Arsenicosis: review of recent advances

Human health in the past and presently is influenced by the amounts and proportion of chemical elements to which humans have been exposed. Arsenic, as a therapeutic agent was known to ancient Greeks and Romans. Ehrlick introduced organic arsenicals as anti linetic agents but with advent of penicillin these have nearly become obsolete. Once considered toxic, harmful to humans, arsenic is now considered an essential ultra trace element at least in animals. Now the impact of arsenic on health is more from industrial and environmental than medicinal exposure. This article reviews human exposure to arsenic in non occupational population, mostly through drinking water which is a worldwide problem, more so in south East Asia. Sources of arsenic, normal and abnormal levels in blood and tissues levels, old and new methods of estimation of arsenic, mechanism of action of arsenic in experimental animal is briefly reviewed. Old described clinical manifestation of arsenic in humans is briefly reviewed and newly described clinical manifestations in human with special emphasis on atherosclerosis, liver and diabetes are discussed. Proposed biological mechanisms in experimental animals included up regulation of inflammatory signals like cytokines and TNF-alpha, oxidative stress, hypomethylation, decreased DNA repair and apoptosis, cell proliferation, angiogenesis, activation of several enzymes like methyl transferase which converts inorganic arsenic to MMA and DMA, and GSH in in-vivo and in-vitro in experimental rat liver slices. Experimentally NAC (N-Acetyl Cysteine) treatment attenuates oxidative stress in atherosclerosis apoptosis and liver injury. GSH probably plays an important role in deactivation of the intermediate products of arsenic metabolism and prevents peroxidation of membrane lipids. Chronic human exposure has been linked to several systems in the human body: dermal (exfoliative dermatitis, keratosis, vitiligo, skin cancer), peripheral neuropathy, encephalopathy, bronchitis, pulmonary fibrosis, hepatosplenomegaly resembling NCPF, portal hypertension, peripheral vascular disease and BFD, arteriosclerosis and cancers of lung, urinary bladder, other internal organs and diabetes. Experimental and epidemiological evidence support diabetes effect of high level arsenic exposure. Low and moderate exposure to arsenic in drinking water is widely prevalent and may play a role in diabetes prevalence and needs to be studied further. Role of arsenic in Indian arteriosclerosis, diabetes and liver diseases, (cirrhosis, NCPF), need to be studied further. Study of mechanisms and enzymes mentioned need to be studied in humans exposed to arsenic and other xenobiotics. Measuring arsenic exposure, metabolic and biologic effects by newly described and simpler urine proteomics may accelerate our understanding of arsenic on health consequences.