ABSTRACT
PAHs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
There is strong epidemiological evidence supported by experimental animal data that complex environmental mixtures pose a risk to human health producing increases in cancer incidence. Understanding the chemical and biological properties of these mixtures leads to a clearer comprehension of the principles inherent in their carcinogenic activities. Rarely are humans exposed to single toxic agents in the environment. They are exposed to complex mixtures containing multiple carcinogens, and these exposures can come from multiple sources (e.g., vehicle exhaust fumes and water disinfection by-products) and by multiple routes (inhalation, oral, dermal). Many of the agents known to be carcinogenic are found in the air, water, and diet. Pharmaceutical exposures combined with these chemicals found in the environment may also have adverse health effects. Within each exposure source, there may be many agents that either directly or indirectly affect the induction, promotion, and progression of cancer. Interactions of noncarcinogens with carcinogens may enhance or inhibit the ultimate tumor response. This chapter focusses on and summarizes the major findings on the carcinogenic effects of complex environmental mixtures and discusses mixture interactions as they pertain to chemical carcinogenesis.
