Blood pressure and renal function responses in workers exposed to lead for up to six years

Objective: As the contemporary environmental lead exposure is comparable to the pre-industry levels in developed countries, whether lead exposure still contributes to the hypertension and renal impairment is controversial. We aimed to assess the association between blood pressure, renal function and lead exposure at contemporary low level in a longitudinal occupational cohort. Design and method: The Study for Promotion of Health in Recycling Lead assessed the blood pressure (BP) including the incidence of hypertension and renal function (RF) responses for up to six years in the workers without previous occupational exposure. BP averaged by 5 consecutive readings and the estimated glomerular filtration rate (eGFR) derived from serum creatinine and cystatin C (eGFRcrt and eGFRcys). Blood lead (BL) was measured by inductively coupled plasma mass spectrometry (detection limit 0.5 mg/dL). The statistical methods included multivariable-adjusted mixed models and interval-censored Cox regression analysis. Results: The 234 workers analysed were on average 28.5 years old and included 91.9% men. The baseline BL concentration was 4.35 microgram/dL and increased 3.17-fold over follow-up (median: 2.03 years; range: 0.92-6.45 years). The changes in BP and RF were not significantly correlated with the follow-up-to-baseline BL ratio (p >= 0.51 and p >= 0.18, respectively). The fully-adjusted changes in systolic/diastolic BP associated with a doubling of BL were -0.25/-0.12 mm Hg (CI: -0.94 to 0.44/-0.66 to 0.42 mm Hg). Accordingly, the incidence of stage-1 or stage-2 hypertension was not associated with the BL change (p >= 0.063). Similarly, the changes in eGFRcrt and eGFRcys associated with a 2 fold BL increment were not significant, amounting to -0.70 mL/min/1.73 m2 (CI: -1.70 to 0.30 mL/min/1.73 m2) and 1.06 ml/min/1.73 m2 (-2.16 to 0.03 mL/min/1.73 m2). Conclusions: The BP and RF responses to an over 3-fold BL increment were small and not significant confirming the safety of modern lead-handing facilities operating under current safety rules.