Mercury in environmental and biological samples from a gold mining area in the Amazon region of Brazil

A massive increase in gold mining in the Amazon region of Brazil has led to an enormous discharge of metallic mercury into the aquatic ecosystem. To investigate the dispersion, total and inorganic mercury concentrations were measured in water, fish and animal tissues, and in blood, urine and hair from members of the local populations. Mercury concentrations in river water, sediments and fish were high compared with those of non-contaminated areas. Cattle and pigs kept in the area and with access to the contaminated rivers had concentrations of mercury of 0.1-1.28 micrograms/g and 11.7-15.7 micrograms/l in hair and blood, respectively. These results are approximately twice those measured in specimens from control animals. Mean mercury concentrations in blood, urine and hair of residents were increased at 11.4 micrograms/l, 22.8 micrograms/l and 4.3 micrograms/g, respectively, and the urine mercury of workers from the gold mining sites were up to 155 micrograms/l. The results demonstrate widespread contamination of the environment by mercury with transfer of the metal to fish and animals used for food, and into the inhabitants of the region. Further investigations for possible adverse health effects need to be undertaken.