Low-Level Environmental Lead Exposure May Adversely Affect Renal Function

Laurie Barclay, MD

January 13, 2010

January 13, 2010 — Low-level environmental lead exposure may adversely affect renal function, according to results from the Third National Health and Nutrition Examination Survey, reported in the January 11 issue of the Archives of Internal Medicine.

"Chronic, high-level lead exposure is a known risk factor for kidney disease," write Jeffrey J. Fadrowski, MD, MHS, from Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, and colleagues. "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."

The study cohort consisted of 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, which took place from 1988 to 1994. The investigators evaluated the association between blood lead level and level of kidney function, reflected in glomerular filtration rate (GFR) calculated from cystatin C–based and creatinine-based estimating equations.

Median whole blood lead level was 1.5 μg/dL (to convert to micromoles per liter, multiply by 0.0483), and median cystatin C–estimated GFR was 112.9 mL/min/1.73 m2. Compared with participants in the first quartile of lead levels (<1 μg/dL), those with lead levels in the highest quartile (≥3.0 μg/dL) had a lower estimated GFR by 6.6 mL/min/1.73 m2 (95% confidence interval [CI], −0.7 to −12.6 mL/min/1.73 m2). Twofold increase in blood lead level was associated with lower estimated GFR by 2.9 mL/min/1.73 m2 (95% CI, −0.7 to −5.0 mL/min/1.73 m2). Although lead levels were also associated with lower creatinine-based estimated GFR levels, this association was not statistically significant and was weaker than with cystatin C–based GFR.

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

Limitations of this study include cross-sectional design precluding determination of causality, possibly incomplete adjustment for confounding factors, relatively small sample size, and single blood measurement.

"Further study should assess whether greater lead exposure contributes to the disproportionate burden of CKD in certain racial/ethnic groups," the study authors conclude. "Efforts to reassess the CDC's current lead level of concern should incorporate the results of this and other recent studies of environmental lead exposure."

The National Kidney Foundation and the National Institutes of Health supported this study. The study authors have disclosed no relevant financial relationships.

Arch Intern Med. 2010;170:75-82. Abstract

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