Toxicology of Art Materials

This chapter presents vignettes on the toxicity of materials used by artists. The organic materials comprise methylene chloride, chloroform, carbon tetrachloride, trichloroethylene, n-hexane, diisocyanates, alcohols, glycols, glycol ethers, mineral spirits and turpentine. For each substance, a chemical mechanism describing the metabolism is presented. For example, halomethanes are metabolized to carbon monoxide or phosgene. N-Hexane is a potent neurotoxin, while the related normal alkanes, pentane and heptane, are merely irritants. Odorless mineral spirits (OMS) have been processed to remove toxic aromatics which have odor. Although the odor has been removed, the long-chain alkanes in OMS are volatile and enter the body by inhalation. They are metabolized at both ends of the carbon chain to yield 1,ω-dialkanoic acids which are metabolized as “food”. Diisocyanates cause occupational asthma by transcarbamoylation with serum albumin. Inorganic materials include the lead, cadmium, mercury, silver, arsenic, chromium and silica dust. The toxicity of silica dust is caused by the particulates which are inhaled into the lung which then becomes dysfunctional. The metallic agents are toxic with the exception of silver, which is employed medicinally to kill bacteria. Silver ions are much more toxic toward bacterial cells compared to mammalian cells because the former lack metallothionines, proteins which scavenge heavy metals and other factors. Lead causes anemia. It has a fatal attraction for an enzyme which is a catalyst for the biosynthesis of heme. In addition, lead binds strongly to proteins in synapses; this is the basis of lead’s neurotoxicity. Cadmium upsets the electron transport chain and causes the formation of excessive amounts of the ROS, reactive oxygen species, including the free-radical anion, superoxide. Chromium (VI) as chromate is isoelectronic with sulfate and enters cells by the sulfate port. Chromate reacts with cellular reductants including ascorbate and cysteine producing Cr⁴⁺ and Cr⁵⁺ and these in turn react with guanine bases of DNA to yield the Sp lesion. Arsenic as the pigment realgar, As₄S₄, is converted to As(OH)₃ and As(O)(OH)₃ in the stomach. These arsenicals are metabolized to permethylated compounds by the systematic replacement of oxygen atoms with methyl groups. Arsenic compounds, organic and inorganic, have been classified as a human carcinogens. However, arsenic trioxide currently used to treat a form of leukemia.