Arsenic metabolism, target tissues, and comorbidities. Chronic As exposure has been associated with increased risk of skin lesions (melanosis, leukomelanosis, and keratosis), cardiovascular disease, hypertension (91), impaired intellectual function, inflammation, diabetes, and cancers. Ingested As accumulates in multiple tissues, including the spleen, liver, lungs, kidneys, bladder, skin, and bone marrow. (Inset) AS3MT is predominantly expressed in the liver, although AS3MT mRNA has also been detected in the kidneys, adrenal gland, bladder, heart, and brain (92). Abbreviations: AS3MT, arsenic-3-methyltransferase; DMAsV, dimethylarsinic acid; InAsIII, arsenite; MMAsIII, monomethylarsonous acid; MMAsV, monomethylarsonic acid; SAH, S-adenosylhomocysteine; SAM, S-adenosylmethionine.