The application of benzo(a)pyrene (BaP)-toxic equivalent factor to polycyclic aromatic hydrocarbons (PAH) concentrations can provide a more accurate risk assessment from environmental exposure to PAH. We hypothesized that BaP-equivalent toxicity determined following residential air monitoring among young urban children may vary by season. Residential indoor and outdoor air levels of PAH measured over two-weeks in a cohort of 5–6 year old children (n = 260) in New York City were normalized to the cancer and mutagen potency equivalent factor of BaP (BaP = 1). Data are presented as carcinogenic equivalents (BaP-TEQ) and mutagenic equivalents (BaP-MEQ) for the sum of 8 PAH (∑₈PAH; MW ³ 228) and individual PAH and compared across heating versus nonheating seasons. Results show that heating compared to nonheating season was associated significantly with higher (BaP-TEQ)_∑8PAH and (BaP-MEQ)_∑8PAH both indoors and outdoors (p < 0.001). Outdoor (BaP-TEQ)_∑8PAH and (BaP-MEQ)_∑8PAH were significantly higher than the corresponding indoor measures during the heating season (p < 0.01). These findings suggest that at levels encountered in New York City air, especially during the heating season, residential exposure to PAH may pose an increased risk of cancer and mutation.

Consideration of the relationship between residential floor level and concentration of traffic-related airborne pollutants may predict individual residential exposure among inner city dwellers more accurately. Our objective was to characterize the vertical gradient of residential levels of polycyclic aromatic hydrocarbons (PAH; dichotomized into Σ₈PAH_semivolatile (MW 178–206), and Σ₈PAH_nonvolatile (MW 228–278), black carbon (BC), PM_2.5 (particulate matter) by floor level (FL), season and building type. We hypothesize that PAH, BC and PM_2.5 concentrations may decrease with higher FL and the vertical gradients of these compounds would be affected by heating season and building type. PAH, BC and PM_2.5 were measured over a two-week period outdoor and indoor of the residences of a cohort of 5–6 year old children (n = 339) living in New York City’s Northern Manhattan and the Bronx. Airborne-pollutant levels were analyzed by three categorized FL groups (0–2nd, 3rd–5th, and 6th–32nd FL) and two building types (low-rise versus high-rise apartment building). Indoor Σ₈PAH_nonvolatile and BC levels declined with increasing FL. During the nonheating season, the median outdoor Σ₈PAH_nonvolatile, but not Σ₈PAH_semivolatile, level at 6th–2nd FL was 1.5–2 times lower than levels measured at lower FL. Similarly, outdoor and indoor BC concentrations at 6th–32nd FL were significantly lower than those at lower FL only during the nonheating season (p < 0.05). In addition, living in a low-rise building was associated significantly with higher levels of Σ₈PAH_nonvolatile and BC. These results suggest that young inner city children may be exposed to varying levels of air pollutants depending on their FL, season, and building type.