But water that passes through fractures is not purified in the same way as it would be if it traveled through compacted glacial till, Christy said. But in reality, water will travel through fractures and cracks in the ground, essentially bypassing the compacted sediment and foregoing any purification. Any land areas once covered by glaciers should be screened for fractures, particularly if those areas are candidates for a landfill site, livestock waste facility or other use that could potentially endanger the water supply. The strategy identifies key scientific questions of greatest importance to the agency, and charts a research program to reduce scientific uncertainties that limit EPA's ability to assess and manage mercury risks. Mercury exposure has been associated with both human nerve damage and growth impairment.
Airborne mercury settles over waterways, polluting rivers and lakes and contaminating fish.
In water, biological processes can transform mercury into a highly toxic form called methylmercury that builds up in animal and human tissue. As a result of their mothers' exposure to methylmercury, as many as 60,000 children are born every year in the U.S. at risk of nervous system damage. In a 1997 mercury report to Congress, EPA concluded that a plausible link exists between mercury from industrial and combustion sources in the U.S. and methylmercury concentrations in humans and wildlife. The study also estimated that from one to three percent of women of childbearing age eat fish in amounts that could put their fetuses at risk from methylmercury exposure. In a special report to Congress issued late on Friday, President Bill Clinton opted to keep Japanese whaling under economic review, leaving to the incoming administration the politically difficult issue whether to impose trade sanctions for Japan's expanded whale hunt.