Legacy Contaminants of Emerging Concern: Lead (Pb), Flint (MI), and Human Health

Abstract As a heavy metal industrially mined for millenia, lead (Pb) is a legacy contaminant. It is also a contaminant of emerging concern because of its persistence, toxicity, and recent discovery of its resurgence in drinking water serving homes and schools, recently and most notoriously in Flint, Michigan. Concern about lead, however, has reemerged beyond Flint, exemplifying adoption of bad science policy despite availability of relevant good science. Much is known about lead toxicity, and profiled here. Whereas adults chronically exposed to lead may experience peripheral neuropathy, infants and children are more susceptible. They constitute sensitive subpopulations because their blood-brain barriers are immature, making them susceptible to central nervous system effects, most notably reduced IQ, when lead penetrates to developing brains. Failure to protect disadvantaged populations in Flint and beyond despite availability of proven science and inexpensive technology also exemplifies instances of environmental injustice. Emerging concern about lead thus illustrates failure of social as well as science policy. A critical lesson to be learned is that vigilance must be maintained, as knowledge about lead exposure and toxic effects provided by science does not automatically result in consistent and evenhanded legal and regulatory protection provided by government.