A range of substances in which mercury is combined with carbon and hydrogen (e.g. a phenyl group, C6H5, or methyl group, CH3) that are used as seed dressings, and sometimes applied to timber, to prevent fungal infestation. Dressed seed is dispersed widely, distributing the mercury present in the fungicide at concentrations well below those present naturally in most soils, but birds have been harmed by ingesting seed dressed with methylmercury compounds. Phenylmercury compounds are of low toxicity to vertebrates; methylmercury compounds are much more toxic.
Subjects: Ecology and Conservation.