Elevated mercury exposure a by-product of Peruvian gold mining

In a recent study, researchers have found that living in Peruvian towns with small-scale mining is associated with an unhealthy body burden of mercury. The risk increased in those eating fish and working as miners. While exposures are known to be high, this small study is one of the first published that confirms the link in this South American nation. Small-scale gold mining along rivers in Madre de Dios, Peru, was long thought to expose locals to harmful levels of mercury. A new study published in the Journal PlosOne confirms the link and shows higher risks in miners and fish eaters. The results show the extent of mercury exposures from the illegal mining in the western Peruvian rainforest. Prior studies of booming gold mine communities in Brazil and other places in South America and Africa also link gold mining with high exposures to the metal. Mercury is used in artisanal mining to separate the gold from the rocks and sediments. Once in the environment, it journeys through the ecosystem and may be transformed into the more harmful methylmercury. Methylmercury can accumulate in fish – a main food source in many gold-mining areas. People in mining communities are mainly exposed by breathing mercury vapours during gold processing and by eating contaminated fish. Elevated mercury levels pose significant public health threats, including problems with brain and nervous system function. The recent increase in the price of gold has lured many – an estimated 30,000 – to work in camps as miners, even though the mining is illegal. Seventy percent of Peru’s 16 tons of gold is mined and processed in Madre de Dios. The practice leads to large-scale deforestation in the most biologically diverse part of the country. This informal gold mining – and specifically, the use of mercury in its processing – is poorly regulated, resulting in a lack of environmental and human health protection. To investigate the connection between mining and total mercury contamination in this area of Peru, 204 people from Puerto Maldonado – the region’s capital city with no mining – were compared with those living in one of 6 mining towns about an hour west on the new Interoceanic Highway. Participants filled out a five-question survey, which asked about place and length of residence, age, sex and monthly fish consumption. A hair sample was analysed for total mercury concentrations. Fish consumption, gender and place of residence were the three main factors associated with unhealthy levels of mercury in hair. The World Health Organisation sets 6 micrograms total mercury per gram of dry hair as a limit of unhealthy levels. Participants who ate fish more than 12 times a month were three times as likely to have unhealthy mercury levels compared to participants who ate fish with less frequency. More than twice as many people living in mining zones had unhealthy levels of mercury compared to people living in Puerto Maldonado. In addition, three times as many men as women had unhealthy levels of mercury. The study did not assess different types of fish consumption or from where people sourced their fish, nor did the authors select participants randomly. These factors could potentially cloud the interpretation of study’s results. In March, the government cracked down on this type of illegal gold mining in Madre de Dios, which may help curb exposures by reducing the extent of the illegal mines.

Environmental Health News, 29 May 2012 ;http://www.environmentalhealthnews.org/ ;