Ruth Lilis

HOUSEHOLD‐CONTACT ASBESTOS NEOPLASTIC RISK*

The occupational risk associated with asbestos exposure has been well documented. Asbestosis-parenchymal fibrosis (described in the ILO/UC Pneumoconiosis Classification as irregular opacities), pleural fibrosis, and pleural calcification-has afflicted many occupational groups exposed to these mineral fibers. Although optimistic forecasts had predicted a decline in the incidence of asbestos-induced disease, recent experience proves that the risk is still present, involving large numbers of workers in various trades. Epidemiologic studies have shown that such asbestos-exposed individuals have a significantly increased risk of death due to malignant (mesothelioma, lung, and gastrointestinal cancers) and nonmalignant (asbestosis) diseases. Asbestos pollution from industrial sources was not anticipated to pose any significant health hazard to the general public. However, Wagner’s work in South Africa and Newhouse’s studies in the United Kingdom suggested that the risk had already spread beyond the factory, mine, or mill gate. In 1960, Wagner et a1.l reported mesothelioma in nonoccupationally asbestos-exposed individuals. In 1964, Newhouse et al.’ reported nine cases of mesothelioma in family contacts of asbestos workers and eleven cases among individuals whose only identified asbestos exposure was associated with living within one-half mile of an asbestos factory. These initial case reports were not isolated occurrences, peculiar to only one or two regions (TABLE 1) . Additional reports from nine countries have brought the total number of reported cases of household mesothelioma to 37.1-lG Thus, household asbestos contact has been established as being potentially hazardous. Such case reports did not assess the actual incidence or extent of risk to household members or the general public. nor did they give any suggestion of the prevalence of asbestos-associated radiologic changes in such populations. We have investigated the problem in order to determine whether the potential for such disease hazard is common or rare, since such evaluation would assist in assessing measures needed for clinical surveillance and for preventive control measures.

Disposition of polychlorinated biphenyl congeners in occupationally exposed persons

Abstract Relative concentrations of 37 polychlorinated biphenyl (PCB) congeners and the adipose-plasma partition of 28 PCB congeners were investigated in 26 persons occupationally exposed to various PCBs (20 to 54% chlorine). Concentrations of PCBs in adipose and plasma were related to duration and intensity of exposure in the workplace. PCB concentration in adipose tissue was proportional to that in plasma, with a partition for total PCBs of approximately 190:1 indicated from regression analysis. PCB congeners with chlorines in both 4-positions of the biphenyl ring were the major components in plasma and adipose tissue. Congeners with unsubstituted 3,4-positions (e.g., 2,5-chlorine substitution) on at least one of the biphenyl rings were observed at lower concentrations and had lower adipose-plasma partition than other congeners. In contrast, those compounds with substituents at the 2,4- and/or 3,4-positions on both rings were present in much higher proportions in blood or adipose than in the PCB mixtures in use. These components also had higher adipose-plasma partition than those with unsubstituted 3,4-positions, regardless of the degree of chlorination. PCBs with 2,4-substitution patterns on both rings, including 2,4,4′-tri- and 2,4,5,4′-tetra-CBs, had somewhat higher adipose-plasma partition than congeners with 3,4-substitution on at least one of the biphenyl rings (e.g., 2,4,3′,4′-tetra-CB).

Prevalence of lead disease among secondary lead smelter workers and biological indicators of lead exposure

The report concerns itself primarily with the assessment of medical and biochemical effects of chronic lead exposure and comparing the usefulness of various biological screening parameters. In addition it appraises the effects of chelation therapy to control blood lead levels in lead workers, which have recently attracted critical attention. It is of considerable importance to ascertain whether such a therapeutic approach may, under some circumstances, in fact contribute to the deleterious effects of undue lead exposure.

ASBESTOSIS AMONG HOUSEHOLD CONTACTS OF ASBESTOS FACTORY WORKERS

Equally ubiquitous in the environment as industrial chemical wastes’ are inorganic microparticles such as asbestos. The environmental burden of asbestos pollution is a recent phenomenon which has grown with the rapid expansion of asbestos-utilizing industries.* The health consequences of poorly controlled occupational exposures to chemicals and dusts now found in the general environment have been known in many instances for well over 100 years.’ Reports of overt disease (usually seen only with occupational exposure) among nonoccupationally exposed individuals have frequently been considered medical curiosities when they appeared in the medical literature. However, the full extent of the health risks due to nonoccupational exposure to toxic agents is not known, for it is uncommon to inquire into the neighborhood residence history or occupation and exposures of a patient’s household contacts when investigating symptoms of a disease. The effects of such exposures may be mild or subclinical manifestations which are only contributory to a current health problem and their role goes unrecognized. In 1976, we reported on a systematic investigation of one such non-occupational exposure to asbestos dusts4 The group studied consisted of household contacts of workers in an asbestos factory manufacturing amosite asbestos insulation materials between 1941 and 1954. None of those reported had personal occupational exposure to asbestos. Yet 35% had asbestos-associated radiographic abnormalities. A source of home contamination in individual exposure was postulated as resulting from dust adhering to shoes, hair, and workclothes brought home for laundering. Changerooms and company laundered coveralls were not available a t this plant. We reported the identification of four pleural mesotheliomas among the family contacts of the 1,664 workers who were employed at some time by the factory. Since that time one additional pleural mesotherlioma death has occurred, raising the total mesothelioma deaths to date among the group under observation to five. This report extends the continuing clinical investigation of this cohort.

Behavioral indicators of lead neurotoxicity: Results of a clinical field survey

SummaryCentral nervous system dysfunction in workers occupationally exposed to lead was investigated by means of performance tests. The test scores of lead-exposed workers were compared with those of control groups (steel workers, papermill workers and farmers). It was found that secondary lead smelter workers showed significantly poorer performance scores than the nonexposed, control groups. The group differences between steel workers and lead workers in test scores were not attributable to differences in age or education. In the lead-exposed workers correlations between test scores and indicators of lead absorption (particularly blood lead and zinc protophyrin levels) were analyzed. Increases in zinc protoporphyrin levels were found to be highly correlated with decreases in test scores. Lower performance test scores were consistent with a sizeable prevalence of central nervous system symptoms among secondary lead smelter workers. Moreover, lead workers without central nervous system symptoms also showed decrements in performance test scores which were also correlated with elevated zinc protoporphyrin levels. The data indicate that certain behavioral tests might be important tools for studying subclinical central nervous system dysfunction due to lead toxicity; significant correlations between zinc protoporphyrin levels and behavioral test scores are considered to be consistent with an etiologic relationship between decrement in performance scores and lead effects on the central nervous system.

Body burden of polychlorinated biphenyls among persons employed in capacitor manufacturing

SummaryIn an effort to assess exposure among workers engaged in capitor manufacture, PCB concentration was determined in plasma (290) and adipose tissue (61). In general, males had higher concentrations of PCBs than females.The correlation of plasma concentration (1–546 ppb) of the more highly chlorinated PCBs, which had been used in the past, with total duration of employment suggested accumulation over time. The gc-ec pattern of these PCB peaks was, in most cases, characteristic of exposure to a PCB mixture with 54% chlorine.The less highly chlorinated PCBs, di-, tri-, and tetrachlorobiphenyls, were the source of current exposure, and were observed in concentrations of 6–2530 ppb in plasma. Higher exposure occurred among persons with direct contact with PCBs, in jobs such as capacitor filling.Adipose tissue concentrations, for both the more highly chlorinated PCBs (1–165 ppm) and lower chlorinated PCBs (0.6-414 ppm), were proportional to those in plasma.

Neurotoxicity of styrene in production and polymerization workers.

Abstract Four-hundred ninety four workers exposed to styrene in a monomer manufacturing and polymerization plant were examined. Prenarcotic symptoms had been experienced by 13% of all examined workers and were significantly more frequent in those with higher styrene exposure. Distal hypoesthesia of the lower extremities was observed in 8.5% of the cases. Radial nerve conduction velocity (RNCV) was found to be less than 55 m/second in 18.8% tested cases. Peroneal nerve conduction velocity (PNCV) was less than 40 m/second in 16.4% of the tested workers. A consistent decrement of PNCV with duration of styrene exposure was found: no such trend was detected for RNCV.

Neurobehavioral changes among shipyard painters exposed to solvents

Painters in three shipyards, exposed to a wide variety of solvents, were examined. A short battery of performance tests, a detailed occupational history, and a special questionnaire to assess acute (prenarcotic, transitory) and chronic (persistent) neurologic symptoms was administered. The results of the neurobehavioral performance tests demonstrated decrements in central nervous system function in painters when compared with a control group matched for age, sex, race, and education. The prevalence of reported acute neurological symptoms among painters was increased significantly compared to other occupational groups in the same yards; for chronic, persistent symptoms the difference was not statistically significant. Performance test scores were significantly, negatively correlated with chronic symptoms but not with acute symptoms. No significant correlations between performance test scores and duration of solvent exposure or between symptoms and duration of solvent exposure were observed. The reversibility of such symptoms and of decrements in central nervous system function after cessation of exposure is still uncertain.

LONG‐TERM MORTALITY EXPERIENCE OF CHRYSOTILE MINERS AND MILLERS IN THETFORD MINES, QUEBEC

Among a cohort of 544 men with at least 20 years of employment in chrysotile mining and milling at Thetford Mines, Canada, 16% of the deaths were from lung cancer and 15% from asbestosis. The excess over expected deaths from these causes account for 43 of 178 deaths in the group. The risk of death of asbestosis, at equal times fron onset of exposure, is very similar in miners and millers, factory workmen and insulators. The ratio of observed to expected deaths from lung cancer is similar in the miners and millers and factory workers, but higher in insulators. The risk of death of mesothelioma in miners and millers is decidedly less than the other two groups. The exact causes of the reduced risk in this category are not yet completely clarified.

Long term radiological effects of short term exposure to amosite asbestos among factory workers.

Chest radiographs were read from a sub-cohort of 386 factory workers with short term exposure to amosite asbestos (median exposure six months) and long follow up (median 25 years). Prevalence of abnormality was determined independently by two readers from the first film available after 20 years from first employment. Serial films were obtainable for 238 men (median interval from first to last film: nine years). Progression was classified with a direct progression scoring scale. Individual dust exposure estimates were derived from dust counts from two similar plants. With as little as one month or less of employment, about 20% of the films showed parenchymal abnormality and about a third showed pleural abnormality. Those in the lowest cumulative exposure stratum (less than 5 fibre-years/ml) were similarly found to have high rates of abnormality. Dose-response relations were present in the data of both readers. Smokers had higher rates of parenchymal abnormality. On multivariate analysis, cumulative exposure was the exposure variable most closely related to parenchymal abnormality, and time from first employment was the variable most closely related to pleural abnormality. Progression (including first attacks) 20 or more years after ceasing employment occurred and was more common for pleural than for parenchymal abnormality. It is concluded that with exposure to high concentrations to amosite such as existed in this factory and with follow up for at least 20 years, (1) exposure for as little as a month was sufficient to produce radiological signs of parenchymal and pleural fibrosis, (2) no cumulative exposure threshold for parenchymal and pleural fibrosis was detectable, and (3) parenchymal and pleural progression were still detectable >/= 20 years after the end of exposure.