Motor neuron disease risk and magnetic field exposures

BACKGROUND

Many studies have investigated magnetic field exposure and the risks of motor neuron disease (MND). Meta-analyses have found positive associations but a causal relationship has not been established.

AIMS

To investigate the risks of MND and occupational exposure to magnetic fields in a large UK cohort.

METHODS

Mortality of 37 986 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1987-2018. Employees were first employed in the period 1942-82 and were still in employment on the 1 November, 1987. Detailed calculations enabled estimates to be made of magnetic field exposures. Observed deaths were compared with expected numbers based on mortality rates for the general population of England and Wales and Poisson regression was used to calculate rate ratios (relative risks) for categories of lifetime, lagged (distant) and lugged (recent) magnetic field exposure.

RESULTS

Mortality from MND in the total cohort was similar to national rates (observed 69, expected 71.3, SMR 97, 95% CI 76-122). There were no statistically significant trends of risks increasing with lifetime, recent or distant magnetic field exposure, although positive associations were observed for some categories of recent exposure.

CONCLUSIONS

The study did not find that the cohort had elevated risks of MND as a consequence of occupational lifetime exposure to magnetic fields, although a possible role for recent exposures could usefully be investigated in other datasets.

Estimation of the global burden of mesothelioma deaths from incomplete national mortality data

Background

Mesothelioma is increasingly recognised as a global health issue and the assessment of its global burden is warranted.

Objectives

To descriptively analyse national mortality data and to use reported and estimated data to calculate the global burden of mesothelioma deaths.

Methods

For the study period of 1994 to 2014, we grouped 230 countries into 59 countries with quality mesothelioma mortality data suitable to be used for reference rates, 45 countries with poor quality data and 126 countries with no data, based on the availability of data in the WHO Mortality Database. To estimate global deaths, we extrapolated the gender-specific and age-specific mortality rates of the countries with quality data to all other countries.

Results

The global numbers and rates of mesothelioma deaths have increased over time. The 59 countries with quality data recorded 15 011 mesothelioma deaths per year over the 3 most recent years with available data (equivalent to 9.9 deaths per million per year). From these reference data, we extrapolated the global mesothelioma deaths to be 38 400 per year, based on extrapolations for asbestos use.

Conclusions

Although the validity of our extrapolation method depends on the adequate identification of quality mesothelioma data and appropriate adjustment for other variables, our estimates can be updated, refined and verified because they are based on commonly accessible data and are derived using a straightforward algorithm. Our estimates are within the range of previously reported values but higher than the most recently reported values.

Radiofrequency Exposure Amongst Employees of Mobile Network Operators and Broadcasters

Little is known about personal exposure to radiofrequency (RF) fields amongst employees in the telecommunications industry responsible for installing and maintaining transmitters. IARC classified RF exposure as a possible carcinogen, although evidence from occupational studies was judged to be inadequate. Hence, there is a need for improved evidence of any potentially adverse health effects amongst the workforce occupationally exposed to RF radiation. In this study, results are presented from an exposure survey using data from personal monitors used by employees in the broadcasting and telecommunication industries of the UK. These data were supplemented by spot measurements using broadband survey metres and information on daily work activities provided by employee questionnaires. The sets of real-time personal data were categorised by four types of site determined by the highest powered antenna present (high, medium or low power and ground-level sites). For measurements gathered at each type of site, the root mean square and a series of box plots were produced. Results from the daily activities diaries suggested that riggers working for radio and television broadcasters were exposed to much longer periods as compared to colleagues working for mobile operators. Combining the results from the measurements and daily activity diaries clearly demonstrate that exposures were highest for riggers working for broadcasting sites. This study demonstrates that it is feasible to carry out exposure surveys within these populations that will provide reliable estimates of exposure that can be used for epidemiological studies of occupational groups exposed to RF fields.

Visualising and Thinking and Interpreting. Response to the Burstyn and De Roos Comments on Sorahan, T. Multiple Myeloma and Glyphosate Use: A Re-Analysis of US Agricultural Health Study (AHS) Data. Int. J. Environ. Res. Public Health 2015, 12, 1548-1559

n/a.

Cancer mortality in cohorts of workers in the European rubber manufacturing industry first employed since 1975

BACKGROUND

Increased cancer risk has been reported among workers in the rubber manufacturing industry employed before the 1960s. It is unclear whether risk remains increased among workers hired subsequently. The present study focused on risk of cancer mortality for rubber workers first employed since 1975 in 64 factories.

PATIENTS AND METHODS

Anonymized data from cohorts of rubber workers employed for at least 1 year from Germany, Italy, Poland, Sweden, and the UK were pooled. Standardized mortality ratios (SMRs), based on country-specific death rates, were reported for bladder and lung cancer (primary outcomes of interest), for other selected cancer sites, and for cancer sites with a minimum of 10 deaths in men or women. Analyses stratified by type of industry, period, and duration of employment were carried out.

RESULTS

A total of 38 457 individuals (29 768 men; 8689 women) contributed to 949 370 person-years. No increased risk of bladder cancer was observed [SMR = 0.80, 95% confidence interval (CI) 0.46; 1.38]. The risk of lung cancer death was reduced (SMR = 0.81, 95% CI 0.70; 0.94). No statistically significant increased risk was observed for any other cause of death. A reduced risk was evident for total cancer mortality (SMR = 0.81, 95% CI 0.76; 0.87). Risks were lower for workers in the tyre industry compared with workers in the general rubber goods sector. Analysis by employment duration showed a negative trend with SMRs decreasing with increasing duration of employment. In an analysis of secondary end points, when stratified by type of industry and period of first employment, excess risks of myeloma and gastric cancer were observed each due, essentially, to results from one centre.

CONCLUSION

No consistent increased risk of cancer death was observed among rubber workers first employed since 1975, no overall analysis of the pooled cohort produced significantly increased risk. Continued surveillance of the present cohorts is required to confirm the absence of long-term risk.

Multiple myeloma and glyphosate use: a re-analysis of US Agricultural Health Study (AHS) data

A previous publication of 57,311 pesticide applicators enrolled in the US Agricultural Health Study (AHS) produced disparate findings in relation to multiple myeloma risks in the period 1993-2001 and ever-use of glyphosate (32 cases of multiple myeloma in the full dataset of 54,315 applicators without adjustment for other variables: rate ratio (RR) 1.1, 95% confidence interval (CI) 0.5 to 2.4; 22 cases of multiple myeloma in restricted dataset of 40,719 applicators with adjustment for other variables: RR 2.6, 95% CI 0.7 to 9.4). It seemed important to determine which result should be preferred. RRs for exposed and non-exposed subjects were calculated using Poisson regression; subjects with missing data were not excluded from the main analyses. Using the full dataset adjusted for age and gender the analysis produced a RR of 1.12 (95% CI 0.50 to 2.49) for ever-use of glyphosate. Additional adjustment for lifestyle factors and use of ten other pesticides had little effect (RR 1.24, 95% CI 0.52 to 2.94). There were no statistically significant trends for multiple myeloma risks in relation to reported cumulative days (or intensity weighted days) of glyphosate use. The doubling of risk reported previously arose from the use of an unrepresentative restricted dataset and analyses of the full dataset provides no convincing evidence in the AHS for a link between multiple myeloma risk and glyphosate use.

Magnetic fields and brain tumour risks in UK electricity supply workers

AIMS

To investigate whether brain tumour risks are related to occupational exposure to low-frequency magnetic fields.

METHODS

Brain tumour risks experienced by 73 051 employees of the former Central Electricity Generating Board of England and Wales were investigated for the period 1973-2010. All employees were hired in the period 1952-82 and were employed for at least 6 months with some employment in the period 1973-82. Detailed calculations had been performed by others to enable an assessment to be made of exposures to magnetic fields. Poisson regression was used to calculate relative risks (rate ratios) of developing a brain tumour (or glioma or meningioma) for categories of lifetime, distant (lagged) and recent (lugged) exposure.

RESULTS

Findings for glioma and for the generality of all brain tumours were unexceptional; risks were close to (or below) unity for all exposure categories and there was no suggestion of risks increasing with cumulative (or recent or distant) magnetic field exposures. There were no statistically significant dose-response effects shown for meningioma, but there was some evidence of elevated risks in the three highest exposure categories for exposures received >10 years ago.

CONCLUSIONS

This study found no evidence to support the hypothesis that exposure to magnetic fields is a risk factor for gliomas, and the findings are consistent with the hypotheses that both distant and recent magnetic field exposures are not causally related to gliomas. The limited positive findings for meningioma may be chance findings; national comparisons argue against a causal interpretation.

Lung cancer risk and solid fuel smoke exposure: a systematic review and meta-analysis

The aim of this systematic review was to quantify the impact of biomass fuel and coal use on lung cancer and to explore reasons for heterogeneity in the reported effect sizes. A systematic review of primary studies reporting the relationship between solid fuel use and lung cancer was carried out, based on pre-defined criteria. Studies that dealt with confounding factors were used in the meta-analysis. Fuel types, smoking, country, cancer cell type and sex were considered in sub-group analyses. Publication bias and heterogeneity were estimated. The pooled effect estimate for coal smoke as a lung carcinogen (OR 1.82, 95% CI 1.60-2.06) was greater than that from biomass smoke (OR 1.50, 95% CI 1.17-1.94). The risk of lung cancer from solid fuel use was greater in females (OR 1.81, 95% CI 1.54-2.12) compared to males (OR 1.16, 95% CI 0.79-1.69). The pooled effect estimates were 2.33 (95% CI 1.72-3.17) for adenocarcinoma, 3.58 (1.58-8.12) for squamous cell carcinoma and 1.57 (1.38-1.80) for tumours of unspecified cell type. These findings suggest that in-home burning of both coal and biomass is consistently associated with an increased risk of lung cancer.

Global mesothelioma deaths reported to the World Health Organization between 1994 and 2008

OBJECTIVE

To carry out a descriptive analysis of mesothelioma deaths reported worldwide between 1994 and 2008.

METHODS

We extracted data on mesothelioma deaths reported to the World Health Organization mortality database since 1994, when the disease was first recorded. We also sought information from other English-language sources. Crude and age-adjusted mortality rates were calculated and mortality trends were assessed from the annual percentage change in the age-adjusted mortality rate.

FINDINGS

In total, 92,253 mesothelioma deaths were reported by 83 countries. Crude and age-adjusted mortality rates were 6.2 and 4.9 per million population, respectively. The age-adjusted mortality rate increased by 5.37% per year and consequently more than doubled during the study period. The mean age at death was 70 years and the male-to-female ratio was 3.6:1. The disease distribution by anatomical site was: pleura, 41.3%; peritoneum, 4.5%; pericardium, 0.3%; and unspecified sites, 43.1%. The geographical distribution of deaths was skewed towards high-income countries: the United States of America reported the highest number, while over 50% of all deaths occurred in Europe. In contrast, less than 12% occurred in middle- and low-income countries. The overall trend in the age-adjusted mortality rate was increasing in Europe and Japan but decreasing in the United States.

CONCLUSION

The number of mesothelioma deaths reported and the number of countries reporting deaths increased during the study period, probably due to better disease recognition and an increase in incidence. The different time trends observed between countries may be an early indication that the disease burden is slowly shifting towards those that have used asbestos more recently.

Global magnitude of reported and unreported mesothelioma

BACKGROUND

Little is known about the global magnitude of mesothelioma. In particular, many developing countries, including some with extensive historical use of asbestos, do not report mesothelioma.

OBJECTIVES

We estimated the global magnitude of mesothelioma accounting for reported and unreported cases.

METHODS

For all countries with available data on mesothelioma frequency and asbestos use (n=56), we calculated the 15-year cumulative number of mesotheliomas during 1994-2008 from data available for fewer years and assessed its relationship with levels of cumulative asbestos use during 1920-1970. We used this relationship to predict the number of unreported mesotheliomas in countries for which no information on mesothelioma is available but which have recorded asbestos use (n=33).

RESULTS

Within the group of 56 countries with data on mesothelioma occurrence and asbestos use, the 15-year cumulative number of mesothelioma was approximately 174,300. There was a statistically significant positive linear relation between the log-transformed national cumulative mesothelioma numbers and the log-transformed cumulative asbestos use (adjusted R(2)=0.83, p<0.0001). Extrapolated to the group of 33 countries without reported mesothelioma, a total of approximately 38,900 (95% confidence interval, 36,700-41,100) mesothelioma cases were estimated to have occurred in the 15-year period (1994-2008).

CONCLUSIONS

We estimate conservatively that, globally, one mesothelioma case has been overlooked for every four to five reported cases. Because our estimation is based on asbestos use until 1970, the many countries that increased asbestos use since then should anticipate a higher disease burden in the immediate decades ahead.

Research recommendations for selected IARC-classified agents

OBJECTIVES

There are some common occupational agents and exposure circumstances for which evidence of carcinogenicity is substantial but not yet conclusive for humans. Our objectives were to identify research gaps and needs for 20 agents prioritized for review based on evidence of widespread human exposures and potential carcinogenicity in animals or humans.

DATA SOURCES

For each chemical agent (or category of agents), a systematic review was conducted of new data published since the most recent pertinent International Agency for Research on Cancer (IARC) Monograph meeting on that agent.

DATA EXTRACTION

Reviewers were charged with identifying data gaps and general and specific approaches to address them, focusing on research that would be important in resolving classification uncertainties. An expert meeting brought reviewers together to discuss each agent and the identified data gaps and approaches.

DATA SYNTHESIS

Several overarching issues were identified that pertained to multiple agents; these included the importance of recognizing that carcinogenic agents can act through multiple toxicity pathways and mechanisms, including epigenetic mechanisms, oxidative stress, and immuno- and hormonal modulation.

CONCLUSIONS

Studies in occupational populations provide important opportunities to understand the mechanisms through which exogenous agents cause cancer and intervene to prevent human exposure and/or prevent or detect cancer among those already exposed. Scientific developments are likely to increase the challenges and complexities of carcinogen testing and evaluation in the future, and epidemiologic studies will be particularly critical to inform carcinogen classification and risk assessment processes.

Cancer risk among Japanese chromium platers, 1976-2003

OBJECTIVE

The aim of our prospective cohort study was to assess cancer mortality risks among chromium platers.

METHODS

The cohort comprised 1193 male platers (626 with exposure to chromium, the remainder with no exposure) with a follow-up period of 27 years (1 October 1976 to 31 December 2003). Mortality risk was assessed by the standardized mortality rate (SMR) with reference to the national population.

RESULTS

Lung cancer mortality was elevated only in the chromium plater subgroup, with borderline statistical significance [SMR=1.46, observations (Obs)=28, 95% confidence interval (95% CI) 0.98-2.04]. The chromium plater subgroup also showed elevated mortality risks for brain tumor (SMR=9.14, Obs=3, 95% CI 1.81-22.09) and malignant lymphoma (SMR=2.84, Obs=6, 95% CI 1.05-5.51). Risks were particularly elevated for lung cancer (SMR=1.59, Obs=23, 95% CI 1.01-2.38) and malignant lymphoma (SMR=3.80, Obs=6, 95% CI 1.39-8.29) among those with initial chromium exposure prior to 1970.

CONCLUSIONS

In Japan, occupational exposure to chromium through work as a chromium plater is a risk factor for lung cancer, especially for platers working prior to 1970. Occupational chromium exposure may also increase the risk of brain tumor and malignant lymphoma.

Lung cancer mortality in arsenic-exposed workers from a cadmium recovery plant

BACKGROUND

There is evidence that arsenic is a late-stage human lung carcinogen.

AIMS

To investigate lung cancer risks in a cohort of cadmium recovery workers in relation to period from ceasing exposure to arsenic.

METHODS

The mortality experience (1940-2001) of a cohort of 625 male workers from a US cadmium recovery plant was compared with expectations based on US national mortality rates.

RESULTS

There was a statistically significant (P < 0.05) negative trend in lung cancer standardized mortality ratios in relation to period from ceasing arsenic exposure.

CONCLUSIONS

The findings are consistent with the hypothesis that arsenic is a late-stage human carcinogen.

Cancer risks in chemical production workers exposed to 2-mercaptobenzothiazole

OBJECTIVES

To investigate cancer risks in chemical production workers exposed to 2-mercaptobenzothiazole (MBT).

METHODS

The mortality (1955-2005) and cancer morbidity experience (1971-2005) of a cohort of 363 male production workers exposed to MBT while employed at a chemical factory in north Wales were investigated. Two analytical approaches were used, indirect standardisation and Poisson regression.

RESULTS

Based on national mortality rates, significant excess mortality was found for cancers of the large intestine (observed; Obs 8, standardised mortality ratio (SMR) 232, 95% CI 100 to 457) and bladder (Obs 8, SMR 374, 95% CI 162 to 737). Non-significant excesses were shown for lung cancer (Obs 27, SMR 138, 95% CI 91 to 201) and multiple myeloma (Obs 3, SMR 440, 95% CI 91 to 1287). Based on national cancer incidence rates, significant excess morbidity was found for cancer of the bladder (Obs 12, standardised registration ratio (SRR) 253, 95% CI 131 to 441) and multiple myeloma (Obs 4, SRR 465, 95% CI 127 to 1191). Non-significant excesses were shown for cancers of the large intestine (Obs 9, SRR 181, 95% CI 83 to 344) and lung (Obs 26, SRR 152, 95% CI 99 to 223). In analyses that included follow-up information on an additional 1797 plant employees not exposed to MBT, Poisson regression showed significant positive trends both for risks of cancer of the large intestine and for risks of multiple myeloma in relation to estimated cumulative exposure to MBT.

CONCLUSIONS

MBT may be a human carcinogen; confident evaluation awaits findings from other studies.

Urinary concentrations of toxic substances: an assessment of alternative approaches to adjusting for specific gravity

Alternative approaches of adjusting urinary concentration of cadmium for differences in specific gravity of biological samples were assessed. The main analysis used 2922 cadmium-in-urine samples collected in the period 1968-1989 from workers at a UK nickel-cadmium battery facility. Geometric means of cadmium-in-urine, adjusted and unadjusted for specific gravity, were obtained for 21 different values of specific gravity ranging from 1.010 to 1.030. There was a highly significant positive trend (P < 0.001) of unadjusted cadmium-in-urine with specific gravity. Conventional adjustment for specific gravity led to a highly significant negative trend (P < 0.001) of adjusted cadmium-in-urine with specific gravity, SG. An approach proposed by Vij and Howell, involving the introduction of a z coefficient, led to satisfactory adjustment. Conventional adjustment of specific gravity leads to overcompensation of the confounding effects of specific gravity. An alternative method is available and should probably be adopted when interpreting urine biological samples for all chemical substances.

Bladder cancer risks in workers manufacturing chemicals for the rubber industry

AIM

To investigate bladder cancer risks in workers from a factory manufacturing chemicals for the rubber industry.

METHODS

The mortality (1955-2005) and cancer morbidity experience (1971-2005) of a cohort of 2160 male production workers from a chemical factory in north Wales were investigated. Exposure estimates (or surrogates) were developed for four chemicals: 2-mercaptobenzothiazole (MBT), aniline, phenyl-beta-naphthylamine (PBN) and ortho-toluidine. Two analytical approaches were used, indirect standardization and Poisson regression.

RESULTS

Based on mortality rates for the general population, there was a statistically significant (P < 0.01) excess mortality from bladder cancer in the 611 study subjects potentially exposed to one or more of the four chemicals being investigated (observed 11, standardized mortality ratio 278, 95% confidence interval 139-497). There was no excess bladder cancer mortality in the remaining 1555 workers. A similar contrast was also shown for bladder cancer incidence. There were 56 study subjects who had suffered from bladder cancer (malignant or benign). In simultaneous analyses of the four exposure history variables, Poisson regression showed a significant positive trend for bladder cancer risk in relation to cumulative duration of employment in the ortho-toluidine department (P < 0.05) and non-significant positive trends in relation to cumulative duration of employment in the PBN department and to cumulative exposure to MBT.

CONCLUSIONS

Some members of this cohort have suffered from occupational bladder cancer. Exposure to ortho-toluidine appears to be responsible for part of this excess and the manufacture of PBN and exposure to MBT may also have been involved.

A "lugged" analysis of lung cancer risks in UK carbon black production workers, 1951-2004

BACKGROUND

Previously published analyses of excess lung cancer risks in UK carbon black production workers attracted no confident interpretation.

METHODS

The mortality of a cohort of 1,147 male manual workers from five UK factories manufacturing carbon black was investigated for the period 1951-2004. All subjects were first employed in the period 1947-74 and were employed for 12 months or more. Limited work histories were available to calculate estimates of individual cumulative exposure to carbon black.

RESULTS

Based on serial rates for the general population of England and Wales, significantly elevated mortality was observed for lung cancer (Obs 67, SMR 146, P < 0.01) but not for all other causes combined (Obs 426, SMR 106). There was highly elevated lung cancer mortality at two of the plants (SMR 230, Obs 35) but no excess mortality at the other three plants combined (SMR 104, Obs 32). Analyses by period since leaving employment indicated elevated lung cancer risks were limited to those workers with some employment in the most recent 15 years. SMR analyses found an overall positive significant trend between lung cancer risks and cumulative carbon black exposure received in the most recent 15 years. Poisson regression analyses provided different results depending on which variables were adjusted for.

CONCLUSIONS

The findings suggest that carbon black, or chemicals associated with the production of carbon black, had an effect on later stages of lung cancer carcinogenesis at two of the plants but that no such effect was found at the other plants.

Mortality from Alzheimer's, motor neuron and Parkinson's disease in relation to magnetic field exposure: findings from the study of UK electricity generation and transmission workers, 1973-2004

BACKGROUND

There are a number of reports linking magnetic field exposure to increased risks of Alzheimer's disease and motor neuron disease.

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 1973-2004. All employees were employed for at least six months with some employment in the period 1973-82. Computerised work histories were available for 79 972 study subjects for the period 1971-93. Information on job and facility (location) were used to estimate exposures to magnetic fields. Two analytical approaches were used to evaluate risks, indirect standardisation (n = 83 997) and Poisson regression (n = 79 972).

RESULTS

Based on serial mortality rates for England and Wales, deaths from Alzheimer's disease and motor neuron disease were unexceptional. There was an excess of deaths from Parkinson's disease of borderline significance. No statistically significant trends were shown for risks of any of these diseases to increase with lifetime cumulative exposure to magnetic fields (RR per 10 μT-y: Alzheimer's disease 1.10 (95% CI 0.90 to 1.33); motor neuron disease 1.06 (95% CI 0.86 to 1.32); Parkinson's disease 0.88 (95% CI 0.74 to 1.05))

CONCLUSIONS

There is no convincing evidence that UK electricity generation and transmission workers have suffered increased risks from neurodegenerative diseases as a consequence of exposure to magnetic fields.

Mortality of UK oil refinery and petroleum distribution workers, 1951-2003

BACKGROUND

The health of UK petroleum industry workers has been monitored for many years.

AIM

To identify any long-term adverse health outcomes from occupational exposures in this industry.

METHODS

The mortality (1951-2003) and cancer morbidity (1971-2003) experienced by cohorts of 28,555 oil refinery workers and 16,477 petroleum distribution workers has been investigated. Study subjects were all those males first employed in the period 1946-74 at one of eight UK oil refineries or 476 UK petroleum distribution centres; all subjects had a minimum of 12 months employment with some employment after 1 January 1951. Observed numbers of cause-specific deaths and site-specific cancer registrations were compared with expectations based on national mortality and cancer incidence rates.

RESULTS

Standardized mortality ratios (SMRs) were significantly <100 for all causes both in oil refinery workers (Obs 11,156, SMR 89) and in petroleum distribution workers (Obs 7320, SMR 96). Significantly elevated SMRs were shown in oil refinery workers for cancer of the pleura (mesothelioma) (Obs 64, SMR 261) and melanoma (Obs 48, SMR 168). Significantly elevated SMRs were not found in petroleum distribution workers for any site of cancer. Significantly elevated standardized registration ratios (SRRs) were only shown in oil refinery workers and for cancer of the pleura (mesothelioma) (Obs 115, SMR 274), melanoma (Obs 85, SMR 129) and other skin cancer (Obs 983, SRR 117).

CONCLUSIONS

The only findings that showed clear evidence of an occupational cancer hazard were those for mesothelioma in oil refinery workers.

A cohort mortality and cancer incidence survey of recent entrants (1982-91) to the UK rubber industry: findings for 1983-2004

AIM

To monitor the occurrence of cancer in a recently defined cohort of UK rubber workers.

METHODS

A cohort of 8651 male and female workers from 41 UK rubber factories has been enumerated. All employees had a minimum of 12 months employment and were first employed at one of the participating factories in the period 1982-91. Mortality and cancer incidence data for the period 1983-2004 were compared with expected values based on appropriate national rates.

RESULTS

Mortality from lung cancer was close to expectation for males [observed 22, standardized mortality ratio (SMR) 93] and females (observed 2, SMR 70). Mortality from stomach cancer was also unexceptional in males (observed 4, SMR 86) and females (observed 0, SMR 0). Although based on small numbers, significantly elevated mortality was shown for multiple myeloma in males (observed 5, SMR 385) and females (observed 2, SMR 952). All seven of these latter deaths occurred in workers from the general rubber goods (GRG) sector.

CONCLUSIONS

The findings should be treated with caution as they relate to a relatively early period of follow-up. Nevertheless, they hold out the prospect that the elevated SMRs for stomach and lung cancers reported for historical cohorts of UK rubber workers will not be present in more recent cohorts. The elevated occurrence of multiple myeloma may represent no more than a chance finding. Alternatively, these findings may reflect the presence of an unrecognized occupational cancer hazard in parts of the GRG sector of the UK rubber industry.

Cancer incidence and cancer mortality in a cohort of UK semiconductor workers, 1970-2002

OBJECTIVE

To examine cancer risks in a cohort of workers employed in the manufacture of semiconductors.

METHODS

The mortality (1970-2002) and cancer morbidity (1971-2001) experienced by a cohort of 1807 male and female workforce employees from a semiconductor factory in the West Midlands (UK) have been investigated. Standardized mortality ratios (SMRs) and standardized registration ratios (SRRs) were used to assess mortality and morbidity, respectively.

RESULTS

Overall mortality was close to expectation in males [SMR 99, 95% (confidence interval) CI 79-122] and significantly below expectation in females (SMR 74, 95% CI 65-85). Incidence of all sites of cancer was somewhat elevated in males (SRR 130, 95% CI 95-173) but close to expectation in females (SRR 94, 95% CI 82-109). There were significant deficits of deaths from cancer of the oesophagus in males and females combined and from cancer of the breast in females. Significantly elevated SRRs were found in males for cancer of the rectum [Observed (Obs) 6, SRR 284, 95% CI 104-619], in females for cancer of the pancreas (Obs 10, SRR 226, 95% CI 108-415) and malignant melanoma (Obs 11, SRR 221, 95% CI 110-396) and in males and females combined for cancer of the rectum (Obs 19, SRR 199, 95% CI 120-310) and malignant melanoma (Obs 12, SRR 217, 95% CI 112-379). Detailed work history data were unavailable for analysis. The finding of excess morbidity was not mirrored in the corresponding mortality findings.

CONCLUSIONS

The study found elevated morbidity for a number of cancer sites that may be unconnected with occupation. Elimination of all possible occupational causes will, however, require more detailed analyses of cancer risks in relation to exposure histories.

Mortality of UK electricity generation and transmission workers, 1973–2002

OBJECTIVE

To examine mortality from cancer and non-malignant causes among a large cohort of UK electricity generation and transmission workers.

METHODS

The mortality experienced by a cohort of 83,923 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973-2002. All employees had worked for at least 6 months with some employment between 1973 and 1982. Standardized mortality ratios (SMRs) were used to assess mortality in the total cohort and in three sub-cohorts: power station workers, substation and transmission workers and workers at non-operational locations. These classifications were based on the place of work of the first known job.

RESULTS

Overall mortality was significantly below that expected, based on national rates [males: observed (Obs) 18,773, expected (Exp) 22,497.9, SMR 83; females: Obs 1122, Exp 1424.9, SMR 79]. Statistically significant deficits of deaths were also found for most of the major disease groupings. However, significant excesses of deaths were found in male power station workers for cancer of the pleura (Obs 129, Exp 30.3, SMR 426) and in male workers from non-operational locations for cancer of the brain (Obs 55, Exp 36.0, SMR 153). There was also a non-significant excess of deaths from cancer of the breast in male power station workers (Obs 10, Exp 5.3, SMR 190).

CONCLUSIONS

Mortality was exceptionally low for most causes of death but late health effects from earlier asbestos exposure were still in evidence.

A Database of Exposures in the Rubber Manufacturing Industry: Design and Quality Control

The concerted action EXASRUB was initiated to create a database management system for information on occupational hygiene measurements that could be used to develop exposure models in the European rubber manufacturing industry. Quality of coding was assessed by calculating percentages of agreement and Cohen's kappa statistics (kappa) for an intra- and inter-centre recoding of randomly selected subsets of the measurements. In a 6-month period, 59 609 measurements from 523 surveys in 333 factories from as early as 1956 to 2003 were coded. The database consists primarily of measurements of N-nitrosamines (36%), rubber dust (23%), solvents (14%) and rubber fumes (10%). Coding of epidemiologically relevant information was done consistently with inter-centre kappa between 0.86 and 1.00. For occupational hygiene information, values of kappa were estimated to be between 0.67 and 1.00. The proposed method resulted in a large quantity of exposure measurements with auxiliary information of varying completeness and quality. Analyses showed that coding of epidemiologically relevant information in such a multi-centre, multi-country study was coded consistently. Larger errors however, occurred in coding of occupational hygiene information. This was primarily caused by lack of information in the primary records of measurements, emphasizing the importance of having a universal system in place to collect and store measurement information by occupational hygienists for future use.

Cancer risks in a historical UK cohort of benzene exposed workers

AIMS

To examine mortality from different causes and cancer incidence among a cohort of benzene workers in England and Wales.

METHODS

A cohort of 5514 workers who had been occupationally exposed to benzene in 1966/67 or earlier was assembled by the former Factory Inspectorate and the Medical Research Council from details provided by 233 employers in England and Wales. The cohort was followed up for mortality (1968-2002) and cancer registrations (1971-2001). National mortality rates and cancer registration (incidence) rates were used to calculate standardised mortality ratios and standardised registration ratios.

RESULTS

Mortality was close to expectation for all causes and significantly increased for cancer of the lip, cancer of the lung and bronchus, secondary and unspecified cancers, acute non-lymphocytic leukaemia (ANLL), and all neoplasms. Significant deficits were shown for three non-malignant categories (mental disorders, diseases of the digestive system, accidents). SMRs for other leukaemia, lymphomas, and multiple myeloma were close to or below expectation. There was some evidence of under-ascertainment of cancer registrations, although significantly increased SRRs were shown for lung cancer and cancer of the pleura (mesothelioma).

CONCLUSIONS

Many study subjects would have been exposed to carcinogens other than benzene (for example, asbestos, rubber industry fumes, foundry fumes, polycyclic aromatic hydrocarbons), and the excesses of lung cancer and mesothelioma are likely to reflect exposures to these other carcinogens. The carcinogenic effects of benzene exposure on the lymphohaematopoietic system were limited to ANLL.

Mortality of workers at a nickel carbonyl refinery, 1958-2000

BACKGROUND

Excess risks of respiratory cancer have been shown in some groups of nickel exposed workers. It is clear, however, that not all forms of nickel exposure are implicated in these excess risks.

AIM

To determine whether occupational exposures received in a modern nickel carbonyl refinery lead to increased risks of cancer, in particular nasal cancer and lung cancer.

METHODS

The mortality experienced by a cohort of 812 workers employed at a nickel refinery was investigated. Study subjects were all male workforce employees first employed in the period 1953-92 who had at least five years' employment with the company. Observed numbers of cause specific deaths were compared with expectations based on national mortality rates; SMRs were also calculated by period from commencing employment, year of commencing employment, and type of work.

RESULTS

Overall, standardised mortality ratios (SMRs) were close to 100 for all causes (Obs 191, SMR 96, 95% CI 83 to 111), all neoplasms (Obs 63, SMR 104, 95% CI 80 to 133), non-malignant diseases of the respiratory system (Obs 18, SMR 97, 95% CI 57 to 153), and diseases of the circulatory system (Obs 85, SMR 94, 95% CI 75 to 116). There were no significantly increased SMRs for any site of cancer. There was a non-significant excess for lung cancer (Obs 28, Exp 20.17, SMR 139, 95% CI 92 to 201), and in subgroup analyses a significantly increased SMR of 231 (Obs 9) was found for those 142 workers with at least five years' employment in the feed handling and nickel extraction departments. In the total cohort there was a single death from nasal cancer (Exp 0.10).

CONCLUSIONS

The non-significant excess of lung cancer deaths may well be a chance finding, but in light of previous studies some role for nickel exposures cannot be excluded.

Mortality of workers at a plant manufacturing nickel alloys, 1958-2000

BACKGROUND

Excess risks of respiratory cancer have been demonstrated in some groups of nickel-exposed workers. It is clear, however, that not all forms of nickel exposure are implicated in these excess risks. Aim To determine whether occupational exposures received in the manufacture of nickel alloys lead to increased risks of cancer, in particular nasal cancer and lung cancer.

METHODS

The mortality experienced by a cohort of 1999 workers employed at a plant manufacturing nickel alloys has been investigated. Study subjects were all those male workforce employees first employed in the period 1953-1992 who had at least 5 years employment with the company. Observed numbers of cause-specific deaths were compared with expectations based on national mortality rates. Standardized mortality ratios (SMRs) were calculated by period from commencing employment and by operating area of first job. In addition, rate ratios derived from Poisson regression and based on an internal standard were calculated by levels of duration of employment.

RESULTS

SMRs were significantly below 100 for all causes (observed 557, expected 704.3, SMR 79), all neoplasms (observed 169, expected 209.4, SMR 81) non-malignant diseases of the respiratory system (observed 50, expected 73.0, SMR 69) and diseases of the circulatory system (observed 261, expected 335.5, SMR 78). Significantly elevated SMRs were not shown for any cause of death and mortality was below expectation for stomach cancer (observed 8, expected 16.0, SMR 50), lung cancer (observed 64, expected 73.6, SMR 87) and bladder cancer (observed 3, expected 8.0, SMR 38). There were no deaths from nasal cancer (expected 0.33). More detailed findings were unexceptional.

CONCLUSIONS

The analyses did not suggest the presence of an occupational cancer hazard in the mortality experience of the cohort.

Parental cigarette smoking and childhood risks of hepatoblastoma: OSCC data

Reported cigarette smoking habits for the parents of 43 UK children who died with hepatoblastoma (1953-55 deaths, 1971-81 deaths) have been compared with corresponding information for the parents of 5777 healthy control children by means of unconditional logistic regression. Hepatoblastoma risks were doubled if both parents smoked relative to neither parent smoking (RR 2.28, 95% CI 1.02-5.09).

Lung cancer mortality in UK nickel-cadmium battery workers, 1947-2000

AIMS

To investigate mortality from lung cancer in nickel-cadmium battery workers in relation to cumulative exposure to cadmium hydroxide.

METHODS

The mortality of a cohort of 926 male workers from a factory engaged in the manufacture of nickel-cadmium batteries in the West Midlands of England was investigated for the period 1947-2000. All subjects were first employed at the plant in the period 1947-75 and employed for a minimum period of 12 months. Work histories were available for the period 1947-86; the factory closed down in 1992. Two analytical approaches were used, indirect standardisation and Poisson regression.

RESULTS

Based on serial mortality rates for the general population of England and Wales, significantly increased mortality was shown for cancers of the pharynx (observed (Obs) 4, expected (Exp) 0.7, standardised mortality ratio (SMR) 559, p<0.05), non-malignant diseases of the respiratory system (Obs 61, Exp 43.0, SMR 142, p<0.05), and non-malignant diseases of the genitourinary system (Obs 10, Exp 4.1, SMR 243, p<0.05). Non-significantly increased SMRs were shown for lung cancer (Obs 45, Exp 40.7, SMR 111) and cancer of the prostate (Obs 9, Exp 7.5, SMR 116). Estimated cumulative cadmium exposures were not related to risks of lung cancer or risks of chronic obstructive pulmonary diseases, even when exposure histories were lagged first by 10, then by 20 years.

CONCLUSIONS

The study findings do not support the hypotheses that cadmium compounds are human lung carcinogens.

Mortality from cardiovascular disease in relation to magnetic field exposure: findings from a study of UK electricity generation and transmission workers, 1973-1997

BACKGROUND

Experimental and epidemiological studies have indicated that magnetic field exposure might influence heart rate variability and consequent risks of arrhythmia related deaths.

METHODS

The mortality experience of a cohort of 83,997 employees of the former Central Electricity Generating Board (CEGB) of England and Wales was investigated for the period 1973-1997. Cohort members were employed for at least 6 months from 1973 to 1982. Computerized work histories were available for 79,972 study subjects for the period 1971-1993. 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 standardization (n = 83,997) and Poisson regression (n = 79,972).

RESULTS

Based on serial mortality rates for England and Wales, deaths from four categories of cardiovascular disease were below expectation: arrhythmia-related disease (ICD-9 426-7), observed (obs) 32, expected (exp) 43.5, standardized mortality ratio (SMR) 74; acute myocardial infarction (ICD-9 410), obs 3,320, exp 3878.3, SMR 86; atherosclerosis (ICD-9 440), obs 25, exp 39.2, SMR 64; chronic/sub-acute coronary disease (ICD-9 411-414), obs 1,552, exp 2021.7, SMR 77). No statistically significant trends were shown for risks of any of these four disease groupings to increase 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 mortality from cardiovascular diseases as a consequence of occupational exposure to magnetic fields in UK electricity generation and transmission workers.

Cancer in the offspring of radiation workers: an investigation of employment timing and a reanalysis using updated dose information

An earlier case–control study found no evidence of paternal preconceptional irradiation (PPI) as a cause of childhood leukaemia and non-Hodgkin's lymphoma (LNHL). Although fathers of children with LNHL were more likely to have been radiation workers, the risk was most marked in those with doses below the level of detection. The timing of paternal employment as a radiation worker has now been examined. The previously reported elevated risk of LNHL in the children of male radiation workers was limited to those whose fathers were still radiation workers at conception or whose employment also continued until diagnosis. Children whose fathers stopped radiation work prior to their conception were found to have no excess risk of LNHL. It was not possible to distinguish between the risks associated with paternal radiation work at conception and at the time of diagnosis. A reanalysis of the original study hypothesis incorporating updated dosimetric information gave similar results to those obtained previously. In particular, the risks of LNHL did not show an association with radiation doses received by the father before conception. It seems likely that the increased risk of LNHL among the children of male radiation workers is associated with an increased exposure to some infective agent consequent on high levels of population mixing.

Breastfeeding and childhood cancer risks: OSCC data

Matched pair analysis relating to 3376 mothers of children who died of cancer 1972-1981 and of healthy control children from the Oxford Survey of Childhood Cancers showed no evidence of protection from breastfeeding for acute lymphocytic leukaemia (OR 1.04, 95% CI 0.86-1.26), for all cancers combined (OR 1.04, 95% CI 0.93-1.15) or for other groupings. Analyses by duration of breastfeeding also failed to support the protective hypothesis.