Abstract
Background: Outdoor ambient polycyclic aromatic hydrocarbon (PAH) concentrations are variable throughout an urban environment. However, little is known about how variation in semivolatile and nonvolatile PAHs related to the built environment (open space vs. semi-closed space) contributes to differences in concentrations. Methods: We simultaneously collected 14, two-week samples of PAHs from the outside of windows facing the front (adjacent to the street) open side of a New York City apartment building and the alley, semi-closed side of the same apartment unit between 2007 and 2012. We also analyzed samples of PAHs measured from 35 homes across Northern Manhattan and the Bronx, 17 from street facing windows with a median floor level of 4 (range 2–26) and 18 from alley-facing windows with a median floor level of 4 (range 1–15). Results: Levels of nonvolatile ambient PAHs were significantly higher when measured from a window adjacent to a street (an open space), compared to a window 30 feet away, adjacent to an alley (a semi-closed space) (street geometric mean (GM) 1.32 ng/m3, arithmetic mean ± standard deviation (AM ± SD) 1.61 ± 1.04 ng/m3; alley GM 1.10 ng/m3, AM ± SD 1.37 ± 0.94 ng/m3). In the neighborhood-wide comparison, nonvolatile PAHs were also significantly higher when measured adjacent to streets compared with adjacent to alley sides of apartment buildings (street GM 1.10 ng/m3, AM ± SD 1.46 ± 1.24 ng/m3; alley GM 0.61 ng/m3, AM ± SD 0.81 ± 0.80 ng/m3), but not semivolatile PAHs. Conclusions: Ambient PAHs, nonvolatile PAHs in particular, are significantly higher when measured from a window adjacent to a street compared to a window adjacent to an alley, despite both locations being relatively close to street traffic. This study highlights small-scale spatial variations in ambient PAH concentrations that may be related to the built environment (open space vs. semi-closed space) from which the samples are measured, as well as the relative distance from street traffic, that could impact accurate personal exposure assessments.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are naturally occurring combustion byproducts of coal, petroleum, and gasoline
Σ8 PAHnonvolatile measured from the street side were 18% higher than those measured from the alley side of the central site building (1.32 ng/m3 street side vs. 1.10 ng/m3 alley side)
Most of the individual nonvolatile PAHs were higher at the street side with the greatest relative differences in
Summary
Polycyclic aromatic hydrocarbons (PAHs) are naturally occurring combustion byproducts of coal, petroleum, and gasoline. Of particular concern in urban environments is exposure to PAHs from pervasive outdoor sources including automobile, diesel fuel, and heating oil emissions [8,9]. Important differences in spatial distribution of outdoor ambient PAHs have been described [10,11,12]. Lee et al reported highest PAH concentrations measured at a major intersection with heavy traffic, followed by urban and rural locations in Taiwan [11]. Within a city concentrations of outdoor airborne PAHs can vary significantly [13,14,15]. Nielsen described higher ambient PAH concentrations measured along a busy street in Copenhagen compared to concentrations measured in a park, several meters away [13]. A recent study observed a clear horizontal concentration gradient of PAHs within
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