Chemical Education Today
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Research Advances by Angela G. King
Not all chemistry research workers collect data in laboratories. Two recent studies have analyzed air for pollutants related to tailpipe-emissions. The work of these scientists is helping to guide development of public policy that will improve air quality, and thus benefit our health. Tunnel Study Indicates Policies Reduce PAH Levels Scientists in New Jersey, New York, and North Carolina have collaborated on a study that indicates that approaches developed to help control traffic-related health pollution are working. Their scientific work is helping scientists complete retrospective epidemiological studies that may guide future government initiatives. Jan Beyea and colleagues estimated levels of benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH). PAHs are associated with many forms of cancer and traffic emissions are a major source of PAH exposure, both indoors and outdoors. Beyea and her team focused on BaP, both because it is considered a good marker of overall PAH levels and because it was measured in every PAH tunnel study the researchers could identify. They used data from 13 individual studies including eight different tunnels on U.S. roads during the period 1961–2004 as their starting point. The studies all sampled air from 30 minutes to two-week periods, passing the air over a filter that collected BaP. The filters were then extracted and BaP levels recorded. Traffic emissions are the main BaP source in tunnels, with tires and brake linings making very small contributions. Of the 13 studies the authors considered, three reported BaP levels in terms of vehicle-km traveled based on tunnel output concentrations and measured tunnel ventilation rates. For other studies, Beyea’s team used reported “tracer” emission factors. Tracers are co-pollutants, such as CO and CO2, whose levels can be related to BaP levels. For instance, BaP levels per vehicle-km were established by using a published study of BaP emitted per unit of consumed fuel by dividing by the national fuel economy rates for the relevant year, taking into account the percentages of trucks in each tunnel. The results of standardized unit comparison show that rates of BaP emission fell by more than 30 μg per vehicle-km to 2 μg/ kg averaged over the 1990s (Figure 1). Specifically a 91% drop was observed in the Baltimore Harbor Tunnel between 1975 and 1984 although the percentage of truck traffic remained relatively constant at ~12%. This decline mirrors what has been determined previously for other pollutants, such as VOC and particulate levels. The research team proposes that this in depth analysis will help quantitate many factors involved in a cost-benefit study of air pollution regulations and help support initiatives such as the introduction of automotive pollution controls like those that helped generate the observed 15 fold decrease during the time period of their analysis.
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Figure 1. Emission of benzo(a)pyrene from U.S. vehicles per km of travel, based on data collected in tunnels. Reprinted with permission from Environ. Sci. Technol. 2008, 42, 7315–7320. Copyright 2008 American Chemical Society.
Outside the Tunnel: Air Pollution on a Personal Level Led by Rachel Miller of Columbia University, scientists in New York and Texas recently completed a study that compared data on multiple traffic-related air pollutant levels collected between 1998 and 2006 at five stationary sites in New York City and individual exposure to PAHs as recorded by the monitoring of pregnant women involved in a longitudinal birth cohort study. As part of an investigation of the impact of prenatal and postnatal air pollution on children’s health, the Columbia Center for Children’s Environmental Health at the Mailman School of Public Health recruited pregnant women between 1998 and 2006 to wear backpacks containing mobile personal monitors during the day, and have them beside their beds at night for a 48 hour period. The monitors were equipped with a quartz filter and polyurethane foam cartridge that was then analyzed for eight individual PAHs by standard protocol. The participants also completed questionnaires that reported their exposure to tobacco smoke, sautéing or frying oil, and home heat source. Miller’s team also studied data on levels of carbon, fine particulate matter with a diameter of 2.5 μm or less (PM2.5), and 10 different metals collected at stationary sites throughout New York City (NYC) by the New York Department of Environmental Conservation beginning in 1999. The new report aggregated both personal monitoring data by pregnant women and the stationary site readings to assess any link between personal PAH levels and traffic-related emissions, as well as any changes due to public policy. The results showed significant downward trends in total PAH levels and PM2.5 during the period of study (1998–2006). Carbon and metal levels did not mirror these declines. Additionally, scientists noted that pollutant levels varied across the NYC stationary sites, consistent with variance in traffic patterns.
Journal of Chemical Education • Vol. 86 No. 2 February 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
Chemical Education Today
More Information on These Two Reports 1. Beyea, Jan; Stellman, Steven D.; Hatch, Maureen; Gammon, Marilie D. Airborne Emissions from 1961 to 2004 of Benzo[a]pyrene from U.S. Vehicles per km of Travel Based on Tunnel Studies. Environ. Sci. Technol. 2008, 42, 7315–7320. Available at http://pubs.acs.org/ cgi-bin/sample.cgi/esthag/2008/42/i19/pdf/es8000773.pdf (accessed Nov 2008). 2. Narvaez, Rafael F.; Hoepner, Lori; Chillrud, Steven N.; Yan, Beizhan; Garfinkel, Robin; Whyatt, Robin; Camann, David; Perera, Frederica P.; Kinney, Patrick L.; Miller, Rachel L. Spatial and Temporal Trends of Polycyclic Aromatic Hydrocarbons and Other Traffic-Related Airborne Pollutants in New York City. Environ. Sci. Technol. 2008, 42, 7330–7335. 3. More information on Beyea’s research can be found at http:// cipi.com/artchlth.shtml (accessed Nov 2008). 4. This Journal has published many resources for incorporating air pollution studies into teaching labs. See J. Chem. Educ. 1994, 71, 318; 1972, 49, 643; and 1972, 49, 24. Additional PAH resources in this Journal may be found at J. Chem. Educ. 2004, 81, 245 and 2004, 81, 912 (both JCE Featured Molecules columns); environmental labs that focus on PAHs include J. Chem. Educ. 1998, 75, 1599 (cigarette smoke); 1999, 76, 962 (diesel engines); and 2004, 81, 242. 5. More information on Rachel L. Miller’s research can be found
1.6
PAH concentration
(log [transformed / (ng/m3)])
Self-monitoring showed that individuals’ PAH levels also declined during the study period (Figure 2). Interestingly, while the new study validated self-reported tobacco smoke exposure by pregnant women by correlating reported exposure to cotinine levels in urine, personal exposure to tobacco smoke appeared to have no effect on PAH levels established by personal monitoring. PAH levels also appeared to be independent of ethnicity, cooking behaviors, and source of indoor heat. However, PAH levels during seasons in which homes were heated were higher across the board than non-heating seasons. Clearly the decrease in personal PAH and PM levels reflected in this study indicate that traffic-related policies are working. However, the documented health effects of these pollutants, along with the lack of decline in metals in the air indicate that our society needs to demand increased intervention and initiative to further clean our air.
1.4 1.2 1.0 0.8 1.6 0.4 0.2 0.0
1998 N = 70
1999 131
2000 118
2001 89
2002 57
2003 64
2004 60
2005 81
2006 13
Figure 2. Personal exposure to the sum of 8 PAHs from 1988 to 2006. Data (n = 733) are displayed as natural log transformed averaged each year. Reprinted with permission from Environ. Sci. Technol. 2008, 42, 7330–7335. Copyright 2008 American Chemical Society.
at http://www.cumc.columbia.edu/dept/pulmonary/3Faculty%20Pages/ Miller/Miller%20Page.htm (accessed Nov 2008). 6. Research Advances has previously highlighted research investigating the impact of computer printers on air quality. See J. Chem. Educ. 2007, 84, 1738. 7. The Environmental Protection Agency profiles the health risks of benzo[a]pyrene at http://www.epa.gov/iris/subst/0136.htm (accessed Nov 2008).
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Feb/abs146.html Abstract and keywords Full text (PDF) with links to cited URLs and JCE articles
Angela G. King is Senior Lecturer in Chemistry at Wake Forest University, P.O. Box 7486, Winston-Salem, NC 27109;
[email protected].
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 86 No. 2 February 2009 • Journal of Chemical Education
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