Lead exposure levels long considered safe for adults have been linked to higher death rates from stroke and heart attack, says cheery research in the medical journal Circulation. The Occupational Safety and Health Administration suggests that safe blood lead levels for adults are up to 400 micrograms per liter, but the study -- which tracked 13,946 subjects for 12 years -- found increased risk of cardiovascular death at levels of 20 mcg/liter. The results were steady across socioeconomic classes, ethnic and racial groups, and gender. U.S. citizens' exposure to lead has dropped significantly since it was phased out of gasoline and paint decades ago, but between 1999 and 2002, almost four in 10 Americans had blood lead levels higher than 20 mcg/liter. In a teensy-weensy bit of good news, research from the Harvard School of Public Health indicates that dietary calcium "may be helpful in prevention of hypertension induced by elevated lead burden."