Incident ESRD among participants in a lead surveillance program

Background: Very high levels of lead can cause kidney failure; data about renal effects at lower levels are limited.

Study design: Cohort study, external (vs US population) and internal (by exposure level) comparisons.

Settings & participants: 58,307 men in an occupational surveillance system in 11 US states.

Predictor: Blood lead levels.

Outcome: Incident end-stage renal disease determined by matching the cohort with the US Renal Data System (n=302).

Measurements: Blood lead categories were 0-<5, 5-<25, 25-<40, 40-51, and >51 μg/dL, defined by highest blood lead test result. One analysis for those with data for race (31% of cohort) and another for the whole cohort after imputing race.

Results: Median follow-up was 12 years. Among those with race information, the end-stage renal disease standardized incidence ratio (SIR; US population as referent) was 1.08 (95% CI, 0.89-1.31) overall. The SIR in the highest blood lead category was 1.47 (95% CI, 0.98-2.11), increasing to 1.56 (95% CI, 1.02-2.29) for those followed up for 5 or more years. For the entire cohort (including those with race imputed), the overall SIR was 0.92 (95% CI, 0.82-1.03), increasing to 1.36 (95% CI, 0.99-1.73) in the highest blood lead category (SIR of 1.43 [95% CI, 1.01-1.85] in those with ≥5 years' follow-up). In internal analyses by Cox regression, rate ratios for those with 5 or more years' follow-up in the entire cohort were 1.0 (0-<5 and 5-<25 μg/dL categories combined) and 0.92, 1.08, and 1.96 for the 25-<40, 40-51, and >51 μg/dL categories, respectively (P for trend=0.003). The effect of lead was strongest in nonwhites.

Limitations: Lack of detailed work history, reliance on only a few blood lead tests per person to estimate level of exposure, lack of clinical data at time of exposure.

Conclusions: Data suggest that current US occupational limits on blood lead levels may need to be strengthened to avoid kidney disease.