Associations Between Outdoor Air Pollution and the Retinal Microvasculature in School-aged Children in a Region Impacted by Residential Biomass Burning

Abstract

BACKGROUND AND AIM: Disruptions to the microcirculation may be an important pathway by which fine particulate air pollution (PM2.5) and oxidant gases contribute to cardiovascular disease. To date, little is known about the early-life cardiovascular health impacts of air pollution. This study aimed to evaluate associations between outdoor air pollution (PM2.5 and oxidant gases) and retinal blood vessel diameter (a measure of microvascular health) in children living in a region impacted by residential biomass burning. METHODS: In this repeated-measures panel study in rural British Columbia, Canada, a median of 6 retinal vessel measurements were collected from 64 children (ages 4-12 years), for a total of 344 retinal measurements. Daily mean PM2.5, nitrogen dioxide (NO2) and ozone (O3) were measured, and the combined oxidant capacity of NO2 and O3 was calculated using a redox-weighted average (Ox). Linear mixed-effect models with a random subject intercept were used to estimate associations between PM2.5 or Ox (same-day, 3-day, 7-day, and 21-day means) and the diameter of retinal arterioles and venules, adjusting for confounding variables. Models with an interaction term between PM2.5 and Ox were also run to assess whether associations between PM2.5 and retinal vessel diameter were modified by Ox. RESULTS:Ox was inversely associated with retinal arteriolar diameter, with the strongest association observed for 7-day mean exposures: each 10 ppb increase in Ox was associated with a 2.63 μm decrease in arteriolar diameter (95% confidence interval: -4.63, -0.63). Moreover, Ox modified associations between PM2.5 and arteriolar diameter, with weak inverse associations observed between PM2.5 and arteriolar diameter only at higher concentrations of Ox. CONCLUSIONS:Our results suggest that outdoor air pollution has a measurable impact on the microvasculature of children. Moreover, our findings indicate that interactions between PM2.5 and Ox may play a role in determining the magnitude and direction of these associations. KEYWORDS: children's environmental health, particulate matter, ozone, cardiovascular diseases, short-term exposure