Even low levels of air pollution may pose stroke risk

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http://www.eurekalert.org/pub_releases/2008-05/uom-ell053008.php

 

Short-term exposure to low levels of particulate air pollution may

increase the risk of stroke or mini-stroke, according to findings that

suggest current exposure standards could be insufficient to protect

the public.

 

" The vast majority of the public is exposed to ambient air pollution

at the levels observed in this community or greater every day,

suggesting a potentially large public health impact, " said Lynda

Lisabeth, lead author and assistant professor in the University of

Michigan School of Public Health.

 

However, Lisabeth stressed that the association requires further study

in other areas with varying climates and alternative study designs.

Stroke is the third leading cause of death in the United States.

 

The study examined particulate air pollution in a southeast Texas

community where there is a large petroleum and petrochemical industry

presence. Particulate matter is one type of air pollution, defined as

tiny particles of solid or liquid that can cause numerous health

problems when inhaled. These particles can be man-made or from natural

sources.

 

In the study, researchers identified ischemic strokes and transient

ischemic attacks (TIA), sometimes called mini strokes but that often

lead to a stroke later. Ischemic attacks are caused by a blockage of

blood flow to the brain by a blood clot.

 

The results showed borderline significant associations between same

day and previous day fine particulate matter exposures and ischemic

stroke/TIA risk. Similar associations were also seen with ozone,

another type of pollution. Despite the fossil fuel industry in the

area, fine particulate matter exposures were low relative to other

regions of the country, probably because of the proximity to the coast

and prevailing wind patterns.

 

Findings suggest that recent exposure to fine particulate matter may

increase the risk of ischemic cerebrovascular events specifically.

Some research has shown that particulate air pollution is associated

with acute artery vasoconstriction and with increased thickening of

the blood, which may enhance the potential for blood clots. However,

this requires further study.

 

Researchers looked at data from the Brain Attack Surveillance in

Corpus Christi Project, a population-based stroke surveillance project

designed to capture all strokes in Nueces County, Texas. Ischemic

stroke and TIA cases between 2001 and 2005 were identified using

trained staff and later verified by neurologists. Daily historical air

pollutant and meteorological data were obtained for the same time

period from the Texas Commission on Environmental Quality's Monitoring

Operations database. Data on fine particulate matter and ozone were

available from a centrally located monitor in Corpus Christi, Tex.,

located upwind of the local industrial facilities. The majority of

stroke/TIA cases were also located upwind of local chemical plants and

refineries.

 

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The study, " Ambient Air Pollution and Risk of Ischemic Stroke and

TIA, " will be published in the July 2008 issue of Annals of Neurology

(http://www.interscience.wiley.com/), the official journal of the

American Neurological Association.

 

Co-authors are James Escobar, Joseph Dvonch, Brisa Sanchez, Jennifer

Majersik, Devin Brown, Melinda Smith, Lewis Morgenstern.

 

The University of Michigan School of Public Health has been working to

promote health and prevent disease since 1941, and is consistently

ranked among the top five public health schools in the nation. Faculty

and students in the school's five academic departments and dozens of

collaborative centers and initiatives are forging new solutions to the

complex health challenges of today, including chronic disease, health

care quality and finance, emerging genetic technologies, climate

change, socioeconomic inequalities and their impact on health,

infectious disease, and the globalization of health.