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Home HortTechnology Looking for Links between Urban Greenspace and Childhood Asthma
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SAN MARCOS, TX--The number of asthma cases in children has increased significantly during the past several decades. Numerous studies of hospital admissions and emergency visits have suggested a connection between particulate air pollution and asthma attacks, while other reports have suggested that long-term exposure to urban air pollution is related to the prevalence of asthma and allergies in both children and adults. Looking for ways to reduce the incidence of asthma among urban residents, scientists and urban planners are looking to trees and green spaces as natural ways to improve community’s air quality.

"Trees remove airborne dust and chemical matter, or particulate matter from the air, where it is stored on leaves, twigs, and trunks," explained Monica Ann Pilat from the Department of Agriculture at Texas State University-San Marcos. Pilat, lead author of a recent research study (HortTechnology), noted that previous research has suggested that an increase in tree density is related to a decrease in the prevalence of asthma in urban areas such as New York City. Pilat added that, although many studies have been done, research on links between outdoor air pollutants and asthma have had "mixed results." To look more closely at the relationship between childhood asthma rates and tree cover and vegetation, Pilat and a team of scientists collected 2005 and 2006 childhood asthma data from the Center for Health Statistics and the Texas Department of State Health Services. They mapped asthma rates for each metropolitan statistical area (MSA) in Texas, and then used geographical mapping software to insert the data into a corresponding map showing tree coverage and vegetation rates in each MSA.

The results did not show that childhood asthma rates in the areas studied were related to tree cover or vegetation. "Childhood asthma occurrence has many extraneous variables such as tobacco smoke, pet dander, dust mites, and cockroaches related to the disease that may have influenced the research and results," the scientists noted. They said that their findings may have been a result of the small sample sizes in the study and recommended repeating the study to include MSAs in other states. "Increasing the sample size would increase the power of the study, improving the ability to detect a relationship," Pilat said.

Another possible reason for the outcomes is that the results were affected by the large variation of vegetation in each MSA. "Obtaining data at a community level may be difficult but may yield significant results, and is recommended for future research," the authors said. They noted that the influence of vehicular pollution, wind, altitude, precipitation, and other demographics related to human stress--and in turn to asthma--should be also considered in future research studies.


The complete study and abstract are available on the ASHS HortTechnology electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at


Original Article:

The Effect of Tree Cover and Vegetation on Incidence of Childhood Asthma in Metropolitan Statistical Areas of Texas
Monica Ann Pilat, Amy McFarland, Amy Snelgrove, Kevin Collins, Tina Marie Waliczek, and Jayne Zajicek
HortTechnology 22:631–637. [Abstract][Full Text][PDF]

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