Blood lead level and kidney function in US adolescents: The Third National Health and Nutrition Examination Survey

Abstract

Background: Chronic, high-level lead exposure is a known risk factor for kidney disease. The effect of current low-level environmental lead exposure is less well known, particularly among children, a population generally free from kidney disease risk factors such as hypertension and diabetes mellitus. Therefore, in this study, we investigated the association between lead exposure and kidney function in a representative sample of US adolescents.

Methods: Participants included 769 adolescents aged 12 to 20 years for whom whole blood lead and serum cystatin C were measured in the Third National Health and Nutrition Examination Survey, conducted from 1988-1994. The association between blood lead level and level of kidney function (glomerular filtration rate [GFR]), determined by cystatin C-based and creatinine-based estimating equations, was examined.

Results: Median whole blood lead level was 1.5 microg/dL (to convert to micromoles per liter, multiply by 0.0483), and median cystatin C-estimated GFR was 112.9 mL/min/1.73 m(2). Participants with lead levels in the highest quartile (> or =3.0 microg/dL) had 6.6 mL/min/1.73 m(2)-lower estimated GFR (95% confidence interval, -0.7 to -12.6 mL/min/1.73 m(2)) compared with those in the first quartile (<1 microg/dL). A doubling of blood lead level was associated with a 2.9 mL/min/1.73 m(2)-lower estimated GFR (95% confidence interval, -0.7 to -5.0 mL/min/1.73 m(2)). Lead levels were also associated with lower creatinine-based estimated GFR levels, but the association was weaker than with cystatin C-based GFR and not statistically significant.

Conclusions: Higher blood lead levels in a range below the current Centers for Disease Control and Prevention-designated level of concern (10 microg/dL) were associated with lower estimated GFRs in a representative sample of US adolescents. This finding contributes to the increasing epidemiologic evidence indicating an adverse effect of low-level environmental lead exposure.

Figure

Cystatin C–estimated glomerular filtration rate (GFR) by blood lead levels. The thick line represents estimated GFR based on restricted quadratic splines transformation for log-transformed blood lead levels (restricted to ≤10 μg/dL [to convert to micromoles per liter, multiply by 0.0483]) with knots at the 10th, 50th, and 90th percentiles. Thin lines represent corresponding 95% confidence intervals. Data points for the scatterplot represent adjusted blood lead and estimated GFR values and were calculated as the residuals from the weighted linear regression models of log-lead and estimated GFR on the covariates used in model 3 in Table 2. Mean log-lead and estimated GFR levels were added to the residuals to facilitate interpretation of the scatterplot. The horizontal axis is in log scale.