Skin and respiratory ill-health attributed to occupational face mask use

BACKGROUND

Face mask use in the workplace has become widespread since the onset of the Covid-19 pandemic and has been anecdotally linked to adverse health consequences.

AIMS

To examine reports of adverse health consequences of occupational face mask use received by The Health and Occupation Research (THOR) network before and after the pandemic onset.

METHODS

THOR databases were searched to identify all cases of ill-health attributed to 'face mask' or similar suspected causative agent between 1 January 2010 and 30 June 2021.

RESULTS

Thirty two cases were identified in total, 18 reported by occupational physicians and 14 by dermatologists. Seventy-five per cent of cases were reported after the pandemic onset and 91% cases were in the health and social care sector. 25 of the 35 (71%) diagnoses were dermatological, the most frequent diagnoses being contact dermatitis (14 cases) and folliculitis/acne (6 cases). Of the seven respiratory diagnoses, four were exacerbation of pre-existing asthma.

CONCLUSIONS

There is evidence of an abrupt increase in reports of predominantly dermatological ill-health attributed to occupational face mask use since the start of the pandemic. Respiratory presentations have also occurred.

Maternal occupational exposure to endocrine-disrupting chemicals and urogenital anomalies in the offspring

STUDY QUESTION

Is there an association between maternal occupational exposure to endocrine-disrupting chemicals (EDCs) early in pregnancy and subgroups of congenital anomalies of kidney and urinary tract (CAKUT), and hypospadias?

SUMMARY ANSWER

Exposure to specific EDCs can increase the risk of CAKUT and no association with hypospadias was observed.

WHAT IS KNOWN ALREADY

Previous studies showed an association between maternal occupational exposure to EDCs and hypospadias. However, little is known about the effect of these chemicals on the development of CAKUT, especially subgroups of urinary tract anomalies.

STUDY DESIGN, SIZE, DURATION

For this case-control study, cases with urogenital anomalies from the European Concerted Action on Congenital Anomalies and Twins Northern Netherlands (Eurocat NNL) registry and non-malformed controls from the Lifelines children cohort (living in the same catchment region as Eurocat NNL) born between 1997 and 2013 were selected. This study included 530 cases with CAKUT, 364 cases with hypospadias, 7 cases with both a urinary tract anomaly and hypospadias and 5602 non-malformed controls. Cases with a genetic or chromosomal anomaly were excluded, and to avoid genetic correlation, we also excluded cases in which a sibling with the same defect was included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Information on maternal occupation held early in pregnancy was collected via self-administered questionnaires. Job titles were translated into occupational exposure to EDCs using a job-exposure matrix (JEM). Adjusted odds ratios (aORs) and 95% CIs were estimated to assess the association between maternal occupational exposure to EDCs (and to specific types of EDCs) and CAKUT and hypospadias.

MAIN RESULTS AND THE ROLE OF CHANCE

For CAKUT and hypospadias, 23.1% and 22.9% of the cases were exposed to EDCs, respectively, whereas 19.8% of the controls were exposed. We found an association between maternal occupational exposure to organic solvents/alkylphenolic compounds and CAKUT (aOR 1.41, 95% CI 1.01-1.97) that became stronger when combinations of urinary tract anomalies co-occurred with other defects (aOR 7.51, 95% CI 2.41-23.43). An association was also observed for exposure to phthalates/benzophenones/parabens/siloxanes and CAKUT (aOR 1.56, 95% CI 1.06-2.29), specifically urinary collecting system anomalies (aOR 1.62, 95% CI 1.03-2.54) and combinations of urinary tract anomalies (aOR 2.90, 95% CI 1.09-7.71). We observed no association between EDC exposure and hypospadias.

LIMITATIONS, REASONS FOR CAUTION

The different study designs of Eurocat NNL and Lifelines could have introduced differential information bias. Also, exposure misclassification could be an issue: it is possible that the actual exposure differed from the exposure estimated by the JEM. In addition, women could also have been exposed to other exposures not included in the analysis, which could have resulted in residual confounding by co-exposures.

WIDER IMPLICATIONS OF THE FINDINGS

Women, their healthcare providers, and their employers need to be aware that occupational exposure to specific EDCs early in pregnancy may be associated with CAKUT in their offspring. An occupational hygienist should be consulted in order to take exposure to those specific EDCs into consideration when risk assessments are carried out at the workplace.

STUDY FUNDING/COMPETING INTEREST(S)

N.S. was paid by the Graduate School of Medical Sciences (MD/PhD programme), University Medical Center Groningen (UMCG), Groningen, the Netherlands. Eurocat Northern Netherlands is funded by the Dutch Ministry of Health, Welfare and Sports. The Lifelines Biobank initiative has been made possible by subsidy from the Dutch Ministry of Health, Welfare and Sport, the Dutch Ministry of Economic Affairs, the University Medical Center Groningen (UMCG the Netherlands), University Groningen and the Northern Provinces of the Netherlands. The authors report no conflict of interest.

TRIAL REGISTRATION NO

N/A.

An approach to classifying occupational exposures to endocrine disrupting chemicals by sex hormone function using an expert judgment process

Endocrine disrupting chemicals (EDCs) are exogenous substances that interfere with the endocrine system and cause adverse effects. We aimed to classify the effects of 24 known EDCs, prevalent in certain occupations, according to four modes of action (estrogenic, antiestrogenic, androgenic, and/or antiandrogenic). A literature search, stratified into four types of literature was conducted (namely: national and international agency reports; review articles; primary studies; ToxCast^TM). The state of the evidence of each EDC on sex hormone function was summarized and reviewed by an expert panel. For each mode of action, the experts evaluated the likelihood of endocrine disruption in five categories: "No", "Unlikely", "Possibly", "Probably", and "Yes". Seven agents were categorized as "Yes," or having strong evidence for their effects on sex hormone function (antiandrogenic: lead, arsenic, butylbenzyl phthalate, dibutyl phthalate, dicyclohexyl phthalate; estrogenic: nonylphenol, bisphenol A). Nine agents were categorized as "Probable," or having probable evidence (antiandrogenic: bis(2-ethylhexyl)phthalate, nonylphenol, toluene, bisphenol A, diisononyl phthalate; androgenic: cadmium; estrogenic: copper, cadmium and; anti-estrogenic: lead). Two agents (arsenic, polychlorinated biphenyls) had opposing conclusions supporting both "probably" estrogenic and antiestrogenic effects. This synthesis will allow researchers to evaluate the health effects of selected EDCs with an added level of precision related to the mode of action.

Development of a Task-Exposure Matrix (TEM) for Pesticide Use (TEMPEST)

INTRODUCTION

Pesticides have been associated with increased risks for a range of conditions including Parkinson's disease, but identifying the agents responsible has proven challenging. Improved pesticide exposure estimates would increase the power of epidemiological studies to detect such an association if one exists.

METHODS

Categories of pesticide use were identified from the tasks reported in a previous community-based case-control study in Scotland. Typical pesticides used in each task in each decade were identified from published scientific and grey literature and from expert interviews, with the number of potential agents collapsed into 10 groups of pesticides. A pesticide usage database was then created, using the task list and the typical pesticide groups employed in those tasks across seven decades spanning the period 1945-2005. Information about the method of application and concentration of pesticides used in these tasks was then incorporated into the database.

RESULTS

A list was generated of 81 tasks involving pesticide exposure in Scotland covering seven decades producing a total of 846 task per pesticide per decade combinations. A Task-Exposure Matrix for PESTicides (TEMPEST) was produced by two occupational hygienists who quantified the likely probability and intensity of inhalation and dermal exposures for each pesticide group for a given use during each decade.

CONCLUSIONS

TEMPEST provides a basis for assessing exposures to specific pesticide groups in Scotland covering the period 1945-2005. The methods used to develop TEMPEST could be used in a retrospective assessment of occupational exposure to pesticides for Scottish epidemiological studies or adapted for use in other countries.

Detergent protease exposure and respiratory disease: case-referent analysis of a retrospective cohort

OBJECTIVES

To examine the relationship between protease exposure and respiratory disease in a cohort of detergent enzyme manufacturers.

METHODS

Case-referent analysis of a cohort of employees working in a European detergent factory between 1989 and 2002. Cases with new lower or upper respiratory disease were ascertained by examination of occupational health records and matched to referents on date of first employment. Personal exposures to airborne detergent protease were estimated, using a job exposure matrix, from >12,000 measurements taken in the factory during the period of study.

RESULTS

We found clear, monotonic relationships between estimated protease exposure and both lower and upper respiratory disease. After control for age, sex and smoking, the odds ratio of lower respiratory disease was significantly elevated (1.98, 95% CI 1.04 to 3.79) in those employees working in jobs in the highest quartile of protease exposure (geometric mean 7.9 ng x m(-3)). For employees with upper respiratory disease, the risk was significantly elevated at a lower level of estimated protease exposure (geometric mean 2.3 ng x m(-3)).

CONCLUSIONS

These findings provide strong evidence of an association between detergent enzyme exposure and the development of respiratory disease in an occupational setting. Using the routinely collected information on specific sensitisation and the close attention to workplace exposures that are characteristic of this industry, it should be possible to derive meaningful occupational exposure standards for most detergent enzymes.

Occupational exposure to potential endocrine disruptors: further development of a job exposure matrix

OBJECTIVES

The aim was to develop a new up-to-date and comprehensive job exposure matrix (JEM) for estimating exposure to potential endocrine disruptors in epidemiological research.

METHODS

Chemicals with endocrine disrupting properties were identified from the literature and classified into 10 chemical groups: polycyclic aromatic hydrocarbons (PAHs), polychlorinated organic compounds, pesticides, phthalates, organic solvents, bisphenol A, alkylphenolic compounds, brominated flame retardants, metals and a miscellaneous group. Most chemical groups were divided into three to six subgroups. Focusing on the years 1996-2006, three experts scored the probability of exposure to each chemical group and subgroup for 353 job titles as "unlikely" (0), "possible" (1) or "probable" (2). Job titles with positive exposure probability scores were provided with exposure scenarios that described the reasoning behind the scores.

RESULTS

Exposure to any chemical group was unlikely for 238 job titles (67%), whereas 102 (29%) job titles were classified as possibly (17%) or probably (12%) exposed to one or several endocrine disruptors. The remaining 13 job titles provided too little information to classify exposure. PAHs, pesticides, phthalates, organic solvents, alkylphenolic compounds and metals were often linked to a job title in the JEM. The remaining chemical groups were found to involve very few occupations.

CONCLUSIONS

Despite some important limitations, this JEM could be a valuable tool for exposure assessment in studies on the health risks of endocrine disruptors, especially when task specific information is incorporated. The documented exposure scenarios are meant to facilitate further adjustments to the JEM to allow more widespread use.

Changes in air quality and second-hand smoke exposure in hospitality sector businesses after introduction of the English Smoke-free legislation

BACKGROUND

To monitor and disseminate the short-term effects of the English Smoke-free legislation on air quality and employee exposure in businesses of the hospitality industry.

METHODS

Indoor particle concentrations and salivary cotinine levels were measured in businesses in the hospitality sector and non-smoking employees one month before and after the implementation of the legislation. Results were immediately released to the media to announce the improvements in air quality and employee exposure to the wider public.

RESULTS

Measurements were collected in 49 businesses and from 75 non-smoking individuals. Indoor PM(2.5) concentrations decreased by 95% from 217 microg/m(3) at baseline to 11 microg/m(3) at follow-up (P < 0.001). Salivary cotinine in employees was reduced by 75%, from 3.6 ng/ml at baseline to 0.9 ng/ml at follow-up (P < 0.001). The findings were presented to the public through press releases and interviews and were cited in over 20 media articles.

CONCLUSION

The project demonstrates the positive effects of the English Smoke-free legislation on air quality and second-hand smoke exposure in the hospitality industry sector. We believe that quick and positive feedback to the public on the effects of smoking restrictions is essential when introducing public health legislation such as the Smoke-free legislation.

Dietary zinc intake and brain cancer in adults: a case–control study

Little is known about the aetiology of brain tumours. One putative factor suggested from animal models is a protective effect of dietary Zn. We tested the hypothesis that increased compared with low dietary Zn intake is protective against brain tumour development. We conducted a population-based case–control study in the UK, of adults aged 18–69 years, between 2001 and 2004 aiming to identify possible risk factors. Dietary information was collected from 637 cases diagnosed with a glioma or meningioma, and 876 controls. Data were obtained from a self-completed FFQ. Multivariate logistic regression analysis was conducted, adjusting for socio-demographic factors, season of questionnaire return, multivitamin supplementation and energy intake. Although a weak protective effect was observed for the third quartile of intake (normal compared with low intake) in the meningioma group, this was limited to the specific brain tumour subtype and quartile, and was not significant after also adjusting for intake of other elements. Overall there was no significant effect of Zn intake. No association or dose–response relationship was observed between increased compared with low Zn intake and risk of glioma or meningioma.

The LLP risk model: an individual risk prediction model for lung cancer

Using a model-based approach, we estimated the probability that an individual, with a specified combination of risk factors, would develop lung cancer within a 5-year period. Data from 579 lung cancer cases and 1157 age- and sex-matched population-based controls were available for this analysis. Significant risk factors were fitted into multivariate conditional logistic regression models. The final multivariate model was combined with age-standardised lung cancer incidence data to calculate absolute risk estimates. Combinations of lifestyle risk factors were modelled to create risk profiles. For example, a 77-year-old male non-smoker, with a family history of lung cancer (early onset) and occupational exposure to asbestos has an absolute risk of 3.17% (95% CI, 1.67-5.95). Choosing a 2.5% cutoff to trigger increased surveillance, gave a sensitivity of 0.62 and specificity of 0.70, while a 6.0% cutoff gave a sensitivity of 0.34 and specificity of 0.90. A 10-fold cross validation produced an AUC statistic of 0.70, indicating good discrimination.If independent validation studies confirm these results, the LLP risk models' application as the first stage in an early detection strategy is a logical evolution in patient care.

The incidence of occupational skin disease as reported to The Health and Occupation Reporting (THOR) network between 2002 and 2005

BACKGROUND

Estimated incidence rates for occupational skin disease in the U.K. are provided by voluntary surveillance schemes involving dermatologists and occupational physicians. These rates allow monitoring of occupational dermatoses, and intervention planning aimed at reducing workplace risks.

OBJECTIVES

To summarize occupational skin disease reported to The Health and Occupation Reporting (THOR) network (2002-2005), and to provide baseline information for comparison with future studies of occupational skin disease in the U.K. and beyond.

METHODS

Incidence rates for occupational dermatoses were calculated using THOR data as numerators, and Labour Force Survey data or information from the most recent U.K. survey on provision of occupational physician services as denominators.

RESULTS

In the U.K. (2002-2005) the average annual incidence rate of work-related skin disease reported to THOR by dermatologists was 91.3 [95% confidence interval (CI) 81.8-101.1] per million, and by occupational physicians was 316.6 (95% CI 251.8-381.3) per million. Most reports were of contact dermatitis: dermatologists 68.0 (95% CI 59.8-76.2) per million, occupational physicians 259.7 (95% CI 200.8-318.6) per million.

CONCLUSIONS

Information produced by THOR is an important source for calculating incidence rates of occupational skin disease. A range of reporting groups should also be used when building an overall picture of occupational skin disease incidence in the U.K.

History of allergic disease and risk of meningioma

Epidemiologic studies have consistently shown inverse associations of allergic disease with risk of glioma, but it is unclear whether this association also applies to meningioma. The authors conducted a pooled analysis of meningioma risk in relation to a history of allergic disease based on data from two population-based, case-control studies with 475 cases and 1,716 controls in the United Kingdom (2001-2004). Meningioma risk was significantly reduced in relation to self-reported, physician-diagnosed allergic disease (odds ratio = 0.76, 95% confidence interval (CI): 0.61, 0.96) but was nonsignificantly reduced for individual conditions: asthma (odds ratio = 0.85, 95% CI: 0.61, 1.18), hay fever (odds ratio = 0.81, 95% CI: 0.62, 1.06), and eczema (odds ratio = 0.72, 95% CI: 0.51, 1.02). Risk reductions were greatest for asthma (odds ratio = 0.43, 95% CI: 0.21, 0.89) and hay fever (odds ratio = 0.50, 95% CI: 0.25, 1.00) with an early age at onset (<10 years) and for eczema (odds ratio = 0.46, 95% CI: 0.21, 1.07) with an onset at ages 10-19 years; they were near unity for onset in adulthood. This study suggests an inverse association between a history of allergies and meningioma risk, but with smaller risk reductions than for glioma. The reasons for this association need clarification, as well as an etiologic explanation. Consideration also needs to be given to confounding or bias.

Assigning exposure to pesticides and solvents from self-reports collected by a computer assisted personal interview and expert assessment of job codes: the UK Adult Brain Tumour Study

OBJECTIVES

To compare assignment of occupational pesticide and solvent exposure using self-reported data collected by a computer assisted personal interview (CAPI) with exposure based on expert assessment of job codes. To discuss the advantages and disadvantages of using a CAPI to collect individual occupational exposure data.

METHODS

Between 2001 and 2004, 1495 participants were interviewed using a CAPI for a case-control study of adult brain tumours and acoustic neuromas. Two types of occupational data were collected: (1) a full history, including job title from which a job code was assigned from the Standard Occupational Classification; and (2) specific details on pesticide and solvent exposure reported by participants. Study members' experiences of using the CAPI were recorded and advantages and disadvantages summarised.

RESULTS

Of 7192 jobs recorded, the prevalence of self-reported exposure was 1.3% for pesticides and 11.5% for solvents. Comparing this with exposure expertly assessed from job titles showed 53.6% and 45.8% concordance for pesticides and solvents respectively. Advantages of the CAPI include no data entry stage, automatic input validation, and a reduction in interviewer bias. Disadvantages include an adverse effect on study implementation as a consequence of resources required for programming and difficulties encountered with data management prior to analysis.

CONCLUSIONS

Different methods of exposure assessment derive different exposure levels for pesticide and solvent exposure at work. Agreement between self-reported and expert assessment of exposure was greater for pesticides compared to solvents. The advantages of using a CAPI for the collection of complex data outweigh the disadvantages for interviewers and data quality but using such a method requires extra resources at the study outset.

Second-hand smoke levels in UK pubs and bars: do the English Public Health White Paper proposals go far enough?

BACKGROUND

The English Public Health White Paper proposes introducing smoke-free workplaces except in pubs and bars that do not prepare and serve food. The bar area will be non-smoking in exempted pubs.

OBJECTIVE

To explore the likely impact of these proposals in UK pubs and bars.

METHODS

A total of 59 pubs and bars within Greater Manchester in 2001 were chosen. Thirteen were mechanically ventilated, 12 were naturally ventilated and 34 had extractor fans; 23 provided non-smoking areas. We measured time-weighted average concentrations of respirable suspended particles (RSP), solanesol tobacco-specific particles and vapour-phase nicotine (VPN) over a 4-h sampling period on a Tuesday or Saturday night.

RESULTS

Second-hand smoke (SHS) levels in smoking areas were high (mean RSP 114.5 microg/m3, VPN 88.2 microg/m3, solanesol 101.7 microg/m3). There were only small (5-13 per cent) reductions in bar areas. Mean levels were lower in non-smoking areas: by 33 per cent for RSPs, 52 per cent for solanesol particles and 69 per cent for VPN. Compared with other settings (homes and other workplaces) with unrestricted smoking, mean SHS levels were high throughout all areas of the pubs regardless of ventilation strategy.

CONCLUSION

Partial measures, like those in the English Public Health White Paper, will leave bar staff in exempted pubs unprotected from the occupational hazard of SHS.

Risk of hypospadias in relation to maternal occupational exposure to potential endocrine disrupting chemicals

BACKGROUND

Reported rises in the prevalence of hypospadias and other abnormalities of the male reproductive system may be a result of exposure to endocrine disrupting chemicals.

AIMS

To analyse the relation between risk of hypospadias and maternal occupation, particularly with regard to exposure to potential endocrine disrupting chemicals (EDCs).

METHODS

Data (1980-96) from the National Congenital Anomaly System (NCAS) were used to analyse the proportion of all congenital anomaly cases (n = 35 962) which were notified with hypospadias (n = 3471) by occupational codes (348 individual job titles) and by categories of exposure to potential EDCs from a job exposure matrix.

RESULTS

Five individual occupations (of 348) showed nominally statistically significant excesses, none of which had possible or probable exposure to potential EDCs. Odds ratios for "possible" or "probable" compared to "unlikely" exposure to potential EDCs did not show statistically significant increases in any of the EDC categories after adjustment for social class of the mother and father, nor was there evidence of an upward trend in risk with likelihood of exposure. In the 1992-96 time period odds ratios were increased for hairdressers (the largest group exposed to potential EDCs) and for probable exposure to phthalates (of which hairdressers form the largest group) before social class adjustment.

CONCLUSIONS

There was little evidence for a relation between risk of hypospadias and maternal occupation or occupational exposure to potential EDCs, but as the exposure classification was necessarily crude, these findings should be interpreted with caution.

Occupational exposure to magnetic fields relative to mortality from brain tumours: updated and revised findings from a study of United Kingdom electricity generation and transmission workers, 1973-97

OBJECTIVE

To investigate whether risk of brain tumour is related to occupational exposure to magnetic fields.

METHODS

The mortality experienced by a cohort of 83 997 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973-97. All workers were employed for at least 6 months with some employment in the period 1973-82. Computerised work histories were available for 79 972 study subjects for the period 1971-93. Detailed calculations had been performed by others to enable a novel assessment to be made of exposures to magnetic fields. Two analytical approaches were used, indirect standardisation (n=83 997) and Poisson regression (n=79 972).

RESULTS

Based on serial mortalities for England and Wales, deaths from brain cancer were close to expectation (observed 158, expected 146.4). No significant positive trends were shown for risks of brain tumours either with lifetime cumulative exposure to magnetic fields or with such exposures received in the most recent 5 years.

CONCLUSIONS

There are no discernible excess risks of brain tumours as a consequence of occupational exposure to magnetic fields in United Kingdom electricity generation and transmission workers.

Respiratory health effects from exposure to carbon black: results of the phase 2 and 3 cross sectional studies in the European carbon black manufacturing industry

OBJECTIVES

To assess respiratory morbidity over several cross sectional phases in the European carbon black manufacturing industry.

METHODS

Participants completed an amended (and translated) MRC respiratory morbidity questionnaire with additional questions on previous exposures, job history, etc, and spirometry traces in each phase. Concurrent with the health outcome measures, personal exposure to inhalable dust was measured.

RESULTS

Percentage participation rose from 90% in phase 2 (19 factories) to 95% in phase 3 (16 factories). Exposure dropped slightly between the 2 and 3 phases; as did the prevalence of reporting symptoms. Percentage of predicted lung function volumes exceeded 100% for forced expired volume in 1 second (FEV(1)) and forced vital capacity (FVC), whereas forced mid-expiratory flow (FEF(25%-75%)) and FEV(1)/FVC ratio were below 100% in both phases. The multiple linear and logistic regressions showed that carbon black had a significant effect on lung function and on most respiratory symptoms, respectively.

CONCLUSION

Both current and cumulative exposure to carbon black have a deleterious effect on respiratory morbidity. Due to the drop in exposure between phases 2 and 3, recent exposures seem to have less of an impact on the respiratory morbidity in the workers in phase 3 than those in phase 2.

Leukaemia mortality in relation to magnetic field exposure: findings from a study of United Kingdom electricity generation and transmission workers, 1973-97

OBJECTIVE

To investigate whether risks of leukaemia are related to occupational exposure to magnetic fields.

METHODS

The mortality experienced by a cohort of 83 997 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973-97. All employees were employed for at least 6 months with some employment in the period 1973-82. Computerised work histories were available for 79 972 study subjects for the period 1971-93. Detailed calculations were performed by others to enable a novel assessment to be made of exposures to magnetic fields. Two analytical approaches were used, indirect standardisation (n=83 997) and Poisson regression (n=79 972).

RESULTS

Based on serial mortalities for England and Wales, the standardised mortality ratio of 84 for all leukaemias (observed 111, expected 132.3) was similar to that of 83 for all causes (observed 14 845, expected 17 918). No significant positive trends were found for the risks of various types of leukaemia (chronic lymphatic leukaemia, acute myeloid leukaemia, chronic myeloid leukaemia, all leukaemia) either with lifetime cumulative exposure to magnetic fields or with such exposures received in the most recent 5 years.

CONCLUSIONS

There are no discernible excess risks of leukaemia as a consequence of occupational exposure to magnetic fields in United Kingdom electricity generation and transmission workers.

A cohort mortality study of U.K. carbon black workers, 1951-1996

BACKGROUND

Carbon black, a powdered form of elemental carbon is used in the manufacture of rubber products, paints, plastics, and inks. In 1974, the Health and Safety Executive initiated a cohort mortality study on possible carcinogenic effects on carbon black workers.

METHODS

The mortality of a cohort of 1,147 male manual workers from five U.K. factories manufacturing carbon black was investigated for the period 1951-1996. All subjects were employed in the carbon black industry for 12 months or more, and all were first employed before 1975. Limited work histories were used to calculate estimates of individual cumulative exposure to carbon black, using a job-exposure matrix derived by the study team.

RESULTS

Based on serial rates for the general population of England and Wales, significantly elevated mortality was observed in the main study cohort for all causes (Obs 372, Exp 328.7, SMR 113, P < 0.05) and for lung cancer (Obs 61, Exp 35.3, SMR 173, P < 0.001). There were highly elevated lung cancer SMRs at two of the factories, and unexceptional SMRs at the remaining three factories. There was no indication of lung cancer SMRs increasing with period from first employment. Poisson regression analyses failed to find significant trends of lung cancer risks increasing either with cumulative exposure to carbon black (4 levels) or with duration of employment at the participating factories (4 levels).

CONCLUSIONS

Confident interpretation of the elevated SMRs found for lung cancer in two of the factory subcohorts is not possible but the study has been unable to link cumulative exposure to carbon black with elevated risks of lung cancer.

Efficiency of different grouping schemes for dust exposure in the European carbon black respiratory morbidity study

OBJECTIVES

The aim of this study was to assess the theoretical efficiencies of different grouping strategies and its effect on the exposure-response relation in a study of respiratory morbidity associated with exposure to total inhalable and respirable carbon black dust.

METHODS

A large epidemiological study is being undertaken to investigate the respiratory health of employees in the European carbon black manufacturing industry in relation to exposure to carbon black dust. In phase 2 of the study, repeated measurements of total inhalable and respirable dust were taken which enabled estimation of various components of variability in the exposure data (within and between worker variance and within and between group variance). These variance components were used to calculate the contrast in exposure between the groups in various classification schemes and to calculate the theoretical attenuation of the exposure-response relation and the standard error (SE) of the slope.

RESULTS

High contrast in exposure was found when workers were classified according to the combination of their factory and job category as well as when these combinations were amalgamated into five exposure groups. Attenuation was minimal with most grouping schemes; only with the individual based strategy was the attenuation large. The SE of the theoretically attenuated exposure-response slope was smallest for the strategy based on individual people followed by the classification scheme based on factory and job category.

CONCLUSIONS

It was concluded that, although some assumptions for the calculations of the attenuation of the exposure-response slope were not met, the most appropriate classification scheme of the worker seems to be by the combination of factory and job category.

Occupational exposure to magnetic fields in relation to mortality from brain cancer among electricity generation and transmission workers

OBJECTIVE

To investigate whether the risks of mortality from brain cancer are related to occupational exposure to magnetic fields.

METHODS

A total of 112 cases of primary brain cancer (1972-91) were identified from a cohort of 84,018 male and female employees of the (then) Central Electricity Generating Board and its privatised successor companies. Individual cumulative occupational exposures to magnetic fields were estimated by linking available computerised job history data with magnetic field measurements collected over 675 person-workshifts. Estimated exposure histories of the case workers were compared with those of 654 control workers drawn from the cohort (nested case-control study), by means of conditional logistic regression.

RESULTS

For exposure assessments based on arithmetic means, the risk of mortality from brain cancer for subjects with an estimated cumulative exposure to magnetic fields of 5.4-13.4 microT.y v subjects with lower exposures (0.0-5.3 microT.y) was 1.04 (95% confidence interval (95% CI) 0.60 to 1.80). The corresponding relative risk in subjects with higher exposures (> or = 13.5 microT.y) was 0.95 (95% CI 0.54 to 1.69). There was no indication of a positive trend for cumulative exposure and risk of mortality from brain cancer either when the analysis used exposure assessments based on geometric means or when the analysis was restricted to exposures received within five years of the case diagnosis (or corresponding period for controls).

CONCLUSIONS

Although the exposure categorisation was based solely on recent observations, the study findings do not support the hypothesis that the risk of brain cancer is associated with occupational exposure to magnetic fields.