Accuracy in the determination of blood lead is of primary importance in such diverse activities as screening for childhood lead poisoning, occupational exposure monitoring and population surveys. To meet the stringent requirements of the third National Health and Nutrition Examination Survey (NHANES Ill), a large normative population study to be held from 1988-1994, we needed a method for the determination of lead in blood that was simple, accurate, rugged and of defined accuracy for both calibration and control materials. The recent availability of the National Bureau of Standards Standard Reference Materials 2121-2 and 955, a lead standard solution (10 000 mg 1-1) and a certified lead in blood reference material has made it possible to evaluate a method against definitive values and NBS reference materials.In the proposed method, sample preparation consists of a simple dilution (1 + 9) with a matrix modifier which contains 0.5% VNTriton X-100,0.2%0 VN16 M nitric acid and 0.2% mNdibasic ammonium phosphate. This matrix modifier stabilises lead so that the majority of the blood matrix may be removed during the char step. Maximum accuracy in dilution is achieved with the use of autopipettes which have been shown to deliver viscous materials such as blood and serum with high accuracy. The method described in this study has a detection limit of about 0.07 pmol I-' (3 SD) and a precision and accuracy of +2-5'/0 at the 0.24-2.4 pmol I-' concentration level. Linearity has been demonstrated up to about 4 pmol I-'. Comparability has been established with the previous blood lead analytical method used in other surveys via the analysis of 435 specimens by both the previous (modified Delves cup) and proposed methods. The equation of the resulting line is [ETA-AAS] = 1.0007[Delves] -0.051, r = 0.924.

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