Exposure to in-vehicle respirable particulate matter in passenger vehicles under different ventilation conditions and seasons

This study presents the in-vehicle particulate matter (PM) concentration in a number of passenger vehicles under various ventilation modes, land use land cover (LULC) in different seasons in megacity Delhi, India. In-vehicle monitoring was conducted in buses, cars and autos (three-wheeler) using air-conditioned (AC) and Non-AC during peak and off-peak hours. The site selected is a ∼15 km long stretch from Punjabi Bagh to Safdarjung Hospital, based on diversity in LULC, availability of vehicles and heavy traffic flow along the direction of travelling. In-vehicle PM was measured using GRIMM aerosol spectrometer and categorised in three classes (PM1, PM2.5 and PM10). The study found that concentration of PM1, PM2.5 and PM10 were significantly (p ≤ 0.05) higher in winters as compared to summers. It was observed that PM concentration was significantly (p ≤ 0.05) higher in Non-AC travel modes compared to AC modes. PM concentrations were high near industrial and commercial areas and during traffic congestion showing the influence of LULC. It is also important to highlight that PM1, PM2.5 and PM10 concentrations were significantly (p ≤ 0.05) higher in case of taxis (cars) compared to personal cars which varied from 2.5 to 3.5 times higher in case of AC mode and ∼1.5 times in case of Non-AC mode. Exposures to PM concentration were highest in case of Non-AC bus compared AC-Bus, Non-AC cars, autos and AC-cars. PM concentrations in case of autos and Non-AC cars were almost comparable without any significant (p > 0.05) difference. Regression analysis showed significant correlation between ambient and in-vehicle concentration for PM2.5. Regional deposition fractions were calculated using International Commission on Radiological Protection model to show the deposition in head air-pass, trachea-bronchial and alveolar regions. It was found that deposition of PM1 was highest in the alveolar region