Guidelines for medical screening in the workplace.

This chapter deals with general principles of conducting medical examinations to detect adverse health effects of workplace exposures and thereby prevent occupational disease or slow its progression. Much of the discussion is most relevant to screening for effects of chemical hazards, but many of the principles presented apply to physical and biological hazards as well. Procedural and administrative aspects of workplace medical examinations that are not "exposure specific" and are applicable to all medical programs are reviewed.

Environmental epidemiologic investigations in the styrene-butadiene rubber production industry.

A review of the literature and an update that is in progress of a previous retrospective cohort mortality study of the styrene-1,3-butadiene industry are discussed. The follow-up has now been extended from April 1, 1976, through December 31, 1981, for plant B and December 31, 1982, for plant A. The person-years at risk of death have gone from 34,187 to 43,341 in plant A and from 19,742 to 26,314 in plant B. Among the death certificates received to date, observed deaths have increased in both plants, with increases in cancers of the trachea, bronchus and lung and in lymphosarcomas, reticulosarcomas, and cancers of the overall lymphatic and hematopoietic system.

Quantitative risk assessment of lung cancer in U.S. uranium miners.

The National Institute for Occupational Safety and Health (NIOSH) has recently updated the vital status of the U.S. cohort of U miners through the end of 1982. This represents 69 additional lung cancer deaths since the last published follow-up through 1977. This more recent data was used to generate quantitative risk estimates of lung cancer after exposure to Rn daughters. Relative risks were estimated through use of the Cox proportional hazards model with an internal referent group. Results indicated that the exposure-response relationship was a slightly convex curve, predicting excess relative risks between 0.9 and 1.4 per 100 working level months (WLM) in the lower cumulative exposure range. Other findings of interest include a significant exposure-rate effect with low exposure rates more harmful per unit of cumulative exposure (WLM). Two temporal effects which modify relative risk estimates were also found. Relative risk increased with age at initial exposure to underground U mining. However, relative risk of lung cancer fell dramatically in the years following cessation of exposure.

Mortality patterns among styrene-exposed boatbuilders.

In order to test the hypothesis that leukemia and lymphoma may be associated with exposure to styrene, cause-of-death patterns were studied at two reinforced plastic boatbuilding facilities. There were 5,021 workers who met the criterion of having worked at the two plants between 1959 and 1978. Based on industrial hygiene surveys conducted at the two plants, 2,060 individuals were determined to have worked in departments classified as having high exposure to styrene. There were 176 deaths observed among the total cohort, in comparison to 195.3 deaths expected (standardized mortality ratio [SMR] = 90). Among the high styrene exposure group, 47 deaths were observed in comparison to 41.5 deaths expected (SMR = 113). No leukemia or lymphoma deaths were observed in either the high exposure group or the total cohort. An excess of accidental deaths among the high exposure group (18 observed vs 12.4 expected) did not appear to be due to styrene's acute central nervous system effects, since none of the individuals were employed at the facilities at the time of their death. However, the possibility of a chronic effect could not be dismissed. While leukemia and lymphoma did not appear to be related to styrene exposure, the study had little statistical power to detect excesses of these diseases, due to the short length of observation and the young age of most cohort members. It was concluded that the cohort should provide increasingly useful information on chronic styrene toxicity as the population ages and the observation period increases.

Ethylene oxide: an overview of toxicologic and epidemiologic research.

Ethylene oxide (EtO) is a reactive epoxide and potent biocide. It is used widely in gas sterilization of hospital equipment. An estimated 75,000 health care workers in the United States have potential exposure. EtO binds covalently to deoxyribonucleic acid (DNA) and has been shown in 13 species to cause point mutations. Apparently, as a consequence of its alkylating ability, EtO exposure can result in chromosomal damage. In monkeys EtO exposure produces increased frequencies of sister chromatid exchanges (SCEs) and chromosomal aberrations. In man, five cytogenetic studies have shown dose-related increased frequencies of either SCE or chromosomal aberrations; in one study SCEs developed after regular exposures lasting less than five minutes per day. EtO is a reproductive toxin. In adult male rats, exposure produces decreased fertility, increased fetal deaths, and heritable chromosomal translocations. In pregnant female rats and rabbits, exposure causes increased fetal losses, and in one study in pregnant mice exposure was associated with increased numbers of malformed fetuses. In male monkeys EtO causes dose-related reductions in sperm count and sperm motility. In pregnant women, one study suggests that brief occupational exposure twice daily in concentrations of 20 ppm or above was associated with increased spontaneous abortions. EtO is carcinogenic to animals. In rats it causes dose-related increases in mononuclear cell leukemias, peritoneal mesotheliomas, and cerebral gliomas. In man, exposure has been associated in two epidemiologic studies with increased leukemias: 3 leukemias observed versus 0.2 expected in one study, and 2 observed versus 0.14 expected in the other; two additional small studies of limited power found no excess leukemias. Quantitative risk assessment indicates that from 634 to 1,093 excess deaths from cancer will occur per 10,000 workers exposed to EtO at 50 ppm over a working lifetime, and that 12 to 23 excess cancer deaths will occur per 10,000 workers exposed at 1 ppm. The National Institute for Occupational Safety and Health (NIOSH) recommends that EtO be regarded as a potential human carcinogen. NIOSH has recommended that eight-hour time-weighted average exposure to EtO be less than 0.1 ppm and that short-term peak exposure not exceed 5 ppm for more than ten minutes per working day.

Environmental epidemiologic investigation of the styrene-butadiene rubber industry. Mortality patterns with discussion of the hematopoietic and lymphatic malignancies.

A retrospective cohort mortality study and an industrial hygiene assessment were undertaken in two styrene-butadiene rubber producing facilities in eastern Texas. Occupational history records were available from 1943 at plant A and from 1950 at plant B to the study cut-off date of 31 March 1976. With a two-sided test statistic, no statistically significant excesses in total or cause-specific mortality were observed for the overall worker population of either plant. However, the plant A study group demonstrated a nonsignificant statistical excess [standardized mortality ratio (SMR) of 203] for the cause-specific category of leukemia and aleukemia. Additional analyses were performed on a subgroup consisting of all white males with at least six months of employment at plant A between the beginning of 1943 and the end of 1945, a time which coincided with process and operational changes. An SMR of 278, also not statistically significant, was demonstrated for the leukemia and aleukemia cause-specific category. Due to the relative modest study population sizes, the power of this study to detect statistically significant excesses in leukemias or other malignancies of the hematopoietic and lymphatic tissues is not very large unless one is interested in substantial excesses, such as those that would correspond to a fourfold increase in risk.

Epidemiologic investigations of styrene-butadiene rubber production and reinforced plastics production.

The United States National Institute for Occupational Safety and Health (NIOSH) began an epidemiologic study of workers employed in the styrene-butadiene rubber (SBR) industry during 1976. This study was prompted by reports of relatively high numbers of leukemia deaths occurring within SBR production work populations. Simultaneous with the initiation of this investigation, the University of North Carolina released a report associating an excess risk of death due to hematopoietic and lymphatic malignancies among workers producing several synthetic rubbers, including SBR. This report presents NIOSH's preliminary mortality observations and a discussion of progress made on the analyses of contaminants found in two SBR production facilities. Currently, NIOSH is determining the feasibility of doing an epidemiologic study in the reinforced plastics industry. Interest in this study developed as part of an effort to determine health hazards associated with occupational exposure to styrene. Most of the technology for the reinforced plastics industry developed in the 1950s, and therefore this process represents a relatively new industry. This report also includes information on environmental conditions observed in the reinforced plastics industry and enumerates some of the complicating characteristics of this industry which increase the complexity of this study.