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A new method for assessment of dermal exposure to pesticides in subsistence farmers by use of determinants of dermal exposure is described. The method, called the determinants of dermal exposure ranking method (DERM), is a combination of checklists and expert rating assessment. Thus, determinants are listed in a form, which is used to check their presence and to assess them using a simple algorithm based on two factors, the type of transport process (T value) and the area of body surface exposed (A value). In addition, the type of clothing worn during applications is included as a protection factor. We applied the DERM to real pesticide applications, characterizing dermal exposure and comparing DERM estimates with earlier developed semiquantitative visual scores based on fluorescent tracer, the total visual score (TVS) and contaminated body area (CBA). DERM showed a very good level of agreement with both the TVS (r = 0.69; P = 0.000) and the CBA (r = 0.67; P = 0.000). DERM allowed identification of the determinants that had the highest effect on exposure and the farmers with the highest exposure. In conclusion, DERM provided information on the determinants responsible for dermal exposure in a group of subsistence farmers. This can be useful to design monitoring and preventive programs, define priorities for intervention and prioritize and select most adequate measurement strategies. DERM promises to be a low-cost easy-to-use method to assess dermal exposure to pesticides in developing country conditions.

Objectives: Parental exposure to pesticides and the risk of leukemia in offspring were examined in a population-based case-control study in Costa Rica., Methods: All cases of childhood leukemia (N=334), in 1995-2000, were identified at the Cancer Registry and the Children's Hospital. Population controls (N=579) were drawn from the National Birth Registry. Interviews of parents were conducted using conventional and icon-based calendar forms. An exposure model was constructed for 25 pesticides in five time periods., Results: Mothers' exposures to any pesticides during the year before conception and during the first and second trimesters were associated with the risk [odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0-5.9; OR 22, 95% CI 2.8-171.5; OR 4.5, 95% CI 1.4-14.7, respectively] and during anytime (OR 2.2, 95% CI 1.0-4.8). An association was found for fathers' exposures to any pesticides during the second trimester (OR 1.5, 95% CI 1.0-2.3). An increased risk with respect to organophosphates was found for mothers during the first trimester (OR 3.5, 95% CI 1.0-12.2) and for fathers during the year before conception and the first trimester (OR 1.5, 95% CI 1.0-2.2 and OR 1.6, 95% CI 1.0-2.6, respectively), and benzimidazoles during the first, second, and third trimesters of pregnancy (OR 2.2, 95% CI 1.0-4.4; OR 2.2, 95% CI 1.0-5.0; OR 2.2, 95% CI 1.0-5.2, respectively). There was a suggestion of an exposure-response gradient for fathers as regards picloram, benomyl, and paraquat. Age at diagnosis was positively associated with fathers' exposures and inversely associated with mothers' exposures., Conclusions: The results suggest that parental exposure to certain pesticides may increase the risk of leukemia in offspring.

Objectives: Identification of pesticide exposure determinants has become an issue in explaining exposure variability and improving control measures. Most studies have been conducted in industrialized countries. The aim of this study was to identify relevant dermal exposure determinants among Nicaraguan subsistence farmers., Methods: Field data on possible determinants were collected during 32 pesticide applications through observation and supplementary videorecording. A multistep reduction strategy brought down the 110 potential exposure determinants to 27 variables, which were grouped as worksite, spray equipment, working practices, clothing or hygiene practices related. Dermal exposure was quantified with a modification of Fenske's visual scoring method. Multivariate linear regression modeling within groups and across groups was performed., Results: In the within-group analyses, work practices, spray equipment and worksite related determinants explained 52, 33 and 25% of the exposure variability, respectively. Clothing and hygiene practices were weaker determinants and did not always reduce the exposure. The final model included determinants from all groups except hygiene practices and explained 69% of the exposure variability. A less restricted model increased the explained variability to 75%. Several novel determinants were identified, including spraying on a muddy terrain, dew on plants, sealing the tank lid with a cloth and wiping sweat from the face., Conclusions: This study showed that a combination of observation and visual scoring techniques can provide valuable information on determinants of pesticide exposure and affected body parts under developing country conditions. The results could be used to develop job-specific questionnaires and to design training and preventive programs.

The aim of the present study was to investigate the association between exposure to mineral oil and the risk of developing rheumatoid arthritis (RA), and in addition to perform a separate analysis on the major subphenotypes for the disease; namely, rheumatoid factor (RF)-positive RA, RF-negative RA, anticitrulline-positive RA and anticitrulline-negative RA, respectively. A population-based case-control study of incident cases of RA was performed among the population aged 18-70 years in a defined area of Sweden during May 1996-December 2003. A case was defined as an individual from the study base who for the first time received a diagnosis of RA according to the American College of Rheumatology criteria of 1987. Controls were randomly selected from the study base with consideration taken for age, gender and residential area. Cases (n = 1,419) and controls (n = 1,674) answered an extensive questionnaire regarding lifestyle factors and occupational exposures, including different types of mineral oils. Sera from cases and controls were investigated for RF and anticitrulline antibodies. Among men, exposure to any mineral oil was associated with a 30% increased relative risk of developing RA (relative risk = 1.3, 95% confidence interval = 1.0-1.7). When cases were subdivided into RF-positive RA and RF-negative RA, an increased risk was only observed for RF-positive RA (relative risk = 1.4, 95% confidence interval 1.0-2.0). When RA cases were subdivided according to the presence of anticitrulline antibodies, an increased risk associated with exposure to any mineral oil was observed only for anticitrulline-positive RA (relative risk = 1.6, 95% confidence interval = 1.1-2.2). Analysis of the interaction between oil exposure and the presence of HLA-DR shared epitope genes regarding the incidence of RA indicated that the increased risk associated with exposure to mineral oil was not related to the presence of shared epitope genotypes. In conclusion, our study shows that exposure to mineral oil is associated with an increased risk to develop RF-positive RA and anticitrulline-positive RA, respectively. The findings are of particular interest since the same mineral oils can induce polyarthritis in rats.

Review of the literature regarding ischemic heart disease (IHD) among female cleaners in Medline and NIOSHTIC for 1990-2001 yielded one specifically relevant study, three surveys of several occupations, and one case-referent study. All showed minor increases of standardized mortality ratios or relative risks regarding diseases of the circulatory system, IHD, or myocardial infarction among female cleaners. Many determinants might explain the female cleaners' increased risk for IHD, e.g., imbalances regarding job strain and effort-reward, anxiety and depression, periodontal disease, smoking habits and air pollutants. These factors need further exploration.

This study evaluated the association between acute poisoning with organophosphate pesticides (OPs) and quantitative tactile vibration thresholds. Thresholds of the dominant index fingers and big toes of 56 men hospitalized for acute poisoning with OPs were measured at hospital discharge (1-24 days after poisoning) and around seven weeks later (24-176 days after poisoning), and compared with those of controls. Thresholds of the big toes of men with severe intentional poisonings due to neuropathic OPs (metamidophos and chlorpyrifos) increased between the first and second examinations. Threshold impairment was not detected in the index finger regardless of poisoning agent or severity. The development of threshold impairment as a consequence of severe intentional poisonings with neuropathic OPs is consistent with other reports indicating that only severe OP poisonings produce sensory peripheral nerve effects.

The course of organophosphate-induced delayed polyneuropathy (OPIDP) in humans has not been quantitatively measured in epidemiologic studies. This study evaluated the association of acute OP poisonings with motor neurologic impairment. Hand grip and pinch strength were evaluated among 62 Nicaraguan men hospitalized for acute OP poisoning between 1992 and 1996; 39 cattle ranchers and fishermen who had never experienced pesticide poisoning were controls. Exposure categories were moderate and severe poisonings with neuropathic and non-neuropathic OPs. Strength was measured at hospital discharge and seven weeks after poisoning. Grip and pinch strength were impaired among all OP-poisoned subjects at both examinations, more noticeably among those poisoned with OPs with suspected neuropathic effects, methamidophos and chlorpyrifos. In those with severe poisonings with neuropathic OPs, impairments were more marked among intentional than among occupational poisonings. The performances of suicidal subjects worsened at the second examination, consistent with OPIDP. Early motor impairment at the time of hospital discharge is consistent with cholinergic depolarization blockade after acute poisoning. The persistence of deficits in motor strength in all severely poisoned patients regardless of pesticide type was unexpected, and may reflect persistent cholinergic blockade or intermediate syndrome, neuropathy, or a combination of these.

Although vinyl chloride is an established cause of liver angiosarcoma, the evidence is inconclusive on whether it also causes other neoplastic and nonneoplastic chronic liver diseases as well as neoplasms in other organs. Furthermore, the shape of the dose-response relation for angiosarcoma is uncertain. We have extended for approximately 8 years the mortality and cancer incidence follow-up of 12,700 male workers in the vinyl chloride industry in four European countries. All-cause mortality was lower than expected, whereas cancer mortality was close to expected. A total of 53 deaths from primary liver cancer (standardized mortality ratio 2.40, 95% confidence interval = 1.80-3.14) and 18 incident cases of liver cancer were identified, including 37 angiosarcomas, 10 hepatocellular carcinomas, and 24 liver cancers of other and unknown histology. In Poisson regression analyses we observed a marked exposure response for all liver cancers, angiosarcoma, and hepatocellular carcinoma. The exposure-response trend estimated for liver cancer in analyses restricted to cohort members with cumulative exposures of <1,500 parts per million-years was close to that estimated for the full cohort (relative risk of 2.0 per logarithmic unit of cumulative dose). No strong relation was observed between cumulative vinyl chloride exposure and other cancers. Although cirrhosis mortality was decreased overall, there was a trend with cumulative exposure.

Objectives: The aim of this update on a cohort of male paint industry workers was to determine whether an excess of mortality and incidence of lymphatic and hematopoietic tumors, particularly multiple myeloma, still exists, and, if so, to determine if it is due to exposures occurring before the mid-1950s, when benzene disappeared as a solvent in the Swedish paint industry., Methods: The cohort of 411 men who had worked in the Swedish paint industry and had been exposed to organic solvents for at least 5 years during 1955-1975 was followed from 1961 to 1994 for causes of death in the mortality register and from 1961 to 1992 for cases of cancer in the Swedish cancer register., Results: The number of paint industry workers who had died, plus the number of deaths in the major disease groups and the number of cancers reported to the cancer registry, was close to the expected. The incidence of prostatic cancer increased somewhat [standardized incidence ratio (SIR) 1.5, 95% confidence interval (95% CI) 1.0-2.2]. Among the workers first employed in 1956 or earlier, there was an increase in both the incidence and mortality from all lymphatic and hematopoietic tumors [SIR 2.3, 95% CI 1.0-2.2; standardized mortality ratio (SMR) 2.0, 95% CI 0.7-4.4]. The excess was particularly marked for multiple myeloma (SIR 3.8, 95% CI 0.8-11; SMR 4.4, 95% CI 0.9-13)., Conclusions: Employment in the Swedish paint industry before 1957 may have entailed some excess risk of lymphatic and hematopoietic tumors, particularly multiple myeloma. A significant excess of prostatic cancer was not linked to any particular employment period and deserves further investigation.

Objectives: The questionnaire 16 (Q16) is commonly used to study prevalences of neurotoxic symptoms among workers exposed to organic solvents. It has also been recommended that exposed workers reporting more than six symptoms should be referred for further examination of possible chronic toxic encephalopathy. It would be useful to know whether symptoms reported in the questionnaire also reflect impairment of similar functions measured with objective or semiobjective methods in a formerly highly exposed group., Methods: 135 painters and 71 carpenters answered the Q16, were interviewed about symptoms compatible with an organic brain damage, and took a battery of psychometric tests. A subsample of 52 painters and 45 carpenters were interviewed for psychiatric diagnosis according to Diagnostic and Statistical Manual for Mental Disorders, 3rd version (DSM III) and their vibration thresholds in hands and feet were measured. The entire group was followed up in the register of diagnoses at early retirement 1971-93. The lifetime exposure to organic solvents was assessed. Current exposure to organic solvents was found to be low or none., Results: The prevalence of people with more than six symptoms in the Q16 rose with increasing cumulative exposure to solvents. The sensitivity of the questionnaire (more than six symptoms) to detect people who were assessed to exhibit symptoms compatible with an organic brain damage was only 38%. One of seven people who had retired early with a diagnosis compatible with a chronic toxic encephalopathy, and two of five people with a psychiatric diagnosis compatible with this condition, had more than six symptoms in the Q16. The agreement between Q16 replies and psychometric test results, as well as other examinations, was low., Conclusions: The notable exposure-response relation indicates that the questionnaire is useful for comparison of groups with different exposures to organic solvents. There was low agreement between the number of symptoms on the questionnaire and the assessment of symptoms compatible with organic brain damage, as well as psychiatric, or early retirement diagnoses compatible with chronic toxic encephalopathy. The questionnaire does not seem useful for screening of patients with chronic toxic encephalopathy in groups without ongoing exposure to organic solvents.

Objectives: In epidemiological studies of neurotoxic effects neuropsychological tests are often applied to assess possible functional changes. In these studies tests presumed to be resistant to neurotoxic effects, "hold tests", are often used to adjust performance in tests presumed to be sensitive to neurotoxic effects, "nonhold tests", in assessment of pre-exposure ability. This conception is based on experience from the examination of patients with organic brain disorders. For this adjustment to be valid hold tests should change comparatively little over time and should not change differently in groups of people with different exposures to neurotoxic agents., Methods: These assumptions were examined in 71 carpenters and 135 painters divided in three subgroups according to level of cumulative exposure to organic solvents. The results were noted from two verbal tests (test A, which involved following verbal instructions and test C, word comprehension), which were performed at conscription (age 18-20). The tests resemble hold tests used in occupational studies. The same tests were performed again at the age of 45-60 together with a conventional synonym test (SRB 1), often used in occupational studies., Results: In the three tests given at the time of the investigation some differences were found between the carpenters and the subgroups of painters. The painters with low exposure tended to perform better than the carpenters in all three tests and the heavily exposed painters tended to perform less well in the tests. These differences were not present at the age of 18-20. In one of the conscription tests painters with different cumulative exposure to organic solvents developed differently over time. There was little improvement among painters with heavy and intermediate exposure and obvious improvement among painters with low exposure. The results in the other conscription test showed similar tendencies., Conclusions: The results indicate that the hold tests examined do not meet basic criteria for hold tests used in occupational studies. Thus adjustments for conventional verbal tests seem inappropriate in such studies. It is possible that other presumed hold tests may meet the criteria but our results suggest that such tests also should be evaluated before being used as hold tests in working populations.

A cohort of 34,560 men and 6128 women employed in 660 European factories manufacturing reinforced plastic products, followed up originally to assess the risk of cancer, was used to assess the risk of non-malignant respiratory diseases associated with exposure to styrene. Mortality from pneumonia was associated with intensity of exposure to styrene, but this may have been due to chance. Mortality from bronchitis, emphysema, and asthma was not associated with styrene exposure.

Objective: The aim of this study was to study the incidence of cancer and deaths from cancer and other diseases among patients referred to the 11 clinics of occupational medicine in Sweden between 1967 and 1987 for examination because of exposure to organic solvents., Methods: The cohort comprised 5791 persons, 5283 men and 508 women. Information about cancer incidence and causes of death was collected from the Cancer Register of the National Board of Health and Welfare and the National Death Register of Statistics Sweden, respectively. The expected values were calculated from the national death rates and incidence rates of cancer., Results: The overall mortality rate was close to expected, but the mortality rate was decreased for diseases of the circulatory system [standardized mortality ratio (SMR) 0.7, 95% confidence limit (95% CI) 0.5-0.9] and increased for suicide (SMR 2.0, 95% CI 1.2-3.2). The total cancer incidence was slightly elevated [standardized incidence ratio (SIR) 1.2, 95% CI 0.99-1.4], and some specific cancer sites showed an increased incidence, although the lower confidence limits surpassed one. Malignancies of the lymphohematopoietic system and cancer of the uterine cervix had an increased risk (SIR 1.9, 95% CI 1.2-3.2, and SIR 3.7, 95% CI 2.2-6.2, respectively). Patients with presumerably high solvent exposure had an SIR of 1.4 for all malignancies (95% CI 0.9-2.1) and those with presumerably low exposure had an SIR of 1.1 (95% CI 0.9-1.4)., Conclusions: The study showed an increased risk for malignancies of the hematopoietic system and the uterine cervix among patients originally examined with regard to solvent-induced disorders. There was also an increased risk of suicide and a decreased risk of death from diseases of the circulatory system. There was no increased risk for deaths from mental or neurological disorders.

A questionnaire in Spanish (with yes/no answers) was developed in order to study effects of neurotoxic agents in groups of workers in Nicaragua. Since many workers in Latin America are illiterate, the questions were read to the subjects. The questionnaire initially contained 34 questions, which were reduced to 16 after studying whether the questions were interpreted in the intended way by the subjects, whether the answers were reasonably reproducible over a 3-week period, and whether the questions discriminated between groups exposed to different neurotoxic agents (mercury, lead, organic solvents, and organophosphate insecticides) and nonexposed groups. In total, 851 male workers in Nicaragua and Venezuela participated in the evaluation. The questionnaire is submitted for use in the monitoring of groups exposed to neurotoxic agents, particularly in Latin America. The authors welcome further evaluation.

Neuropsychiatric effects were examined among 206 men, of whom 135 had been house painters and 71 had been house carpenters, affiliated with their respective trade unions for at least 10 years before 1970. Their lifetime organic solvent exposure was evaluated through the aid of an interview. Relevant potential confounding factors were accounted for in the statistical analysis. Neuropsychiatric symptoms compatible with chronic toxic encephalopathy were more common among the painters than among the carpenters, and these symptoms became increasingly prevalent with increasing cumulative solvent exposure. On only one of 12 psychometric tests, block design, did the painters perform worse than the carpenters, and in this test the painters' performance deteriorated with increasing cumulative exposure. For the majority of the psychometric tests, and for the coordination tests, there were no differences between the painters and carpenters, but the painters with "low" exposure tended to show better, and "heavily" exposed painters worse, results than the carpenters. The 52 painters with the heaviest cumulative exposures and 45 carpenters were examined for psychiatric diagnosis according to DSM-III, with electroencephalography and auditory evoked potential, P-300. Three painters and two carpenters had diagnoses compatible with an organic mental disorder. There were no overall differences between the painters and carpenters, either for the visually examined electroencephalograms or the P-300 latencies. The excess of neuropsychiatric symptoms among the painters was probably causally linked to solvent exposure. However, these symptoms seemed only rarely, if ever, serious enough to entail a psychiatric diagnosis. Concerning other outcomes, the investigation may not lead to a determination of whether the exposure-response relationship among the painters, with no difference between the entire group of painters and carpenters, is caused by solvent exposure or by selection factors within the group of painters.

Objectives: The goal of this study was to determine whether exposure to styrene is associated with an increased risk for neoplasms of the lymphatic and hematopoietic tissues., Methods: A historical cohort study was conducted in Denmark, Finland, Italy, Norway, Sweden, and the United Kingdom. It involved 40,688 workers ever employed in the reinforced plastics industry, where high exposure to styrene occurs. Exposure to styrene was reconstructed through job histories and environmental and biological monitoring data. Cause-specific national death rates were used as the reference. Poisson regression was applied for internal comparisons., Results: Among the exposed workers, no excess was observed for mortality from all neoplasms. Mortality from neoplasms of the lymphatic and hematopoietic tissues increased with time since first exposure and average level of exposure to styrene, but was not consistently associated with duration of exposure or with cumulative exposure., Conclusions: These findings leave open the possibility of an excess risk of neoplasms of the lymphatic and hematopoietic tissues among workers exposed to styrene.

The serum activities or concentrations of aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), albumin, gamma-glutamyl transpeptidase (GGT), bilirubin (BIL), cholic acid (CHOL), chenodeoxycholic acid (CHENO), and transferrin with isoelectric point 5.7, and the urinary excretion of albumin were determined among male current or former house painters (n = 135) and house carpenters (n = 71) who had worked in their trades for at least 10 years before 1970. Workers who showed a value above the 90th percentile among the carpenters in at least one of the tests ASAT, ALAT, GGT, BIL, CHOL, or CHENO were regarded as showing "possible signs of liver dysfunction". Each participant's lifetime solvent exposure was evaluated by interview. The painters were divided into categories with low, intermediate, and heavy cumulative exposure during life (LTSE) or during the most exposed year (MEYSE). All participants stated none or slight recent exposure. The prevalence of possible signs of liver dysfunction increased with solvent exposure category according to LTSE as well as MEYSE with a numerically higher risk estimate in the heavy exposure category for MEYSE than for LTSE. ALP activity increased with exposure category according to both exposure estimates. This increase seemed to be due to an interaction between exposure to solvents and current or previous long term intake of medicines potentially toxic to the liver. None of these results was affected by whether or not the subjects had been exposed to solvents during the year before the investigation. The exposure to solvents was not significantly related to any other outcome variable. It is concluded that long term heavy exposure to solvents may elicit changes in conventional liver function tests indicative of a mild chronic effect on the liver. The findings also suggest that heavy solvent exposure during short time periods is a more likely cause of the findings than lifetime cumulative solvent exposure and that an interaction between solvent exposure and medicines potentially harmful to the liver may be important in the causation of the effects.

The cumulative incidence of rheumatoid arthritis (RA) was compared between different occupations, and between different exposure groups based on a job-exposure matrix (JEM). The study population comprised those subjects who in 1980 lived in one of 13 Swedish counties, were born between 1905 and 1945, and who had stated the same occupation in the censuses of 1960 and 1970, a total of 375,035 men and 140,139 women. The study population was followed concerning hospital care for rheumatoid arthritis in 1981-1983 by lineage to the Swedish Hospital Discharge Register. In general there were rather small differences in the relative risk of RA in different exposure groups and different occupations. Most of the occupations associated with an increased risk of RA were occupations in which it was possible to work when the disease was present, i.e. cost accountants, estimating clerks and working proprietors in the retail trade. However, an increased relative risk of RA was also observed in some occupations where selection of RA patients out of heavy work should have biased genuinely increased relative risks towards unity. Such occupations were farmers, upholsterers, lacquerers, concrete workers, and hair-dressers. Substantial handling of organic solvents, according to the JEM, was associated with an increased relative risk.

The mortality pattern and the cancer incidence were investigated among 717 men who had been employed for at least 3 months during 1964-1974 in three Swedish PVC-processing plants. The mortality was followed 1964-1986 and the cancer incidence 1964-1984. Expected figures were calculated from Swedish national rates. Among Swedish citizens, the observed mortality and cancer incidence was close to the expected in most diagnoses. Among immigrants, mostly from Finland, there was a marked excess of circulatory deaths. This finding was probably due to the higher incidence of coronary mortality in Finland compared to Sweden. In the whole cohort, five cases of malignant melanoma had occurred as compared to 1.5 expected (SMR = 3.4, 95% confidence limit 1.1-7.9). This may be due to chance but merits further investigation since an increased incidence of malignant melanoma has previously been found among Norwegian PVC-manufacturing workers.

The incidence of alcoholism and the incidence of other neuropsychiatric diagnoses were compared between the 767 house painters and the 1212 house carpenters, born in 1925 or later, who were members of the Stockholm branches of their respective trade unions in 1965 and who had been members for at least 10 years before 1970. Four different outcome registers were used: (1) the alcohol crime register, which contained all persons who had broken any law regulating the handling and consumption of alcohol (follow up period 1972-6). (2) The register of diagnoses at early retirement (follow up period 1971-84). (3) The register of diagnoses at discharge from inpatient psychiatric care (follow up period 1968-83). (4) The register of causes of death (follow up period 1965-86). Exposures to solvents and consumption of alcohol were evaluated by interviews with samples of the cohorts. A high average cumulative exposure to solvents was found among the painters. The mean consumption of alcohol was similar in the two cohorts. The incidence of diagnoses of neuropsychiatric disorders was higher in painters than in carpenters in all registers. Alcoholism was the most common neuropsychiatric disorder diagnosed and showed the highest relative risk. The excess of alcoholism among the painters was, however, due singularly to painters who had several registrations in the alcohol crime register or diagnoses of alcoholism in multiple registers. Thus the study implies that excessive alcohol consumption or severe damage due to alcohol, or both, but not less severe problems, were more common in painters than in carpenters. This suggests an interaction between exposure to solvents and intake of alcohol causing an increase in diagnosis of alcoholism among painters.

Neurobehavioral hazards have been identified since long in occupational health, e.g. lead, mercury, certain solvents, and many others agents. There are reviews and books on "Occupational neurology" or "Prevention of neurotoxic illness in working populations". Many methods have been applied for studies of the central and peripheral nervous systems in humans: registered diagnoses, questionnaire ratings, clinical evaluation, psychometric tests, neurophysiological and neuroradiological methods, cerebrospinal fluid components etc. Some neurological disorders are well defined, while neuropsychiatric syndromes often are less precisely diagnosed. Decreased subclinical test results in exposed groups might predict an increased risk for later, more serious disorders but the longitudinal information on clinical importance is often lacking. Some historical lessons from the epidemiology of occupational neurology will be repeated and a few reflections on the suitability of different diagnostic entities for epidemiological research shall be made. Since the beginning of the 1970s' a number of studies from the Scandinavian countries have demonstrated long-term neurobehavioral effects from working conditions with relatively moderate exposure to organic solvents. Similar findings have been verified in studies from some countries outside Scandinavia while other studies have been inconclusive. Those results have caused considerable controversy and have been discussed at international conferences and in scientific journals. Very different outcomes have been investigated in those solvent studies, however, and most studies have had a cross-sectional design with inherent problems. The exposure has been assessed in different ways, e.g. by years of occupation, hygienic measurements of the present working conditions, biological monitoring, retrospective assessments on qualitative or semi-quantitative scales. Sometimes single solvent exposures have been studied but most of the studies concern mixtures of solvents from aromatic and aliphatic hydrocarbons. As the designs have varied the exposure assessment has been crude and many different outcomes have been studied, it is hardly surprising that the results and the interpretations have differed. The first results from a comprehensive investigation on 135 solvent exposed painters and 71 carpenters as referents, selected from active members of the respective trade union 1965-70 and investigated in the late 80s, will be presented. Clinical, including psychiatric, diagnostic work up and neuropsychological as well as neurophysiological tests have been performed. Psychological test results from military conscripts at age 19 were available for all. The individual exposure history has been carefully assessed.(ABSTRACT TRUNCATED AT 400 WORDS)