Ans. is 'a' i.e., Arsenic Chronic arsenic exposure can cause 'black foot disease' a severe form of peripheral vascular disease, causing gangrene of lower limbs. Arsenic poisoning may be acute or chronic. Acute arsenic poisoning It can present in any of the two ways : Gastrointestinal type : It is the common form and resembles bacterial gastroenteritis (e.g. cholera). There is garlic adour with hemorrhagic gastroenteritis and necrosis of intestinal mucosa. There is tenesmus and anal irritation. Dehydration may cause acute circulatory collapse, with hypotension, oliguria and acute tubular necrosis (ATN). Fulminant narcotic form : Large dose of arsenic is rapidly absorbed without producing GI symptoms. These are giddiness, headache, myalgia, formication, veigo and death in 2-3 hours. Postmoem appearance include : Red velvety mucosa of stomach and submucous petechial haemorrhage. Subendocardial petechial haemorrhage. Fatty degeneration of liver, kidney and hea. Chronic arsenic poisoning Chronic arsenic poisoning has four stages : First stage (nutritional and gastrointestinal disturbances) : The earliest sign is gradual emaciation. There is loss of appetite, nausea and intermittent vomiting and diarrhea. Second stage (catarrhal changes) : It resembles common cold, i.e. conjunctivitis, running nose and eyes, coughing etc. Third stage (skin rash) : There is classical 'rain drop pigmentation', i.e. patchy brown pigmentation of skin. At initial stages, there is a vesicular eruption which may resemble nettle rash. Hyperkeratosis of palms and soles occur. There are white transverse bands crossing the nails, known as Mee's line, and indicate periods of arrested growth due to interference with normal metabolism. There is alopecia and exfoliative dermatitis. Fouh stage (nervous disturbances) : There is sensory and motor (i.e. mixed) polyneuropathy, with painful paresthesia of hands and feet and muscle tenderness. There may be evidence of liver (fatty liver) and kidney damage and bone marrow suppression (causing anemia and other cytopenias). Hea may also be involved. Chronic arsenic exposure can also cause 'black foot disease' a severe form of peripheral vascular disease, causing gangrene of lower limbs. Arsenic is carcinogenic, can cause cancers of skin (squamous cell carcinoma and basal cell carcinoma), lung, liver, bladder, kidney, larynx and lymphoid system (leukemia).