Exposures to polycyclic aromatic hydrocarbons among adults and children: Contributions from multiple pathways and sources.

Polycyclic aromatic hydrocarbons (PAHs) exist ubiquitously in the natural environment; however, studies seldom evaluate health risks from aggregate exposures to PAHs from multiple environmental media. This study aimed to estimate the doses and risks of 16 priority PAHs in soil and air for both children and adults and quantify their contributors. Soil and ambient air samples were collected at 50 and 8 sites, respectively, in Memphis, Tennessee, USA. Grab soil samples were taken from the upper 2 inches of the soil and air samples were collected every 12 days for over one year. The sum concentration of 16 PAHs (ΣPAH) averaged 7.6 ± 15.0 mg/kg (range 1.5-98.8 mg/kg) in soil and 73.6 ± 25.3 ng/m (range 47.0-121.2 ng/m) in air. Source apportionment identified five broad sources of soil and airborne PAHs: vehicle emissions, petrogenic sources, coal combustion, emissions from coal tar, and natural gas combustion. For children aged 3-6 years, the average daily dose (ADD) of ΣPAH was 58.3 ng/kg-day, with 66%, 27%, and 7% from inhalation, ingestion, and dermal contact, respectively. The lifetime cancer risk from all PAHs was 0.42 × 10, with ingestion being the primary contributor (75%). For adults aged 21-30 years, the ADD of ΣPAH was 46.2 ng/kg-day, with contributions of 67%, 31%, and 2% from dermal contact, inhalation, and ingestion, respectively. The lifetime cancer risk from all PAHs was 0.55 × 10, mainly due to dermal contact (96%). Vehicle emissions, petrogenic sources, and coal combustion together contributed over 85% of the cancer risk. The findings provided bases for designing effective exposure controls, including source control and personal behavioral changes.