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 (PM 2.5 , 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/cm 3 , PM 2.5 by 6 (95%CI: 5, 8) μg/m 3 , and BC by 1348 (95%CI: 1042, 1654) ng/m 3 , or 28, 30, and 32%, respectively. Each IQR increase in PM 2.5 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 PM 2.5 was associated with increased reaction latency, indicating slower responses (5% [95%CI: 1, 10]). CAF can reduce particulate exposures by almost a third.

A review of air pollution as a driver of cardiovascular disease risk across the diabetes spectrum

“…Thus, people with prediabetes or diabetes could be encouraged to use central air conditioning, if accessible and affordable, instead of electric fans and especially instead of opening windows for indoor temperature regulation. The results of a few experimental studies also support the use of in-vehicle air conditioning to reduce air pollution exposure while driving ( 192 – 194 ).…”

Correspondence on “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”

“…In addition, adherence to reporting guidelines such as recruitment time and information about time intervals for intervention are unclear. We also found discrepancies between study periods mentioned in the registered protocol (October and November 2014) and published paper (October and November 2015) …”

“…We also found discrepancies between study periods mentioned in the registered protocol (October and November 2014) 2 and published paper (October and November 2015). 1 In conclusion, the study by Mallach et al provides insights into cabin air filtration, but we consider that the reporting of results may not follow a standard in RCT such as CONSORT. 5 We hope randomized studies in environmental sciences will be reported in accordance with the standard.…”

“…I n their recent study, Mallach et al present a randomized crossover investigation into the efficacy of cabin air filtration. 1 While the study employed a randomized, doublemasked, placebo-controlled crossover approach, our critical reading reveals key concerns in the statistical methods and resulting reporting.…”

Personal Strategies to Reduce the Cardiovascular Impacts of Environmental Exposures

“…Instead, they designed high-efficiency filters that were highly effective at reducing in-cabin UFP (93% reduction) compared with standard filters (35%–70% reduction). Mallach et al 22 studied the effect of commercially available in-cabin electrostatic air filters compared with sham filters on HRV using a randomized, double-blind, crossover design. Healthy adult participants were driven through Montreal morning traffic.…”