In a study conducted by the University of California, Los Angeles, scientists examined the level of mercury pollution in nine countries in Central and South America, as well as the Caribbean. Record concentrations of mercury, previously unseen in songbirds, were found in these regions. One of the reasons for such pollution is the use of mercury in the gold mining process.
A study conducted by the University of California, Los Angeles, covered the level of mercury pollution in nine countries in Central and South America, as well as the Caribbean. Scientists found the highest levels of mercury ever recorded in songbirds in these regions: in one green kingfisher, the mercury content was 30 times above safe levels.
According to Chris Seyers, the lead author of the study, the primary reason for such high mercury levels is gold mining: “The most important finding of our study was that mercury concentrations were nearly four times higher in areas impacted by artisanal gold mining.”
Artisanal and small-scale gold mining is the largest source of mercury pollution in the world, accounting for nearly 38% of anthropogenic mercury emissions. In such operations, mercury is used to extract small particles of gold from soil and sediment. Mercury binds with gold to form an amalgam, and when the resulting nuggets are heated, the mercury evaporates, leaving behind gold. Meanwhile, mercury is released into the soil and water as waste, as well as into the atmosphere in vapor form.
Controlling such small operations is extremely difficult, and miners claim that the use of mercury is necessary for quick and efficient extraction, Seyers notes.
Where Does All the Mercury Come From
Mercury is also present in the environment as a naturally occurring element, released from volcanoes and volcanic rocks, which are most commonly found in geologically active tropics. Intense rainfall in these regions can exacerbate the problem by washing mercury that has settled on land and in riverbeds, increasing the likelihood of it entering the bodies of animals.
Researchers also recorded high levels of mercury in carnivorous birds and species that inhabit aquatic environments. According to scientists, mercury accumulates more in the bodies of predatory animals because it first accumulates in their prey. The higher an animal is in the food chain, the greater the risk of high mercury levels. Aquatic birds are also exposed to additional mercury exposure, as the toxic metal accumulates in riverbeds.
This study, involving 37 scientists from seven countries, is the largest to date examining mercury levels in tropical birds. The researchers reached their conclusions by analyzing 2,316 samples of blood and feathers from 322 bird species — this is the most extensive database on mercury concentration in tropical birds in the world.
The findings are significant not only for tropical birds, which serve as ecological indicators of the overall health of ecosystems due to their sensitivity to pollution, habitat interactions, and ease of study. If birds in an ecosystem show elevated mercury levels, it may indicate a similar problem in other species.
This also concerns humans. Communities, especially villages engaged in subsistence fishing and located downstream from gold mining operations, are particularly vulnerable to mercury pollution. Birds that have consumed large amounts of mercury may experience immunological issues, making them more susceptible to diseases, some of which can be transmitted to humans.
However, stopping gold mining or making it more environmentally friendly is extremely challenging. Gold, aside from its use in jewelry, is an important component of many electronic devices — from smartphones to vital medical instruments. Although governments around the world are taking steps to improve the environmental sustainability of the mining industry, pushback from the gold mining industry hinders many of these efforts, Seyers says. At the very least, he adds, consumers can help by choosing products that contain only certified environmentally friendly gold.
