Symptoms of<unk>  begin with headaches, confusion, severe diarrhea, and drowsiness. As the poisoning develops, convulsions and changes in fingernail pigmentation called leukonychia striata (Mees's lines, or Aldrich-Mees's lines) may occur. When the poisoning becomes acute, symptoms may include diarrhea, vomiting, vomiting blood, blood in the urine, cramping muscles, hair loss, stomach pain, and more convulsions. The organs of the body that are usually affected by<unk>  are the lungs, skin, kidneys, and liver. The final result of<unk>  is coma and death.<unk>  is related to heart disease (hypertension-related cardiovascular disease), cancer, stroke (cerebrovascular diseases), chronic lower respiratory diseases, and diabetes. Skin effects can include skin cancer in the long term, but often prior to skin cancer are different skin lesions. Other effects may include darkening of skin and thickening of skin. Chronic exposure to<unk>  is related to vitamin A deficiency, which is related to heart disease and night blindness. The acute minimal lethal dose of<unk>  in adults is estimated to be 70 to 200 mg or 1 mg/kg/day. Cancer<unk>  increases the risk of cancer. Exposure is related to skin, lung, liver, and kidney cancer among others. Its comutagenic effects may be explained by interference with base and nucleotide excision repair, eventually through interaction with zinc finger structures. Dimethylarsinic acid, DMA(V), caused DNA single strand breaks resulting from inhibition of repair enzymes at levels of 5 to 100 mM in human epithelial cells. MMA(III) and DMA(III) were also shown to be directly genotoxic by effectuating scissions in supercoiled ΦX174 DNA. Increased<unk>  exposure is associated with an increased frequency of chromosomal aberrations, micronuclei and sister-chromatid exchanges. An explanation for chromosomal aberrations is the sensitivity of the protein tubulin and the mitotic spindle to<unk> . Histological observations confirm effects on cellular integrity, shape and locomotion. DMA(III) is able to form reactive oxygen species by reaction with molecular oxygen. Resulting metabolites are the dimethylarsenic radical and the dimethylarsenic peroxyl radical. Both DMA(III) and DMA(V) were shown to release iron from horse spleen as well as from human liver ferritin if ascorbic acid was administered simultaneously. Thus, formation of reactive oxygen species can be promoted. Moreover,<unk>  could cause oxidative stress by depleting the cell's antioxidants, especially the ones containing thiol groups. The accumulation of reactive oxygen species like that cited above and hydroxyl radicals, superoxide radicals and hydrogen peroxides causes aberrant gene expression at low concentrations and lesions of lipids, proteins and DNA in higher concentrations which eventually lead to cellular death. In a rat animal model, urine levels of 8-hydroxy-2’-deoxyguanosine (as a biomarker of DNA damage byreactive oxygen species) were measured after treatment with DMA(V). In comparison to control levels, they turned out to be significantly increased. This theory is further supported by a cross-sectional study which found elevated mean serum lipid peroxides in the As exposed individuals which correlated with blood levels of inorganic<unk>  and methylated metabolites and inversely correlated with nonprotein sulfhydryl (NPSH) levels in whole blood. Another study found an association of As levels in whole blood with the level of reactive oxidants in plasma and an inverse relationship with plasma antioxidants. A finding of the latter study indicates that methylation might in fact be a detoxification pathway with regard to oxidative stress: the results showed that the lower the As methylation capacity was, the lower the level of plasma antioxidant capacity. As reviewed by Kitchin (2001), the oxidative stress theory provides an explanation for the preferred tumor sites connected with<unk>  exposure. Considering that a high partial pressure of oxygen is present in lungs and DMA(III) is excreted in gaseous state via the lungs, this seems to be a plausible mechanism for special vulnerability. The fact that DMA is produced by methylation in the liver, excreted via the kidneys and later on stored in the bladder accounts for the other tumor localizations. Regarding DNA methylation, some studies suggest interaction of As with methyltransferases which leads to an inactivation of tumor suppressor genes through hypermethylation; others state that hypomethylation might occur due to a lack of SAM resulting in aberrant gene activation. An experiment by Zhong et al. (2001) with<unk> e-exposed human lung A549, kidney UOK123, UOK109 and UOK121 cells isolated eight different DNA fragments by methylation-sensitive arbitrarily primed polymerase chain reactions. It turned out that six of the fragments were hyper- and two of them were hypomethylated. Higher levels of DNA methyltransferase mRNA and enzyme activity were found. Kitchin (2001) proposed a model of altered growth factors which lead to cell proliferation and thus to carcinogenesis. From observations, it is known that chronic low-dose<unk>  can lead to increased tolerance to its acute toxicity. MRP1-overexpressing lung tumor GLC4/Sb30 cells poorly accumulate<unk> e and arsenate. This is mediated through MRP-1 dependent efflux. The efflux requires glutathione, but no<unk> -glutathione complex formation. Although many mechanisms have been proposed, no definite model can be given for the mechanisms of chronic<unk> . The prevailing events of toxicity and carcinogenicity might be quite tissue-specific. Current consensus on the mode of carcinogenesis is that it acts primarily as a tumor promoter. Its co-carcinogenicity has been demonstrated in several models. However, the finding of several studies that chronically<unk> -exposed Andean populations (as most extremely exposed to UV-light) do not develop skin cancer with chronic<unk>  exposure, is puzzling.
Arsenic poisoning
Mercury poisoning
Cadmium poisoning
Chlorine gas poisoning
Salicylate poisoning
Mercury Poisoning
Tin poisoning
Cobalt poisoning