William J. Nicholson

MORTALITY EXPERIENCE OF A COHORT OF VINYL CHLORIDE-POLYVINYL CHLORIDE WORKERS*

These data are derived from early follow-up of individuals exposed for 5 or more years to vinyl chloride in a polymerization facility. At least 17 percent of the deaths that occurred were causally related to exposure to vinyl chloride. Longer periods of observation are required to provide information concerning the full spectrum of vinyl chloride-induced malignancies and their incidence among exposed workers. These data speak for the need to prevent exposure to vinyl chloride and for surveillance and early disease detection of those who have experienced vinyl chloride exposures in the past.

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.

Application of sprayed inorganic fiber containing asbestos: occupational health hazards.

Over 40,000 tons of inorganic fibrous insulation containing asbestos were used in 1970 by the construction industry as a fireproofing material in the erection of multistoried buildings. The application of this material by a spraying technique produces serious contamination of the working environment. Asbestos fiber concentrations may range from 30u2009f/cc to more than 100u2009f/cc. Some early observations of the exposures and health of the workmen in this comparatively new occupation are given with photographs of the working areas. Nearby workers may be indirectly exposed. Such concentrations were found to be 70u2009f/cc ten feet from the spraying and 46u2009f/cc seventy-five feet away. Control measures are discussed.

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.

BRAIN TUMORS AMONG OPERATING ENGINEERS IN THE CHEMICAL AND PETROCHEMICAL INDUSTRY IN TEXAS AND LOUISIANA

A variety of epidemiological studies have indicated a higher incidence of cancer among individuals employed in the chemical and petrochemical industries. ’-’ These include reports of increased malignancy rates among chemists’ and excess cancer mortality among workers employed in the rubber ind~s t ry , ’ ,~ the dye or vinyl chloride polyrner izat i~n.~-~ More recently, the refining industry has come under suspicion with an analysis of 3105 deaths of members of the Oil, Chemical and Atomic Workers International Union suggesting excess cancer of the brain, stomach, lung, leukemia, and multiple A study of cancer rates by county has shown those counties with petroleum or petrochemical industries to have higher rates than demographically similar areas for cancers of the lung, nasal cavity and sinuses, and skin including melanoma.’ Brain cancer, in particular, has been cited as a risk among petrochemical workers with the finding of 18 primary malignancies among employees at one Texas petrochemical plant from 1965 through March 1980.“ The preliminary estimates suggested that the excess risk was twice that expected among white males of the area in which the plant was located. While an excess brain tumor mortality appeared to be present, no common chemical exposures or work assignments were identified among the cases. In particular, although vinyl chloride was produced at the plant in question, an examination of the work histories of the 18 cases did not provide a significant positive correlation with exposure to the monomer. In order to obtain further information on the possible extent of the risk of brain malignancy from exposure to chemical agents, we have conducted a proportionate mortality analysis of the deaths of 590 members of the International Union of Operating Engineers from locals whose membership is predominantly from the chemical and petrochemical industries. At the same time, we have also analyzed 742 deaths of members of the same union in the same geographic area, but who were employed as construction or maintenance workers. This comparison population will assist us in identifying biases that may arise from the use of proportionate mortality analysis. For example, proportionate mortality analyses of groups that are primarily composed of employed individuals typically show increased risks of cancer relative to other causes. This is a manifestation of different time courses of a “healthy worker effect” for cancer and for other diseases.

ASBESTOS CONTAMINATION IN UNITED STATES SCHOOLS FROM USE OF ASBESTOS SURFACING MATERIALS

Until recently there was only limited awareness of the extent of asbestos use in public school buildings. Reports existed of damaged asbestos surfaces in a grade school in Wyoming,’ a university dormitory in California,’ and in the Yale School of Arts and Architecture in New Haven, C o n n ~ t i c u t . ~ In each case, public concern led to the removal of the asbestos material. In both the Wyoming school and the Yale Library, air measurements by optical microscopy showed asbestos concentrations that in some circumstances exceeded 5 f/ml, the time-weighted-average occupational standard in effect a t the time. In the fall of 1976, flaking of sprayed-on asbestos was reported in a school in Howell Township, New Jersey, leading to its removal and to further concern about the presence of deteriorating asbestos in other school buildings in New Jersey. As a consequence, the New Jersey Department of Education requested that the school administrators report the presence and condition of asbestos surfaces in all school buildings within the state. Responses revealed that 265 (of approximately 2400) schools in all 142 districts in the State had nearly three million square feet of what they considered to be asbestos material in classrooms, auditoriums, hallways and other rooms accessible to pupils.

Cancer following occupational exposure to asbestos and vinyl chloride.

A review is presented of the various factors important in the identification of carcinogenic disease from occupational and environmental exposure to asbestos and vinyl chloride. The long lapsed period, usually of 20 or more years from first exposure to these materials, is discussed, as well as the requirement for sufficiently long observation periods in prospective epidemiological studies. The multiple‐factor etiology of lung cancer involving cigarette smoking and asbestos exposure is illustrated. The risks of asbestos‐related cancers to other than those directly working with the material are discussed in a variety of circumstances, and finally the effectiveness of control procedures for vinyl chloride and asbestos are compared.

Distribution of blood lead, blood cadmium, urinary cadmium, and urinary arsenic levels in employees of a copper smelter

A cross-sectional medical examination of a copper smelter work force included determination of blood lead (Pb-B), zinc protoporphyrin (ZPP), blood cadmium (Cd-B), urinary cadmium (Cd-U), and urinary arsenic (As-U), since it was known that such metal impurities were present in the copper concentrate. A total of 776 copper smelter employees (680 active and 96 retirees and ex-employees) were examined. Another 144 men, never employed in the smelter, but who had worked in copper mines (and sometimes in gold mines) were also examined. Mean Pb-B, ZPP, Cd-B, and As-U were significantly higher in active copper smelter employees than in retirees or miners, indicating exposure and absorption in the copper smelter. Significant correlations between Pb-B and Cd-B, and Cd-U and As-U were present, confirming the common source of absorption. Although there was evidence for an increased lead absorption, this was very moderate, with practically no Pb-B levels in excess of 60 micrograms/dl. A marked effect of smoking on blood cadmium levels was present; nevertheless, for all smoking categories Cd-B levels were significantly higher in active employees, indicating the independent contribution of exposure to cadmium in the smelter. Cd-U did not exceed 10 micrograms/g creatinine, the generally accepted critical level for the kidney, but was higher than 2 micrograms/g creatinine, a level very rarely exceeded in the general population, in a sizable proportion of those examined. The highest Cd-U levels were found in retired copper smelter employees; age might have been a contributing factor, besides a longer duration of exposure in the smelter.

Comparative lead emissions from conventional and jacketed ammunition

Because of the adverse health effects associated with excessive exposure to lead in firing ranges, attempts have been made to develop ammunition which could prevent such undesirable exposure. This study provides evidence that it is possible to reduce lead exposure significantly at the source of emission with the use of copper and nylon jacketed bullets.