title: Long-term trends (1990-2014), health risks, and sources of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the U.S.
abstract: Polycyclic aromatic hydrocarbons (PAHs) are a category of over 100 various chemicals released from numerous combustion sources. The ubiquity and toxicity of PAHs have posed high health risks on human populations. This study aims to examine the long-term trends of atmospheric PAHs at the national-level in the U.S., and evaluate their cancer risks. Daily concentrations of PAHs measured at 169 monitoring stations between 1990 and 2014 were obtained from the U.S. Environmental Protection Agency's Air Quality System. Temporal trends were examined using generalized linear model with generalized estimating equations. Random-effects analysis of variance was performed to explore variance between regions, sites, years, and months with a hierarchical structure. Source categories were identified using diagnostic ratios. National population level cancer risks were estimated using the relative potency factors and inhalation unit risk method. Ambient PAH concentrations displayed an overall downward trend (6-9% annual reduction) in urban areas, but not in rural areas. Seasonal and weekday/weekend effects were significant. Urban concentrations were twice of the rural level. The between-site variation outweighed the temporal variation, indicating large spatial heterogeneity. The predominant PAH sources were from traffic and non-traffic related fuel combustions with a dominant contribution from diesel emissions. The average excess lifetime cancer risk was estimated to be 9.3 ± 30.1 × 10-6(GM: 4.2 × 10-6) from exposure to ten carcinogenic PAHs. This is the first comprehensive study of the spatiotemporal trends of ambient PAHs at the U.S. national level. The results indicate that future efforts aimed to reduce PAH exposures should focus on diesel emission controls and extending the geographic coverage of air monitoring.
authors.affiliation: Icahn School of Medicine at Mount Saini, New York City, NY, USA.
authors.forename: Bian
authors.initials: B
authors.lastname: Liu
authors.affiliation: School of Public Health, University of Memphis, Memphis, TN, USA.
authors.forename: Zhuqing
authors.initials: Z
authors.lastname: Xue
authors.affiliation: College of Geosciences, China University of Petroleum-Beijing, Beijing, PR China.
authors.forename: Xianlei
authors.initials: X
authors.lastname: Zhu
authors.affiliation: School of Public Health, University of Memphis, Memphis, TN, USA. Electronic address: cjia@memphis.edu.
authors.forename: Chunrong
authors.initials: C
authors.lastname: Jia
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis* / Q000706:statistics & numerical data*; D002947:Cities / Q000706:statistics & numerical data; D004781:Environmental Exposure; D004784:Environmental Monitoring; D006306:Health Surveys; D006801:Humans; D019570:Inhalation Exposure; D016014:Linear Models; D009369:Neoplasms / Q000139:chemically induced / Q000453:epidemiology; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D011050:Policy Making; D011084:Polycyclic Aromatic Hydrocarbons / Q000009:adverse effects / Q000032:analysis*; D018570:Risk Assessment; D012423:Rural Health; D012621:Seasons; D014481:United States / Q000453:epidemiology; D014484:United States Environmental Protection Agency; D014504:Urban Health; D001335:Vehicle Emissions / Q000032:analysis* / Q000633:toxicity
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons; D001335:Vehicle Emissions
keywords: Cancer risk; Long-term; PAH; Polycyclic aromatic hydrocarbon; Source