6. What are the effects of arsenic on the environment?
Water and land-living plants and animals show a wide range of sensitivities to different chemical forms of arsenic. Their sensitivity is modified both by biological factors and by their surrounding physical and chemical environment. In general, inorganic forms of arsenic are more toxic to the environment than organic forms and, among inorganic forms, arsenite is more toxic than arsenate. This is probably because the way in which the various forms are taken up into the body differs and once taken up, they act in different ways in the body. The reason why arsenite is toxic is thought to be because it binds to particular chemical groups - sulfhydryl groups - found on proteins. Arsenate, on the other hand, affects the key energy producing process that take place in all cells.
Arsenic compounds cause short-term and long-term effects in individual plants and animals and in populations and communities of organisms. These effects are evident, for example, in aquatic species at concentrations ranging from a few micrograms to milligrams per litre. The nature of the effects depends on the species and time of exposure. The effects include death, inhibition of growth, photosynthesis and reproduction, and behavioral effects. Environments contaminated with arsenic contain only a few species and fewer numbers within species. If levels of arsenate are high enough, only resistant organisms, such as certain microbes, may be present. More...