Particulate phase polycyclic aromatic hydrocarbons in the ambient atmosphere of a protected and ecologically sensitive area in a tropical megacity

•Particulate polycyclic aromatic hydrocarbons at an urban protected area studied.•Significantly higher levels of PAH found in winter than in other seasons.•Vehicular, wood and coal combustion contributed to the observed PAH levels.•Carcinogenic PAHs contributed substantially and inhalation risks were considerable. This study reports, for the first time, the profiles and source analysis of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) associated with PM10 (particulate matter with aerodynamic diameter ≤10μm) at a protected and ecologically sensitive area – the Yamuna Biodiversity Park – located in the megacity Delhi, India. Weekly PM10 sampling was carried out at this location for 1 year (2009–2010) and the annual mean PM10 level was found to be ∼9 times the World Health Organization limit. Seasonal variation of PAHs (range 37.2–74.0ngm−3) was significant with winter values being 72% and 68% higher than summer and monsoon respectively. Principal component analysis coupled with multiple linear regression identified diesel, natural gas and lubricating oil combustion (49.5%), wood combustion (25.4%), gasoline (15.5%) and coal combustion (9.6%) sources for the observed PAHs. Heavy traffic on the national highway and arterial roads and domestic emissions from suburban households in the vicinity of the park appeared to have significantly affected its air quality. A substantial portion (∼55%) of the aerosol PAH load was comprised of carcinogenic species, which yielded a considerably high lifetime inhalation cancer risk estimate (8.7E−04). If considered as a conservative lower-bound estimate, this risk translates into ∼211 excess cancer cases for lifetime inhalation exposure to the observed PAH concentrations in Delhi.