Chapter 3C. Biomarkers of Exposure: Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofuranes

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are unwanted by-products formed in a variety of industrial and thermal processes. Humans may become contaminated with PCDD/PCDFs through environmental, occupational or accidental exposure.In summary, a broad spectrum of biomarkers have been analysed in human populations highly exposed to dioxins. These include changes in liver enzymes, blood lipids, thyroid and steroid hormones, and glucose tolerance. None of these markers can be considered to be specific for dioxin exposure because they can be elicited by a broad spectrum of diseases and/or exposures to other types of chemicals. Even chloracne, one of the most reliable marker/diseases observed after high exposure to dioxins in humans, can be caused by other chemicals.Among the biomarkers closely related to arylhydrocarbon receptor (AhR) activation, cytochrome P (CYP) induction plays the most prominent role. It is usually measured as a change in caffeine metabolism. In addition, these markers are not absolutely specific for dioxin exposure but can also result from exposure to certain polycyclicaromatic hydrocarbons (PAHs), e.g., in workers or in smokers. Furthermore, CYP activity measurements in peripheral blood lymphocytes have been reported to be highly variable, even in among individuals without evidence for different exposure.Taken together, biomarkers of dioxin exposure can be useful in combination with chemical analysis of dioxins in blood, adipose tissue, etc. Here, they can provide a suitable tool for the follow-up of intoxication cases or after local high exposure of certain populations in order to obtain information on biological responses over time. As an isolated tool for exposure or risk assessment of dioxins they should not be used.For a number of years a decreasing trend in dioxins has been observed in the environment and in humans. Despite this declining PCDD/PCDF trend, the exposure of babies during the breast-feeding period is still a matter of concern and justifies taking measures to reduce PCDD/PCDF emissions into the environment.