Ewan MacFarlane

Training and other predictors of personal protective equipment use in Australian grain farmers using pesticides

Objectives: To investigate patterns of use of personal protective equipment (PPE) to reduce pesticide exposure in a sample of Australian farmers and also to assess the influence of possible predictive factors. Methods: A cross-sectional survey of 1102 farmers recruited through the Victorian Farmers Federation (VFF) was conducted. A written questionnaire was filled out by participants at VFF meetings attended by a visiting research assistant. Participants answered questions about frequency of pesticide use and PPE items they usually used when doing two different pesticide-related tasks, mixing and application, of each of four classes of pesticides. They also answered questions about personal characteristics, farm characteristics, farming activities, career and health. Results: Nearly all surveyed farmers had ever used pesticides, and over 87% had used Herbicides or Animal Health Products in the previous 12 months. Non-use of PPE was frequently reported, with up to 10–40% of farmers routinely using no PPE at all when using pesticides. Across all pesticide classes, PPE use was higher for pesticide mixing than for application. In multivariate analyses PPE use appeared to be most strongly associated with younger age and farm chemical training. Conclusions: PPE use across all pesticide classes was poor, indicating the possibility of clinically significant pesticide exposure in many farmers. Given that PPE use was found to be associated with farm chemical training, the authors suggest that training is likely to be an important intervention for reducing farmers’ pesticide exposure. Poor uptake of farm chemical training by farmers and the aging farming workforce are causes for concern in the light of these findings.

Dermal exposure associated with occupational end use of pesticides and the role of protective measures.

Background Occupational end users of pesticides may experience bodily absorption of the pesticide products they use, risking possible health effects. The purpose of this paper is to provide a guide for researchers, practitioners, and policy makers working in the field of agricultural health or other areas where occupational end use of pesticides and exposure issues are of interest. Methods This paper characterizes the health effects of pesticide exposure, jobs associated with pesticide use, pesticide-related tasks, absorption of pesticides through the skin, and the use of personal protective equipment (PPE) for reducing exposure. Conclusions Although international and national efforts to reduce pesticide exposure through regulatory means should continue, it is difficult in the agricultural sector to implement engineering or system controls. It is clear that use of PPE does reduce dermal pesticide exposure but compliance among the majority of occupationally exposed pesticide end users appears to be poor. More research is needed on higher-order controls to reduce pesticide exposure and to understand the reasons for poor compliance with PPE and identify effective training methods.

Is farm-related job title an adequate surrogate for pesticide exposure in occupational cancer epidemiology?

Objectives: Accurate assessment of exposure is a key factor in occupational epidemiology but can be problematic, particularly where exposures of interest may be many decades removed from relevant health outcomes. Studies have traditionally relied on crude surrogates of exposure based on job title only, for instance farm-related job title as a surrogate for pesticide exposure. Methods: This analysis was based on data collected in Western Australia in 2000–2001. Using a multivariate regression model, we compared expert-assessed likelihood of pesticide exposure based on detailed, individual-specific questionnaire and job specific module interview information with reported farm-related job titles as a surrogate for pesticide exposure. Results: Most (68.8%) jobs with likely pesticide exposure were farm jobs, but 78.3% of farm jobs were assessed as having no likelihood of pesticide exposure. Likely pesticide exposure was more frequent among jobs on crop farms than on livestock farms. Likely pesticide exposure was also more frequent among jobs commenced in more recent decades and jobs of longer duration. Our results suggest that very little misclassification would have resulted from the inverse assumption that all non-farming jobs are not pesticide exposed since only a very small fraction of non-agricultural jobs were likely to have had pesticide exposure. Conclusions: Classification of all farm jobs as pesticide exposed is likely to substantially over-estimate the number of individuals exposed. Our results also suggest that researchers should pay special attention to farm type, length of service and historical period of employment when assessing the likelihood of pesticide exposure in farming jobs.

Mortality and cancer incidence in workers in two Australian prebake aluminium smelters

Background: Exposures in the aluminium production industry have been declining and this study aimed to investigate cancer and mortality in two Australian prebake aluminium smelters. Methods: The cohort included 4396 males who had worked in a prebake smelter for at least 3 months. They were matched against the National Death Index and the National Cancer Statistics Clearing House to obtain cause of death and type of cancer. Standardised Mortality Ratios (SMRs) and Standardised Incidence Ratios (SIRs) were calculated for the whole cohort, for production or maintenance work categories and for duration of employment categories. Results: The SMRs for all causes, circulatory, respiratory and injury deaths were at or below expected. Mesothelioma was the only significantly increased cause of death (SMR 3.52, 95% CI 1.47 to 8.46). Death from prostate cancer in production workers was elevated (SMR 2.39, 95% CI 1.29 to 4.44) and in those who had worked for more than 20 years in production or maintenance jobs (SMR 3.67, 95% CI 1.53 to 8.81). There were statistically significant excesses of incident stomach cancer, mesothelioma, and kidney cancer cases, while the SIR for melanoma was significantly reduced. There was no significant trend for duration of exposure for any type of incident cancer. Conclusions: This study found no overall excess of mortality or cancer, but incident mesothelioma and kidney cancer risks were elevated. The lack of excess risk for lung or bladder cancer or deaths from respiratory disease may be related to the different level and pattern of exposure between Søderberg and prebake smelters.

Cancer incidence, mortality, and blood lead levels among workers exposed to inorganic lead.

PURPOSE We aimed to measure mortality and cancer incidence in a cohort of lead-exposed workers by using blood lead levels to assess exposure. METHODS The cohort comprised male lead workers. Subjects were matched to cancer and death registries. Observed death and cancer incidence rates were compared with population rates to obtain standardized mortality ratios (SMR) and standardized incidence ratios (SIR). RESULTS There were 4114 male subjects with average follow-up time of 16.2 years, and 406 deaths were observed. There were significant results for overall death (SMR, 111; 95% confidence interval [95% CI], 101-123), digestive system deaths (SMR, 167; 95% CI, 110-250), and deaths from external causes (SMR, 135; 95% CI, 105-174). A total of 228 subjects had cancer, with an overall SIR of 83 (95% CI, 73-95); liver cancer SIR of 217 (95% CI, 103-454) and esophageal cancer SIR of 240 (95% CI, 129-447). The latter was seven-fold greater (SIR 755; 95% CI, 314-1813) among those with a blood lead level result above 30 μg/dL compared with population rates. No other increases in cancers were observed. CONCLUSIONS Overall mortality was elevated. Although incidence rates of overall cancer were low, further studies and analysis are required to investigate any biologically plausible associations between inorganic lead and liver or esophageal cancer.

All cause mortality and incidence of cancer in workers in bauxite mines and alumina refineries

Bauxite is a reddish clay that is refined to produce alumina, which is then reduced to aluminium. There have been studies examining the health of workers in aluminium smelters, but not workers in bauxite mining and alumina refining. A cohort of employees of 1 large aluminium company since 1983 was assembled (n = 6,485, 5,828 men). Deaths and incident cancers to 2002 were ascertained by linkage to national and state cancer and death registries. SIRs and SMRs were calculated compared to national rates standardizing for calendar year, sex and 5‐year age group. The mortality from all causes (SMR 0.68, 95% CI: 0.60–0.77), and from circulatory and respiratory diseases, all cancers combined and injury in the male cohort were lower than in the Australian male population and were similar across work groups and with duration of employment. The only significant increased mortality risk was from pleural mesothelioma. The incidence of all cancers combined was similar to the Australian rate. The cohort had a lower risk of incident lymphohaematopoietic cancer (SIR 0.50, 95% CI: 0.31–0.88) and a higher risk of melanoma (SIR 1.30, 95% CI: 1.00–1.69) although no dose‐responses were seen. There was also an increased risk of mesothelioma (SIR 3.49, 95% CI: 1.82–6.71), which was associated with exposures outside the aluminium industry. This study is the first to examine cancer and mortality amongst workers in bauxite mines and alumina refineries and found little evidence for increased cancer incidence or mortality in these workers.

Suicide in Australian pesticide-exposed workers

BACKGROUND Epidemiological research has observed that workers with exposure to anticholinesterase pesticides, and particularly those with a history of acute overexposure, may be at increased risk of depression. However, there is little published research about the risk of suicide in relation to pesticide exposure. AIMS To investigate risk of suicide in relation to metrics of pesticide exposure and type of work. METHODS A nested case-control study was performed within a retrospective cohort study of pesticide-exposed workers from various industries. Ninety male suicide deaths and 270 male controls were matched by age bands, state of residence and live status. Cholinesterase inhibition was determined using subject-specific biomonitoring records collected at the time of exposure. RESULTS Suicide risk was not significantly elevated in relation to exposure to any particular pesticide classes nor in relation to pesticide overexposure, confirmed by blood test. While the risk of suicide associated with a history of cholinesterase inhibition was raised, this was not significant (odds ratio = 1.90, 95% confidence interval = 0.73-4.93). CONCLUSIONS This study did not find an elevated suicide risk associated with use of any major class of pesticide and there was little evidence that overexposure was associated with increased risk of suicide. A non-significant association between overexposure to anticholinesterase pesticides may be consistent with previous research showing increased depression in workers with a history of cholinesterase inhibition and warrants further investigation.

Causes of death and incidence of cancer in a cohort of Australian pesticide-exposed workers.

PURPOSE To determine the rates of mortality and of cancer incidence in a cohort of pesticide-exposed Australian workers. METHODS The study cohort was assembled using records of former government occupational health surveillance programs. The cohort was then linked to the Australian national registries of cancer and mortality and analyzed in comparison with the general Australian population. RESULTS Consistent with a healthy worker effect, we found no overall excesses in mortality or incident cancer. Non-injury-related causes of death were less than expected; however, non-intentional poisoning and suicide mortality were significantly elevated. All types of suicide were elevated, and firearm suicide deaths were significantly in excess. The suicides by poisoning were predominantly associated with pesticides, although other published research suggests this pattern is more often associated with developing countries. CONCLUSIONS This study did not find evidence of a relationship between occupational pesticide exposure and cancer or non-injury-related mortality. However, accidental poisoning and intentional self-harm warrant further investigation.

Cancer incidence and mortality in a historical cohort of Australian pest control workers

Objectives: To determine the rates of mortality and incident cancer in a historical cohort of pest control operators. Methods: A retrospective cohort was assembled from former state government occupational health surveillance programmes. This cohort was linked to the Australian national registries of cancer and mortality and the results were compared with the general Australian population rates. Results: 125 deaths and 89 incident cancers were found during the periods of observation (mortality 1983–2004 and cancer 1983–2002). Overall cancer incidence and mortality rates were not found to be significantly different from the general population. Among the specific causes of death, suicide (standardised mortality ratio; SMR 1.78; 95% CI 1.12 to 2.83) and unintentional falls (SMR 4.57; 95% CI 1.72 to 12.19) were significantly in excess, although the latter was based on only 4 deaths. Melanoma was the only specific incident cancer found significantly in excess (standardised incidence ratio 1.56; 95% CI 1.03 to 2.37). Conclusions: Pest control workers have overall mortality and cancer rates similar to the general population. Excess rates of incident melanoma and intentional self-poisoning mortality are of concern and warrant further investigation. Follow-up of this cohort as its members age, will provide more insight into these possible associations.

Relationships between alumina and bauxite dust exposure and cancer, respiratory and circulatory disease.

Objectives: To examine the associations between alumina and bauxite dust exposure and cancer incidence and circulatory and respiratory disease mortality among bauxite miners and alumina refinery workers. Methods: This cohort of 5770 males has previously been linked to national mortality and national and state cancer incidence registries (1983–2002). In this paper, Poisson regression was used to undertake internal comparisons within the cohort based on subgroups of cumulative exposure to inhalable bauxite and alumina dust. Exposure was estimated using job histories and historical air monitoring data. Results: There was no association between ever bauxite exposure and any of the outcomes. There was a borderline significant association between ever alumina exposure and cerebrovascular disease mortality (10 deaths, RR 3.8, 95% CI 1.1 to 13). There was some evidence of an exposure–response relationship between cumulative bauxite exposure and non-malignant respiratory disease mortality (seven deaths, trend p value: 0.01) and between cumulative alumina exposure and cerebrovascular disease mortality (trend p value: 0.04). These associations were based on very few cases and for non-malignant respiratory disease the deaths represented a heterogeneous mixture of causes. There was no evidence of an excess risk for any cancer type with bauxite or alumina exposure. Conclusions: These preliminary findings, based on very few cases, suggest that cumulative inhalable bauxite exposure may be associated with an excess risk of death from non-malignant respiratory disease and that cumulative inhalable alumina dust exposure may be associated with an excess risk of death from cerebrovascular disease. Neither exposure appears to increase the risk of incident cancers.