods The Alberta Workers Compensation Board (WCB) identified all workers from four Canadian Atlantic provinces who sustained a work injury in Alberta resulting in greater than 5 total temporary disability days (TTDDays) from January 2015 to June 2017. Each was matched on sex, age, and injury date with an Alberta claimant also with greater than 5 TTDDays. WCB information extracted included employment, injury, cost and place of treatment, and modified work. Cox regression identified factors associated with TTDDays. Semi-structured interviews were also undertaken. Results Two-hundred forty pairs were identified and 60 interviews completed. Those from the Atlantic provinces had more TTDDays (median 63 days) than Alberta (median 22 days) with an unadjusted hazard ratio (HR) 0.50 (95% confidence interval [CI], 0.42-0.61). When adjusted for all factors, the HR moved closer to unity (HR = 0.62; 95% CI, 0.50-0.76). Total health care costs were the strongest predictor, with modified work, injury type, and claim status also explanatory factors. Among the Atlantic workers, leaving Alberta for treatment was strongly related to a lower likelihood of ending wage replacement (HR = 0.45; 95% CI, 0.32-0.62). Participants in the interview study emphasized the importance of returning to the family after injury and the financial difficulties of maintaining a second home with reduced income after the injury. Conclusion The higher costs of wage replacement associated with extended time off work may be inherent to the practice of employing out-of-province workers for jobs for which there is a shortage of local labor.

INTRODUCTION It is not known whether out-of-province Canadians, who travel to Alberta for work, are at increased risk of occupational injury. METHODS Workers' compensation board (WCB) claims in 2013 to 2015 for those injured in Alberta were extracted by home province. Denominator data, from Statistics Canada, indicated the numbers from Alberta and Newfoundland and Labrador (NL) employed in Alberta in 2012. Both datasets were stratified by industry, age, and gender. Logistic regression estimated the risk of a worker from NL making a WCB claim in 2013 or 2014, stratified by time lost from work. Bias from under-reporting was examined in responses to injury questions in a cohort of trades' workers across Canada and in a pilot study in Fort McMurray, Alberta. RESULTS Injury reporting rate in workers from NL was lower than those from Alberta, with a marked deficit (odds ratio [OR] = 0.17; 95% confidence interval [CI], 0.12-0.27) for injuries resulting in 1 to 30 days off work. Among the 1520 from Alberta in the trades' cohort, 327 participants reported 444 work injuries: 34.5% were reported to the WCB, rising to 69.4% in those treated by a physician. A total of 52 injuries in Alberta were recorded by 151 workers in the Fort McMurray cohort. In logistic regression, very similar factors predicted WCB reporting in the trades and Fort McMurray cohorts, but those from out-of-province or recently settled in Alberta were much less likely to report (OR = 0.02; 95% CI, 0.00-0.40). CONCLUSION Differential rates of under-reporting explain in part the overall low estimates of injuries in interprovincial workers but not the deficit in time-loss 1 to 30 days.

Background In May 2016, firefighters from the province of Alberta, Canada deployed to a fire that engulfed the urban area of Fort McMurray. During the first days of the fire, firefighters experienced heavy smoke exposures during greatly extended work shifts. Urinary samples were collected post-deployment from three fire services for estimation of 1-hydroxypyrene (1-HP) concentration, reflecting exposure to polycyclic aromatic hydrocarbons (PAHs), to determine the effects of respiratory protective equipment (RPE) and skin hygiene in reducing internal dose Methods Urine samples from one fire service (n = 62) were analyzed for 1-HP by two laboratories, using different assays (LC-MS/MS: GC-MS): remaining samples were analyzed just by LC-MS/MS. A Skin Exposure Mitigation Index (SEMI) was computed from questions on opportunities for changing clothing, showering, and washing during breaks. Regression analyses, using 1-HP ng/g creatinine as the dependent variable, assessed the effect of RPE and skin factors on PAH absorption, allowing for environmental exposure and potential confounders. Stratification identified key groups with equal delay in sample collection. Results 1-HP was detected in 71.0% of 62 samples by LC-MS/MS and 98.4% by GC-MS, with good mutual agreement between the methods. In 171 post-fire samples, 1-HP corrected for creatinine was related to current cigarette smoking and recent barbeque. Among those with samples collected within 48 h, urinary 1-HP was correlated with estimated exposure(r = 0.53, P < 0.001). In those with only one rotation before urine sample collection, no effect was seen of RPE use but I-HP was significantly lower (P = 0.003) in those with those with a high score on the SEMI scale, indicating better access to factors mitigating skin absorption. Conclusion Skin exposure to PAHs is an important route of absorption in firefighters, which can be mitigated by good skin hygiene.

Introduction: Firefighters were working in exceptionally difficult conditions during the Fort McMurray/Horse River fire in May 2016.Methods: From mid-May, we recruited firefighters from 13 fire services as they returned from the fire. In October 2016 we extended recruitment to all Alberta-based firefighters deployed to the fire. In December 2017–May 2018 we sent a first online follow-up: this concentrated on mental health supports. The second follow-up, in October 2018–January 2019, included screening scales for respiratory ill-health and PTSD. All three contacts included visual analogue scales for chest symptoms and the Hospital Anxiety and Depression Scale. We estimated exposure to PM2.5, and calculated an exposure mitigation index from reports of respiratory protective equipment (RPE).Results: We recruited 1,234 firefighters and examined the relation of respiratory symptoms to estimated particulate exposure. The relation was strong immediately post fire but weakened over time. We found less chest tightness and cough in those whose RPE in the first week mitigated exposure by at least 10%. We examined the relation between particulate exposure and mental ill-health from screening questionnaires and found those with high exposure (reflecting the ferocity of the fire) had poorer mental health scores. Firefighters reporting their “worst moment during the fire” was life threatening were more anxious at second follow-up. Overall both anxiety and depression scores increased at successive contacts, more so in those with mental ill-health recorded in physician billing records before the fire.Discussion: The results from this study overall suggest on-going fire-related health effects in a substantial minority of firefighters, similar to those reported in the longitudinal follow-up of firefighters after the collapse of the World Trade Centre. Self-reports of both respiratory symptoms and mental ill-health were strongly related, soon after the fire, to estimated particulate exposures. Anxiety increased over time since the fire in those who felt their life or safety had been threatened, underlining the need for ongoing support. Our conclusions about the benefits of rapid research relate particularly to the collection of biomarkers of exposure as quickly and widely as possible, and the establishment of a nominal list of participants before they are too widely dispersed.

Background\ud \ud Few potentially modifiable risk factors of male infertility have been identified, and while different diets and food groups have been associated with male infertility, evidence linking dietary factors including phytoestrogens and semen quality is limited and contradictory.\ud \ud \ud \ud Objectives\ud \ud To study the associations between phytoestrogen intake and other dietary factors and semen quality.\ud \ud \ud \ud Materials and Methods\ud \ud A case‐referent study was undertaken of the male partners, of couples attempting conception with unprotected intercourse for 12 months or more without success, recruited from 14 UK assisted reproduction clinics. A total of 1907 participants completed occupational, lifestyle and dietary questionnaires before semen quality (concentration, motility and morphology) were assessed. Food intake was estimated by a 65‐item food frequency questionnaire (FFQ) covering the 12 months prior to recruitment. Analyses of dietary risk factors for low motile sperm concentration (MSC: 3 times/wk.\ud \ud \ud \ud Discussion\ud \ud In this case‐referent study of men attending an infertility clinic for fertility diagnosis, we have identified that low MSC is inversely associated with daidzein intake. In contrast, daidzein intake was not associated with PM but eating red milk and drinking whole milk were protective.\ud \ud \ud \ud Conclusions\ud \ud Dietary factors associated with semen quality were identified, suggesting that male fertility might be improved by dietary changes.

Objectives In epidemiological studies of work-related ill-health only current exposures can, at best, be measured. Previous exposures may be estimated using contemporaneous hygiene records or published data. This study aimed to create a job exposure matrix for exposure in bakers for use in an ongoing cohort study. Methods A systematic review was conducted of English language publications on exposures in bakeries. All publications that appeared to contain quantitative measures of exposure to flour dust, wheat allergen, or fungal α-amylase were read independently by two investigators and relevant data extracted. A third investigator reviewed these data and publications were retained that reported full-shift exposures to inhalable dust, wheat allergen, or α-amylase, and for which geometric means (GMs) were given or could be estimated. For each study, the number of sampling results contributing to each GM was recorded together with information on task, bakery size, product, filter type, sampling head, the country in which the study was conducted, and the estimated year of sampling. Multivariable models were elaborated for each exposure using a linear mixed effects approach. The predictive capacity of the model for inhaled particles was tested against samples collected in eight Alberta bakeries. The capacity of exposure intensity, estimated from each of the three models, to predict sensitization was tested against skin prick testing (SPT) for bakery allergens in bakers currently employed in Alberta. Results One thousand three hundred and ninety-seven publications were identified through the systematic search, of which 27 had data used to create one or more of the predictive models. Weighted GMs were used as outcome variables. For inhalable dust, task, bakery size, type of sampling head, and year of sampling contributed to the final model. For wheat allergen and α-amylase, task, bakery size, sampling head, and year of sampling again contributed. Product (bread rather than confectionary or mixed products) was also important in these two latter measures. The model for inhalable dust was used to predict the concentration in 33 samples from Alberta bakeries. Overall, 91% of observed samples had 95% confidence intervals (CIs) overlapping the 95% CIs of the predicted values. A model including the Alberta samples found no effect attributable to Alberta provenance. Using this model for inhalable dust and the models developed solely from the literature for wheat allergen and α-amylase, a positive SPT for bakery allergens in 57 bakers recruited for this study was significantly related to log cumulative exposure for each of the three outcome variables and to log exposure intensity for wheat allergen and α-amylase. Conclusions The exposure models developed from the literature provide useful estimates of exposure. Calibration of the models against locally collected samples may be useful for countries poorly represented in the modeling dataset.

Little information exists about socio-economic, environmental or occupational determinants of low Apgar scores among Nigerian neonates. Mothers in lying-in wards of four hospitals in Ibadan were interviewed on socio-demographic characteristics, obstetric history and work activities during index pregnancy. Apgar scores and clinical data were extracted from case notes. Of the 1349 respondents, 20% had Apgar score7 at one minute, 4% at five minutes. Lower education, cooking with kerosene, physical exertion at work, nulliparity, hypertension in pregnancy, prolonged rupture of membranes, breech presentation and caesarean section were predictors for low Apgar scores at one minute; nulliparity, male infant and breech presentation at five minutes. Occupations with lower socio-economic status or those requiring physical exertion; tailoring, catering and hairdressing recorded higher rates of low Apgar scores at one minute (p = .08). Physical exertion at work and cooking with kerosene may be predictive of low Apgar scores and require further study.

Background Wildfire engulfed Fort McMurray, Alberta on May 3, 2016, leading to a total evacuation. Access to 2 active cohorts allowed us to rapidly assess health effects in those evacuated. Methods People working in Fort McMurray who had been recruited before the fire for 2 occupational health cohort studies completed a questionnaire (online or via telephone) 3-26 weeks after evacuation. The questionnaire asked about respiratory and mental health and experiences since the fire. Results Of the 129 participants, 109 were in the Fort McMurray area on May 3. Thirty-seven (33.9%) of the participants who were in Fort McMurray on May 3 reported a health condition, including respiratory symptoms (n = 17) and mental ill health (n = 17), immediately after the fire. At follow-up, a mean of 102 days after the fire, 11 participants (10.1%) reported a fire-related health condition, including mental ill health (n = 8) and respiratory symptoms (n = 2). There was no difference before and after the fire in use of alcohol, cigarettes, recreational drugs or medication. One in 4 participants (32 [24.6%]) had not worked since the fire, and fewer than half (58 [44.6%]) had returned to Fort McMurray. Of the 90 participants evacuated, 15 (16.7%) had scores indicative of moderate or severe anxiety or depression on the Hospital Anxiety and Depression Scale. Those evacuated had significantly higher mean anxiety (p = 0.01) and depression (p = 0.04) scores than those not evacuated. Regression modelling showed that anxiety scores were higher for women, with longer time since the fire and with evacuation to a motel. Depression scores were higher for women and with financial loss because of lack of work. Interpretation Although evacuation was associated with higher anxiety and depression scores, persisting ill health was not widespread at early follow-up after the fire. Although these results are encouraging, these "healthy worker" results cannot be generalized to all evacuees.

Background The Foundation Course in Occupational Medicine for community-based physicians was started in Alberta in 2012 and has since been implemented across Canada. As part of the evaluation of the first 4 years, two studies were initiated to assess the impact of the course on assessment of work-relatedness and case-reporting. Aims To determine whether assessment of work-relatedness, intention to report cases and number of cases reported to the Workers’ Compensation Board (WCB) changed during/after the course. Methods In study 1, course participants were asked to rate scenarios describing ill-health potentially resulting from work. They rated work-relatedness on a visual analogue scale and recorded whether they would report to the WCB. Assessments were made before the course started, after course completion or both. In study 2, numbers of reports to the WCB were documented for physicians giving consent, both for Foundation Course participants and a comparison group of community-based physicians. Multilevel regression models were fitted to allow for potential confounders and clustering within respondent. Results Among 102 physicians completing at least one set of scenario assessments, ratings of work-relatedness (β = 6.5; 95% CI 2.6–10.4) and likelihood of reporting to the WCB (OR = 1.9; 95% CI 1.2–3.1) increased significantly post-course. The mean annual number of cases reported to the WCB increased from 91.8 to 125.7 among the 35 Alberta physicians included in study 2. This change was only significant (P < 0.05) on a one-sided test. Conclusion The two evaluative studies showed good evidence of changes in perceptions and intentions but only weak evidence of behavioural change.

Background We aimed to determine the relationship between childhood abuse and mental ill-health in firefighters deployed to a devastating fire that engulfed Fort McMurray Methods A stratified sample of 282 firefighters was selected from a cohort of 1234 for assessment by Structured Clinical Interview (SCID) for DSM-5 diagnostic criteria and the Childhood Experience of Care and Abuse questionnaire (CECA-Q). Diagnoses were grouped as post-traumatic stress disorder (PTSD), anxiety disorders, depressive disorders and substance use disorders. Scales extracted from the CECA-Q included parental loss, antipathy, neglect, physical punishment, sexual abuse and support from a same-age confidant. The relation to diagnostic group was examined by multivariable logistic regression Results 192 SCID interviews and 188 CECA-Qs were completed: 124 met DSM-5 criteria for diagnoses including anxiety disorder (56), depressive disorder (54), PTSD (77) and substance use disorder (43). Childhood sexual abuse was reported by 24 firefighters all of whom met DSM-5 diagnostic criteria. Sexual abuse and a childhood confidant differentiated diagnoses in an initial multivariable model of those with psychiatric disorders. Compared to those without a psychiatric diagnosis, father's antipathy was related to anxiety and substance use, physical punishment to PTSD and substance use. A childhood same-age confidant protected against anxiety, depression and PTSD. Fire exposures related only to PTSD. Limitations The comparison group without mental disorders was small. Childhood abuse information was collected retrospectively and may be biased by current state. Conclusions Firefighters’ mental health is a function of both work-role traumas and childhood events. Occupational health provision must address this complexity.

Objective: Sarcoidosis is thought to be an aberrant immune response to environmental agents, with rural living as a risk factor. We aimed to determine if farm living, consumption of farm (untreated) milk, or untreated water increased the risk of sarcoidosis. Methods: In a case-referent design, patients aged 18–60 with pulmonary sarcoidosis together with referents with other chronic respiratory disease, diagnosed 1999–2005 in Alberta, Canada, were approached through their specialist physician. Participants completed a telephone questionnaire about farm living, use of untreated water and farm milk for each residence from birth to diagnosis. Exposures at birth, up to age five, and up to diagnosis were calculated. Results: The study included 615 cases and 1334 referents. The consumption of farm milk, but not of unpiped water or farm living overall, appeared to be consistently associated with sarcoidosis in a fully adjusted analysis. The association was present for farm milk used in the residence of birth (odds ratios (OR): 1.59, 95% confidence intervals (CI): 1.08–2.34) and persisted for those drinking farm milk to age five years (OR: 1.52, 95% CI: 1.04–2.21), and for those drinking farm milk for &gt, 16 years to diagnosis (OR: 1.50, 95% CI: 1.04–2.15). The association with sarcoidosis was stronger when the referent was in the subgroup diagnosed with asthma but was present also with referents with other chronic respiratory disease. Among those whose family used farm milk at birth and to age 5 years, continued use of farm milk into adulthood increased the risk of sarcoidosis. Conclusion: We observed evidence of positive association between consumption of farm milk and sarcoidosis.

Urinary 1-hydroxypyrene (OH-Pyr) is widely used for biomonitoring human exposures to polycyclic aromatic hydrocarbons (PAHs) from air pollution and tobacco smoke. However, there have been few rigorous validation studies reported to ensure reliable OH-Pyr determination for occupational health and risk assessment. Herein, we report an inter-laboratory method comparison for urinary OH-Pyr when using gas chromatography-high-resolution mass spectrometry (GC-HRMS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) on urine specimens collected from firefighters (n = 42) deployed at the 2016 Fort McMurray wildfire. Overall, there was good mutual agreement in urinary OH-Pyr quantification following enzyme deconjugation with an average bias of 39% with no significant deviation from linearity (slope = 1.36; p 0.05), whereas technical precision ( 12%) and average recovery ( 85%) were acceptable when using a stable-isotope internal standard. Faster analysis times (4 min) were achieved by LC-MS/MS without chemical derivatization, whereas lower detection limits (0.64 ng/L, S/N = 3) was realized with solid-phase extraction prior to GC-HRMS. A median creatinine normalized OH-Pyr concentration of 128 ng/g was measured for firefighters that were below the recommended biological exposure index due to delays between early stages of emergency firefighting and urine sample collection. Similar outcomes were also measured for 3-hydroxyphenanthrene and 9-hydroxyfluorene that were positively correlated with urinary OH-Pyr (p 0.05), implying similar uptake, distribution, and liver biotransformation processes. Optimal specimen collection strategies post-deployment together with standardized protocols for OH-PAH analysis are critical to accurately evaluate smoke exposure in firefighters, including experimental conditions to ensure quantitative enzyme hydrolysis of urine samples. Graphical abstract.

A study of the respiratory health of grain farmers in Alberta, Canada was carried out in March 2002. Two populations were identified: members, in 1983, of a province-wide farm organisation, and grain farmers registered with the provincial agriculture department. A telephone interview addressed pesticide use (using pre-circulated trade names), chronic disease and respiratory symptoms. Pesticide ingredients were identified from provincial crop protection guides. Total years of use were calculated for seven chemical groups. Consent for linkage to administrative health records was obtained in 2009. A likelihood score (Lscore) is computed, relating symptoms to asthma diagnosis. Self-reported asthma and the Lscore are examined against duration of pesticide exposures. Of the 10,767 farmers listed, 2426 were still living, had farmed grain and were interviewed; 1371 were re-contacted and matched to health records. After allowance for confounders, years of exposure to phenoxy compounds are related to self-reported asthma and Lscore. Compared to no exposure, the adjusted odds ratios (95% Confidence Intervals for self-reported asthma for short, medium and long exposure to phenoxy compounds are 1.29 (0.66–2.52), 2.52 (1.25–5.09), and 3.18 (1.54–6.58), and for Lscore are 1.19 (0.91–1.55), 1.50 (1.13–1.99), and 1.58 (1.18–2.12). We conclude that lifetime exposure to phenoxy herbicides is associated with an increased risk of asthma.

Objectives There is little information on how work tasks, demands, and exposures differ between women and men in nominally the same job. This is critical in setting workplace standards that will protect the health of both men and those women moving into less traditional work roles. Information used in setting standards is currently based almost entirely on male workers. This paper describes differences in work and health, and the relation between them, in women and men who have undergone the same trade training for the welding or electrical trades. Method Four cohorts were established. Two were women across Canada in the welding and electrical trades who had been in an apprenticeship since 2005. Cohorts of men in the same trades during the same period were established in the province of Alberta, Canada. Participants completed a baseline questionnaire at recruitment and were followed up every 6 months to collect detailed information on work carried out and on their health and habits. At the end of the study (up to 5 years for women and up to 3 years for men), the cohort members completed a final questionnaire including questions on mental health, harassment, and gender. Results The four cohorts comprised 1001 welders (447 female; 554 male) and 885 in the electrical trades (438 female; 447 male). Follow-up information was available for 89%. Women were more likely than men to have had some post-secondary education before starting their trade and were less likely to be living as married or to have a child. More welders smoked, and more men were heavy drinkers. At recruitment, more welders than those in the electrical trades reported rhinitis (sneezing and runny nose), depression, and anxiety. Female welders reported more depression (38%) than male welders (30%), compared to 24% in the electrical trades. At first follow-up, new-onset shoulder pain was more frequent in men and new-onset asthma or wheezing in welders. Within each trade, women reported less variety in tasks. Women welders were less likely to be employed in construction than men, and women were less likely to become industrial electricians. Overall, 54% of women and 46% of men reported never using respiratory protection when welding. In the end-of-study questionnaires received to date, 49% reported bullying or harassment during the apprenticeship, with higher proportions in welding than electrical trades and in women compared with men. Such harassment was reflected in higher anxiety and depression scores. Conclusions This is the first report on these four cohorts and demonstrates the capacity for detailed analysis of the differences in exposure and new-onset occupationally related ill-health. While women and men in the same trades appear to be doing broadly similar work, and to have similar patterns on health at the first follow-up, there are some significant differences in the types of employment and variety of tasks. The very detailed information collected will allow more precise estimates of exposures to be correlated with health outcomes at the end of the follow-up period.

Arsenic in drinking water is causally linked with cancer of the skin, lung, and urinary bladder, but there is very little data on a possible role for arsenic in the etiology of cervical cancer, a disease in which human papilloma virus is held to be a necessary but not sufficient cause. All histopathology results from cervical specimens from the National Institute of Cancer Research and Hospital (NICRH), Dhaka (1997–2015), and the Anowara Medical Services (2003–2015), both serving the whole of Bangladesh, were classified by cell type. Arsenic concentrations in well water in the thana of residence were estimated from systematic sampling carried out by the British Geological Survey. In a case-referent analysis arsenic estimates for cases of cervical cancer were compared with those found to have benign lesions. In this study, 3464 NICRH (CH) cervical specimens and 30,050 community medical service (CMS) specimens were available: 3329 (CH) and 899 (CMS) were recorded as malignant. Most were squamous cell carcinoma, of which 4.9% were poorly differentiated. Overall, there was no increase in cervical cancer with increasing arsenic concentration. Among those with squamous cell histology, a strong dose response was seen for poorly differentiated cancer with increasing arsenic exposure. The odds ratio increased monotonically, compared with exposure 200 μg/L (p < 0.001). Given the high proportion of Bangladeshis using drinking water containing >50 μg/L of arsenic, the evidence that arsenic is implicated in cancer grade suggests a need for further investigation and the introduction of cervical screening in high arsenic areas.

The study was designed to investigate whether beryllium exposure was related to illness diagnosed as sarcoidosis. Chronic beryllium disease (CBD) and sarcoidosis are clinically and pathologically indistinguishable, with only the presence of beryllium-specific T-lymphocytes identifying CBD. Testing for such cells is not feasible in community studies of sarcoidosis but a second characteristic of CBD, its much greater incidence in those with a glutamic acid residue at position 69 of the HLA-DPB1 gene (Glu69), provides an alternative approach to answering this question.Cases of sarcoidosis aged 18-60 years diagnosed in Alberta, Canada, from 1999 to 2005 were approached through their specialist physician, together with age-matched and sex-matched referents with other chronic lung disease. Referents were grouped into chronic obstructive pulmonary disease (COPD), asthma and other lung disease. Participants completed a telephone questionnaire, including industry-specific questionnaires. DNA was extracted from mailed-in mouthwash samples and genotyped for Glu69. Duration of employment in types of work with independently documented beryllium exposure was calculated.DNA was extracted for 655 cases (270 Glu69 positive) and 1382 referents (561 positive). No increase in sarcoidosis was seen with either Glu69 or beryllium exposure (none,10, ≥10 years) as main effects: longer duration in possible beryllium jobs was related to COPD. In Glu69 positive men with exposure ≥10 years, the trend towards increasing rate of COPD was reversed, and a significant interaction of duration of exposure and Glu69 was detected (OR=4.51 95% CI 1.17 to 17.48).The gene-environment interaction supports the hypothesis that some cases diagnosed as sarcoidosis result from occupational beryllium exposure.

Objective We examined occupational exposures and sperm morphology to establish whether exposures implicated differed from those affecting motile sperm concentration. Methods Computer aided sperm morphometric assessment was undertaken on morphology slides obtained as part of a multi-centre study in 1999–2002 of occupational factors in male infertility. Men attending 14 fertility clinics across the UK were recruited and gave a semen sample. Before results of the semen analysis were known, the men completed detailed questionnaires about their employment and lifestyle. Occupational exposures were assessed by occupational hygienists. Data were analysed using an unmatched case-referent design, allowing for clustering and for confounders. Three case definitions were used: poor morphology (normal morphology 6 ) and either condition. Results Morphology results were available for 1861/2011 men employed at the time of recruitment. Of these 1861, 296 (15.9%) had poor morphology; of the 2011with sperm count, 453 (22.5%) had low MSC; 654/1981 (33.0%) had either condition. Poor morphology, adjusted for confounding, was related to self-reported lifetime exposure to lead (OR=1.33; 95% CI 1.00 to 1.75). Low MSC was also related to self-reported lead and to hygienist-assessed glycol ether exposure. Self-reported use of paint stripper (OR=1.47; 95% CI 1.07 to 2.03) and lead, but not glycol ether, were significantly related to the combined case definition. Conclusions While this study did not identify any occupational exposure uniquely related to sperm morphology, the capacity of the study to detect risk was increased by including morphology with sperm concentration and motility.

IntroductionIn 2016 firefighters from Alberta, Canada deployed to a catastrophic fire in Fort McMurray. In the first few days, firefighters experienced heavy smoke exposures during greatly extended work shifts. Blood samples were collected to determine whether inflammatory markers might constitute a useful biomarker of exposure. In first responders exposed during the Word Trade Center disaster, inflammatory markers in serum samples collected within 6 months post-event were associated with poor recovery from exposure-related lung disorders.MethodsBlood samples were collected at two fire services. At Service A, first samples were drawn two weeks from the start of the fire and second samples after 3–4 months. At Service B samples were collected over 4 weeks, starting 4 months from the first exposure. Samples were immediately centrifuged and the plasma stored at −80C before being evaluated for 42 cytokines or chemokines using a multiplex assay. A principal component analysis was carried out to reduce the number of correlated outcomes. Exposure to particulates was estimated for each firefighter using environmental PM2.5, total hours exposed, tasks carried out and the use of respiratory protection. Respiratory symptoms immediately before the fire, immediately post fire and at 4 months were collected using visual analogue (VA) scales.ResultsInflammatory markers were assayed for 242 plasma samples from 175 firefighters. Six components were extracted of which only one, labelled the inflammatory marker component (IMC) was related to estimated exposure (pConclusionsInflammatory markers were related to exposure but did not improve prediction of symptoms in the first months post fire.

IntroductionWith few female occupational cohorts, little is known about the contribution of work exposures to female infertility.MethodsA cohort of 888 tradeswomen across Canada was established (450 welders and 438 in the electrical trades) to examine effects on the fetus, with investigation of infertility a secondary objective. Women completed an extensive questionnaire at recruitment and follow-up questionnaires every six-months for up to 5 years. At each contact she was asked about attempts to get pregnant and barriers to conception. Fertility issues were identified both by self-report of failure to conceive for ≥12 months and as the likelihood of conceiving in any month at risk. Determinants of infertility were examined in a Cox regression with time dependent covariates. Employment factors examined in each month were paid work, trade work and cumulative months in trade. Maternal age, prior conceptions, smoking, use of alcohol and BMI were examined as confounders.Results96 periods of infertility ≥12 months were reported among 38 women from welding and 52 from electrical trades giving the risk of infertility for welders relative to electricians of 0.71 (95%CI 0.48–1.06). Total person months at risk (excluding months with no sex, pregnancy, surgical sterility or menopause) were 12 696 for welders and 13 313 for electricians. Likelihood of conceiving in any month at risk was significantly reduced with use of better contraception, drinking >7 units of alcohol, increasing age, number of previous pregnancies and, for welders, smoking >10 cigarettes/day. No effect of either current or cumulative work in trade was evident having adjusted for confounding. HR for working as a welder was −0.07 95% CI −0.49–0.35.ConclusionsFemale infertility presents challenges as an outcome in occupational epidemiology, but data can be structured to allow for time at risk. Analysis to date has demonstrated no important effect of exposure to welding.

Data on the role of arsenic in renal cancer are suggestive but inconclusive. The present analysis aimed to determine whether renal cancers were more likely in Bangladeshi villagers exposed to high arsenic concentration in well water and, if so, whether this excess was limited to transitional cell cancers (TCC) or occurred also for renal cell cancers (RCC).Histology/cytology results from renal biopsies carried out at a single clinic in Dhaka, Bangladesh, from January 2008 to October 2011 were classified into four groups: RCC, TCC, other malignancy and benign. Patients aged ≥18 years using hand-pumped well water were identified by questionnaire, blind to diagnosis. Arsenic concentration was estimated from British Geological Survey reports for administrative area (thana) of residence. In a case-referent design (with benign results as referents), ORs were calculated by multilevel logistic regression adjusted for confounding. Time since well installation and smoking were examined by stratification.Among 1489 cases included, 896 were RCC, 90 TCC and 503 benign. Arsenic concentration was estimated for 301 thanas with 63% of cases and 40% referents with arsenic concentration ≥50 µg/L (p0.001). Risk increased monotonically with arsenic concentration ≥50 µg/L for both cell types (RCC and TCC). Risk estimates were greater in thana with early well installation where risk was increased for RCC in exposure stratum 1050 µg/L (OR=2.47 95% CI 1.52 to 4.01). Stratification by 'ever smoked' confirmed the presence of risk in non-smokers.The relationship between arsenic concentration and both RCC and TCC suggests that arsenic is a causal factor in renal cancer.

Background Although many studies have investigated the relationship between the introduction of the New Cooperative Medical Scheme (NCMS) in rural China in 2003 and increased use of medical services, the effect on health status, objectively measured, is seldom reported. In Anhui Province a chronic disease scheme (CDS) for reimbursing part of the cost of outpatient care is designed to improve management of those with chronic conditions, including diabetes. Methods A follow-up study was designed in which patients with diabetes aged 40–70 years who had recently (in 2010) been granted a chronic disease card were individually matched on age, sex and village with a patient with diabetes not yet in the scheme. Each subject gave a fingertip sample of blood to give the concentration of glycosylated hemoglobin (HbA1c), a measure indicating blood glucose control during the previous 3 months. This measure was made on recruitment and at 12 month follow-up: information on use of health services, quality of life and financial burden was also collected at the two contacts. Results Of 602 pairs initially recruited, 528 pairs were contacted at follow-up and are the subject of this report. To distinguish between outcomes associated with application and those of membership of the scheme, the primary analysis was of 256 pairs in which one had been a member of the CDS throughout and the other never applied. No difference between pairs on HbA1c was found either at recruitment or follow-up but those in the CDS reported more hospital visits, more tests and more use of high level hospitals. However they had poorer scores on quality of life scales (SF-12, EQ-5D) and were more likely to report that the financial costs were very burdensome. Those recently applying for the scheme, or being accepted since recruitment, had lower HbA1c scores. Conclusions On-going membership of the CDS was associated with increased use of services but this did not appear to result in better management of blood glucose or improved quality of life. Those who had recently joined the scheme had signs of improvement, suggesting a need for active follow-up to maintain and reinforce early gains.

Zinc supplementation reduces the duration, severity and recurrence of diarrhoea in young children. This study examines whether zinc, found naturally in drinking water, reduced infant deaths from diarrhoea in rural Bangladesh. Information was compiled for births over two calendar years with follow-up for deaths within one year of birth. The study included 29,744 live births and 934 deaths in some 600 villages under the care of Gonoshasthaya Kendra (GK), grouped into 15 health centre regions within 12 upazillas. Individual matching of death to birth data was not possible, but information on exposures through well water and on potential confounders was available for each upazilla. Average concentration of zinc in well water, reported by the British Geological Survey, was grouped into high (>0.07 mg/L), moderate (0.020–0.070 mg/L) and low (&lt 0.020 mg/L) concentrations. Odds ratios (OR) were calculated for zinc by age and cause of death. Zinc concentration was unrelated to all-cause mortality but a decrease in deaths from diarrhoea (N = 50) was seen in areas with high zinc (OR = 0.30, 95% CI 0.13–0.69). No relation to diarrhoeal deaths was found with other well contaminants (arsenic, manganese) having accounted for zinc. Upazillas with a high proportion of women without education had higher rates of death from diarrhea, but the decrease in risk with high zinc remained (OR adjusted = 0.41, 95% CI 0.20–0.84). It is concluded that exposure to zinc through drinking water may reduce risk of diarrhoeal deaths.

Perfluorinated acids (PFAs) are prominent and widespread contaminants of human blood. In animal studies there is evidence that suggests certain PFAs can disrupt thyroid hormone homeostasis. A commonly reported condition in exposed animals is hypothyroxinemia, whereby serum free thyroxine (fT4) is decreased despite normal thyroid stimulating hormone (TSH) concentrations. We designed an individually matched case-control study to investigate whether exposure to perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) was associated with hypothyroxinemia in pregnant women from Edmonton, Alberta, Canada, in 2005-2006, who underwent a "triple screen" blood test at 15-20 weeks gestation as part of ante-natal care. Thyroid hormones, fT4 and TSH, were measured in serum from 974 women, and from these we measured PFAs in the sera of 96 hypothyroxinemic cases (normal TSH, the lowest 10th percentile of fT4) and 175 controls (normal TSH, fT4 between the 50th and 90th percentiles) matched on age and referring physician. Analyses by conditional logistic regression indicated that the concentrations of PFAs in this population were not associated with hypothyroxinemia among pregnant women. The current findings do not support a causal link between PFA exposure and maternal hypothyroxinemia in the studied population.

Objectives In developed countries, poultry are raised in totally confined buildings in which workers are exposed to indoor airborne contaminants. A prospective study was conducted to investigate the relationship between workers9 respiratory health and airborne contaminants during the life cycle of broiler and layer flocks. Methods Seventeen layer and 16 broiler operations were chosen within a 200 km radius of Edmonton. An attempt was made to visit each broiler operation twice during the winter and summer seasons in the early and later periods of the 6-week production cycle and visit each layer operation three times during the early, middle and later periods of the 40-week production cycle. Results In broiler operations, respirable particle counts, total dust and endotoxin concentrations, and ammonia levels increased with flock age, while mean endotoxin load (EU/mg) decreased in the winter and summer seasons. Increases in dust and endotoxin concentrations in the winter season were not statistically significance. Mean endotoxin concentration increased and mean dust concentration and ammonia level decreased with flock age in layer operations, although not all these changes were statistically significant. Mean across-shift decrements in FEV 1 and FVC increased with flock age among workers from layer operations. Endotoxin concentration was significantly associated with across-shift changes in FEV 1 among workers in layer operations. Conclusion In our study, changes in lung function appear more closely associated with changes in endotoxin than other contaminants. Changes in indoor environmental conditions occurring in poultry barns which are dependent on the flock age may affect workers9 health in poultry operations.

Recent studies in Bangladesh indicate that arsenic and manganese in tube-well water may increase the incidence of infant mortality. The study reported here examined whether these findings could be replicated. Data available from some 600 villages under the care of the nongovernmental organization (NGO) Gonoshasthaya Kendra included details of 29744 live births and 934 infant deaths in a 2-year period, with age and cause. These were analyzed by mean well levels of arsenic and manganese as reported by the British Geological Survey for the 12 upazillas. Odds ratios were calculated by age at death and cause. The effect of arsenic on all-cause infant mortality, although small and not significant, was consistent with earlier reports. The previous finding of an increased risk of infant mortality at concentrations of manganese > or =0.4 mg/L was not evident.

Background: Few studies, and none in Canada, have examined the relation between maternal smoking, alcohol consumption and drug dependence during pregnancy and early neonatal morbidity. Methods: We analyzed records of singleton live births in Alberta, Canada. Markers of neonatal morbidity were Apgar scores (

Background: Although occupational asthma is a well recognized and preventable disease, the numbers of cases presenting for compensation may be far lower than the true incidence. Methods: Workers' Compensation Board (WCB) claims for any reason 1995-2004 were linked to physician billing data. New onset adult asthma (NOAA) was defined as a billing for asthma (ICD-9 code of 493) in the 12 months prior to a WCB claim without asthma in the previous 3 years. Incidence was calculated by occupation, industry and, in a case-referent analysis, exposures estimated from an asthma specific job exposure matrix. Results: There were 782,908 WCB eligible claims, with an incidence rate for NOAA of 1.6%: 23 occupations and 21 industries had a significantly increased risk. Isocyanates (OR 1.54: 95% CI 1.01-2.36) and exposure to mixed agricultural allergens (OR=1.59: 95% CI 1.17-2.18) were related to NOAA overall, as were exposures to cleaning chemicals in men (OR=1.91:95% CI 1.34-2.73). Estimates of the number of cases of occupational asthma suggested a range of 4% to about half for the proportion compensated. Conclusions: Data linkage of administrative records can demonstrate under-reporting of occupational asthma and indicate areas for prevention.

We propose a Bayesian adjustment for the misclassification of a binary exposure variable in a matched case-control study. The method admits a priori knowledge about both the misclassification parameters and the exposure-disease association. The standard Dirichlet prior distribution for a multinomial model is extended to allow separation of prior assertions about the exposure-disease association from assertions about other parameters. The method is applied to a study of occupational risk factors for new-onset adult asthma.

BACKGROUND: Work-related carpal tunnel syndrome (CTS) is a complex and costly condition. There is some evidence that the employment outcome may be worse in cases of CTS where the condition is being considered for compensation. AIM: To examine whether workers' compensation status is an important determinant of outcome of CTS. METHODS: Cases, with a Workers' Compensation Board (WCB) claim, and referents, in work but without a WCB claim, were identified from the practice of a single specialist physician. Data on history prior to and at the time of diagnosis, and events since diagnosis, were collected from clinical records and by a telephone-administered questionnaire. Prior events, severity, treatment and outcome associated with a WCB claim were assessed by logistic regression. RESULTS: Interviews were successfully completed for 46 cases and 50 referents. In the model adjusted only for age and gender, claimants had a worse outcome in terms of changing job or stopping work with time loss from work due to CTS [odds ratio (OR) 5.1, 95% confidence interval (CI) 1.9-13.3]. The OR was much influenced by the inclusion of treatment in the model (OR = 9.6, 95% CI 1.6-58.6) with WCB cases more likely to have surgical and physiotherapy treatments. Cases with a WCB claim cost more to treat and reported greater loss in income than those not seeking compensation. CONCLUSIONS: Although these data are limited, the results are suggestive of poorer outcome among WCB claimants despite greater use of treatment and comparable severity of disease.

To use data collected by Gonoshasthaya Kendra, a large nongovernmental organization providing health care to some 600 villages, to describe the epidemiological pattern of stillbirth and any additional contribution made by arsenic contamination of hand-pump wells in Bangladesh.Completed pregnancies and outcomes (n = 30 984) for two calendar years, together with existing data on 26 socioeconomic and health factors were selected for study. The health care in these villages was administered from 16 geographical centres; information on the average arsenic concentration in each centre was obtained from the National Hydrochemical Survey. After univariate analysis, a multivariate, multilevel, logistic model for stillbirth was developed. The additional effect of arsenic was calculated having adjusted for all potential confounders thus identified.The overall stillbirth rate was 3.4% (1056/30 984) and increased with estimated arsenic concentration (2.96% at10 microg/l; 3.79% at 10 microg/l to50 microg/l; 4.43% at50 microg/l). Having adjusted for 17 socioeconomic and health factors, the odds ratios estimated for arsenic (with10 microg/l as reference) remained raised: 1.23 (95% confidence interval, CI: 0.87A1.74) at 10 microg/l to50 microg/l and 1.80 (95% CI: 1.14A2.86) at 50 microg/l or greater.A increased risk of stillbirth is associated with arsenic contamination. This risk, substantial enough to be detected by an ecological approach and not readily attributable to unmeasured confounding, is essentially preventable and all efforts must be made to protect women at high risk.

To investigate the relation between male infertility and occupational exposures, particularly glycol ethers.A case-referent study was designed in which men attending 14 fertility clinics in 11 centres across the UK in 1999-2002 were recruited following 12 months of unprotected intercourse and without a previous semen analysis. Cases were those with low motile sperm concentration (MSC) relative to the time since their last ejaculation (MSC12 x 10(6) for 3 days of abstinence). Referents were other men attending these clinics and meeting the inclusion criteria. A single semen sample was collected at the clinic and analysed at the andrology laboratory serving each hospital. Concentration was determined manually with motility assessed centrally from video recordings. Exposures and confounding factors were assessed from self-completed and nurse-interviewer questionnaires, completed prior to the results of the semen analysis. The occupational histories were assessed for exposures relative to UK norms by a team of occupational hygienists blind to case status.Of 2118 men in employment at the time of the interview, 874 (41.3%) were cases. Work with organic solvents, particularly glycol ethers, in the 3 months before the first clinic visit was associated with the likelihood of low motile sperm count. Unadjusted odds ratios (OR) for moderate and high glycol ether exposure (compared with none) were 1.70 (95% CI: 1.11 to 2.61) and 2.54 (95% CI: 1.24 to 5.21). Adjustment for potential confounders (surgery to the testes, previous conception, wearing boxer shorts, drinking alcohol, employed in manual work) reduced the risk associated with glycol ether exposure: moderate OR = 1.46 (95% CI: 0.93 to 2.28), high OR = 2.25 (95% CI: 1.08 to 4.69). No other occupational risk factor was identified.Glycol ether exposure was related to low motile sperm count in men attending fertility clinics. This suggests that, at the time of the study, glycol ethers continued to be a hazard for male fertility.

This study estimated the level and determinants of airborne benzene concentrations in rural western Canada. A multi-site, multi-month unbalanced two-factorial design was used to collect air samples at 1206 fixed sites across a geographic area associated with primary oil and gas industry in Canadian provinces of Alberta, north-eastern British Columbia, and central and southern Saskatchewan from April 2001 to December 2002. Benzene concentrations integrated over 1 calendar month were determined using passive organic vapour monitors. Linear mixed effects models were applied to identify the determinants of airborne benzene concentrations, in particular the proximity to oil and gas facilities. The observed geometric mean of benzene concentrations was 158 ng m−3, with large geometric standard deviation: 4.9. Benzene concentrations showed a seasonal variation with maxima in winter and minima in summer. Emissions from oil well (within 2 km) and compressor influenced monthly airborne benzene concentrations. However, in our study, being located in the general area of a gas plant seems to be the most important in determining monthly airborne benzene concentrations. These findings support the need for investigation of the impact of oil and gas industry on quality of rural air.

Objective Arsenic concentrations in 25% of tube wells in Bangladesh exceed 50μg/L, a level known to be hazardous. Levels in individual wells vary widely. We gathered data on arsenic exposure levels and skin lesion prevalence to address the lack of knowledge about risks where the average arsenic concentrations was lower. Methods The nongovernmental organization Gonoshasthaya Kendra did three related studies of keratotic skin lesions since 2004: (1) an ecological prevalence survey among 13 705 women aged > 18 in a random sample of 53 villages; (2) a case-control study of 176 cases and age- and village-matched referents; and (3) a prevalence survey of the entire population of 11 670 in two additional villages. We calculated prevalence as a function of average arsenic concentrations as reported in the National Hydrochemical Survey, and measured arsenic concentrations in wells used by subjects in the case-control study. Findings The prevalence of skin lesions was 0.37% in people exposed to arsenic concentrations below 5μg/L, 0.63% at 6–50μg/L, and 6.84% at 81μg/L. In the case-control analysis, relative risk of skin lesions increased threefold at concentrations above 50μg/L (P < 0.05). Conclusion Little serious skin disease is likely to occur if the arsenic concentration in drinking water is kept below 50μg/L, but ensuring this water quality will require systematic surveillance and reliable testing of all wells, which may be impractical. More research is needed on feasible prevention of toxic effects from arsenic exposure in Bangladesh.

In earlier analyses, we demonstrated dose-response relationships between renal and lung cancer and local arsenic concentrations in wells used by Bangladeshi villagers. We used the same case-referent approach to examine the relation of arsenic to biopsy confirmed transition cell cancer (TCC) of the ureter, bladder or urethra in these villagers. As the International Agency for Research on Cancer (IARC) has conclude that arsenic in drinking water causes bladder cancer, we expected to find higher risk with increasing arsenic concentration. We used histology/cytology results from biopsies carried out at a single clinic in Dhaka, Bangladesh from January 2008 to October 2011. We classified these into four groups, TCC (n = 1466), other malignancies (n = 145), chronic cystitis (CC) (n = 844) and other benign (n = 194). Arsenic concentration was estimated from British Geological Survey reports. Odds ratios were calculated by multilevel logistic regression adjusted for confounding and allowing for geographic clustering. We found no consistent trend for TCC with increasing arsenic concentration but the likelihood of a patient with benign disease having CC was significantly increased at arsenic concentrations &gt, 100 µg/L. We conclude that the expected relationship of TCC to arsenic was masked by over-matching that resulted from the previously unreported relationship between arsenic and CC. We hypothesize that CC may be a precursor of TCC in high arsenic areas.

Aims: To investigate the validity of measures of noise exposure derived retrospectively for a cohort of nuclear energy workers for the period 1950–98, by investigating their ability to predict hearing loss. Methods: Subjects were men aged 45–65 chosen from a larger group of employees—assembled for a nested case-control study of noise and death from ischaemic heart disease—who had had at least one audiogram after at least five years’ work. Average hearing loss, across both ears and the frequencies 0.5, 1, 2, and 4 kHz, was calculated from the last audiogram for each man. Previous noise exposure at work was assessed retrospectively by three hygienists using work histories, noise survey records from 1965–98, and judgement about use of hearing protection devices. Smoking and age at the time of the audiogram were extracted from records. Differences in hearing loss between men categorised by cumulative noise exposure were assessed after controlling for age, smoking, year of test, and previous test experience. Results: There were 186 and 150 eligible subjects at sites A and B of the company respectively who were employed for an average of 20 years. Compared to men with less than one year’s exposure to levels of 85dB(A) or greater, hearing loss was greater by 3.7 dB (90% CI −2.6 to 10.1), 3.8 dB (90% CI −2.6 to 10.3), 7.0 dB (90% CI 1.1 to 12.9) and 10.1 dB (90% CI 4.2 to 16.0) in the lowest to highest categories of cumulative noise exposure at site B. In contrast, at site A, the corresponding figures were −2.2 dB, −2.4 dB, −1.8 dB, and −4.4 dB, with no confidence interval excluding zero. Conclusions: Noise estimation at one site was shown to have predictive validity in terms of hearing loss, but not at the other site. Reasons for the differences between sites are discussed.