The changing goal line for blood lead concentration makes SRM 955c especially useful to laboratories. The lowest lead concentration level in the previous standard was 4 micrograms per deciliter or 40 parts per billion. In contrast, the lowest lead concentration level of SRM 955c is 0.4 microgram per deciliter or four parts per billion, the level of lead in an undosed animal. It is intended to represent the natural level of lead in an unexposed human population (although it is not yet known if any lead is naturally present in human blood). The lowest concentration in the SRM is 25 times lower than the DHHS 2010 goal, and will enable the development of next generation clinical methods that will be needed to accurately measure blood lead levels in children as progress is made toward eliminating lead exposure.
In addition to lead, levels two through four of SRM 955c contain added amounts of arsenic, cadmium, mercury, methylmercury and ethylmercury to facilitate future efforts to develop clinical methods to measure these toxins in human blood. At present, NIST provides information values only for the concentrations of cadmium and total mercury (including methylmercury and ethylmercury.) As values become available for arsenic, methylmercury and ethylmercury, the cert
Contact: John Blair
National Institute of Standards and Technology (NIST)