Biomethylation of Toxic Elements in the Environment

Abstract

Mechanisms for methyl transfer to Hg, Pd, Pa, Pt, Au, Sn, Cr, Se, As and S were examined. The oxidation-reduction chemistry of these elements provided information about the environmental conditions required for the biomethylation of each element. Vitamin B12 dependent reactions and S-adenosylmethionine dependent reactions were discussed. Oxidation-reduction conditions can be correlated with biomethylation processes. A biogeochemical cycle was formulated for Sn. The biomethylation of Sn is interesting in 2 respects: the use of Sn by advanced industrial societies has more than doubled in the last 10 yr and the analytical methods to definitively establish whether methyl tin compounds accumulate in the food chain, including humans, have not yet been developed. Since methyl tin compounds are poisonous to the CNS systems of higher organisms, it is critical to examine whether higher organisms provide a reservoir for some of the methyl tin compounds established as intermediates in the biogeochemical cycle for Sn.