Associations between Three Specific A-Cellular Measures of the Oxidative Potential of Particulate Matter and Markers of Acute Airway and Nasal Inflammation

Abstract

Background: The oxidative potential (OP) of particulate matter (PM) has been proposed as a more health relevant metric than PM mass. However, there is little evidence in epidemiological studies that OP is more closely associated with health effects than PM mass or other PM characteristics. Aim: To evaluate the associations between 3 specific a-cellular metrics of OP of PM and acute health effects. Methods: We exposed 31 volunteers to ambient air pollution at five different locations in the Netherlands: an underground train station, 2 traffic sites, a farm and an urban background site. Each volunteer visited at least 3 different sites, and was exposed for 5 h including intermittent exercise. Health measurements were conducted before exposure, 2 h after exposure and the next morning. Air pollution was measured on site, including PM mass and number concentrations, PM composition (e.g. EC/OC, metals, PAHs). The OP of PM2.5 and PM10 was measured using 3 a-cellular assays; dithiotreitol (OPDTT), electron spin resonance (OPESR) and ascorbate depletion (OPAA). One and two pollutant mixed models were used to analyse associations between exposure and health outcomes. Results: In single-pollutant models, all measures of OP were significantly associated with increases in FENO and increases in IL-6 in nasal lavage (NAL) 2 hours after exposure. Effect estimates increased considerably after excluding or adjusting for the underground; the site with by far the highest levels of OP. Results from two-pollutant models also differed depending on how the underground was considered: For all sites PNC and NO2 were consistently associated with FENO and NAL IL-6, respectively, whereas after excluding the underground we found consistent associations with OP. Conclusion: We found significant associations between the OP of PM and markers of airway and nasal inflammation. However, consistency of effects in two pollutant models depended on how measurements at the underground site were considered.