Skip common site navigation and headers
United States Environmental Protection Agency
Environmental Justice


EJBib - Publication Details

Site Navigation
EJBib Home
View Publications
Simple Search
Advanced Search
PDF Files
State Map Search
New Publications
About & Help
Glossary of Terms    Go back to the List of Publications

Name of Article:
Application of an Ir Tracer to Determine Soot Exposure to Students Commuting to School on Baltimore Public Buses 
Title of Book/Journal:
Atmospheric Environment 
English Translation:
Publication Date:
Et al:
A. E. Suarez
Z. Lin
Issue: 11
Pages: 1911 - 1919  
Corporate Author:
EPA Number:
Other Number:
This article discusses a method to estimate student exposure to diesel soot, an important component of urban aerosol and a known respiratory irritant that contains mutagenic and carcinogenic organic compounds. To estimate student exposures to soot emitted from public diesel buses during commutes to city high schools, a portion of the Baltimore, Maryland, municipal fuel supply was tagged with an iridium (Ir) tracer and exposure monitored during commutes with personal aerosol monitors as a part of an environmental justice project. A total of 68.2 g of Ir as iridium(III)-2,4-pentanedionate was used to induce a concentration of 48.5 micrograms Ir l-1 of fuel. Twenty samples were collected over 10 days while four students commuted on regularly scheduled buses and a fifth student commuted by private car. Individual samples integrated from 1 to 4 round trips. Iridium analyses were performed instrumentally after neutron activation with a detection limit (DL) of about 500 femtograms (fg). For students commuting by bus and following protocols, Ir tracer concentrations ranged from 53 plus or minus 38 to greater than 1980 plus or minus 49 fg per cubic meter. Concentrations up to 3530 plus or minus 220 fg per cubic meter were observed for student 5, who sampled only when boarding and disembarking. Exposures were greatest for students commuting through the heavily trafficked central business district. Corresponding estimates of exposures to soot emitted from municipal buses ranged from ltoreq 3 to 82 nonogram (ng) soot per cubic meter (ltoreq 145 ng per cubic meter for student 5), i.e. well below the exposure level of 2-10 micrograms per cubic meter total C from all sources, including the more than 30,000 diesel trucks which pass through the city's major toll facilities each day. It was undetectable in samples collected by the student commuting by car when its windows were closed, but comparable to those of the other students when commutes were made with windows open.

Return to top


Planning & Results | Compliance Assistance | Compliance Incentives & Auditing | Compliance Monitoring
Civil Enforcement | Cleanup Enforcement | Criminal Enforcement | Environmental Justice | NEPA
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us

Last updated on Monday, December 2nd, 2002