A new study reveals high concentrations of mercury in rainfall over central North America. Data from 19 sites that had records for the time period 1997-2013 revealed significant positive trends in mercury concentration in the Rocky Mountains, Plains, and Upper Midwest regions for the recent time periods as well as positive trends in mercury deposition for the continent as a whole.
The results were surprising and discouraging, stated the scientists. Mercury had been in decline since the late 1990s due to tighter Environmental Protection Agency regulations on coal-fired power plants. The data suggests that coal plants in Asia is the source of the increase in Hg levels.
The results, recently published in Science of the Total Environment, is surprising because long-term trends had shown a decrease in mercury emissions whereas data collected between 2007 and 2013 indicate an unsettling upturn from the Rocky Mountains to the Midwest. The trend, however, is not due to regional activity. The authors speculate that because the U.S. has controlled its emissions since the 1970s, the toxic element was initially released via coal-burning power plants in Asia, drifted through the upper atmosphere for months, hit turbulence over the Rocky Mountains and was then pulled from the air in the form of rain.
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Given that it is such a recent phenomenon, scientists cannot be sure what an increase will mean for the environment and public health. “As a general rule, we are very concerned about mercury because it can be present at very dilute levels in the environment, parts per trillion, but in the food chain—in a food that we eat and that other animals eat—it can reach levels that are toxic,” says Peter Weiss-Penzias from the University of California, Santa Cruz, who led the study. Mercury magnifies as it travels up the food chain from minnows to fish to large mammals, including human beings. Pregnant women, for example, are often discouraged from eating fish because the element poses extreme risks to the developing fetus, particularly the central nervous system and brain.
All of us have low levels of mercury in our bodies. Those unfortunate enough to ingest high concentrations of mercury have a powerful neurotoxin in their body. This poisoning may include loss of peripheral vision, "pins and needles" feelings, usually in the hands, feet, and around the mouth, lack of coordination of movements, impairment of speech, hearing, walking and muscle weakness.
Children exposed to mercury while they are in the womb can have impacts to their cognitive thinking, memory attention, language, fine motor skills, and visual spatial skills.
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