Biomarkers for assessing environmental exposure to carcinogens in the diet.

The major sources of human exposure to environmental carcinogens are through inhalation, ingestion, and percutaneous absorption. Food-borne carcinogens constitute the primary source of ingested carcinogens. Epidemiological analyses indicate that 20-50% of all human cancer is due to dietary causes, unfortunately, few specific etiologic agents have been identified. The use of chemical-specific molecular biomarkers in studies of several classes of carcinogens to which humans are exposed through the ingestion of food may provide the necessary data to identify these etiologic agents. These molecular biological markers can be classified into several categories: markers of exposure reflecting dose of toxic agents, markers of effect indicating a biological response to an exposure, and markers of susceptibility providing information about the inherent sensitivity of an individual to the toxic agent. By definition some of these markers are chemical-agent specific, such as a carcinogen-DNA or carcinogen-protein adduct, whereas others are biological process-specific such as the altered expression of a gene. In the future, information obtained from studies of molecular biomarkers in humans and experimental animals can be used for a range of public health applications from primary and secondary prevention to the design of clinical therapies. Aflatoxins have been extensively studied with validated biomarkers, and, currently, dietary polycyclic aromatic hydrocarbons (PAH) and heterocyclic amines (HA) derived from cooking meats and other staples are being intensively investigated. This article reviews some of the recent information on aflatoxins and describes future potential of PAH and HA biomarkers.