Epidemiology laboratory data

The existing evidence does not exclude the existence of a threshold for some (perhaps even aU) forms of cancer, but the available epidemiological and laboratory data do not favor such a possibility. Hence, the interpolation models used by national and international experts for estimating the carcinogenic risks of low-level ionizing radiation are generally based on the assumption of a non-threshold dose-incidence relationship (ICRP, 1977 UNSCEAR, 1977 NAS/NRC, 1980 NCRP, 1980 Sinclair, 1981 Rail eta/., 1985). 

Laboratory analysis of human samples for trace contaminants or their metabolites inevitably produces results that deviate quantitatively from the actual concentrations. Such deviations can, for example, complicate exposure classifications in epidemiologic studies, detection of time trends in exposure, and comparison of studies that use data produced with different analytic methods. Individual laboratories can use standard QA-QC methods to minimize and define the magnitude of the variations. However, federal agencies and statutes, such as CDC, the National Institute of Standards and Technology, and statutes such as CLIA, could play important roles in improving the overall quality of biomonitoring laboratory data and their utility in health-related applications. 

It was not until the 1930 s that the epidemiologic data were mirrored by definitive laboratory data on the carcinogenicity of pure chemicals for experimental animals. 

A comprehensive study of the tolerance of laboratory animals to vapors of 2-nitropropane was reported in 1952 (100). In a study pubHshed in 1979, rabbits and rats survived exposure to nitromethane for six months at 750 and 100 ppm, respectively, with no unexpected findings (101). Similarly, no compound-related effects were found for rabbits exposed to 2-nitropropane at 200 ppm or for rabbits or rats exposed at 27 ppm. Liver damage was extensive in male rats exposed at 207 ppm for six months, and hepatocellular carcinomas were observed. Subsequendy, the International Agency for Research on Cancer (lARC) found that there is "sufficient evidence" to conclude that 2-nitropropane causes cancer in rats but that epidemiologic data are inadequate to reinforce the conclusion in humans (102). The National Toxicology Program also concluded that it "may reasonably be anticipated to be a carcinogen" (103). 

Lopman, B., Armstrong, B., Atchison, C., and Gray, J. J. (2009). Host, weather and virological factors drive norovirus epidemiology Time-series analysis of laboratory surveillance data in lingland and Wales. PLoS ONE 4, e6671. 

Deseriptive data are available from reports of humans exposed to 1,4-diehlorobenzene by inhalation (and possibly dermal contact). It is important to note that the case studies discussed in this section should be interpreted with caution since they reflect incidents in which individuals have reportedly been exposed to 1,4-dichlorobenzene, and they assume that there has been no other exposure to potentially toxic or infectious agents. There is usually little or no verification of these assumptions. Case studies in general are not scientifically equivalent to carefiilly designed epidemiological studies or to adequately controlled and monitored laboratory experiments. Thus, the case studies described below should be considered only as providing supplementary evidence that 1,4-dichlorobenzene may cause the reported effects. 

Kaldor, John, and Nicholas Day. 1985. The Use of Epidemiological Data for the Assessment of Human Cancer Risk. In Risk Quantitation and Regulatory Policy. Edited by David Hoel, Richard Merrill, and Frederica Perera. Cold Spring Harbor, N.Y. Cold Spring Harbor Laboratory. 

Laboratory and epidemiological data suggest that various polychlorinated biphenyls, dioxins, flame retardants, pesticides (e.g., DDT), perfluorinated chemicals, phthalates, bisphenols, and ultraviolet filters may inhibit thyroid function through a variety of mechanisms [31-33]. 

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