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.