Environmental Distribution, Analysis, and Toxicity of Organometal(loid) Compounds

Abstract

The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed.

Identification of a Bioactive Impurity in a Commercial Sample of 6‐Methyl‐2‐p‐Tolylaminobenzo[d][1,3]Oxazin‐4‐One (URB754)

“…18 This explains the inactivity of URB754 observed by Saario et al. 19 In addition, the present study highlights all the side products deriving from Garin et al's procedure thus giving some hints for its mechanistic aspects and the inconveniences that might result from its use.…”

Urban environmental geochemistry of trace metals

“…Mercury, Sn and their organic compounds are chosen for their toxicity, increasing prevalence in the urban environment and a general paucity of information in terms of their distribution, behaviours and ecotoxicity in the urban environment. Future studies of urban environmental geochemistry may emphasize on organic Hg and organic Sn, for it is well recognized that the toxicity of these compounds is significantly more severe than that of their inorganic counterparts (Dopp et al, 2004). Many previous studies have investigated their distribution, biogeochemical behaviours and toxicity of organic Hg and organic Sn (Schroeder and Munthe, 1998;Hoch, 2001;Pacyna et al, 2003;Seigneur et al, 2004).…”

When are metal complexes bioavailable?

“…Furthermore, uptake is sensitive to the pH of the medium, with a decreased bioaccumulation of the lipophilic metal complexes at low pH, potentially due to a reduction in the electrostatic repulsion between adjacent phospholipids, leading to their tighter packing and a decreased membrane permeability. [11,18,19] With the exception of what is known about such hydrophobic metal species as the methylated forms of Hg, Sn, As and Sb [20][21][22] and the hydrophobic complexes described above, it is currently unclear to what extent lipophilic ligands are present in natural systems. Owing in large part to the analytical difficulties associated with measurements of (likely low concentrations of) hydrophobic complexes in aquatic systems, few data are available to estimate metal uptake fluxes for these species.…”