Blood lead concentrations in marine mammals validate estimates of 10(2)- to 10(3)-fold increase in human blood lead concentrations.

Measurements of ultra-low ambient blood lead (PbB) concentrations (mean +/- SD = 0.13 +/- 0.06 micrograms/dL) in Northern elephant seal (Mirounga angustirostris) validate previous estimates of ultra-low PbB levels in preindustrial humans. These estimates had been unsubstantiated, since PbB levels in this range had never been measured in any organisms prior to this study. Similarities in PbB levels among these contemporary and preindustrial mammals are consistent with similarities in their measured and estimated lead exposures, respectively. The marginally higher PbB levels and rates of lead exposure in contemporary marine mammals are, also, consistent with lead isotopic composition analyses that indicate their PbB levels have been elevated from exposure to industrial lead. Consequently, these analyses substantiate concerns that current baseline PbB levels in humans, which are estimated to be two to three orders of magnitude above natural levels, may still constitute public health risks.