Worker population, mortality studies

Death. Occupational mortality studies of pesticide workers exposed to heptachlor have not revealed an excess number of deaths in these cohorts compared to the general U.S. population. This may possibly be explained as a healthy worker effect. The ERA has described human case reports in which convulsions and death were reported following suicidal ingestion of technical-grade chlordane, which typically contains 6-30% heptachlor, but these effects cannot be attributed to heptachlor or heptachlor epoxide. There are no controlled, quantitative human data for any route of exposure. Acute lethality data were located for animals exposed via the oral and dermal routes. Both heptachlor and heptachlor epoxide may be considered very toxic via the oral route on the basis of acute animal data in rats and mice. Intermediate oral exposure to these compounds also caused up to 40% and 100% mortality in rats and mice, respectively. There appear to be differences in sensitivity in males and females in some species with the males being most sensitive. Heptachlor epoxide is more toxic than heptachlor. Heptachlor may be considered very toxic to extremely toxic via the dermal route on the basis of acute lethality data in rats and mice. The severity of acute effects may possibly depend upon the extent of formation of heptachlor epoxide and the species tested. 

In a retrospective mortality study of over 900 workers exposed from 3 months to 23 years to median time-weighted acetone concentrations up to 1070 ppm there was no significant risk of death from any cause (all causes, malignant neoplasm, circulatory system disease, ischemic heart disease) compared with rates for the general population. ... 

In humans, cases of hepatomas have appeared years after acute exposure to carbon tetrachloride, however, none of the cases could establish a causal link between the exposure and development of neoplasms." Epidemiological studies have also given inconclusive results. A cancer mortality study of a population of rubber workers reported a significantly elevated odds ratio relating carbon tetrachloride with lymphatic leukemia, and lymphosarcoma and reticulum cell carcinoma." A recent retrospective cohort mortality study of aircraft maintenance workers found an increased risk of... 

In a cohort mortality study design, the study population is chosen on the basis of exposure to a particular substance. The mortality rates in the exposed group are compared to mortality rates in an unexposed group. Often the unexposed comparison group is a standard population, such as the U.S. male population or an appropriate unexposed group such as unexposed workers in the same plant. 

Mortality Studies The mortality study is the usual initial approach towards assessment of health effects in a worker population. The reason for this is that any serious health hazard is likely to be reflected ultimately in excess mortality from a specific cause or group of causes. Another is that detailed information on causes of death in the general population is readily available. 

The investigative strategy for a mortality study involves i-dentification of all workers at a location who have been exposed to the product since start-up of the production of the product. Workers who have retired or left employment are traced with the assistance of the Social Security Administration to determine if they are living or deceased. Copies of death certificates are then obtained for all deceased individuals and the causes of death as listed on the death certificates are used to compute death rates. These death rates are then compared to rates in the national population to determine if there are more deaths attributable to a specific cause than one would expect in the national population. 

Leonard RC, Kreckmann KH, Sakr CJ, Symons JM (2008) Retrospective cohort mortality study of workers in a polymer production plant including a reftaence population of tegiraial workers. Ann Epidemiol 18 15-22... 

The mortality of Et4Pb-exposed workers has been studied by Robinson (1974). Among 592 workers 51 deaths occurred during a 20 yr period, and Robinson (1974) could not detect any excess mortality as compared to a controF group and data for the U.S.A. white male population in 1950. However, most of the workers (89.2% ) were under 40 yr of age at the beginning of the study. From these limited data it is, therefore, difficult to evaluate the mortality of Et4Pb-exposed workers. 

An increased mortality from cerebrovascular disease has been observed in a study on lead battery workers (Dingwall-Fordyce and Lane, 1963). An association between lead absorption and the development of hypertension has been claimed, initially in lead-exposed workers. In a US population-based study on adult males, lead was found to be significantly related to both systolic and diastolic blood pressure after controlling for a number of confounding variables (Schwartz, 1985). However, a British population-based study on men aged 40-59 found only a very weak association between PbB and either systolic or diastolic blood pressure. The investigators commented on the problem of adjusting adequately for all relevant confounders, and concluded that it is premature to consider that an elevated lead body burden has a causal influence on blood pressure (Pocock et al, 1985). 

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