A Space/Time Particulate Matter Mass Fraction Framework for the Assessment of Outdoor Exposure to Polycyclic Aromatic Hydrocarbons After 9/11 in New York City

Abstract

P-061 Introduction: Recent papers indicate that Particle-bound Polycyclic Aromatic Hydrocarbons (PAHs) may have adverse effects on birth outcomes. A recently developed method is available for analyzing the concentration of PAHs in archived PM2.5 samples. Using the expansive PM2.5 monitoring network available, this work proposes a space/time estimation method for the exposure assessment of atmospheric PAH where PM2.5 data are available, with a few re-analyzed for PAHs. This method is tested and implemented using data collected after 9/11 around the World Trade Center site. Methods: Nine particle-bound PAHs: benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, and benzo(e)pyrene were measured in archived PM2.5 samples at four locations around Ground Zero from September 22, 2001 until March 27, 2002. The EPA AIRS monitoring system regularly collected PM2.5 data during this time period across the entire New York/New Jersey area. Using the small subset of archived PM2.5 samples that were re-analysed for PAHs, we developed a non-parametric, probabilistic model predicting the PAH mass fraction in the neighbourhood of the WTC. This model is used at remaining PM2.5 samples to obtain soft PAH data. Bayesian Maximum Entropy data integration of the few directly measured PAH data with the more numerous soft data was performed to obtain an assessment of the population exposure to PAHs after 9/11. Results: Even with the limited spatial domain of available PAH data and a mass fraction created only as a function of time, a spatial validation showed the addition of PAH data derived from PM2.5 reduced the mean squared error from 7–22%. Since the maximum spatial distance available for validation was small, the MSE reduction should only improve at greater distances. Temporally, there was an exponential improvement in MSE positively associated with the number of days of PAH data removed. Discussion/Conclusions: PAH compounds were elevated in New York after 9/11 due to burning jet fuel, the towers' collapse and ensuing fires, diesel equipment used in the clean-up process, and the background concentrations already present. Our results provide the first maps using a mass fraction approach to obtain an assessment of the space/time exposure of the population to atmospheric PAHs after 9/11. These maps show the highest cumulated PAH exposure to be southwest of the WTC site, but with its high population density, the largest effect should be in eastern lower Manhattan. The mass fraction approach combined with optimal PAH sampling looks promising as an exposure index for future PAH research.