A small increased risk of cancer in workers exposed to diesel exhaust has
been suggested by some epidemiologic studies [Bhatia et al. 1998;
Boffetta et al. 1988, 1990, 1997; Garshick et al. 1987, 1988; Steenland
et al. 1990, 1992]. Exposure is almost always to mixtures that pose a
challenge in developing conclusions [Samet 1995]