A neurotoxic poison, mercury is especially worrisome to developing fetuses. A nationwide study reveals that a significant number of women of child-bearing age have too much of the metal in their systems. Researchers at the University of North Carolina at Asheville based their results on hair samples from nearly 1,500 people of all ages. As hair grows, it incorporates mercury from the bloodstream. Interim results from the Greenpeace-commissioned survey released October 20 revealed that one fifth of those studied had mercury levels above the EPA recommendation of one part per million in hair. The investigators report no other pollutant has anywhere near this high a percentage of the U.S. population with exposure levels above federal standards. The biggest sources of airborne mercury are coal-fired power plants. The investigators will gather an estimated 5,000 samples or more in total and issue their final report in March.