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Objectives In the analysis of tissue for asbestos fibers, some measurements may be below the analytical detection limit (nondetects). The use of maximum likelihood and survival analysis methods have been recommended to perform comparisons between subjects in the presence of nondetects. When the data consist of “counts” another method is useful. This method is discussed, and illustrated with an analysis of asbestos lung burden data among brake mechanics previously analyzed by other methods. Methods Statistical models for count data, namely Poisson and negative binomial regression, were used to compare the asbestos fiber concentrations in the lungs of brake mechanics with those of control subjects. The fit of the models was assessed with an analysis of residuals. Results The negative binomial regression models fit the data well. The concentrations of Quebec asbestos fibers in the lungs of the brake mechanics were significantly higher than in the control population. Conclusions Helsel recommended the use of maximum likelihood and survival analysis methods to perform comparisons in the presence of nondetects. When analyzing asbestos fiber count data, or other count data arising in occupational or environmental health, the use of models such as the Poisson and negative binomial may be added to the analyst's toolbox. Benefits are that neither of these methods requires the substitution of arbitrary values for the nondetects and that programs for the computation of count data models are contained in popular statistical software packages. Am. J. Ind. Med. 56:1482–1489, 2013. © 2013 Wiley Periodicals, Inc.

Background The United States is second only to the People's Republic of China in annual talc production. U.S. talc is used in the production of ceramics, paint, paper, plastics, roofing, rubber, cosmetics, flooring, caulking, and agricultural applications. A number of U.S. talc deposits consistently contain talc intergrown with amphiboles such as tremolite and/or anthophyllite. It has long been recognized that miners and millers of talc deposits are at risk for pneumoconiosis and it has recently been reported that it is prudent, on the balance of probabilities, to conclude that dusts from New York State talc ores are capable of causing mesothelioma in exposed workers. This is a report of the diagnosis of pneumoconiosis and mesothelioma in a husband and wife who operated a small metal casting business that used industrial talc from New York as a parting agent. Methods Case reports, including medical records and exposure histories, were provided by an attorney who had also commissioned laboratory investigation of the industrial talc product used in the factory. Results Mrs X was diagnosed with pneumoconiosis characterized by interstitial fibrosis and heavily calcified pleural plaques. Mr X had calcified pleural plaques and developed a fatal pleural mesothelioma. Samples of the industrial talc contained fibrous tremolite and anthophyllite. Conclusions The author concludes that end users of industrial talc from New York State may be at risk of pneumoconiosis and malignant disease. End users of talcs from other regions of the United States, where talc formation arose from processes driven by regional metamorphism, might also be at risk. Am. J. Ind. Med. 56:550–555, 2013. © 2013 Wiley Periodicals, Inc.

Background There is controversy about the potential for dust from the talc mines and mills of New York State to cause mesothelioma. Honda et al. published a study of mortality among New York talc workers and concluded that it was unlikely that the two deaths from mesothelioma were caused by talc ore dust. However, fibers of tremolite and anthophyllite have been found in the lungs of talc workers and Hull concluded that “New York talc exposure is associated with mesothelioma, and deserves further public health attention.” Methods Data concerning additional cases of mesothelioma in the cohort have been posted by NIOSH. I used information from the NIOSH website and the Honda report to analyze the incidence of mesothelioma during the years 1990–2007. Results There were at least five new cases of mesothelioma in the cohort and mesothelioma incidence rates were at least five (1.6–11.7) times the rate in the general population (P

Background It has been a matter of controversy whether there is an increased risk of lung cancer among asbestos-exposed workers without radiographic asbestosis. A previous study of lung cancer risk among asbestos-cement workers has been updated with an additional 12 years of follow-up. Methods Subjects had received radiographic examination at 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single National Institute of Safety and Health (NIOSH)-certified B-reader using the 1971 International Labor Office (ILO) Classification of the pneumoconioses as reference standard. Asbestosis was defined as an ILO coding of 1/0 or higher. Standardized Mortality Ratios (SMRs) were calculated using the general population of Ontario as reference. Results Among asbestos-cement workers without radiographic asbestosis at 20 years latency the lung cancer SMR was 3.84 (2.24–6.14). Among workers without asbestosis when examined at 25 years latency the SMR was 3.69 (1.59–7.26). Conclusions Workers from an Ontario asbestos-cement factory who did not have radiographic asbestosis at 20 or 25 years from first exposure to asbestos continued to have an increased risk of death from lung cancer during an additional 12 years of follow-up. Am. J. Ind. Med. 53:1065–1069, 2010. © 2010 Wiley-Liss, Inc.

We recently conducted a re-analysis [Gennaro et al. 2000] of two independent studies among oil refineries workers: an Italian cohort study [Gennaro et al., 1994,1995] and a Canadian case-control study [Finkelstein, 1996]. In the re-analysis we reported that maintenance workers (MW) experienced an asbestos-attributable risk (AR) of 96-100% for mesothelioma; the same subgroup of workers showed an asbestos AR for lung cancer of 49.2 (95% Confidence Interval (CI) = 26.4-72.4) in the Italian cohort study and an AR of 42.2 (95% CI=10.8-82.6) in the Canadian study. White collar workers (WCW), likely unexposed to asbestos, were considered the internal referent population in the Italian cohort study, while other workers were the comparison group in the Canadian study.

Summary of the Silicosis Studies Table II summarizes the findings of the silicosisexposure–response studies and shows estimates of silicosisrisk in relation to 20 or 40 years of exposure at levels of0.1mg/m 3 . Silicosis is variously defined in relation to deathcertificates and radiographic readings ( 1/0, 1/1, and 2/1). The results can be seen to fall into two groups; agroup with relatively low risk (Muir, Rosenman, andHughes) and a group with high risk (Hnizdo, Ng, Steenland,Kreiss, and Miller). The studies of Muir and Hughesprobably underestimate the long term risks of silicosisbecause many of the workers in their cohorts were followedfor too short a period of time. This suggests that the true riskwould be closer to the estimates of the other authors. Thebest studies for quantitative risk assessment have longfollow-up, a well-defined endpoint, and good exposureestimates. On this basis, the Hnizdo study [Hnizdo andSluis-Cremer, 1993] makes a prominent contribution. Thereis, however, substantial uncertainty about the actual expo-sures of the study subjects. As a result, there is a fair marginof error attributable to the risk estimates.The dose–response relationship for silicosis is non-linear [Hnizdo and Sluis-Cremer, 1993]. This means that therisk of silicosis increases more rapidly at high cumulativeexposures than it does at lower cumulative exposures. Inview of the results of the studies in Table II, I will use asworking estimates a cumulative risk of silicosis (ILOcategory 1/1 or more) of about 5% at 2mg/m

Background Benzene is a human leukemogen. Risk assessment, and the setting of occupational and environmental standards, has assumed that risk is constant in time after a unit of exposure. Leukemia risk is known to vary with time after exposure to ionizing radiation. Methods A matched case-control study of leukemia risk in relation to the temporal pattern of benzene exposures was performed using data from the National Institute of Occupational Safety and Health. Results Leukemia risk following exposure to benzene varied with time in a manner similar to that following exposure to ionizing radiation. More recent exposures were more strongly associated with risk than were more distant ones. There was no significant relation between leukemia death and benzene exposures incurred more than 20 years previously. Conclusions Recent analyses of specific occupational and environmental carcinogens, including benzene and radon, have indicated that cancer risk tends to decline as the time from exposure increases. This suggests that standards for the control of occupational or public risk must be selected to control exposures over a narrower time frame than the usual lifetime one. In the case of benzene, it would appear that risk is attributable primarily to exposures incurred during the previous 10 to 20 years, with exposures in the most recent 10 years being the most potent. To limit risk, exposures must be controlled during that interval. It is important that epidemiologists explore the temporal pattern of risk in their studies to facilitate the risk assessment of other carcinogens. Am. J. Ind.

Background: The health effects of asbestos are intimately related to the fate of inhaled fibers in the lungs. The kinetics of asbestos fibers have been studied primarily in rodents. The objective of this study was to explore the application of these kinetic models to human autopsy data. Methods: We analyzed the asbestos fiber content of the lungs of 72 Quebec chrysotile miners and millers and 49 control subjects using analytical transmission electron microscopy. Statistical methods included standard multivariate linear regression and locally weighted regression methods. Results: The lung burdens of asbestos bodies and chrysotile and tremolite fibers were correlated, as were the concentrations of short, medium, and long fibers of each asbestos variety. There were significant associations between the duration of occupational exposure and the burdens of chrysotile and tremolite. The concentration of chrysotile decreased with the time since last exposure but the concentration of tremolite did not. The clearance rate varied inversely with the length of chrysotile fibers. For fibers greater than 10μ in length the clearance half-time was estimated to be 8 years. Conclusions: The patterns in our data are compatible with both of the hypotheses suggested from rodent experiments; the existence of a long-term sequestration compartment and overload of clearance mechanisms in this compartment. Am. J. Ind. Med. 35:401–412, 1999. © 1999 Wiley-Liss, Inc.

A case-control study, nested in a cohort of workers under surveillance for silicosis in 1979 or later, was undertaken to assess lung cancer risk in relation to the ILO coding scheme for the pneumoconioses. The subjects of this study are from the 41 matched quarters, consisting of one workers with silicosis and three age-matched controls, in which a lung cancer case was diagnosed. The odds ratio for lung cancer among subjects with ILO classification 1/0 or more, in comparison to subjects with category or = 1/0 and lung cancer. Although small smoking differences could account for the increased lung cancer odds ratio among workers with silicosis, the empirical evidence suggests that these smoking differences do not exist. It is concluded on the basis of two North American studies of silica exposed workers that radiographic silicosis is a marker for an increased risk of lung cancer.

The National Institute for Occupational Safety and Health (NIOSH) published a report in 1995 suggesting the possibility of increased incidence of testicular cancer, leukemia, and cancers of the brain, eye, and skin among police officers working with traffic radar. NIOSH recommended epidemiologic study of the issue. This report presents the results of a retrospective cohort cancer incidence study among 22,197 officers employed by 83 Ontario police departments. The standardized incidence ration (SIR) for all tumors sites was 0.9% (95% confidence interval [CI] = 0.83-0.98). There was an increased incidence of testicular cancer (SIR = 1.3, 90% CI = 0.9-1.8) and melanoma skin cancer (SIR = 1.45, 90% CI = 1.1-1.9). These anatomical sites might absorb energy from radar units, but at this time the author has no information about individual exposures to radar emissions, and it is not possible to draw etiologic conclusions. Nested case-control studies are planned to assess individual radar exposures.

In recent years, controversy has developed about whether pre-existing asbestosis is a prerequisite for the diagnosis of asbestos-related lung cancer. This paper presents the results of a prospective study, in a cohort of Ontario asbestos-cement workers, of lung cancer in relation to radiographs obtained 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single NIOSH-certified "B" reader, and asbestosis was defined to mean an ILO code of 1/0 or greater. There were 143 subjects (123 without asbestosis, 20 with asbestosis), with a radiograph available for interpretation at 20 years from first exposure or later. The lung cancer standardized mortality ratio (SMR) among men without asbestosis at 20 years latency was 5.53 (95% CI: 2.9-9.7). There were 128 subjects (114 without asbestosis, 14 with asbestosis) with a radiograph available for interpretation at 25 years from first exposure or later. The lung cancer SMR among men without asbestosis at 25 years latency was 5.81 (95% CI 2.7-11). The results of this study are consistent with those of epidemiologic studies of asbestos-exposed populations in a variety of exposure situations. These studies have demonstrated that lung cancer risk is elevated in the presence of radiographic asbestosis, but they have also shown that lung cancer risk may be elevated in the absence of radiographic asbestosis.

Asbestos has been widely used in the refinery and petrochemical sector. Mesothelioma has occurred among maintenance employees, and it was hypothesized that mesothelioma is a marker for exposures which might increase lung cancer risk. A death certificate-based case-control study of mesothelioma and lung cancer from 1980 to 1992 was conducted in an Ontario county with a substantial presence of these industries. Each of the 17 men who died of mesothelioma and 424 with lung cancer were matched with controls who died of other causes. The Job and Industry fields on the death certificates were abstracted. Employment as a maintenance worker in the refinery and petrochemical sector was associated with an increased risk of mesothelioma (odds ratio: 24.5; 90% confidence interval 3.1–102). The risk of lung cancer among petrochemical workers, in comparison with all other workers in the county, was 0.88. In an internal comparison of maintenance employees with other blue-collar workers in the refinery and petrochemical sector, the odds ratio for lung cancer was 1.73 (90% confidence interval 0.83–3.6). This finding is consistent with no difference in risk between maintenance and other employees, but it is also compatible with study power being too low to achieve statistical significance. The hypothesis of increased lung cancer risk could be examined more fully with nested case-control studies in existing cohorts. Meanwhile, it would be prudent to reinforce adherence to asbestos control measures in the refinery and petrochemical sector. © 1996 Wiley-Liss, Inc.

The United States is second only to the People's Republic of China in annual talc production. U.S. talc is used in the production of ceramics, paint, paper, plastics, roofing, rubber, cosmetics, flooring, caulking, and agricultural applications. A number of U.S. talc deposits consistently contain talc intergrown with amphiboles such as tremolite and/or anthophyllite. It has long been recognized that miners and millers of talc deposits are at risk for pneumoconiosis and it has recently been reported that it is prudent, on the balance of probabilities, to conclude that dusts from New York State talc ores are capable of causing mesothelioma in exposed workers. This is a report of the diagnosis of pneumoconiosis and mesothelioma in a husband and wife who operated a small metal casting business that used industrial talc from New York as a parting agent.Case reports, including medical records and exposure histories, were provided by an attorney who had also commissioned laboratory investigation of the industrial talc product used in the factory.Mrs X was diagnosed with pneumoconiosis characterized by interstitial fibrosis and heavily calcified pleural plaques. Mr X had calcified pleural plaques and developed a fatal pleural mesothelioma. Samples of the industrial talc contained fibrous tremolite and anthophyllite.The author concludes that end users of industrial talc from New York State may be at risk of pneumoconiosis and malignant disease. End users of talcs from other regions of the United States, where talc formation arose from processes driven by regional metamorphism, might also be at risk.

Cumulative exposure is frequently used as a measure of exposure in the quantitative analysis of epidemiologic studies. It is recognized that the imposed symmetry between duration and intensity of exposure is a potential problem with this measure, but it is less widely recognized that the finding of an exposure-response relationship, using cumulative exposure as the exposure metric, does not necessarily imply that exposures were accurately or even consistently estimated. This report describes a simulation study drawn from a nested case-control analysis of mesothelioma in a cohort of asbestos cement workers. Intensity of exposure in the range of 0.1-40 fibers/ml was randomly assigned to subjects. Logistic regression analysis demonstrated that there was no association between mesothelioma risk and the randomly assigned intensity of exposure. However, in 171 (86%) of 200 trials, mesothelioma risk was significantly associated with cumulative exposure, even though intensity of exposure remained randomly assigned. A strong exposure-response relationship might thus be misleading. One would be more confident about quantitative risk assessment when there are a large number of independent studies available for analysis. © 1995 Wiley-Liss, Inc.

The Province of Ontario has had a surveillance program for workers in dusty industries for almost 70 years. This paper reports the detection rates of silicosis among 68,701 silica-exposed individuals who were first exposed to dust in 1950 or later, and who were still employed in 1979 or later. The detection rate varied strongly with latency, being less than two new cases per 10,000 examinations during the first two decades from first exposure, reaching two new cases per 1,000 examinations at 27 years from first exposure, and averaging between two and four new cases per 1,000 examinations thereafter. The silicosis incidence rate among miners was only about half that among foundry workers. Cigarette smoking was also found to be a risk factor for the diagnosis of silicosis. These data were used to model the detection rate of new cases of silicosis as a function of the time interval between examinations, and results are presented for examination cycles between 2 and 10 years.

Workers' concerns about an excess of cancer in an electric arc steelmaking operation were investigated. In comparison with men who had worked elsewhere in the plant, an increased risk of lung cancer death was observed among men who had been employed in the melt shop. The hypothesis that the association might be related to occupational exposures is supported by the persistence of the association when the hypothesis-generating cases were removed from the analysis (p = 0.063) and by a significant trend in the risk of lung cancer with years of exposure in the melt shop. No air sampling had been performed in earlier years. Current environmental analyses in the melt shop found no polycyclic aromatic hydrocarbons (detection limit: 0.001 mg/m3), and silica levels were below 0.1 mg/m3. The carcinogenic metals arsenic and chromium were detected, but their concentrations in earlier years are unknown.

Background Dustexposedworkersmaybeatincreasedriskofpneumoconiosis,stomach cancer, lung cancer, and obstructive lung disease. Bricklayers may experience high exposures to silica and inorganic dusts. The aim of this study was to examine the mortality pattern of bricklayers to identify occupational associations with mortality. Methods A cohort of 10,953 workers was assembled from records of the International Union of Bricklayers and Allied Craftworkers (IUBAC). Mortality was ascertained by linkage to the Canadian Mortality Registry at Statistics Canada. Standardized Mortality Ratios (SMRs) were computed using Ontario general population mortality rates as the reference. Results Twenty or more years from first membership, SMRs for lung (158; 130‐190) and stomach(235; 140‐370) cancers were significantly elevated. Therewere fourdeaths from pneumoconiosis, but non-malignant respiratory mortality SMRs were not increased. Conclusions Bricklayers and Allied Craftworkers are at risk from diseases associated with heavyexposure to inorganic dust: lung cancer,stomachcancer, and pneumoconiosis. Dust control as well as education and training of these workers to protect themselves against inhalation hazards is necessary. Am. J. Ind. Med. 47:4–9, 2005. 2004 Wiley-Liss, Inc.

Background Inhalation of fine particulate is hypothesized to increase risk of heart disease events. Methods Seven Ontario construction unions participated in a retrospective cohort mortality study. Proportional mortality ratios (PMRs) were computed and a mortality odds ratio (MOR) analysis was performed to compare the risk of ischemic heart disease (IHD) mortality among heavy equipment operators (HEO) to that of members of other unions. Deaths attributed to lung cancer, mesothelioma, and accidental causes were excluded from the comparison. Results Two hundred fifty nine of 1,009 deaths among the HEO were attributed to IHD. The PMR was 1.09 (0.96–1.2). None of the IHD PMRs among the other six unions exceeded 0.89. The MOR for IHD mortality, comparing the HEO to all other workers combined was 1.47 (1.17–1.84) for ages 25–64, was 1.20 (0.96–1.50) for ages 65 or more, and was 1.32 (1.13–1.55) for all ages combined. Conclusions Increased risk of IHD mortality among HEO is consistent with the hypothesis that exposure to diesel fume has adverse effects upon the heart and circulatory system. Am. J. Ind. Med. 46:16–22, 2004. © 2004 Wiley-Liss, Inc.

To investigate exposure-response relationships for silica, silicosis, and lung cancer.Quantitative review of the literature identified in a computerized literature search.The risk of silicosis (ILO category 1/1 or more) following a lifetime of exposure at the current OSHA standard of 0.1 mg/m(3) is likely to be at least 5-10% and lung cancer risk is likely to be increased by 30% or more. The exposure-response relation for silicosis is nonlinear and reduction of dust exposures would have a greater than linear benefit in terms of risk reduction. Available data suggests that 30 years exposure at 0.1 mg/m(3) might lead to a lifetime silicosis risk of about 25%, whereas reduction of the exposure to 0.05 mg/m(3) might reduce the risk to under 5%.The lifetime risk of silicosis and lung cancer at an exposure level of 0.1 mg/m(3) is high. Lowering exposures to the NIOSH recommended limit if 0.05 mg/m(3) may have substantial benefit.

Benzene is a human leukemogen. Risk assessment, and the setting of occupational and environmental standards, has assumed that risk is constant in time after a unit of exposure. Leukemia risk is known to vary with time after exposure to ionizing radiation.A matched case-control study of leukemia risk in relation to the temporal pattern of benzene exposures was performed using data from the National Institute of Occupational Safety and Health.Leukemia risk following exposure to benzene varied with time in a manner similar to that following exposure to ionizing radiation. More recent exposures were more strongly associated with risk than were more distant ones. There was no significant relation between leukemia death and benzene exposures incurred more than 20 years previously.Recent analyses of specific occupational and environmental carcinogens, including benzene and radon, have indicated that cancer risk tends to decline as the time from exposure increases. This suggests that standards for the control of occupational or public risk must be selected to control exposures over a narrower time frame than the usual lifetime one. In the case of benzene, it would appear that risk is attributable primarily to exposures incurred during the previous 10 to 20 years, with exposures in the most recent 10 years being the most potent. To limit risk, exposures must be controlled during that interval. It is important that epidemiologists explore the temporal pattern of risk in their studies to facilitate the risk assessment of other carcinogens.

The health effects of asbestos are intimately related to the fate of inhaled fibers in the lungs. The kinetics of asbestos fibers have been studied primarily in rodents. The objective of this study was to explore the application of these kinetic models to human autopsy data.We analyzed the asbestos fiber content of the lungs of 72 Quebec chrysotile miners and millers and 49 control subjects using analytical transmission electron microscopy. Statistical methods included standard multivariate linear regression and locally weighted regression methods.The lung burdens of asbestos bodies and chrysotile and tremolite fibers were correlated, as were the concentrations of short, medium, and long fibers of each asbestos variety. There were significant associations between the duration of occupational exposure and the burdens of chrysotile and tremolite. The concentration of chrysotile decreased with the time since last exposure but the concentration of tremolite did not. The clearance rate varied inversely with the length of chrysotile fibers. For fibers greater than 10 mu in length the clearance half-time was estimated to be 8 years.The patterns in our data are compatible with both of the hypotheses suggested from rodent experiments; the existence of a long-term sequestration compartment and overload of clearance mechanisms in this compartment.

A case-control study, nested in a cohort of workers under surveillance for silicosis in 1979 or later, was undertaken to assess lung cancer risk in relation to the ILO coding scheme for the pneumoconioses. The subjects of this study are from the 41 matched quarters, consisting of one workers with silicosis and three age-matched controls, in which a lung cancer case was diagnosed. The odds ratio for lung cancer among subjects with ILO classification 1/0 or more, in comparison to subjects with categoryor = 0/1, was 3.27 (95% CI =1.32-8.2). Adjustment of the radiographic risk for the effect of cumulative radon exposure had the effect of increasing the odds ratio for the association between ILO categoryor = 1/0 and lung cancer. Although small smoking differences could account for the increased lung cancer odds ratio among workers with silicosis, the empirical evidence suggests that these smoking differences do not exist. It is concluded on the basis of two North American studies of silica exposed workers that radiographic silicosis is a marker for an increased risk of lung cancer.

The National Institute for Occupational Safety and Health (NIOSH) published a report in 1995 suggesting the possibility of increased incidence of testicular cancer, leukemia, and cancers of the brain, eye, and skin among police officers working with traffic radar. NIOSH recommended epidemiologic study of the issue. This report presents the results of a retrospective cohort cancer incidence study among 22,197 officers employed by 83 Ontario police departments. The standardized incidence ration (SIR) for all tumors sites was 0.9% (95% confidence interval [CI] = 0.83-0.98). There was an increased incidence of testicular cancer (SIR = 1.3, 90% CI = 0.9-1.8) and melanoma skin cancer (SIR = 1.45, 90% CI = 1.1-1.9). These anatomical sites might absorb energy from radar units, but at this time the author has no information about individual exposures to radar emissions, and it is not possible to draw etiologic conclusions. Nested case-control studies are planned to assess individual radar exposures.

In recent years, controversy has developed about whether pre-existing asbestosis is a prerequisite for the diagnosis of asbestos-related lung cancer. This paper presents the results of a prospective study, in a cohort of Ontario asbestos-cement workers, of lung cancer in relation to radiographs obtained 20 and 25 years from first exposure to asbestos. Radiographs were interpreted by a single NIOSH-certified "B" reader, and asbestosis was defined to mean an ILO code of 1/0 or greater. There were 143 subjects (123 without asbestosis, 20 with asbestosis), with a radiograph available for interpretation at 20 years from first exposure or later. The lung cancer standardized mortality ratio (SMR) among men without asbestosis at 20 years latency was 5.53 (95% CI: 2.9-9.7). There were 128 subjects (114 without asbestosis, 14 with asbestosis) with a radiograph available for interpretation at 25 years from first exposure or later. The lung cancer SMR among men without asbestosis at 25 years latency was 5.81 (95% CI 2.7-11). The results of this study are consistent with those of epidemiologic studies of asbestos-exposed populations in a variety of exposure situations. These studies have demonstrated that lung cancer risk is elevated in the presence of radiographic asbestosis, but they have also shown that lung cancer risk may be elevated in the absence of radiographic asbestosis.

Asbestos has been widely used in the refinery and petrochemical sector. Mesothelioma has occurred among maintenance employees, and it was hypothesized that mesothelioma is a marker for exposures which might increase lung cancer risk. A death certificate-based case-control study of mesothelioma and lung cancer from 1980 to 1992 was conducted in an Ontario county with a substantial presence of these industries. Each of the 17 men who died of mesothelioma and 424 with lung cancer were matched with controls who died of other causes. The Job and Industry fields on the death certificates were abstracted. Employment as a maintenance worker in the refinery and petrochemical sector was associated with an increased risk of mesothelioma (odds ratio: 24.5; 90% confidence interval 3.1-102). The risk of lung cancer among petrochemical workers, in comparison with all other workers in the county, was 0.88. In an internal comparison of maintenance employees with other blue-collar workers in the refinery and petrochemical sector, the odds ratio for lung cancer was 1.73 (90% confidence interval 0.83-3.6). This finding is consistent with no difference in risk between maintenance and other employees, but it is also compatible with study power being too low to achieve statistical significance. The hypothesis of increased lung cancer risk could be examined more fully with nested case-control studies in existing cohorts. Meanwhile, it would be prudent to reinforce adherence to asbestos control measures in the refinery and petrochemical sector.

We are quite suprised by this request for explanation, since we think that our previous papers [Gennaro et al., 1994, 1995, 2000] already answered the questions raised. At the same time, we are pleased to have the opportunity to provide AJIM readers with additional information about how we have tried to demonstrate and explain the causal relationship between lung cancer and asbestos exposure among workers employed in the oil refinery industry, a relationship that, for various reasons, the epidemiologists of oil corporations do not see.

A study of lung cancer among workers at an electric arc steel making operation was performed to follow up on the observation of a lung cancer cluster in the melt shop of another plant. The study group comprised 335 deceased men identified from plant records. Eight of thirty men who had ever worked in the pouring pit area died of lung cancer (PMR 276; p less than 0.01), but increased risk was not found elsewhere in the melting department. There was a significant trend in lung cancer risk with the length of employment in the pit area during a time window 18-30 years before death. Smoking data suggested that smoking alone could not account for the increased risk. An industrial hygiene assessment found present exposures to carcinogenic metals and silica to be within current guidelines. No polycyclic aromatic hydrocarbons were detected. This is the second steel plant for which we have found increased lung cancer risk in the pouring areas. The causative factors have not yet been identified.

This paper describes an application of the time windows method to an examination of the temporal pattern of lung cancer risk among steel workers. Case-control methodology was utilized. The cases were 36 men who had died of lung cancer and the controls were 289 men who had died of any other cause. The number of years of employment in the steel pouring area was used as a surrogate measure of exposure. The data were examined by contingency table analysis and by logistic regression, which permitted adjustment for exposures in multiple time windows and the use of continuous, rather than categorical, measures of exposure. It was found that lung cancer risk was associated with exposures occurring between 18 and 30 years before death. It cannot yet be determined whether this time course reflects a biological response or the temporal pattern of exposure to an as yet unidentified toxic agent.