Absorption, biotransformation, and excretion of environmental chemicals

Foreign chemicals are continually present in the environment of man and animals. Mammalian systems are in a constant state of balance-the intake compensated for by the outflow. The intake is largely determined by the route of exposure and the chemical characteristics of the environmental compound. Under normal conditions of exposure to small or moderate amounts of environmental chemicals, the system is capable of biotransforming and detoxifying such materials into compounds more easily handled by the mammalian system. These are largely converted to more water-soluble materials and excreted in the urine, bile, and less commonly through other excretory routes. In situations of massive exposure to foreign materials, or when repeated exposure to moderate amounts of chemicals results in accumulation in body systems, toxicoses may result. These are essentially an overwhelming of the biological mechanisms for detoxifying and excreting such materials. The hazard associated with environmental chemicals is greatly increased if a preexisting disease modifies the normal biological detoxification processes. Therapy to assist intoxicated individuals is largely aimed at increasing excretory processes and maintaining or restoring the physiological balance between the amount of environmental chemical absorbed and the level capable of being excreted.