When the flood waters of Hurricane Katrina receded from New Orleans, some of the city's dangerously high lead levels washed away, too. Prior to the Hurricane, 15 neighborhoods had soil lead levels higher than the federal standard. Tests done in the same places post-Katrina found only 6 neighborhoods exceeding the limit. Across 29 neighborhoods, lead levels dropped an average of 45% between 2000 and 2006—a change attributed to Katrina as the levels had sat, basically unchanged, between 1990 and 2000. The effect shows up in kids, as well as the yards they play in. On average, New Orleans' children under the age of six experienced a 30% drop in blood lead levels.