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Trees cut pollution and improve air quality, reduce respiratory symptoms

Trees save 850 lives per year, says National Forest Service. While trees’ pollution removal equated to an average air quality improvement of less than 1 percent, the impacts of that improvement are substantial. Researchers valued the human health effects of the reduced air pollution at nearly $7 billion every year in a recently published study in the journal Environmental Pollution. “Tree and Forest Effects on Air Quality and Human Health in the United States,” is available online as a PDF file article.

Trees cut pollution and improve air quality, reduce respiratory symptoms.
Anne Hart, photography.

Researchers have attempted to estimate the direct impact of trees on air pollution and human health. What they found was that trees improved overall air quality in th United States by only one percent. However, that one percent improvement prevents 850 premature deaths, 670,000 incidences of acute respiratory symptoms and saves $7 billion in health care spending, says the July 27, 2014 Daily Digest News article, "Trees save 850 lives per year, says National Forest Service."

The first national study finds that trees save lives by reducing respiratory problems through absorbing some of the air pollution

The first national study finds trees saving lives, reducing respiratory problems: Air pollution modeling reveals broad-scale impacts of pollution removal by trees. In the first broad-scale estimate of air pollution removal by trees nationwide, U.S. Forest Service scientists and collaborators calculated that trees are saving more than 850 human lives a year and preventing 670,000 incidences of acute respiratory symptoms.

The study by Dave Nowak and Eric Greenfield of the U.S. Forest Service’s Northern Research Station and Satoshi Hirabayashi and Allison Bodine of the Davey Institute is unique in that it directly links the removal of air pollution with improved human health effects and associated health values. The scientists found that pollution removal is substantially higher in rural areas than urban areas, however the effects on human health are substantially greater in urban areas than rural areas.

“With more than 80 percent of Americans living in urban area, this research underscores how truly essential urban forests are to people across the nation,” said Michael T. Rains, according to the USDA's NRS July 25, 2015 news release, "First national study finds trees saving lives, reducing respiratory problems." Rains is the Director of the Forest Service’s Northern Research Station and the Forest Products Laboratory. “Information and tools developed by Forest Service research are contributing to communities valuing and managing the 138 million acres of trees and forests that grace the nation’s cities, towns and communities.”

The four air pollutants

The study considered four pollutants for which the U.S. EPA has established air quality standards: nitrogen dioxide, ozone, sulfur dioxide, and particulate matter less than 2.5 microns (PM2.5) in aerodynamic diameter. Health effects related to air pollution include impacts on pulmonary, cardiac, vascular, and neurological systems. In the United States, approximately 130,000 PM2.5-related deaths and 4,700 ozone-related deaths in 2005 were attributed to air pollution.

Trees’ benefits vary with tree cover across the nation. Tree cover in the United States is estimated at 34.2 percent but varies from 2.6 percent in North Dakota to 88.9 percent in New Hampshire. “In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people,” Nowak said, according to the news release. “We found that in general, the greater the tree cover, the greater the pollution removal, and the greater the removal and population density, the greater the value of human health benefits.” For more information, you may wish to check out the website of the USDA Forest Service - Northern Research Station. Or check out, "Tree and forest effects on air quality and human health in the United States."

The mission of the U.S. Forest Service is to sustain the health, diversity, and productivity of the nation’s forests and grasslands to meet the needs of present and future generations. The agency has either a direct or indirect role in stewardship of about 80 percent of our nation’s forests, amounting to 850 million acres including 100 million acres of urban forests gracing the nation’s cities, where 80 percent of Americans live. The mission of the Forest Service’s Northern Research Station is to improve people’s lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

Can a tree branch filter harmful E. coli bacteria out of water?

A small piece of freshly cut sapwood can filter out more than 99 percent of the bacteria E. coli from water, says a new study. The sapwood of pine trees contains xylem, a porous tissue that moves sap from a tree's roots to its top through a system of vessels and pores. It's a natural water filter.

A small piece of freshly cut sapwood can filter out more than 99 percent of the bacteria E. coli from water, In fact, you can use a tree branch to filter your water if the sapwood contains zylem, that porous tissue good for filtering the bacteria out of water. The plant uses the zylem to move sap from the roots to the top of the tree. The new study, "Water Filtration Using Plant Xylem," by authors Boutilier MSH, Lee J, Chambers V, Venkatesh V, and Karnik R was published online today, February 26, 2014 in the journal PLoS ONE. The new study reports that pine tree sapwood filters bacteria from contaminated water.

Researchers were interested in studying low-cost and easy-to-make options for filtering dirty water, a major cause of human mortality in the developing world.

To investigate sapwood's water-filtering potential, researchers collected white pine branches, stripped the outer bark, and cut them into small inch-long sections. They then mounted each in plastic tubing, sealed and secured, and filtered water through that either contained small particles or E. coli bacteria.

The authors found that sapwood filtered out particles greater than 70 nanometers wide, but was unable to separate out 20-nanometer particles, suggesting that there is a particle size limit to what coniferous sapwood can filter. Sapwood also filtered out more than 99% of E. coli from water, which mostly accumulated in the first few millimeters of the wood in what are known as pit membranes.

The small- branch filtration system produced water at rates up to four liters of clean drinking water a day, typically enough for one person.

Be aware, however, that the authors caution only hydrated sapwood (and not dried-out wood) will filter out contaminants. "There's huge variation between plants," says Rohit Karnik, according to the February 26, 2014 news release, "Tree branch filters water." Karnik is senior author on the paper.

"There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away, and replace at almost no cost. It's orders of magnitude cheaper than the high-end membranes (currently) on the market today, Karnik observes, according to the news release."

This work was supported by the James H. Ferry, Jr. Fund for Innovation in Research Education award to R.K. administered by the Massachusetts Institute of Technology. SEM imaging was performed at the Harvard Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have declared that no competing interests exist. You may also wish to check out the American Society for Microbiology site.

Harvested rainwater harbors pathogens

South Africa has been financing domestic rainwater harvesting tanks in informal low-income settlements and rural areas in five of that nation's nine provinces. But pathogens inhabit such harvested rainwater, potentially posing a public health hazard, especially for children and immunocompromised individuals, according to another study, by different researchers.

This study, "Distribution of indigenous bacterial and potential pathogens associated with roof-harvested rainwater," involved a team from the University of Stellenbosch. The research was published online ahead of print on January 31, 2014 in the journal Applied and Environmental Microbiology. International studies had indicated that harvested rainwater frequently harbors pathogens, and that, in light of the financing of harvesting tanks, drove the investigators to study the matter locally, says principal investigator Wesaal Khan, according to the February 26, 2014 news release, "Harvested rainwater harbors pathogens."

The sampling was conducted in the Kleinmond Housing Scheme, which was initiated by the South African Council for Scientific and Industrial Research and the Department of Science and Technology. The houses, designed to be sustainable, are approximately 400 square feet, with alternative technologies such as solar panels and the rainwater tanks.

What kinds of bacteria were found in the harvested rainwater?

The list of predatory prokaryotes the investigators found includes Legionella (found in 73% of samples), Klebsiella (47%) Pseudomonas (19% of samples), Yersinia (28%), Shigella (27%), and others. They also found some protozoan parasites, including Giardia (25% of samples).

Many of the pathogens are normal fresh water inhabitants, but Salmonella (6% of samples) indicates human fecal contamination, while Yersinia are markers of fecal contamination by wild and domestic animals, according to the report.

Residents, many of whom are little-educated and unemployed, typically use the rainwater for washing clothes and house-cleaning, but about one quarter of people polled in the study said they used it for drinking, as well. The finding that coliforms and Escherichia coli counts from rainwater samples—markers of fecal contamination—always significantly exceeded drinking water guidelines, reinforces the World Health Organization's opinion that rainwater must be pretreated prior to use for drinking, says Khan, according to the news release.

Residents often depend on communal 'standpipe' systems

Rainwater harvesting is needed in South Africa's "informal communities" because residents often depend on communal 'standpipe' systems that frequently serve more than 100 people, who may have to walk as far as a third of a mile to get water, says Khan. Approximately 23,000 rainwater tanks have been installed, two thirds of them in the Eastern Cape and one third in KwaZulu Natal. Nearly 20% of South Africans lack sustainable access to water. The final version of the article is scheduled for the April 2014 issue of Applied and Environmental Microbiology. On another note, you also may enjoy the article, "How walnuts and flaxseeds may improve your blood pressure and your reaction to stress."

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