Relationship between particle and metal concentrations in subway workers’ personal breath zone (PBZ), exhaled breath condensate (EBC), and urine

Abstract

BACKGROUND AND AIM: Subway exposure health effects are still unknown. We analyzed particle and metal exposure in the PBZ, EBC and urine of subway workers METHODS: PBZ of nine station agents, locomotive operators and security guards was sampled during 6-h shifts over two weeks. Urine and EBC samples were collected pre- and post-shift. Mass concentrations of PM10, PM2.5 and their metal constituents were determined in PBZ, urine and EBC, along with ultrafine particle (UFP) number in PBZ and EBC. Urine and EBC metal concentrations were standardized by creatinine and EBC volume, respectively, and log-transformed. RESULTS:PBZ PM mass concentrations were above the WHO guideline for indoor air but varied significantly between jobs. Locomotive operators had the highest exposure (189 and 137 μg/m3 for PM10 and PM2.5, respectively), while station agents had the highest UFP exposure (1.97x104 #/cm3). Only Al, Fe and Zn in both PM2.5 and PM10 and Cu and Mn in PM2.5 were above the limit of quantification. By mass fraction, Fe, Cu, Al and Zn were the most abundant. Security guards had the highest Al exposure in both PM2.5 and PM10, while locomotive operators had the highest PM10 Fe exposure. In EBC, the pre/post-shift metal concentrations ordered ZnCuNiBaMn. Security guards had the highest EBC metal concentrations, particularly Zn and Cu. Urinary concentrations ordered SiZnMoTiCuBa≈NiCo. Station agents and locomotive operators had the highest Si and Zn concentrations, respectively. Post-shift EBC Zn and Cu were associated with Zn and Cu concentrations in PM10 and with post-shift urinary Zn and Cu concentrations. Particle number in EBC was significantly correlated with UFP number in PBZ. CONCLUSIONS:This is the first study exploring a triple assessment of particle and metal exposure in a subway. The use of EBC in addition to urine seems more informative for individual airborne exposure biomonitoring in subways. KEYWORDS: particulate matter, ultrafine particles, mass concentration, exposure biomarquer