Randomized Cross-Over Study of In-Vehicle Cabin Air Filtration, Air Pollution Exposure, and Acute Changes to Heart Rate Variability, Saliva Cortisol, and Cognitive Function.

ABSTRACT

To determine how traffic-related air pollution (TRAP) exposures affect commuter health, and whether cabin air filtration (CAF) can mitigate exposures, we conducted a cross-over study of 48 adults exposed to TRAP during two commutes with and without CAF. Measurements included particulate air pollutants (PM2.5, black carbon [BC], ultrafine particles [UFPs]), volatile organic compounds, and nitrogen dioxide. We measured participants' heart rate variability (HRV), saliva cortisol, and cognitive function. On average, CAF reduced concentrations of UFPs by 26,232 (95%CI 11,734, 40,730) n/cm3, PM2.5 by 6 (95%CI 5, 8) µg/m3, and BC by 1348 (95%CI 1042, 1654) ng/m3, or 28, 30, and 32%, respectively. Each IQR increase in PM2.5 was associated with a 28% (95%CI 2, 60) increase in high-frequency power HRV at the end of the commute and a 22% (95%CI 7, 39) increase 45 min afterward. IQR increases in UFPs were associated with increased saliva cortisol in women during the commute (18% [95%CI 0, 40]). IQR increases in UFPs were associated with strong switching costs (19% [95%CI 2, 39]), indicating a reduced capacity for multitasking, and PM2.5 was associated with increased reaction latency, indicating slower responses (5% [95%CI 1, 10]). CAF can reduce particulate exposures by almost a third.