DITHIOCARBAMATES AS POTENTIAL CONFOUNDERS IN BUTADIENE EPIDEMIOLOGY

Hematopoietic neoplasms associated with occupational exposure to 1,3-b utadiene (BD) have been the subject of controversy, This has largely b een due to the inconsistent results of epidemiology studies that have reported alternatively no or weak associations between exposure to BD and hematopoietic neoplasms, Moreover, the specificity of association of ED exposure with individual leukemia types remains unclear. In addi tion, a distinct difference in the pattern of leukemia risk has been o bserved between workers employed in ED monomer production and those in volved in styrene-butadiene rubber (SBR) production: with no increase in leukemia risk observed for exposure to ED monomer alone. These obse rvations are consistent with an increase in leukemia risk associated w ith the SBR process but not ED monomer and suggest the possibility tha t the increase may be the result of exposure to confounding factors pr eviously not considered. In this regard, evidence is accumulating to s uggest that SBR studies may be confounded by the presence of an import ant class of biologically active chemicals employed in the rubber indu stry, dithiocarbamates. The hematotoxicity and immunotoxicity of dithi ocarbamates have been implicated in a wide range of clinical, animal a nd molecular studies, and an extremely high concordance exists between the risk of developing leukemia in SBR production and opportunity for exposure to this class of agents. Based on these findings additional studies on the epidemiology, carcinogenesis and molecular biology of d ithiocarbamates are clearly warranted.