Biomedical subjects
Publications and source records attributed to D F Goldsmith.
When cancer is possibly related to occupation, the family physician's task is to put the matter in perspective by educating the patient and carefully documenting the appearance of the tumor and the patient's work history. Occasionally, physicians are the first to recognize new associations between chemicals and cancer and can help to bring hazards under control.
Silica is not generally considered to be a carcinogen, however, occupations characterized by high exposure to crystalline silica have excessive rates of lung cancer mortality. Respiratory cancer excesses have been reported from North America and from Europe for the following dusty trades in which exposure to silica is a common factor: iron and steel foundry workers, steel casting workers, sand blasters, metal molders, non-uranium miners, and ceramic workers. These findings have been reinforced by two reports from the Swedish Pneumoconiosis Register and the Ontario Ministry of Labor indicating that silicotics have statistically significant risks of lung cancer mortality. Animal studies suggest that silica can be an initiating carcinogen or can act as a cocarcinogen or promoter when combined with benzo(a)pyrene. We propose three candidate hypotheses and two pathways for silicocarcinogenesis.
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A matched case-control study was conducted to test the hypothesis that prostate cancer is associated with employment in the compounding area of a rubber and tire manufacturing plant. A search of death certificates from the years 1964 to 1975 led to the identification of 88 cases of prostate cancer. These were individually matched with 258 controls on the factors of age, race, and date of entry into the plant. To eliminate possible confounding by sociodemographic differences, several variables were assessed but none differed significantly between cases and controls. The batch preparation work area showed statistically significant (p < 0.025) risk ratios over three exposure periods -- more than one month, more than 24 months, and more than 60 months. The service to batch preparation and shipping and receiving work areas showed significant risks for blacks. The data were used to assess a latent period or etilogic fraction for prostate cancer for those employed in batch preparation. Twenty-nine years was estimated to be the latent period while the period of greatest risk occurred during the years 1940 to 1947.
Recent activities of the World Health Organization and other international agencies have placed new emphasis on occupational health in developing nations. Venezuela is a nation in transition from a developing society dominated economically by petroleum and agriculture to an economically-diversified industrialized urban society. It provides a case study which illuminates the problems of extending occupational health services in developing economies and questions of public policy regarding utilization of medical resources and the priority that occupational health should hold in such a society. Occupational health has become a serious problem in the developing world as new industries and accelerating ecnomic development occur without adequate resources for worker protection. The study of cases such as that of Venezuela may provide guidance for anticipating and preventing problems in other nations. This paper should be considered a pilot study to explore a social aspect of occupational health that has not received adequate attention.
We compared measurements of urinary alkylphosphate metabolites and oxime-induced reactivation of plasma cholinesterase (P-ChE) and erythrocyte acetylcholinesterase (RBC-AChE) with measurements of foliar residues, skin and clothing contamination, and P-ChE and RBC-AChE activities among 20 Northern California peach orchard workers exposed to the organophosphate agent azinphosmethyl (Guthion). Subjects entered orchards treated 30 d previously with azinphosmethyl and worked 21 d in treated fields during the ensuing 6 wk. Dislodgeable foliar residues ranged from 0.32-0.96 micrograms/cm2. Median reduction in RBC-AChE activity was 7% (p < .001) over the initial 3-d period of exposure and 19% (p < .01) over the 6-wk season. Urinary metabolites were the most sensitive indicator of recent exposure and correlated moderately with dermal and clothing levels (rs = +0.31-(+)0.55); urinary metabolites correlated well with RBC-AChE drawn 3 d after exposure began (rs = -0.77). No significant oxime-induced reactivation was found.
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One of the most important roles for occupational epidemiology is to provide a scientific basis for assessing causation. This chapter discusses the criteria for causation considered by the U.S. Surgeon General, the International Agency for Research on Cancer, and others to place the evidence in historical context. As a case study, the criteria for judging the evidence for potential carcinogenicity of silica dust are examined. The importance of communication with workers and management about causal concerns from workplace exposures is also discussed.
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Although there has been debate in the medical community about silica's carcinogenicity since the 1930s, only in the past decade have there emerged scientific data supporting a causal association between industrial silica exposure and lung cancer. This paper examines the evidence for the association, with a particular focus on those studies appropriate for cancer risk assessment. The cancer risk extrapolations from epidemiology studies suggest that the levels of risks are approximately two factors less than that derived from animal studies. Additional research is needed to provide a stronger basis for the extrapolations so that policy makers can have more confidence in their estimates.
This paper reviews the ambient air literature and discusses the link between particulate matter with an MMAD < or = 10 micrograms (PM10) emissions and estimates of silica particulate concentrations. Silica appears to represent a range of 0.4-21% of PM10 emissions, although this estimation needs more research (including direct measurements) to contribute to increased confidence in the methodology.
Should quantitative risk assessment using epidemiologic data be performed for a substance such as silica dust? The criteria for conducting this step have been described by Hertz-Picciotto (1995) for individual epidemiology studies, and this paper applies the criteria to a body of cancer epidemiology research, indicating what the evidence is lacking. Discussion focuses on the cancer risk assessment calculations currently in the literature, the need for more research, and the relevance to decision making.
Improvements in workplace health among silica exposed workers followed demonstrations of the severity of the risk of silicosis and means of controlling high dust levels on the job. Current ambient environmental analyses include either an adoption of air quality goals for reducing emissions of criteria pollutants or the conduct of risk assessments to determine if regulatory procedures are needed. Although silica has been regulated as a workplace hazard for most of the 20th century, only recently has it been considered for ambient control, and most of the thrust for this action has evolved from environmental regulatory work in California, where both state initiative (Proposition 65) and legislative law (Air Toxics Hot Spots Information and Assessment Act; Assembly Bill number 2588) have required risk assessments for silica dust emissions as carcinogens.
Contrary to general opinion, workers' compensation data can be helpful in epidemiologic research. Dr. Goldsmith assesses several studies based on data culled from workers' compensation or disability programs and explains how valuable information was derived.