Response to Sinks and Jackson

value, a maternal BPb value of 10 pg/dl, as seen in Table 1, should not be exceeded. If no more than 5% of breast-feeding infants are to exceed the 10 pg/dI action level, then a maternal BPb <10 jig/dl is required. A sensitivity analysis using various IEUBK modeling runs shows that the infant body lead burden at birth, from in utero accumulation via maternal lead exposures, is mainly expressed through estimated BPb values in the first 6 months of infant life, as compared to the second 6 months of infant life or as compared to exposure integrated over the entire first year of infant life. This is to be expected, given the relatively high bio-kinetic mobility of lead in the very young. However, it is precisely in the first 6 months of infant life that breast-feeding is done. Therefore, both breast milk lead and prior infant body lead burden are significant sources of lead in breast-feeding infants of mothers with elevated lead exposures. In essence, the only maternal BPb level that is in fact "safe" in terms of CDC Class III elevated infant BPb figures also approximates the CDC infant BPb action level of 10 pg/dl. In terms of the child action level of 10 pg/dl, a maternal BPb <10 pg/dl appears prudent. The 1991 CDC statement on childhood lead poisoning (6) identified a BPb level of 10 pg/dl as being the body lead threshold associated with the earliest toxic effects in infants and toddlers. The CDC document also accepted the risk assessment premise that there is no known threshold for lead's subtle toxicity. Sinks and Jackson argue that the most recent NHANES III, 1991-1994, indicates that there are no women in the United States who are likely to be nursing their infants and who have BPb values anywhere dose to the 40 pg/dl Sinks and Jackson daimed as permissible for nursing mothers. They cite some actual numbers noted in the NHANES III data tapes (7). Such prevalence data are aggregated cluster sample depictions at a single time point of the U.S. population lead exposure picture, stratified by national socioeconomic and demographic strata. One cannot legitimately disaggregate such national depictions or "snapshots" to generate comparisons for individual community prevalences or to use actual BPb values contained in any particular statistical sampling cell in the aggregation process. Such limits are discussed in, among other things, the Executive Summary of the 1988 …