This book evaluates the risks to human health and the environment posed by exposure to acrolein, a chemical produced in large quantities and used as an intermediate in the synthesis of several chemicals, most notably acrylic acid and its esters and DL-methionine, an essential amino acid used as a feed supplement for poultry and cattle. Acrolein also has direct application as an aquatic biocide used against algae, molluscs, and herbs in reciruclating process water systems, irrigation channels, cooling water towers, and water treatment ponds. Acrolein is estimated to account for 3 to 10% of total automobile exhaust aldehydes, 1 to 13% of total wood-smoke aldehydes, and up to 7% of the aldehydes in cigarette smoke. The opening section summarizes data on chemical and physical properties and outlines methods for sampling and analysis. Other sections describe the main sources of human and environmental exposure, review what is known about the behaviour of acrolein in the environment, and examine the mechanisms by which acrolein is absorbed, distributed, metabolized, and eliminated in different organisms. The most extensive section reveiws the large number of studies of toxicological effects conducted in laboratory mammals and in vitro test systems. The main effects linked to exposure via inhalation include reduced pulmonary function and pathological changes in the nose, upper airways and lungs. Studies support the conclusion that acrolein is acutely cytotoxic, produces teratogenic and embryotoxic effects, and is weakly mutagenic. Data on carcinogenicity were judged inadequate.