Gardner's aim is to detect lower levels of contamination. According to Kirshner, the average blood lead content in adults is 4 micrograms per deciliter. The action level set by the national Centers for Disease Control and Prevention is 10 micrograms per deciliter, and anyone with a blood level over that amount needs treatment for lead poisoning. Kirshner estimates that four million children in the U.S. are over this limit. Kirshner cited a researcher in child development at the National Institute for Health who has found that for every 10 micrograms per deciliter of lead in the blood, a person loses three to four IQ points.
Adults can take in lead any number of ways.
For example, people who make stained glass use lead for joining the pieces of glass together, and workers who remove leaded paint from structures also are exposed. Smelter workers are particularly vulnerable because they breathe vaporized lead, which gets into the blood very quickly. Such repeated occupational and hobby exposure can damage the kidneys and lead to high blood pressure. Inhaled lead enters the blood more rapidly than ingested lead. Because a blood test measures only recent exposures to lead, Gardner's work to improve bone lead testing is critical.