Airborne heavy metals and blood pressure: Modification by sex and obesity in the MMDA traffic enforcers’ health study

Abstract

Epidemiological studies have linked exposure to heavy metals and increased blood pressure (BP). We conducted a repeated measures study to examine the associations between airborne heavy metals and BP, and we looked at effect modification by participant characteristics. We assessed blood cadmium (B–Cd), lead (B–Pb), and mercury (B–Hg), and studied measurements of systolic (SBP) and diastolic (DBP) blood pressure on 140 traffic enforcers from the Metropolitan Manila Development Authority Traffic Enforcers’ Health Study. Linear mixed-effects models with random subject-specific intercepts were fitted to estimate the effect of B-CD, B–Pb, and B–Hg exposure on the percent change in mean SBP and DBP, adjusting for potential confounding factors. Moreover, effect modification by sex and obesity were assessed. B–Pb and B–Cd concentrations were related to increased BP. A unit (1.0 μg/dL) increase in B–Pb was associated with 2.5% [95% confidence interval (CI): 1.3–3.7] and 2.1% (95% CI: 0.7–3.5) increases in mean SBP and DBP, respectively. A similar result was observed for the effect of B–Cd on SBP (2.2% increase, 95% CI: 0.6–3.7) but not on DBP (0.9% increase, 95% CI: −0.9–2.7). However, no association between B–Hg and BP was observed. The associations between B–Pb and both DBP and SBP were stronger among males (SBP: 2.7% increase, 95% CI: 1.5–4.0; DBP: 2.3% increase, 95% CI: 0.8–3.7) versus females, or traffic enforcers who were nonobese (SBP: 2.8% increase, 95% CI: 1.5–4.2; DBP: 2.9% increase, 95% CI: 1.3–4.4) versus obese. In summary, B–Pb and B–Cd are associated with increased BP. B–Pb may both increase SBP and DBP among male, or nonobese traffic enforcers.