People Near Freeways Are Exposed To 30 Times The Concentration Of Dangerous Particles

[Guest guest]

http://www.sciencedaily.com/releases/2002/10/021021052522.htm

Source: University Of California - Los Angeles (http://www.ucla.edu/)

Date: Posted 10/21/2002

People Near Freeways Are Exposed To 30 Times The Concentration Of Dangerous

Particles

People who live, work or travel within 165 feet downwind of a major freeway

or busy intersection are exposed to potentially hazardous particle

concentrations up to 30 times greater than normal background concentrations

found at a greater distance, according to two recently published UCLA

studies. The studies -- published in the Journal of the Air and Waste

Management Association and in Atmospheric Environment -- show that proximity

to a major freeway or highway dramatically increases exposure to " ultrafine "

particles (tiny particles less than 0.1 micrometers in diameter), which are

linked to neurological changes, mild pulmonary inflammation and

cardiovascular problems. The U.S. Environmental Protection Agency (EPA)

currently regulates particles less than 2.5 micrometers in diameter, and

ultrafines represent the very smallest particles inhaled by the public.

Traffic-related air pollution is of great concern to Los Angeles, which has

the most severe particle air-quality problem in the United States. The Los

Angeles Basin is home to more than 15 million residents and 10 million

vehicles contributing to its daily traffic. Motor vehicle emissions

represent the most significant source of ultrafine particles. Moreover,

recent toxicological studies have shown that ultrafine particles are more

toxic than larger particles, potentially leading to increased mortality and

illness with increased exposure to particulate matter.

" We believe this is the first study conducted in the United States that

provides a detailed spatial profile of ultrafine particles near freeways, "

said C. Hinds, a professor of environmental health sciences in the

UCLA School of Public Health, who co-authored the studies with Yifang Zhu, a

doctoral candidate in the School of Public Health.

The studies, conducted through the Southern California Particle Center and

Supersite (SCPCS), assessed the size-distribution and concentration of the

tiny ultrafine particles near major freeways. The first study focused on

Interstate 405, one of the nation's busiest freeways, with 93 percent of the

traffic composed of gasoline-powered cars. The second study looked at the

710 freeway, which has more than 25 percent of its traffic derived from

heavy-duty diesel trucks.

By measuring the number of particles and their size at varying distances

from the 405 and 710, Hinds and Zhu concluded that the number of ultrafine

particles downwind near both freeways was approximately 25 to 30 times

greater than the number upwind. The drop in the number of ultrafine

particles occurred rapidly with increasing distance from the freeway,

falling to 30 percent of peak concentration at 330 feet. The rapid decrease

and dilution in particle concentration was due to several factors, including

atmospheric dispersion, coagulation, and wind direction and speed.

Both Hinds and Zhu concur that better understanding of the size and

concentration of ultrafine particles is vital, particularly in a city with

85 million vehicle-miles traveled on its freeways on an average day.

" The objectives of the study include providing scientists with a way to

predict exposure concentrations to ultrafine particles near freeways in

order to facilitate health studies and provide data for the development of

an air-quality standard for ultrafine particles, " Zhu said.

The studies also examined the concentrations of carbon monoxide (CO), black

carbon (BC) and particle mass. Both CO and BC concentrations are closely

related to vehicle emissions. Like ultrafines, CO and BC concentrations

decreased significantly (70 percent to 80 percent) within the first 330 feet

downwind of the freeway. This confirms the notion that vehicular exhaust is

a major source of these pollutants near a major roadway.

The SCPCS -- housed in the School of Public Health and the Institute of the

Environment at UCLA, and funded by the EPA's Science To Achieve Results

(STAR) program and California Air Resources Board -- brings together

outstanding scientists from leading universities throughout the nation to

create dynamic new ways of investigating the health effects of particulate

matter and to secure the protection of public health by better informing

policy.

Funding for the studies was provided by the EPA and the California Air

Resources Board, and supported by the National Institute of Environmental

Health Sciences. Other study authors include Constantinos Sioutas, deputy

director of SCPCS and associate professor of environmental engineering at

USC, and Seongheon Kim and Si Shen of the department of civil and

environmental engineering at USC.

Editor's Note: The original news release can be found at

http://www.newsroom.ucla.edu/page.asp?id=3600

Note: This story has been adapted from a news release issued by University

Of California - Los Angeles for journalists and other members of the public.

If you wish to quote from any part of this story, please credit University

Of California - Los Angeles as the original source. You may also wish to

include the following link in any citation:

http://www.sciencedaily.com/releases/2002/10/021021052522.htm