ABSTRACT
Inhalation of substances through the nose or mouth into the lungs represents a major route of contact for environmental substances. Along the way, substances or their metabolites may be available for interaction with tissues lining the respiratory tract. Cells and tis-
sues at the site of entry can respond or the substances can be transported systemically where interaction with other internal organs and tissues can occur. As with the routes of exposure (dermal or oral) the ultimate response of the organism to inhaled substances will depend on the integrated amount and form of the substance in the body.
