Urinary lead in relation to combustion-derived air pollution in urban environments. A longitudinal study of an international panel

Abstract

Background:Urinary lead (Pb) is generally considered to have limited use in biomonitoring environmental ex-posure to lead. Carbon load in airway macrophages (AM BC) is an internal marker to assess long-term exposureto combustion-derived aerosol particles. In urban environments, atmospheric Pb and black carbon may havecommon sources. We aimed to study the temporal change of urinary Pb (U-Pb) when exposure to outdoor airpollution changes, and the relationship between U-Pb and AM BC.Methods:A panel of 50 young healthy adults [mean (SD) 26.7 (5.2) years], including 17 long-term (> 1 year)residents in Leuven, Belgium (BE), 15 and 18 newcomers (arrived < 3 weeks) from low- and middle-incomecountries (LMIC) and high-income countries (HIC), respectively, underwent 8 repeated measurements at 6 weeksintervals. In urine spot samples obtained at 5 time points (T1, T2, T4, T6, T8), 24 trace elements were quantifiedby inductively coupled plasma-mass spectrometry. At each time point, AM BC was quantified as the mediansurface of black inclusions (inμm2) by means of image analysis of 25 macrophages obtained by induced sputum.Changes in urinary metal concentrations (with and without creatinine correction) and the relationship betweenU-Pb and AM BC were estimated using linear mixed models adjusted for covariates and potential confounders.Results:Only U-Pb differed between groups and exhibited significant time trends. Participants from the LMICgroup had significantly higher initial U-Pb (1.18μg/g creat) than the HIC group (0.44μg/g creat) and BE group(0.45μg/g creat). In the LMIC group, U-Pb decreased significantly with time by 0.061μg/g creatinine per30 days [95% confidence interval (CI): 0.034, 0.088]. U-Pb remained unchanged in the other two groups. Anincrease in AM BC of 1μm2was associated with an increase in U-Pb of 0.369μg/g creat (95% CI: 0.145, 0.593).Conclusion:This panel study demonstrates that U-Pb may be a valid alternative to blood Pb for biomonitoringchanges in exposure to lead, at least at group level. In addition, we identified a positive association between U-Pband AM BC, a biomarker of exposure to traffic-related air pollution, suggesting the existence of common sourcesof Pb and black carbon in urban environments.