Mercury

This is the most common and most toxic in water bodies. It occurs in water as monomethyl mercury. Most industrial effluents have mercury. Methyl mercury vapours cause fatal poisoning.

High levels of mercury in fish stocks have been found, mainly in coastal areas. Mumbai, Kolkata, Karwar (in Karnataka) and North Koel (in Bihar) are some of the severely affected areas.

The recent popularity of energy efficient compact to fluorescent lamps or CFLs has added another dimension to the controversy.

Toxicity of mercury is much greater than any other substance, about 1000 times more potent than colchicines.