Exploring the Nexus of Two-Wheeler Gaseous Contributions and Driver Exposure in a Million-Plus Population City

In Indian metropolitan cities, two-wheelers (2W) constitute 60–70% of traffic, making their emissions a significant contributor to urban air pollution. This study measured 2W exhaust emissions and driver exposure under real-world traffic conditions in the Chennai metropolitan area. Emission factors for CO, HC, and NO were 1.1, 0.02, and 0.03 g/km, respectively. However, limited studies on 2W are available due to the complexity of real-world measurements in Indian traffic conditions. The gaseous emissions from the measured vehicles are lower than their respective Bharat Stage (BS) standards except for CO. Personal exposure levels for PM₁₀, PM_2.5, and PM₁ were 212.5, 78.1, and 58.9 µg/m³, with the highest exposures occurring during idling and driving behind heavy-duty vehicles. The Multiple Particle Path Dosimetry (MPPD) model was used to estimate the deposition fractions in the human respiratory tract (HRT). Results indicated that PM_2.5 and PM₁ deposition fractions are higher in the pulmonary region, whereas PM₁₀ deposition is higher in the head region. 2W drivers are exposed to higher concentrations than any other motor vehicle driver. Since there is no substantiation of a tolerable limit of PM₁ exposure or a threshold beyond which no detrimental health implications occur, cautious planning is needed when developing the roads.