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Purpose Based on a previous case report of menometrorrhagia (prolonged/excessive uterine bleeding, occurring at irregular and/or frequent intervals) in MRI workers with intrauterine devices (IUDs), it was evaluated whether this association could be confirmed. Methods A survey was performed among 381 female radiographers registered with their national association. Logistic regression was used to analyze associations of abnormal uterine bleeding with the frequency of working with MRI scanners, presence near the scanner/in the scanner room during image acquisition, and with scanner strength or type. Results A total of 68 women reported using IUDs, and 72 reported abnormal uterine bleeding. Compared with unexposed women not using IUDs, the odds ratio in women with IUDs working with MRI scanners was 2.09 (95% confidence interval 0.83-3.66). Associations were stronger if women working with MRI reported being present during image acquisition (odds ratio 3.43, 95% CI 1.26-9.34). Associations with scanner strength or type were not consistent. Conclusions Radiographers using IUDs who are occupationally exposed to stray fields from MRI scanners report abnormal uterine bleeding more often than their co-workers without an IUD, or nonexposed co-workers with an IUD. In particular, radiographers present inside the scanner room during image acquisition showed an increased risk. Magn Reson Med 79:1083-1089, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

The article explores the prevalence and factors related to musculoskeletal pain in women working in small-scale agriculture in rural northern KwaZulu-Natal, South Africa. Around 67% of the 911 women surveyed reported any chronic musculoskeletal pain. The 12-month prevalence of pain ranged from 63.9% to 73.3% and the prevalence of specific chronic pain that persists over three months ranged from 42.8% to 48.3%. Factors associated with chronic musculoskeletal pain include older age, carrying heavy loads, frequently squatting and kneeling and working with hands above shoulder height.

The article describes a job-exposure matrix (JEM) for inhalable aerosols, aromatic amines and cyclohexane soluble matter (CSM) in a rubber factory in Poland. Researchers grouped the data based on similarities in exposure levels and time trends in different departments. They found that inhalable aerosol exposure decreased after changes in production volume and implementation of exposure reduction measures in mid-1980s. Additionally, aromatic amines concentrations first increased following the factory's production volume. They explain that JEM will enable estimation of lifetime exposure for individual workers in a Polish rubber workers cohort and further investigation of the associations between specific exposures and cancer risk.

The goal of this investigation was to assess if and when a crew of paving workers is uniformly exposed to bitumen fume, organic vapor, and benzo(a)pyrene. Data on paving workers with up to six repeated exposure measurements were extracted from a database of exposure measurements developed within a study of the European asphalt industry (N = 591). The uniformity of exposures to bitumen fume, organic vapor, and benzo(a)pyrene was evaluated while grouping individuals by job title, primary tasks, crew membership, and use of coal tar (discontinued in Western Europe). The estimated ranges within which 95% of individual mean exposures were expected to fall ([sub BW]R[sub 0.95]) were used to assess exposure uniformity. Variance components were estimated by constructing mixed-effects models, with grouping variables as fixed effects and worker identity as random effect. The influence of duration of the sampling survey on estimates of exposure variability for a crew was also examined. There was a substantial variability in exposures between paving crews, as well as persons holding the same job or doing the same task, but each crew was uniformly exposed to bitumen fume and benzo(a)pyrene ([sub BW]R[sub 0.95] 2 and 1, respectively). Workers within the same crew engaged in paving with coal tar – containing binders were not, however, uniformly exposed to benzo(a)pyrene. Also, organic vapor exposures were not uniform among the members of a paving crew ([sub BW]R[sub 0.95] = 15). Sampling campaigns of up to 7 months had little impact on the estimates of within- and between-worker variability. These findings should assist investigators studying paving operations in optimizing their sampling, exposure assessment, and risk evaluation protocols. The results support the notion that only empirically determined predictors of exposure can yield optimal grouping, unlike a priori grouping strategies based on general descriptors such as jobs title or tasks performed. [ABSTRACT FROM AUTHOR]

Background: Occupational exposures may be associated with non-vascular dementia., Methods: We analyzed the effects of occupational exposures to solvents, pesticides, metals, extremely low frequency magnetic fields (ELF-MF), electrical shocks, and diesel motor exhaust on non-vascular dementia related mortality in the Netherlands Cohort Study (NLCS). Exposures were assigned using job-exposure matrices. After 17.3 years of follow-up, 682 male and 870 female cases were available. Analyses were performed using Cox regression., Results: Occupational exposure to metals, chlorinated solvents and ELF-MF showed positive associations with non-vascular dementia among men, which seemed driven by metals (hazard ratio ever high vs. background exposure: 1.35 [0.98-1.86]). Pesticide exposure showed statistically significant, inverse associations with non-vascular dementia among men. We found no associations for shocks, aromatic solvents, and diesel motor exhaust., Conclusions: Consistent positive associations were found between occupational exposure to metals and non-vascular dementia. The finding on pesticides is not supported in the overall literature., (© 2015 Wiley Periodicals, Inc.)

Objective: We documented previously that if study quality is accounted for, evidence from occupational cohort studies on benzene supports a possible association with some lymphoma subtypes, in particular multiple myeloma, and acute and chronic lymphocytic leukemia. Here, we extend these analyses to chronic myeloid leukemia (CML)., Methods: Three strategies to assess study quality (stratification by the year-of-start of follow-up, stratification by the strength of the reported acute myeloid leukemia (AML) association, and stratification by the quality of benzene exposure assessment) were employed in a meta-analysis of occupational benzene exposure and CML. We hypothesized that stratification by these study quality dimensions would identify a subgroup of occupational cohort studies that is most informative for the evaluation of the possible association between benzene and CML., Results: The overall meta-relative risk (mRR) was non-significantly elevated (1.23; 95% confidence interval (CI): 0.93-1.63). The mRRs increased with increasing study quality for all dimensions with a significant elevation for studies with start of follow-up after 1970 (1.67; 95% CI: 1.02-2.74). The highest study quality stratum for AML significance and exposure quality showed an elevated but non-significant increased mRR (1.40; 95% CI: 0.86-2.27, and 1.68; 95% CI: 0.74-3.84, respectively)., Conclusions: Although limited by low statistical power, the current meta-analysis provides support for a possible association of occupational exposure to benzene and the risk of CML., (Copyright © 2012 Wiley Periodicals, Inc.)

Background: There are many proven and suspected occupational causes of lung cancer, which will become relatively more important over time, as smoking prevalence decreases., Methods: We interviewed 457 cases aged 20-75 years notified to the New Zealand Cancer Registry during 2007-2008, and 792 population controls. We collected information on demographic details, potential confounders, and employment history. Associations were estimated using logistic regression adjusted for gender, age, ethnicity, smoking, and socio-economic status., Results: Among occupations of a priori interest, elevated odds ratios (ORs) were observed for sawmill, wood panel and related wood-processing plant operators (OR 4.63; 95% CI 1.05-20.29), butchers (OR 8.77, 95% CI 1.06-72.55), rubber and plastics products machine operators (4.27; 1.16-15.66), heavy truck drivers (2.24; 1.19-4.21) and workers in petroleum, coal, chemical and associated product manufacturing (1.80; 1.11-2.90); non-significantly elevated risks were also observed for loggers (4.67; 0.81-27.03), welders and flame-cutters (2.50; 0.86-7.25), pressers (5.74; 0.96-34.42), and electric and electronic equipment assemblers (3.61; 0.96-13.57). Several occupations and industries not of a priori interest also showed increased risks, including nursing associate professionals (5.45; 2.29-12.99), enrolled nurses (7.95; 3.10-20.42), care givers (3.47; 1.40-8.59), plant and machine operators and assemblers (1.61; 1.20-2.16), stationary machine operators and assemblers (1.67; 1.22-2.28), food and related products processing machine operators (1.98; 1.23-3.19), laborers and related elementary service workers (1.45; 1.05-2.00), manufacturing (1.34; 1.02-1.77), car retailing (3.08; 1.36-6.94), and road freight transport (3.02; 1.45-6.27)., Conclusions: Certain occupations and industries have increased lung cancer risks in New Zealand, including wood workers, metal workers, meat workers, textile workers and drivers. Am. J. Ind. Med. 54:89-101, 2011. © 2010 Wiley-Liss, Inc., (Copyright © 2010 Wiley-Liss, Inc.)

Background: Construction workers are educated at vocational training centers before they begin their working lives. Future bricklayers and their instructors are exposed to respirable dust and possibly to hazardous respirable crystalline silica from trial mortar., Methods: Thirty-six personal air samples were collected at six training centers to estimate exposure to respirable dust for both students and teachers. A selection of 22 samples was analyzed for crystalline silica., Results: Average respirable dust exposures ranged from 0.59 mg/m(3) for teachers to 1.45 mg/m(3) for students performing recycling and cleaning tasks. In 45% of the analyzed samples, respirable crystalline silica was detected. Exposure to silica remained below the Dutch OEL (75 microg/m(3)). Exposure was significantly less for teachers than for students. This effect was found in both types of vocational training centers present in the Netherlands. Dry sweeping, as performed at all locations in this study, contributed considerably to the exposure to respirable dust. A first step in reducing exposure to dust and silica at training centers would therefore be to avoid dry sweeping. The presence of a dust extraction system, although not optimally designed, also significantly lowered exposure., Conclusions: To assess a construction worker's lifetime exposure to respirable dust and crystalline silica, the vocational training period should also be taken into account. Several epidemiological studies have shown that time since first exposure can be an important risk factor for chronic health effects., (2010 Wiley-Liss, Inc.)

Background: Inhalation incidents are an important cause of acute respiratory symptoms, but little is known about how these incidents affect chronic respiratory health., Methods: We assessed reported inhalation incidents among 3,763 European Community Respiratory Health Survey (ECRHS) participants with and without cough, phlegm, asthma, wheezing or bronchial hyperresponsiveness. We then examined whether inhalation incidents during the 9-year ECRHS follow-up period were associated with a new onset of any of these respiratory outcomes among 2,809 participants who were free of all five outcomes at the time of the baseline ECRHS survey., Results: Inhalation incidents were reported by 5% of participants, with higher percentages reported among individuals with asthma-related outcomes at the time of the baseline survey. Among participants without symptoms at baseline, our analyses generated non-statistically significant elevated estimates of the risk of cough, phlegm, asthma and wheezing and a non-statistically significant inverse estimate of the risk of bronchial hyperresponsiveness among participants who reported an inhalation incident compared to those without such an event reported., Discussion: Our findings provide limited evidence of an association between inhalation incidents and asthma-related symptoms. These data could be affected by differences in the reporting of inhalation incidents according to symptom status at the time of the baseline survey; they should thus be interpreted with caution., ((c) 2008 Wiley-Liss, Inc.)

Background: Self-reports are frequently used to assess occupational exposures in epidemiological studies on asthma, but the validity and influence of asthma status on performance is unclear., Methods: Data on self-reported exposure to air pollutants were obtained for 16,752 randomly selected working individuals from 40 study centers, and compared to exposures obtained by a job exposure matrix (JEM). The influence of current asthma symptoms or medication was investigated., Results: Specificity of self-reports amounted to 0.83 and 0.87, and sensitivity 0.48 and 0.42 for asthmatics and non-asthmatics, respectively, when compared with the JEM. Self-reported exposure, but not exposure assessed by the JEM, was more prevalent in areas with a higher community prevalence of asthma., Conclusions: The prevalence of self-reported occupational exposures seems to depend on asthmatic health status at both the individual and the community level. Associations between self-reports and asthma are likely to be biased, especially in pooled analyses combining different areas with varying prevalence rates of asthma., ((c) 2005 Wiley-Liss, Inc.)

Background: Suicide using pesticides as agent is recognized as a major cause of pesticide poisoning., Methods: A literature review of mortality and morbidity studies related to suicide among pesticide-exposed populations, and of human and animal studies of central nervous system toxicity related to organophosphate (OP) pesticides was performed., Results: Suicide rates are high in farming populations. Animal studies link OP exposure to serotonin disturbances in the central nervous system, which are implicated in depression and suicide in humans. Epidemiological studies conclude that acute and chronic OP exposure is associated with affective disorders. Case series and ecological studies also support a causal association between OP use and suicide., Conclusions: OPs are not only agents for suicide. They may be part of the causal pathway. Emphasizing OPs solely as agents for suicide shifts responsibility for prevention to the individual, reducing corporate responsibility and limiting policy options available for control., (Copyright (c) 2005 Wiley-Liss, Inc.)

Background: Standard approaches to assessing exposures for epidemiologic studies tend to concentrate resources on obtaining detailed data for each study participant at the expense of characterizing within-person variability., Methods: This paper presents some basic, generalizeable concepts concerning exposure and its variability, describes methods that can be used to analyze, describe, and understand that variability, and reviews related implications for the design and interpretation of epidemiologic studies., Results and Conclusions: Insufficient attention to the balance of within- and between-person variation in exposure can reduce the efficiency of measurement efforts and attenuate estimates of exposure-disease association. Exposure variability should consequently be considered carefully in the planning, analysis, and interpretation of epidemiologic studies. Greater attention to these matters can lead to more meaningful characterization of exposure itself, and, most importantly, improve the chances that epidemiologic studies can identify and accurately characterize health hazards., (Copyright 2003 Wiley-Liss, Inc.)

Background: An exposure matrix (EM) for known and suspected carcinogens was required for a multicenter international cohort study of cancer risk and bitumen among asphalt workers., Methods: Production characteristics in companies enrolled in the study were ascertained through use of a company questionnaire (CQ). Exposures to coal tar, bitumen fume, organic vapor, polycyclic aromatic hydrocarbons, diesel fume, silica, and asbestos were assessed semi-quantitatively using information from CQs, expert judgment, and statistical models. Exposures of road paving workers to bitumen fume, organic vapor, and benzo(a)pyrene were estimated quantitatively by applying regression models, based on monitoring data, to exposure scenarios identified by the CQs., Results: Exposures estimates were derived for 217 companies enrolled in the cohort, plus the Swedish asphalt paving industry in general. Most companies were engaged in road paving and asphalt mixing, but some also participated in general construction and roofing. Coal tar use was most common in Denmark and The Netherlands, but the practice is now obsolete. Quantitative estimates of exposure to bitumen fume, organic vapor, and benzo(a)pyrene for pavers, and semi-quantitative estimates of exposure to these agents among all subjects were strongly correlated. Semi-quantitative estimates of exposure to bitumen fume and coal tar exposures were only moderately correlated. EM assessed non-monotonic historical decrease in exposures to all agents assessed except silica and diesel exhaust., Conclusions: We produced a data-driven EM using methodology that can be adapted for other multicenter studies., (Copyright 2003 Wiley-Liss, Inc.)

Background: Using data from a Dutch cohort of workers in road construction and asphalt mixing companies, this article describes possible confounding of the association between exposure to bitumen fume and lung cancer mortality by smoking., Methods: A retrospective cohort of 3,714 workers with at least one season of employment was identified. Semi-quantitative exposure to bitumen fume was assessed by a job-exposure matrix. Information on smoking habits was available for a sub-cohort of 1,138 workers, who underwent medical examinations by the occupational health services in the past., Results: Smoking habits differed between occupational title groups and there was a positive association between cumulative exposure and smoking. Internal analyses using the non-exposed subjects as reference category, showed a positive association between semi-quantitative bitumen fume exposure and lung cancer risk. After adjusting for differences in smoking habits, all relative risks were reduced, but a weak positive association could still be observed., Conclusion: Confounding by smoking on the association between exposure to bitumen fume and lung cancer mortality is possible, although the positive trend (not statistically significant) for lung cancer mortality remained. Only a nested case-control study may allow proper treatment of potential (residual) confounding by smoking in this population., (Copyright 2003 Wiley-Liss, Inc.)

Background: Inhalation of bitumen fumes is potentially carcinogenic to humans., Methods: We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow-up during 1953-2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers., Results: The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90-0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04-1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89-1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89-1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers., Conclusions: European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out., (Copyright 2003 Wiley-Liss, Inc.)

Background: We describe the results of a cancer mortality study among asphalt workers in Israel., Methods: Personal identifiers and employment histories of 2,176 workers were extracted from company records., Results: Mortality from all malignant neoplasms was significantly reduced in the whole cohort (SMR 0.68, 95% confidence interval (CI) 0.56-0.83). SMR for lung cancer was elevated in workers exposed to bitumen (SMR 1.05, 95% CI 0.62-1.66). No significant elevation or reduction in mortality was observed in relation to a specific site. SMRs for lung cancer was higher among ever exposed to bitumen than among unexposed. There was no association between lung cancer risk and estimated exposure to bitumen fume, and no dose-response was apparent., Conclusions: While the results of this cohort study indicate a slightly increased SMR for lung cancer, it did not produce evidence of a causal link between lung cancer and exposure to bitumen fume., (Copyright 2003 Wiley-Liss, Inc.)

Background: An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses., Methods: In a multi-country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953-2000. Exposures to bitumen fume, coal tar, 4-6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job-exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated., Results: The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99-1.18) was comparable to that of non-exposed workers (SMR 1.05, 95% CI 0.92-1.19). In a sub-cohort of bitumen-exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02-1.48). The analysis based on the semi-quantitative, matrix-based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose-response was suggested for average level of exposure, applying a 15-year lag, which was marginally reduced after adjustment for co-exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm., Conclusions: The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck., (Copyright 2003 Wiley-Liss, Inc.)

Background: We compared performance of different exposure assessment approaches in a cohort study of cancer risk among European asphalt workers., Methods: Three bitumen fume exposure indices (duration of exposure (years), average exposure (mg/m3) and cumulative exposure (mg/m3*years)) and two latency models (with and without a 15 year lag) were considered for an association between lung cancer mortality and bitumen fume., Results: There was no association between lung cancer risk and either duration or cumulative exposure. However, there was the suggestion of an increase in lung cancer risk accompanying rise in average exposure. Only models with average bitumen fume exposure (with or without lag) improved model fit, albeit to the same extent., Conclusions: Constructing quantitative indices of exposure intensity was justified because they produced the greatest improvement in fit of models that explored possible relationship between bitumen fume exposure and lung cancer risk. The identified associations require further investigation., (Copyright 2003 Wiley-Liss, Inc.)

Background: The potential association between occupational electric and magnetic field exposure and cancer is well documented in the literature, but there is uncertainty regarding a causal relation., Methods: Using data from a completed cohort study, we sought to refine the job-exposure matrix in a case-cohort analysis by regrouping jobs into more homogeneous groups, but without making additional measurements. From the original cohort, we selected the 164 men who died of leukemia, 145 men who died of brain cancer, and a random subcohort of 800 men (0.6% of the cohort). Erroneous job assignments were corrected and job groups were subdivided based on differences in work environments or tasks performed., Results: Magnetic field exposure remained unrelated to leukemia mortality and positively associated with brain cancer mortality based on both cumulative and average magnetic field indices. Although not monotonic across the middle intervals, increased risk of brain cancer was found in relation to career exposure, with risk ratios of 1.8 (95% CI = 0.7-4.7) and 2.5 (95% CI = 1.0-6.3) in the uppermost categories for cumulative and average exposure, stronger for exposure 2-10 years past., Conclusions: Improvements in exposure assignment based only on reassignment of job titles to occupational categories had little impact on the measured associations of magnetic fields with leukemia or brain cancer., (Copyright 2000 Wiley-Liss, Inc.)

Background: Equations using variance components in exposure data to predict attenuation and standard error of exposure--response slopes have been published recently. However, to date, no comparisons have been made between results of applying these equations to a real data set with the exposure-response relations estimated directly., Methods: Data on lung function parameters and personal inhalable and respirable dust exposure levels from the European carbon black respiratory health study were used. The predicted attenuation and standard error of the relation between current inhalable and respirable dust levels and lung function parameters (FVC and FEV(1)) were calculated for various exposure grouping schemes. These results were compared with the observed exposure-response relations. Workers were grouped by Job Category, the combination of factory and Job Category and five a posteriori created Exposure Groups. In addition, the individual approach was also used, as exposure data were available for each worker., Results: The rank orders of the coefficients from the regression analyses using the different grouping schemes were similar to those predicted by the equations, although the differences were larger than predicted. When using inhalable dust exposure, the predicted standard errors of the exposure-response slopes were slightly lower than those estimated directly; for respirable dust the predicted standard errors were about a factor two to three smaller than those from the regression analyses. When considering FVC, the predicted exposure-response relations were all statistically significant, whilst the observed relation was only significant when using the five a posteriori Exposure Groups. When reviewing the relations between dust exposure and level of FEV(1), all relations were statistically significant, with the exception of the (observed) relation between respirable dust and FEV(1), when the individual approach was used., Conclusions: Using different grouping schemes for estimating exposure can have large effects on the slope and standard error of the exposure-response relation. It is, therefore, important that the effect of the different grouping schemes on the level and precision of the exposure-response slope be estimated. Despite violation of most of the assumptions when applying the equations to predict attenuation and the standard error of the exposure-response slope, the similarities in predicted and observed exposure-response relations and standard errors are indicative of the robustness of these equations. Therefore, the equations appear to be a useful tool in establishing the most efficient way of utilizing exposure measurements., (Copyright 1999 Wiley-Liss, Inc.)

Epidemiological studies of cancer among workers exposed to magnetic fields have yielded inconsistent results. This variability may be partly explained by differences in study methods. To assess sensitivity to such methods, data from a previous study of brain cancer and leukemia among electric power company workers were reanalyzed using alternative models, which incorporated uncertainty about the intensity of historical exposures, alternative cut points for categorizing the exposure variable for analysis, and a range of lags for describing cancer latency. Mortality rate ratios for leukemia ranged from 0.8-1.5. For brain cancer, increasing cumulative magnetic field exposure was associated with increasing mortality in virtually all models, with rate ratios between 1.3-3.4 for the most exposed workers. These rate ratios are consistent with previous analyses suggesting a 1.5-3.0-fold increase in the risk of brain cancer but no association with leukemia, and confirm that the previous results are not dependent on arbitrary decisions in applying the exposure data.

The relation between dermal and respiratory exposure and uptake into the body of captan, measured as 24 hr cumulative tetrahydrophtalimide (THPI) dose, was studied among 14 male fruit growers applying pesticides in orchards in the Netherlands. No contribution of respiratory exposure was observed on THPI in the urine. Dermal exposure, measured with skin pads, showed a clear relation with THPI in urine when exposure was estimated from exposure on skin pads of ankles and neck. No relation was found for total dermal exposure, calculated from measured exposure on skin pads of representative skin areas according to models described in the literature. Determinants of exposure such as use of a cabin on the tractor, use of gloves during mixing and loading, and use of rubber boots also explained THPI in urine very well. This finding corroborated the findings on measured dermal exposure. Results indicate that more attention should be paid to skin areas which are suspected to be most permeable for a chemical under study. It was concluded that dermal exposure data can be linked better to biological monitoring based on empirical findings as gathered in a pilot study on exposure of specific body areas than on estimations of total skin dose.

The variability of exposure has important implications for the design of occupational epidemiologic studies. To assess the influence of this variability in the rubber industry, the efficiency of different schemes for classification of exposure to particulates, cyclohexane-soluble contaminants, and solvents was assessed. Groupings based on job title, plant, factors affecting exposure, published classifications, and the International Standard Classification of Occupations of the International Labor Organization (ISCO-ILO) were compared. Statistical parameters for contrast in average exposure between groups and precision of average exposure within groups were developed to enable comparison of the efficiency of different classification schemes. Grouping of exposure to particulates and dermal exposure appeared to be less efficient than grouping of exposure to solvents. Grouping of solvent exposure using occupational title groups, existing classification schemes, and schemes based on factors affecting exposure showed comparable high resolution in exposure levels. Even the most detailed grouping schemes based on the combination of plant and occupational title group showed relatively modest resolution in particulate and dermal exposure levels. Groupings based on factors affecting exposure showed similar resolution for these exposures, but had higher precision due to having fewer groups. Application of optimal exposure grouping strategies will benefit new research on cancer among rubber workers. Eventually, this might resolve the situation in which a complete industry was included on the list of proven human carcinogens.

Industry-based cohort studies require systems for organizing work history data. Although the ultimate goal may be to assess the hazards of specific exposures, classification of the job titles that comprise work histories serves an important descriptive purpose in itself and is often necessary before exposure data can be obtained. A system we have created for organizing jobs in a study of 135,000 workers at five electric power companies highlights conceptual and practical issues in managing work history data for epidemiological studies. Job characteristics including function, location, and authority were used to develop a system of 28 occupational categories. Comprehensibility, flexibility, and efficiency were important criteria in designing the system. Assessment of exposures was an implicit goal; the same categories will define job-exposure matrices for numerous agents. A combination of computer algorithms and expert judgment was used to assign individual job titles to the categories. This system facilitates examining the effects of various agents and controlling for confounding. The 28 categories can be collapsed and regrouped to analyze disease risks in relation to exposures to magnetic fields and other agents; even exposures not previously considered could be brought into the study with this generic system for organizing the electric power industry.

A method for qualitative estimation of the exposure at task level was used and validated with actual measurements in five small factories. The results showed that occupational hygienists were in general the most successful estimators. Plant supervisors and workers handled the estimation method less successfully because of more misclassification of the tasks. The method resulted, in general, in a classification of tasks in four exposure categories ranging from no exposure to high exposure. The exposure categories correlated positively with mean concentrations, but showed overlapping exposure distributions. This resulted in misclassification of the exposure for individual workers when a relatively large interindividual variability in exposure levels within an exposure category was present. The results show that this method can be used for workplace exposure zoning, but that the usefulness of the estimates for epidemiological purposes is not clear-cut and depends strongly on the actual exposure characteristics within a workplace. A combination of the qualitative exposure estimation method together with assessment of the exposure levels by measurements makes a rearrangement of tasks or individual workers possible and could improve the validity of this method for epidemiological purposes.