Carcinogenic effects general population exposures

The effects of PCBs alone on reproduction and development, as well as their carcinogenic effects, have yet to be established in humans—whether workers or the general population—even though some subjects have been exposed to very high levels of PCBs. Some adverse behavioral effects in infants are reported to have been observed in two studies involving subjects from the general population, but the adverse effects observed in the two studies were dissimilar furthermore, there are a number of uncertainties about the exposure assessments in both studies (Kimbrough, 1995). 

Toxicologists generally posit that no threshold exists for some effects, notably for most carcinogens. Such effects are characterized by a derived minimal effect level (DMEL) in the European Union in the parlance used in the United States, risks are characterized using oral slope factors and oral or inhalation unit risks. A DMEL represents the exposure level that corresponds to a specified level of risk to the exposed population. In the case of a chemical known or suspected to be a human carcinogen, this exposure level corresponds to a risk of one excess case of cancer in an exposed population. For a hypothetically exposed population of one million people, for example, this risk level of one excess case of cancer in the population of one million is abbreviated... 

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