2-Butenal (also known as crotonaldehyde) is an a,-unsaturated aldehyde and consequently a very reactive compound. It is a chemical intermediate used chiefly in the manufacture of sorbates, solvents, and, to a lesser extent, pharmaceutical products and aroma chemicals. This document studies the pharmacokinetics, environmental exposure, chemical toxicology and carcinogenicity of 2-butenal. However, to enable an understanding and evaluation of this aldehyde in the context of environmental health, other aldehydes, such as formaldehyde, acetaldehyde, and acrolein, are mentioned for comparison, where