Reduction of mercury pollution in the vicinity of a caustic soda plant in Thailand

In 1978 the mercury content of fish samples collected near the caustic soda factory of TASCO in Thailand was recorded as 0.10 to 1.38 ppm, as compared with 0.01 to 0.30 ppm in control fish. This represents a decrease of over one half in mercury concentrations since the construction of a waste-water treatment system in 1974. Bottom mud samples collected in 1978 contained 8.39 to 57.95 ppm as compared to a control area's 0.03 ppm. The mercury content of fish is shown to have decreased sharply and the sediment pollution is localized; this indicates that mercury is readily sedimented or excreted from fish-eating birds. The fish are eaten and represent a health hazard; edible aquatic and terrestial plants are shown to be polluted. The source of most of this contamination is bed sediment.