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

Fish samples collected near the caustic soda factory of TACSCO in Thailand during November and December 1978 were found to contain 0.10 to 1.38 ppm Hg in flesh (on wet weight basis), whereas those of the control areas contained 0.01 to 0.30 ppm. The Hg content of the fish in the TACSCO area had decreased by more than half from the first investigation which took place during 1975–76. This decrease is obviously a result of the functioning of the waste-water-treatment system built by the factory in 1974. The bottom mud collected near the factory in 1978 contained 8.39 to 57.95 ppm Hg (on dry weight basis) as compared with the mean of 0.03 ppm in samples taken from the control area. The Hg content in fish-eating birds were low, 0.04 to 0.44 ppm in the muscles and 0.05 to 1.32 ppm in the livers (on wet weight basis).