Lead health effects in drinking water

Elevated blood lead in young children due to lead-contaminated drinking water: Washington, DC, 2001-2004

Incidence of EBL (blood lead > or =10 microg/dL) for children aged < or = 1.3 years in Washington, DC increased more than 4 times comparing 2001-2003 when lead in water was high versus 2000 when lead in water was low. The incidence of EBL was highly correlated (R2 = 0.81) to 90th percentile lead in water lead levels (WLLs) from 2000 to 2007 for children aged < or = 1.3 years. The risk of exposure to high water lead levels varied markedly in different neighborhoods of the city. For children aged < or =30 months there were not strong correlations between WLLs and EBL, when analyzed for the city as a whole. However, the incidence of EBL increased 2.4 times in high-risk neighborhoods, increased 1.12 times in moderate-risk neighborhoods, and decreased in low-risk neighborhoods comparing 2003 to 2000. The incidence of EBL for children aged < or =30 months also deviated from national trends in a manner that was highly correlated with 90th percentile lead in water levels from 2000 to 2007 (R2 = 0.83) in the high-risk neighborhoods. These effects are consistent with predictions based on biokinetic models and prior research.

Differential ototoxicities induced by lead acetate and tetraethyl lead

Lead poisoning disrupts many biological structures and functions, including those of the auditory system. This study examined the ototoxic effects of lead acetate (LA) and tetraethyl lead (TEL) of equal lead content on cochlear function and the ability of alpha-phenyl-tert-butyl-nitrone (PBN) to attenuate such effects. Baseline 1.0 microV cochlear microphonic (CM) and compound action potential (CAP) responses were recorded and animals administered either PBN (100 mg/kg, i.p.) or an equal volume of 0.9% saline, followed by an i.p. injection of LA (50 mg/kg) in an ethanol vehicle, TEL (42.7 mg/kg) in a corn oil vehicle, corn oil or ethanol vehicle alone. Two hours after administration, post-exposure CM and CAP responses were recorded. CAP threshold shifts in the saline-LA group were elevated by 5-10 dB at mid to high frequencies relative to controls (20-24 kHz, P<0.05). Mean CAP threshold shifts in the saline-TEL were significantly greater than those of both control groups at all tested frequencies except 2 kHz (P<0.001). However, threshold shifts in the group receiving PBN prior to TEL were significantly smaller than shifts in the group receiving saline prior to TEL (P<0.01). These data suggest that TEL is more ototoxic than is LA and that free radicals partially mediate TEL-induced CAP disruption.

Application of clearance concepts to the assessment of exposure to lead in drinking water

This paper explores the application of clearance concepts to environmental toxicology. Lead, for which a clearance of about 0.5 ml/min is estimated from published data, is chosen as an example. An index for the contribution of drinking water to total exposure is developed using these concepts. For lead, this index is shown to increase with the concentration of the metal in water; it is higher for children than for adults. At the maximum contaminant level (MCL) of 10 micrograms/L proposed by the US Environmental Protection Agency (EPA), the average contribution from lead in drinking water is estimated to be 7 percent. The contribution in children is about twice as great. At and above the current MCL of 50 micrograms/L, drinking water becomes a major source of lead exposure.