Joseph K. Wagoner

Lung cancer among uranium miners in the United States

AbstractExcess respiratory cancer has been demonstrated among all groups of uranium miners who have had more than 120 Working Level Months of radon daughter exposure. Lung cancer incidence rose with increasing exposure. Factors which might distort the exposure-response relationship were reviewed. Ex

Carcinogenic, mutagenic and teratogenic risks associated with vinyl chloride.

The data presented demonstrate clearly that vinyl chloride (VC) is related to a significant excess of mortality from cancer of the liver, lung and brain among workers occupationally exposed to VC. The risk of dying from cancer of the lymphatic and hematopoietic system also appears to increase with an increase in latency. These cancer sites could have been predicted by the animal bioassay conducted by Maltoni. With regard to the liver, even the histophthologic type of cancer (angiosarcoma) was observed first in experimental animals. A study of cancer mortality among populations residing proximate to VC polymerization facilities also demonstrated an increased risk of dying from CNS and lymphatic cancer. These latter findings raise cause for concern about out-plant emmissions of VC, but without further study these cancers obviously cannot be interpreted as being related to out-plant exposure to VC. Various test systems now have elicited a positive mutagenic response to VC. Thus, our observations of a significant excess of fetal mortality among the wives of males, who were occupationally exposed to VC, raise public health concern that VC may be mutagenic in humans. With regard to the teratogenicity of VC, observations of a significant excess of children born with birth defects were reported among populations residing proximate to VC polymerization facilities. Additional epidemiologic study is needed to determine whether a repeated pattern of excessive numbers of children born with birth defects can be observed in other communities with VC polymerization facilities.

MORTALITY PATTERNS AMONG FIBROUS GLASS PRODUCTION WORKERS

Both fibrous glass and asbestos are fibrous substances. As a result of the carcinogenic and fibrogenic effects of inhaled asbestos in humans, it was only natural that concern should be directed toward the evaluation of the pathogenicity of inhaled fibrous glass. Until recently, experimental studies using fibrous glass had produced conflicting results.’-9 This is not unexpected as many of these experimental studies suffered from one or more defects, such as insufficient lapse of time since onset of exposure, questionable mode of exposure (route of entry and size of fiber), inadequate sample sue, and lack of controls. Nevertheless, fibrogenicity and carcinogenicity of fibrous glass were demonstrated both by intrapleural and intraperitoneal experiments, and this pathogenicity was related more to the dimensions of the fiber than to its physicochemical propertie~.l~-*~ Only in recent years has sufficient time elapsed to make feasible studies among humans of the potential latent effects of occupational exposure to fibrous glass, since its industrial production and commercial use began about 1933 in the United States. Studies of employees in the fibrous glass industry by Wright,15 Gross er af.,lU Utidjian and deTreville,” Nasr et al.,lS and Hill et af.l@ indicated essentially negative results. All of these studies had a common limitation: they were cross-sectional prevalence studies of current employees only, with no reference to terminated or former employees, groups shown in many other industrial settings to manifest the majority of latent biological effects. In support of this premise are recent observations by Enterline and Henderson 2o of an increased risk of chronic bronchitis as a cause of retirement disability among fibrous glass production workers. With this limitation in mind and the potential carcinogenicity of fibrous glass posed by Stanton and Wrench l2 and Pott and Friedrichs,lo the National Institute for Occupational Safety and Health (NIOSH) undertook a three-part occupational health study of the fibrous glass manufacturing industry. The three parts were a retrospective cohort analysis of mortality patterns, industrial hygiene surveys, and a case-control study of respiratory disease.

MORTALITY PATTERNS AMONG HARD ROCK GOLD MINERS EXPOSED TO AN ASBESTIFORM MINERAL

The first suggestion that asbestos could be a carcinogen was made by Lynch and Smith in 1935,l as they had noticed an association between asbestosis and lung cancer. Since then, all forms of commercial asbestos have repeatedly been shown to be carcinogenic in man, and data from animal studies have corroborated these findings. In 1960 Wagner et al.* reported that pleural and peritoneal mesotheliomas occurred among asbestos miners occupationally exposed to crocidolite in certain areas of South Africa. From 1960 to 1973, studies of anthophyllite miners in Finland by Ki lv i l~oto ,~ M e u ~ m a n , ~ and Meurman et aL5 reported significantly increased proportional mortality from bronchogenic carcinoma. In 1972, Selikoff et ~ 1 . ~ demonstrated a sevenfold excess of lung cancer among insulation workers with 20 or more years since their first exposure to amosite asbestos. In 1973, Wagoner et aL7 reported results of a mortality study of asbestos workers occupationally exposed predominantly to chrysotile and demonstrated significant increases in lung cancer and asbestosis. In 1972, the National Institute for Occupational Safety and Health (NIOSH) recommended an occupational standard for asbestos exposure of 2.0 asbestos fibers greater than 5 pm in length per cubic centimeter of air, as an 8-hr time-weighted average daily concentration.R This standard was recommended with the recognition that it would “prevent asbestosis and more adequately guard against asbestos-induced neoplasms.” In developing this standard, NIOSH recognized the need for additional research due to “the lack of epidemiological studies or clinical reports with supporting environmental data in the exposure range that must be considered” and “the lack of definite information on the biologic response of fibers of different size.’’ Further need for research on possible adverse health effects of occupational and nonoccupational exposures to noncommercial asbestos fibers, and asbestos fibers shorter than 5 pm, was brought out at recent court hearings for a mining company in Minnesota and its disposal of taconite tailingsg Expert testimony

CYTOLOGIC OBSERVATIONS AND CANCER INCIDENCE FOLLOWING EXPOSURE TO BCME

The investigative cycle has now advanced full circle. The carcinogenecity of bis(chloromethyl)ether (BCME), initially discovered in laboratory-animal experiments, spurred occupational epidemiological sputum cytology and cancer-incidence studies which demonstrated the carcinogenicity of BCME in humans. In turn, these observations spurred laboratory investigations into the spontaneous formation of BCME. Subsequently, this spontaneous formation of BCME was demonstrated to occur in select industrial settings. These observations on the carcinogenicity of BCME, first in animals and subsequently in man, strongly support the need for animal testing prior to introduction of agents into the environment.