Epidemiologic studies

The types of epidemiologic studies used by risk assessors include case-control studies, cohort studies, descriptive epidemiologic studies, and case reports  

The association is observed across many different independent studies. 

There is specificity in the observed association such that one exposure leads to one outcome. (Note This is currently believed to be the weakest of all of Hill s criteria.) 

The exposure precedes the outcome, which leads to a temporal relationship between the two factors. 

There is a biological gradient that is the result of a strong correlation between the exposure and the outcome. 

Massey, Landau, and Deane conducted a study on two synthetic 

Another attempt to compare cardiorespiratory deaths with photo-chemical-oxidant pollution was carried out by Mills, who compared seasonally adjusted nursing-home deaths in Los Angeles with measures of photochemical-oxidant pollution. He found a suggestive positive association between photochemical-oxidant concentration and excess deaths when pollution rose above 390 ng/m (0.2 ppm). Although heat and seasonal variability were considered, the statistical analyses used make it questionable whether their effect could be suppressed. 

A variety of methods have been used to assess a relationship between mortality from chronic illness and photochemical-oxidant pollution, but none has been able to demonstrate a clear-cut relationship. The possibility of a ergistic effect has not been ruled out, although the experience of areas other than the Los Angeles basin with lower concentrations of photochemical-oxidant pollution suggests that temperature is an overwhelming factor in these deaths. 

Further studies on mortality in relation to photochemical-oxidant pollution are needed to delineate differences in susceptibility (especially in children and the elderly), to assess the additive effects of various weather conditions, to examine geographic variations in mortality in relation to pollution, and to determine whether excess mortality is attributable to specific diseases (e.g., emphysema), which may have been 

Several studies have attempted to correlate increased numbers of hospital admissions with variations in photochemical-oxidant pollution. The California Department of Public Health study of excess mortalhy also investigated hospital admissions as a possible health indicator of oxidant pollution. Admissions to Los Angeles County General Hospital in September through December 1954 for childhood asthma, tuberculosis, other respiratory diseases, and all other causes were examined. No significant association with oxidant concentrations was found. 

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Epidemiologic studies in Japan indicate an increased risk of stomach cancer owing to consumption of broiled fish and meats (116). In the United States, stomach cancer incidence has steadily declined since the 1940s, whereas consumption of broiled food has increased (108). In addition, the average human intake of PAHs is only 0.002 of that required to produce cancer in half of animals fed. Test results are often contradictory (117) and many components of food, such as vitamin A, unsaturated fatty acids, thiols, nitrites, and even saUva itself, tend to inhibit the mutagenic activity of PAHs (118—120). Therefore, the significance of PAHs in the human diet remains unknown (121,109). 

J. C. Contassot and co-workers, "Epidemiological Study of Cancer Morbidity Among Workers Exposed to Hydrazine," poster presented at the XXII International Congress on Occupational Health, in Sydney, AustraUa, Sept.—Oct., 1987. 

Epidemiological studies of nickel-producing and nickel-using workers seldom indicate excess mortaUty from nonmalignant respiratory disease. Evidence for such effects exists mainly as a few reports of isolated incidents of asthma, pulmonary fibrosis, chronic bronchitis, and emphysema in nickel workers. Nickel may or may not play a causal role in these incidents (131). 

Anxiety disorders and insomnia represent relatively common medical problems within the general population. These problems typically recur over a person s lifetime (3,4). Epidemiological studies in the United States indicate that the lifetime prevalence for significant anxiety disorders is about 15%. Anxiety disorders are serious medical problems affecting not only quaUty of life, but additionally may indirecdy result in considerable morbidity owing to association with depression, cardiovascular disease, suicidal behavior, and substance-related disorders. 

Health ha2ards linked to carbon disulfide are extensively covered (136). Also available are epidemiological studies (144—146), general reviews containing many references (147—150), and a Material Safety Data Sheet (151). 

S. Shindel and S. Ulrich, Report of Epidemiologic Study Warner Electric Brake eV Clutch Co., South Beloit, III, Jan. 1957 to July 1983, Ergotopology Investigative Mediciue for Industry, Milwaukee, Wis., Aug. 1984. 

Effects in Humans. In chlorophenol production, irritation symptoms of the nose, eyes, respiratory tract, and skin resulting ia chloroacne have been observed. The results of epidemiology studies on the long-term effects of chlorophenols are quite contradictory and have not allowed the experts to reach any firm conclusions (54). 

Hecdth effects data come from three types of studies clinical, epidemiological, and toxicological. Clinical and epidemiological studies focus on human subjects, whereas toxicological studies are conducted on animals or simpler cellular systems. Ethical considerations limit human exposure to low levels of air poUutants which do not have irreversible effects. Table 7-1 lists the advantages and disadvantages of each type of experimental informahon. 

Exposure to sulfur dioxide in the ambient air has been associated with reduced lung function, increased incidence of respiratory symptoms and diseases, irritation of the eyes, nose, and throat, and premature mortality. Children, the elderly, and those already suffering from respiratory ailments, such as asthmatics, are especially at risk. Health impacts appear to be linked especially to brief exposures to ambient concentrations above 1,000 ixg/in (acute exposures measured over 10 minutes). Some epidemiologic studies, however, have shown an association between relatively low annual mean levels and excess mortality. It is not clear whether long-... 

Hazard identification through animal experiments, epidemiological studies, or structure activity analyses... 

Exposure assessment to reveal the exposure of different groups of people, and to compare their exposure levels to the doses that cause harmful effects in humans as shown in epidemiological studies, or to doses that cause toxic effects in experimental animals... 

Malker, H. S. R. and Gemne, G. (1987). A register-epidemiology study on cancer among Swedish printing industry workers. Arch. Environ. Health 42, 73-82. 

There has been some controversy over the effect of traces of anesthehc gases in the operating room on the health of personnel working there daily Numerous animal studies usmg low levels of anestheltic gases have failed to show any effects, and several epidemiological studies show that human health is not affected by traces of anesthetic gases [20]... 

Because risk at low exposure levels is difficult to tneasure directly either by animal experiments or by epidemiologic studies, the development of a slope factor generally entails applying a model to the available data set and... 

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