Development of a job-task-exposure matrix to assess occupational exposure to disinfectants among US nurses.

OBJECTIVES: Occupational exposure to disinfectants is associated with work-related asthma, especially in healthcare workers. However, little is known about the specific products involved. To evaluate disinfectant exposures, we designed job-exposure (JEM) and job-task-exposure (JTEM) matrices, which are thought to be less prone to differential misclassification bias than self-reported exposure. We then compared the three assessment methods: self-reported exposure, JEM and JTEM. METHODS: Disinfectant use was assessed by an occupational questionnaire in 9073 US female registered nurses without asthma, aged 49-68 years, drawn from the Nurses' Health Study II. A JEM was created based on self-reported frequency of use (1-3, 4-7 days/week) of 7 disinfectants and sprays in 8 nursing jobs. We then created a JTEM combining jobs and disinfection tasks to further reduce misclassification. Exposure was evaluated in 3 classes (low, medium, high) using product-specific cut-offs (eg, <30%, 30-49.9%, ≥50%, respectively, for alcohol); the cut-offs were defined from the distribution of self-reported exposure per job/task. RESULTS: The most frequently reported disinfectants were alcohol (weekly use: 39%), bleach (22%) and sprays (20%). More nurses were classified as highly exposed by JTEM (alcohol 41%, sprays 41%, bleach 34%) than by JEM (21%, 30%, 26%, respectively). Agreement between JEM and JTEM was fair-to-moderate (κ 0.3-0.5) for most disinfectants. JEM and JTEM exposure estimates were heterogeneous in most nursing jobs, except in emergency room and education/administration. CONCLUSIONS: The JTEM may provide more accurate estimates than the JEM, especially for nursing jobs with heterogeneous tasks. Use of the JTEM is likely to reduce exposure misclassification.

[Causal analysis approaches in epidemiology]. / Approches d'analyse causale en épidémiologie.

Epidemiological research is mostly based on observational studies. Whether such studies can provide evidence of causation remains discussed. Several causal analysis methods have been developed in epidemiology. This paper aims at presenting an overview of these methods: graphical models, path analysis and its extensions, and models based on the counterfactual approach, with a special emphasis on marginal structural models. Graphical approaches have been developed to allow synthetic representations of supposed causal relationships in a given problem. They serve as qualitative support in the study of causal relationships. The sufficient-component cause model has been developed to deal with the issue of multicausality raised by the emergence of chronic multifactorial diseases. Directed acyclic graphs are mostly used as a visual tool to identify possible confounding sources in a study. Structural equations models, the main extension of path analysis, combine a system of equations and a path diagram, representing a set of possible causal relationships. They allow quantifying direct and indirect effects in a general model in which several relationships can be tested simultaneously. Dynamic path analysis further takes into account the role of time. The counterfactual approach defines causality by comparing the observed event and the counterfactual event (the event that would have been observed if, contrary to the fact, the subject had received a different exposure than the one he actually received). This theoretical approach has shown limits of traditional methods to address some causality questions. In particular, in longitudinal studies, when there is time-varying confounding, classical methods (regressions) may be biased. Marginal structural models have been developed to address this issue. In conclusion, "causal models", though they were developed partly independently, are based on equivalent logical foundations. A crucial step in the application of these models is the formulation of causal hypotheses, which will be a basis for all methodological choices. Beyond this step, statistical analysis tools recently developed offer new possibilities to delineate complex relationships, in particular in life course epidemiology.

Farming in childhood, diet in adulthood and asthma history.

The decrease in the number of children living on traditional farms in France during early childhood and changes in diet could both play a role in the increase in asthma prevalence over the last decades. This study aimed to assess 1) the association of farming lifestyle in childhood and asthma, and 2) whether diet in adulthood modifies the association between farming lifestyle in childhood and adult-onset asthma. In the French Etude Epidemiologique des Femmes de la Mutuelle Générale de l'Education Nationale (E3N) study (54,018 females; age 43-68 yrs), three indicators of farming lifestyle were defined: one using individual data (having farmer parents) and two using ecological data (born in a rural area and exposure to cattle). All farming lifestyle indicators were related to childhood- (<16 yrs) and adult-onset asthma (OR (95% CI) values for farmer parents were 0.54 (0.42-0.70) and 0.72 (0.62-0.84), respectively), and to diet in adulthood, in particular to high fruit and low wine intakes. The association between farmer parents and adult-onset asthma was not modified by diet in adulthood. Results extend previous observations in younger cohorts on the protective role of contact with livestock and farming lifestyle on asthma, in particular during childhood.

Do young adults with childhood asthma avoid occupational exposures at first hire?

Information on the healthy worker hire effect in relation to asthma is scant. We aimed to assess whether and how childhood asthma-related characteristics (before hire) relate to occupational exposures at first hire. Analyses were conducted in 298 children examined at the first survey of the Epidemiological Study on the Genetics and Environment of Asthma (1991-1995), who reported a training period or a job at follow-up in 2003-2007 (aged 17-29 yrs; 53% males). Exposure likelihood to dust, gases and/or fumes in their first occupation was estimated by the ALOHA job exposure matrix. Asthma before the first occupation and two asthma classifications for severity (Global Initiative for Asthma 2002 guidelines) and symptoms were defined by questionnaire. In their first job, 47% of subjects were exposed. After adjustment (age, sex and education), pre-hire onset asthmatics (59%) were nonsignificantly less likely to be exposed (OR 0.67, 95% CI 0.41-1.11). Associations were stronger when considering those with severe asthma or high symptom score in childhood (OR 0.27 (95% CI 0.11-0.63) and OR 0.49 (95% CI 0.25-0.99), respectively). The association was observed in those who completed a university degree (OR 0.55, 95% CI 0.29-1.04) but not in the others (OR 0.98, 95% CI 0.44-2.22), with consistent results for all asthma characteristics. Results suggest a healthy worker hire effect in subjects with more severe or more symptomatic asthma in childhood. Education may modulate self-selection.

Under-estimation of self-reported occupational exposure by questionnaire in hospital workers.

OBJECTIVES: The aim of the study was to determine whether self-reported occupational exposure to cleaning/disinfecting agents in hospital workers is accurate, in comparison to expert assessment, taken to be the gold standard. METHODS: In the Epidemiological Study of the Genetics and Environment of Asthma (EGEA), participants were interviewed on occupation with a specific questionnaire for hospital workers regarding tasks and cleaning/disinfecting agents. Two estimates of exposure were available: self-report and expert assessment. The expert assessment involved a standardised procedure to estimate intensity, frequency and probability of exposure for each job. The present analysis focused on eight exposures: formaldehyde, glutaraldehyde, bleach/chlorine, alcohol, quaternary ammonium components, ammonia, sprays and latex gloves. Agreement and differences between self-reported and expert estimates were studied by kappa and phi coefficients and McNemar tests, respectively. RESULTS: In the survey of 1571 adults, 176 ever hospital workers (327 occupations) with both self-reported and expert exposure assessments were studied. An underestimation of self-reported exposure was observed especially for formaldehyde (26.5% vs 32.7%, p=0.01), ammonia (7.4% vs 18.8%, p<0.0001), alcohol (64.9% vs 93.0%, p<0.0001) and quaternary ammonium components (16.6% vs 70.9%, p<0.0001), compared to expert assessment. CONCLUSION: Occupational exposure to disinfecting/cleaning agents is common and high in hospitals. A large underestimation of self-reported exposure and a lack of knowledge of product components was observed. Our results show the relevance of expert assessment in epidemiological studies to limit measurement bias. This work underlines the need for health education programmes on the occupational risks induced by these types of products.

17q21 variants modify the association between early respiratory infections and asthma.

Single nucleotide polymorphisms (SNPs) at chromosome 17q21 confer an increased risk of early-onset asthma. The objective was to study whether 17q21 SNPs modify associations between early respiratory infections and asthma. Association analysis was conducted in 499 children (268 with asthma, median age 11 yrs) from the Epidemiological Study on the Genetics and Environment of Asthma (EGEA). The 12-yr follow-up data were used to assess persistent or remittent asthma in young adulthood. Respiratory infection before 2 yrs of age was assessed retrospectively. For the 12 17q21 SNPs studied, the odds ratios (OR) for association between infection and early-onset asthma (age at onset

Dietary patterns and asthma in the E3N study.

The aim of the present study was to determine dietary patterns and investigate their association with asthma incidence, current asthma and frequent asthma exacerbations. Dietary habits and asthma data were collected from the large E3N study (of French females, mostly teachers). Of the 54,672 females followed-up in 2003, 2,634 reported ever-adulthood asthma, 1,063 reported current asthma, 206 reported frequent asthma attacks (one or more a week), and 628 reported asthma onset between 1993 and 2003. Using principal component analysis, three dietary patterns were identified: the "prudent" pattern (fruits and vegetables); the "Western" pattern (pizza/salty pies, dessert and cured meats); and the "nuts and wine" pattern. Pattern scores were categorised into tertiles, and the incidence and prevalence of asthma was compared between tertiles. After adjustment for confounders, no association of dietary patterns was observed with asthma incidence, ever-asthma or current asthma. The Western pattern was associated with an increased risk of reporting frequent asthma attacks (highest versus lowest tertile odds ratio (OR) 1.79, 95% confidence interval (CI) 1.11-3.73). Increasing scores of the nuts and wine pattern were associated with a decreased risk of reporting frequent asthma attacks (highest versus lowest tertile OR 0.65, 95% CI 0.31-0.96). The results of the present study suggest that overall diet could be involved in frequent asthma exacerbations, one aspect of asthma severity.

[Environmental factors for asthma severity and allergy: results from the EGEA study]. / Facteurs environnementaux de l'asthme sévère et de l'allergie: résultats de l'étude EGEA.

INTRODUCTION: EGEA (Epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), a case control and family study including 2048 individuals, was initiated to look for environmental and genetic risk factors for asthma. A synthesis of the results obtained since 2002 on phenotypic and environmental aspects of asthma severity and allergy are presented in this article. METHODS AND RESULTS: The results support a role for hormonal factors in asthma severity and in various allergic markers of asthma. A greater body mass index was related to a more severe asthma in women with early menarche. Associations between markers of allergy (eosinophils, IgE and atopy) and hormonal dependent events in women (premenstrual asthma, menopause and oral contraceptive use) have been found. In asthmatics, exposure to agents known to be associated with occupational asthma, active and passive smoking were associated with an increased clinical asthma severity score. The study underlines the protective role of country living and exposure to pets in early life on allergy markers in adulthood, supporting the hygiene hypothesis. CONCLUSIONS: New hypothesis will be tested in the near future from the second stage of this survey.

Twenty five year mortality and air pollution: results from the French PAARC survey.

AIMS AND METHODS: Long term effects of air pollution on mortality were studied in 14,284 adults who resided in 24 areas from seven French cities when enrolled in the PAARC survey (air pollution and chronic respiratory diseases) in 1974. Daily measurements of sulphur dioxide, total suspended particles, black smoke, nitrogen dioxide, and nitric oxide were made in 24 areas for three years (1974-76). Cox proportional hazards models controlling for individual confounders (smoking, educational level, body mass index, occupational exposure) were applied, and frailty models used to take into account spatial correlation. Indicators of air pollution were the mean concentration. RESULTS: Models were run before and after exclusion of six area monitors influenced by local traffic (NO/NO2 >3 in ppb). After exclusion of these areas, analyses showed that adjusted risk ratios (95% CI) for TSP, BS, NO2, and NO for non-accidental mortality were 1.05 (1.02 to 1.08), 1.07 (1.03 to 1.10), 1.14 (1.03 to 1.25), and 1.11 (1.05 to 1.17) for 10 microg/m3 respectively. Consistent patterns for lung cancer and cardiopulmonary causes were observed. CONCLUSIONS: Urban air pollution assessed in the 1970s was associated with increased mortality over 25 years in France.

[Genetic and environmental factors of asthma and allergy: Results of the EGEA study]. / Facteurs génétiques et environnementaux de l'asthme et de l'allergie: synthèse des résultats de l'étude EGEA.

INTRODUCTION AND METHODS: The EGEA study (epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), which combines a case-control and a family-based study of asthma case (n=2120 subjects) with three surveys over 20 years, aims to identify environmental and genetic factors associated with asthma and asthma-related phenotypes. We summarize the results of the phenotypic characterization and the investigation of environmental and genetic factors of asthma and asthma-related phenotypes obtained since 2007 in the EGEA study (42 articles). RESULTS: Both epidemiological and genetic results confirm the heterogeneity of asthma. These results strengthen the role of the age of disease onset, the allergic status and the level of disease activity in the identification of the different phenotypes of asthma. The deleterious role of active smoking, exposure to air pollution, occupational asthmogenic agents and cleaning products on the prevalence and/or activity of asthma has been confirmed. Accounting for gene-environment interactions allowed the identification of new genetic factors underlying asthma and asthma-related traits and better understanding of their mode of action. CONCLUSION: The EGEA study is contributing to the advances in respiratory research at the international level. The new phenotypic, environmental and biological data available in EGEA study will help characterizing the long-term evolution of asthma and the factors associated to this evolution.

Occupational risks of bladder cancer in France: a multicentre case-control study.

The relationships between occupational risk factors in France and bladder cancer were assessed from a hospital-based case-control study conducted between 1984 and 1987 in five regions representing various industries, including mining, textile manufacture, metallurgy and the production of rubber and chemicals. The study concerned 765 cases (658 men and 107 women) and the same number of controls. Odds ratios (OR) adjusted for matching variables (age, place of residence and hospital), and tobacco smoking were estimated by unconditional logistic regression. A significantly increased risk of bladder cancer was observed among men employed in coal mining (OR = 2.42; 95% confidence interval (Cl) : 1.25-4.67) and the chemicals industry (OR = 2.36; 95% Cl : 1.23-4.53). Aircraft and ship's officers (OR = 11.8; 95% Cl : 1.46-95.7), managers (OR = 1.64; 95% Cl : 1.11-2.43) and street vendors (OR = 3.60; 95% Cl : 1.15-11.3) also had an increased risk. Among women, employment in the clothing industry was associated with a high OR (= 3.21; 95% Cl : 1.34-7.71). Assessment of individual exposures by a panel of industrial hygiene experts showed that significantly more cases than controls had been exposed to the following substances: chlorinated solvents (OR = 1.86; 95% Cl : 1.19-2.90), industrial oils and greases (OR = 1.44; 95% Cl : 1.10-1.89), welding fumes (OR = 1.40; 95% Cl : 0.98-2.01), coal dust (OR = 1.71; 95% Cl : 1.02-2.89) and metallic oxide dust (OR = 2.99; 95% Cl : 1.12-8.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cancer risk among workers in biomedical research.

OBJECTIVE: This epidemiologic study was undertaken after a cluster of five cases of rare forms of cancer (bone sarcoma, non-Hodgkin's lymphoma) had been observed among biomedical research workers at the Pasteur Institute in Paris to ascertain whether their disease was connected with exposure during this research. METHODS: A mortality study included 3765 people who worked at the Pasteur Institute between 1971 and 1986 and were followed until the end of 1987. Within this cohort a nested case-referent study included 23 cases of cancer [non-Hodgkin's lymphoma (6), multiple myeloma (1), leukemia (3), pancreatic cancer (7), bone cancer (3), brain tumor (3)], and four referents per case, matched for gender and year of birth. RESULTS: Total mortality from cancer was less than expected, the standardized mortality ratio (SMR) being 72 for the men and 82 for the women. Among the women the proportion of pancreatic cancer cases was larger than expected [SMR 490, 95% confidence interval (95% CI) 158-1144], as was the number of brain cancer cases (SMR 239, 95% CI 48-696). Among the men, mortality from bone cancer was greater than expected (SMR 553, 95% CI 62-2006). In the nested case-referent study, more cases than referents had worked in the areas of molecular biology [odds ratio (OR) 7.1, 95% CI 1.5-33] and microbial genetics (OR 6.7, 95% CI 1.3-35). These cases especially included non-Hodgkin's lymphoma and bone cancer. Associated with this finding was the fact that more cases had used certain chemicals, including ethidium bromide, acrylamide, methylnitronitrosoguanidine and ethylmethanesulfonate, and radioactive compounds (essentially 32phosphorus). CONCLUSIONS: As the products used are potent genotoxicants, the present findings suggest that work in biomedical research might well involve an increased risk of certain types of cancer; this conclusion should be balanced by the fact that two of the five index cases were included in the mortality study and four in the nested case-referent study.

[Epidemiological study on the Genetics and Environment of Asthma, bronchial hyperresponsiveness and atopy (EGEA) - First results of a multi-disciplinary study]. / Etude Epidémiologique sur les facteurs Génétiques et Environnementaux de l'Asthme, l'hyperréactivité bronchique et l'atopie (EGEA). Premiers résultats d'une étude multidisciplinaire.

The French co-operative epidemiological study EGEA realised in 1991/95 combines a case control study and a study of the families of asthmatic cases. A synthesis of the results already obtained is presented. Smoking was related to IgE, even in asthmatics and was clearly related to the clinical severity of asthma, an aspect insufficiently taken into account. The relationships of occupational exposures to asthma have been assessed using a job exposure matrix. Segregation analyses on IgE have shown, after correction for the mode of ascertainment, the existence of a dominant major gene and familial residual correlation. A systematic genome screen realised in families with 2 asthmatic siblings showed linkage of various regions in the genome implicated to asthma or related phenotypes (1p, 11p, 11q, 12q, 13q, 17q, 19q), coherent with genome screens realised in other studies. Regarding candidate genes, no association was evidenced between asthma and the AF508 mutation of the cystic fibrosis gene. The analysis is still in progress by studies on the heterogeneity of asthma with refined genetic studies and by searching to integrate results regarding environmental and genetic factors and studying their interactions.

Genome screen in the French EGEA study: detection of linked regions shared or not shared by allergic rhinitis and asthma.

In the sample of 295 French EGEA families with at least one asthmatic subject, a genome screen was conducted to identify potential linkage regions specific either to allergic rhinitis (AR) or to asthma as well as those shared by the two diseases. Two binary rhinitis phenotypes based on (1) diagnosis (ARbin1) and (2) symptoms (ARbin2) and a categorical ordered trait (ARcat) were considered. Asthma phenotype was based on answers to a standardized questionnaire plus the presence of bronchial hyper-responsiveness. Linkage analyses were conducted using the maximum likelihood binomial (MLB) method. These analyses provided potential evidence for linkage to three regions in the whole sample: 1p31 for the phenotype defined by ARbin2 plus asthma (P=0.00016), 2q32 for ARbin2 (P=0.00016) and 3p24-p14 for ARcat (P=0.001). Two other regions were detected in the subset of 185 families with at most one asthmatic sib: 9p22 and 9q22-q34 for ARbin1 (P=0.001 and 0.0007, respectively). No region showed evidence for linkage to asthma without being also linked to AR. While 1p31 may contain a genetic determinant common to asthma and AR, 2q32, 3p24-p14, 9p22 and 9q22-q34 are more likely to harbor genetic factors specific to AR.

Development of an asthma specific job exposure matrix and its application in the epidemiological study of genetics and environment in asthma (EGEA).

OBJECTIVES: To develop a method suitable for estimating exposure risks in population studies of asthma from job titles and international codes, by combining a new job exposure matrix (JEM) with the expert judgement approach. The method was applied in the French epidemiological study of the genetics and environment in asthma (EGEA). METHODS: The JEM contains 22 exposure groups including 18 high risk groups based on known risk factors for occupational asthma, divided into high molecular weight agents, low molecular weight agents, and mixed environments. After applying the JEM to job codes, exposure estimates for each subject were re-evaluated by examining job title texts. Three high risk exposure estimates for asthma were compared: firstly, applying the JEM to original codes (from different coders in each study centre); secondly, applying the JEM to revised codes (from one experienced coder); and thirdly, after reviewing JEM exposure estimates in the light of job title texts. RESULTS: The study comprised 173 cases with asthma and 285 controls (age 18-65). Odds ratios (ORs) for asthma for high risk jobs were 1.0 (95% confidence interval (95% CI) 0.6 to 1.7), applying the JEM to original codes; 1.4 (95% CI 0.8 to 2.3), applying the JEM to revised codes; and 1.7 (95% CI 1.1 to 2.7), applying the JEM and subsequently re-evaluating exposure estimates from job title texts. Asthma ORs were 1.4 (95% CI 0.6 to 2.9) for high molecular weight agents, 2.3 (95% CI 1.2 to 4.4) for low molecular weight agents, and 2.1 (95% CI 0.9 to 5.2) for mixed environments. CONCLUSIONS: This asthma JEM, when enhanced by expert re-evaluation of exposure estimates from job title texts, may be a useful tool in general population studies of asthma. In this study, a 1.7-fold increase in prevalence odds of high risk exposures was found among asthmatic workers compared with controls, with risk magnitude varying for different classes of exposure.

Relationships of active smoking to asthma and asthma severity in the EGEA study. Epidemiological study on the Genetics and Environment of Asthma.

The role of smoking as potential risk factor, selection factor ("healthy smoker" effect) and modifying factor (severity) of asthma was studied in the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyperresponsiveness and atopy (EGEA). The analysis involved 200 adult asthmatic cases recruited in chest clinics, 265 nonasthmatic controls and 586 relatives of asthmatics (147 with asthma). Asthma in childhood was not associated with a reduced take-up of smoking (odds ratio (OR)=1.06 in males and 0.98 in females), but smoker asthmatic cases quit more often than controls (OR = 2.20 (95% confidence interval (95% CI) 1.11-4.34) in males and 2.76 (1.19-6.42) in females). Adult onset asthma was unrelated to ever smoking (OR 1.07 in males and 1.02 in females). In asthmatic cases, active smoking was associated with asthma severity. Current smokers, compared to never and exsmokers, had more asthma symptoms, more frequent (> or =1 attack x day(-1)) asthma attacks (OR 2.39 (95% CI 1.06-5.36)) and higher asthma severity scores. No clear pattern regarding the relationships of smoking habits with asthma was observed in first degree relatives. It is concluded that active smoking is not a risk factor for asthma in adulthood, but that smoking increases asthma severity.

Occupational exposures estimated by means of job exposure matrices in relation to lung function in the PAARC survey.

OBJECTIVES: The aim of this analysis of the French Cooperative PAARC (Pollution Atmosphérique et Affections Respiratoires Chroniques) survey, was to test whether occupational exposures to dusts, gases, or chemical fumes or to specific hazards, estimated by job exposure matrices, were related to a decrease in forced expiratory volume in one second (FEV1). METHODS: The most recent occupation was recorded in adults, aged 25-59, from non-manual worker households. Analysis was restricted to 10,046 subjects whose occupation was encountered at least 10 times in the study and who performed good FEV1 tracings. From occupational title, exposures to dusts, gases, and chemical fumes, and to specific hazards were classified in three categories (no, low, and high) with a British, a French, and an Italian job exposure matrix. Specific hazards were analysed for the British and French job exposure matrices for the same 42 specific dusts, gases, and chemical fumes. To limit spurious associations, a selection of seven hazard groups and 12 specific hazards was set before the start of the analysis. Based on the consistency of the relations according to sex and the British and French job exposure matrices, associations of age, height, city, and smoking adjusted FEV1 score with occupational exposures were classified as very likely, possible, or unlikely. RESULTS: For the three job exposure matrices and both sexes clear exposure-response relations between the level of exposure to dusts, gases, and chemical fumes, and a decrease in FEV1 were found. Associations with FEV1 were classified as very likely for known hazards such as organic dusts and textile dusts, and not previously recognised hazards such as polycyclic aromatic hydrocarbons (PAHs) and detergents, and as possible for solvents, waxes and polishes, and diesel fumes. Associations found for PAHs and solvents were confirmed by the Italian job exposure matrix. Associations remained significant in women, but not in men, after adjustment for educational level. CONCLUSIONS: Hypotheses have been generated for exposure to detergents, PAHs, and solvents, but they need to be interpreted with caution before replication. Significant associations found for known risk factors with a decrease in FEV1 are arguments for the validity of the matrices. Despite the expected limitations of job exposure matrices, these results encourage further work to improve exposure assessment by job exposure matrices.

Performance of population specific job exposure matrices (JEMs): European collaborative analyses on occupational risk factors for chronic obstructive pulmonary disease with job exposure matrices (ECOJEM).

OBJECTIVES: To compare the performance of population specific job exposure matrices (JEMs) and self reported occupational exposure with data on exposure and lung function from three European general populations. METHODS: Self reported occupational exposure (yes or no) and present occupation were recorded in the three general population surveys conducted in France, The Netherlands, and Norway. Analysis was performed on subjects, aged 25-64, who provided good forced expiratory volume in 1 second (FEV1) tracings and whose occupations were performed by at least two people, in the French (6217 men and 5571 women), the Dutch (men from urban (854) and rural (780) areas), and the Norwegian (395 men) surveys. Two population specific JEMs, based on the percentage of subjects who reported themselves exposed in each job, were constructed for each survey and each sex. The first matrix classified jobs into three categories of exposure according to the proportion of subjects who reported themselves exposed in each job (P10-50 JEM, low < 10%, moderate 10-49%, high > or = 50%). For the second matrix, a dichotomous variable was constructed to have the same statistical power as the self reported exposure--that is, the exposure prevalence (p) was the same with both exposure assessment methods (Pp JEM). Relations between occupational exposure, as estimated by the two JEMs and self reported exposure, and age, height, city, and smoking adjusted FEV1 score were compared. RESULTS: Significant associations between occupational exposure estimated by the population specific JEM and lung function were found in the French and the rural Dutch surveys, whereas no significant relation was found with self reported exposure. In populations with few subjects in most jobs, exposure cannot be estimated with sufficient precision by a population specific JEM, which may explain the lack of relation in the Norwegian and the Dutch (urban area) surveys. CONCLUSION: The population specific JEM, which was easy to construct and cost little, seemed to perform better than crude self reported exposures, in populations with sufficient numbers of subjects per job.