Effect of analytical variability on measurements of population blood lead levels.

The effect of analytical error on the interpretation of blood lead data obtained from population studies is discussed. Statistical analysis of measured blood lead values reported in four representative population studies shows over 40 percent of the variability in blood lead measurements is due to analytical error. Because of this analytical error, a large percentage of the observed lead measurements which exceed a threshold limit are "false positives" in that the true blood lead values for these individuals do not exceed the threshold. The EPA has suggested that the distribution of blood lead values could be used as a guide for determining the portion of a population at risk. "At risk" is defined as having blood lead values above a certain threshold. If this is done, the effect of analytical error which causes "false positives" should be considered properly to obtain an accurate estimate of the population at risk.