THURSDAY, June 27 (HealthDay News) -- Parks and tree-lined
streets may give city dwellers more than shade. They may also save
some lives, a new study from the U.S. Forest Service suggests.
Researchers estimate that across 10 U.S. cities, "urban forests"
prevent an average of one death per year, by helping to clear the
air of fine particulate matter -- tiny particles released when
fossil fuels are burned. Car exhaust, wood burning and industrial
sources such as power plants all contribute.
Those fine particles can be inhaled deeply into the lungs, and
they are a particular concern when it comes to people's health,
said David Nowak, a Forest Service researcher who led the
The particles are thought to cause inflammation in the blood
vessels and airways, which can be dangerous for people with
existing heart or lung disease.
The new findings, reported in the July issue of the journal
Environmental Pollution, suggest that trees play a role in
protecting urban dwellers from the health effects of air
But, Nowak said, it's not just a simple matter of "let's plant
This study shows a "large-scale" correlation between tree
coverage and human health. But researchers still have to figure out
the nitty-gritty, Nowak said. "How do we best design to protect
people from [fine particle pollution]? What configuration of plants
do we need? What species of tree?" he said.
And all of that, Nowak added, has to be figured out at the local
and regional levels.
Trees, he noted, do a lot more than clear fine particles from
the air. They have many beneficial effects -- including reducing
other air pollutants such as ozone, and keeping the temperature
down during the summer. But certain other effects are not so good
for human health: Trees release pollen, for example, which can
exacerbate allergies and asthma.
"We need to make smart decisions about what we should plant,
where we should plant and when we should plant, in order to improve
people's quality of life," Nowak said.
The findings are based on daily air-quality data from 10 U.S.
cities, along with information on the cities' tree coverage. To
gauge how trees might be affecting city residents' health, Nowak's
team used a computer program from the U.S. Environmental Protection
Agency (EPA) that estimates the health impact of changes in air
Overall, Atlanta was number one when it came to the amount of
fine particle pollution removed by trees, at 64.5 metric tons --
owing to the city's relatively dense urban forest.
But as far as lives saved, New York City came in on top, with an
average of eight lives saved per year. That, Nowak said, was partly
due to the city's large population, but also to the "moderately
high" removal of fine particles from the air -- thanks to
No one is claiming that trees are the answer to air pollution,
Trees may be a smaller-scale way to give people extra protection
from pollution, said Janice Nolen, assistant vice president of
national policy for the American Lung Association.
"But they're not going to be the solution," Nolen said.
The "big tools," she said, are measures to reduce emissions from
power plants, cars and other sources of pollutants.
One of those wide-scale measures got extra attention this week.
The U.S. Supreme Court on Monday agreed to review a controversial
decision by the D.C. Circuit Court of Appeals that reversed a major
EPA air-quality policy -- dubbed the Cross-State Air Pollution
The regulation would have cut emissions from coal-fired power
plants across more than half of U.S. states. Last August, the D.C.
Circuit Court said the EPA had overstepped its authority in issuing
"We're very pleased the Supreme Court will review this," Nolen
As for trees, she said they are a worthy pollution-fighting
measure to keep studying -- including whether strategic planting
along roadways might be beneficial.
The U.S Environmental Protection Agency has more on
fine particle air