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PARTICULATE MATTER (PM) EXPOSURE FOR COMMUTERS IN LOS ANGELES: CHEMICAL CHARACTERIZATION AND IMPLICATIONS TO PUBLIC HEALTH
by
Winnie Kam
A dissertation presented to the
FACULTY OF THE USC GRADUATE SCHOOL
In partial fulfillment of the requirements for the degree of
Doctor of Philosophy
in
Environmental Engineering
May 2013
Copyright 2013 Winnie Kam
Object Description
| Title | Particulate matter (PM) exposure for commuters in Los Angeles: chemical characterization and implications to public health |
| Author | Kam, Winnie |
| Author email | wkam@usc.edu;miss.winniekam@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Environmental Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2012-11-16 |
| Date submitted | 2013-01-11 |
| Date approved | 2013-01-11 |
| Restricted until | 2013-01-11 |
| Date published | 2013-01-11 |
| Advisor (committee chair) | Sioutas, Constantinos |
| Advisor (committee member) |
Henry, Ronald C. Chen, Jiu-Chiuan Fruin, Scott Moffett, James |
| Abstract | According to the U.S. Census Bureau, 570,000+ commuters in Los Angeles travel for over 60 minutes to work. Studies have shown that a substantial portion of particulate matter (PM) exposure can occur during this commute depending on the mode of transport. This thesis focuses on the PM exposure for commuters of four microenvironments in Los Angeles including subway, light-rail, freeways, and surface streets. ❧ The first part of the thesis focuses on the subway and light-rail commute environments. Elevated concentrations of PM have been found in a number of worldwide underground transit systems, with major implications regarding exposure of commuters to PM and its associated health effects. An extensive sampling campaign was to measure PM concentrations in two lines of the Los Angeles Metro system – an underground subway line (Metro red line) and a ground-level light-rail line (Metro gold line). Considering that a commuter typically spent 75% of time inside the train and 25% of time waiting at a station, subway commuters were exposed on average to PM₁₀ and PM₂.₅ concentrations that were 1.9 and 1.8 times greater than the light-rail commuters. The average PM₁₀ concentrations for the subway at station platforms and inside the train were 78.0 μg/m3 and 31.5 μg/m3, respectively; for the light-rail line, corresponding PM₁₀ concentrations were 38.2 μg/m3 and 16.2 μg/m3. Regression analysis demonstrated that personal exposure concentrations for the light-rail line are strongly associated with ambient PM levels (R2=0.61), while PM concentrations for the subway line are less influenced by ambient conditions (R2=0.38) and have a relatively stable background level of about 21 μg/m3. Mass balance showed that in coarse PM (PM₁₀₋₂.₅), iron makes up 27%, 6%, and 2% of gravimetric mass for red line, gold line, and USC, respectively; in fine PM, iron makes up 32%, 3%, and 1%. Non-crustal metals, particularly Cr, Mn, Co, Ni, Mo, Cd, and Eu were elevated for the red line and, to a lesser degree, the gold line. Bivariate analysis showed that reactive oxygen species (ROS) activity is strongly correlated with water-soluble Fe (R2=0.77), Ni (R2=0.95), and OC (R2=0.92). A multiple linear regression model (R2=0.94, p<0.001) using water-soluble Fe and OC as predictor variables was developed to explain the variance in ROS. ❧ The second part of the thesis focuses on PM exposure for private commuters of freeways and surface streets. An on-road sampling campaign was conducted to assess on-road PM composition for three size fractions (PM₁₀₋₂.₅ ,PM₂.₅₋₀.₂₅, and PM₀.₂₅) on three representative roadways in Los Angeles: 1) the I-110, a high-traffic freeway composed mostly of light-duty vehicles (LDVs), 2) the I-710, a major freeway for heavy-duty vehicles (HDVs) travelling to and from the Ports of Los Angeles and Long Beach, and 3) Wilshire/Sunset Blvd, two major surface streets. Results showed that the PM₀.₂₅ fraction is heavily influenced by vehicular emissions, as indicated by average roadway PM concentrations that were 48.0±9.4% higher than those observed at USC (p<0.05), while the PM₁₀₋₂.₅ fraction is mostly influenced by resuspension of road dust and the PM₂.₅₋₀.₂₅ fraction is mainly composed of secondary species. With very low EC levels in PM₁₀₋₂.₅, the most notable difference among the three roadway environments was the PM₂.₅ EC levels observed on the I-710, which are 2.0±0.2 μg/m3 and 4.1 times greater than USC. ❧ Next, fuel-based emission factors (mass of pollutant per kg of fuel) were calculated to assess the emissions profile of a light-duty vehicle (LDV) traffic fleet characterized by stop-and-go driving conditions that are reflective of urban street driving. Emission factors for metals and trace elements were highest in PM₁₀₋₂.₅ while emission factors for polycyclic aromatic hydrocarbons (PAHs) and hopanes and steranes were highest in PM₀.₂₅. PM₂.₅ emission factors were also compared to previous freeway, roadway tunnel, and dynamometer studies based on an LDV fleet to determine how various environments and driving conditions may influence concentrations of PM components. The on-road sampling methodology deployed in the current study captured substantially higher levels of metals and trace elements associated with vehicular abrasion (Fe, Ca, Cu, and Ba) and crustal origins (Mg and Al) than previous LDV studies. The semi-volatile nature of PAHs resulted in higher levels of PAHs in the particulate phase for LDV tunnel studies (Phuleria et al. 2006) and lower levels of PAHs in the particulate phase for freeway studies (Ning et al. 2008). With the exception of a few high molecular weight PAHs, the current study’s emission factors were in between the LDV tunnel and LDV freeway studies. In contrast, hopane and sterane emission factors were generally comparable between the current study, the LDV tunnel, and LDV freeway, as expected given the greater atmospheric stability of these organic compounds. ❧ Lastly, PM exposures for all commute environments were compared using mass per volume of air as the metric of comparison. Metals associated with stainless steel, notably Fe, Cr, and Mn, were elevated for the red line (subway), most likely from abrasion processes between the rail and brakes; elements associated with tire and brake wear and oil additives (Ca, Ti, Sn, Sb, and Pb) were elevated on roadways. Elemental concentrations on the gold line (light-rail) were the lowest. Overall, the 710 exhibited high levels of PAHs (3.0 ng/m3), most likely due to its high volume of HDVs, while the red and gold lines exhibited low PAH concentrations (0.6 and 0.8 ng/m3 for red and gold lines, respectively). Lastly, lung cancer risk due to inhalation of PAHs was calculated based on a commuter lifetime (45 years for 2 hours per workday). Results showed that lung cancer risk for the 710 is 3.8 and 4.5 times higher than the light-rail (gold line) and subway (red line), respectively. With low levels of both metals and PAH pollutants, our results indicate that commuting on the light-rail (gold line) may have potential health benefits when compared to driving on freeways and busy roadways. |
| Keyword | particulate matter; Los Angeles; transportation; roadways; surface streets; commuter exposure |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Kam, Winnie |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume6/etd-KamWinnie-1391.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Full text | PARTICULATE MATTER (PM) EXPOSURE FOR COMMUTERS IN LOS ANGELES: CHEMICAL CHARACTERIZATION AND IMPLICATIONS TO PUBLIC HEALTH by Winnie Kam A dissertation presented to the FACULTY OF THE USC GRADUATE SCHOOL In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering May 2013 Copyright 2013 Winnie Kam |
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