Blood cell gamma-aminolevulinic acid dehydratase activity in humans exposed to methylmercury

The gamma-aminolevulinic acid dehydratase (ALA-D) activity in blood cells was studied in 15 subjects exposed to methylmercury through consumption of contaminated fish and 19 "unexposed" subjects with a similar sex and age distribution. The exposed subjects had a mean mercury level of 120 (range 15-370) ng/g blood cells while the controls had 9 (range 4-15) ng/g. Both groups had the same mean level of lead in whole blood (10+/-1 mug/100 ml). ALA-D activity decreased statistically significantly as both mercury and lead levels in the blood cells increased.