Lead levels that are currently assumed to be safe for children can significantly impair intellectual development, according to a groundbreaking report published in today’s issue of the New England Journal of Medicine. The current U.S. and international allowable blood lead level is 10 micrograms per deciliter, but researchers found that lead levels lower than that caused a drop in IQ of up to 7.4 points. That’s sobering news, given that an estimated one in 50 U.S. children has lead levels above the federal standard, and one in 10 has levels of five micrograms per deciliter or higher — within the dangerous range, according to today’s report. Some 38 million houses across the country are coated in lead-based paint, making homes the single largest source of the toxic substance. In addition to decreased intelligence, exposure to lead has been associated with slower overall development, behavioral problems, and even criminality.