While data from the Connecticut Department of Environmental Protection show point-source air pollution in New Haven decreased by 13,150 tons between 1997 and 2003 — due in large part, advocates said, to legislation restricting the New Haven Harbor Power Plant’s emissions — the current pollution level is still higher than the EPA considers safe, and a recently published study by Yale researchers lends gravity to the city’s environmental troubles.

New Haven joins a number of cities across the United States, including Los Angeles and Baltimore, in failing to meet Environmental Protection Agency standards for air pollution, according to recent measurements taken by the EPA. A study published this month in the Journal of the American Medical Association conducted by Yale School of Forestry and Johns Hopkins University researchers shows ground-level ozone has a strong short-term effect on mortality in urban areas.

New Haven County and greater Connecticut are listed on the EPA Web site as moderate non-attainment areas for particulate matter and ozone levels, respectively.

Michelle Bell, a professor of Environmental Health at the environment school, who led the study, said the research presents a frightening reality.

“We looked at how ozone levels affect mortality in 95 urban communities over a 14-year period, covering about 40 percent of the United States’ population,” Bell said. “We found that ozone levels are, in fact, associated with higher mortality.”

She said her study is not sufficient in explaining deaths related to air pollution. A broader range of studies including analysis of epidemiological trends will be necessary, but even these improved studies would not be entirely accurate, Bell said. A controlled experiment on humans would be required to confirm the results as a rule, but would be ethically problematic, she said.

“You can’t have controlled experiments for pollution, so our results can show an association but cannot not prove causality,” Bell said.

The study only took deaths not caused by accident, terminal illness or homicide into account and isolated the impacts of particulate matter and ozone. Bell said dangerous ground-level ozone is generated by automobiles and power-plant emissions, and can be affected by wind patterns.

“There are lots of thing we can do to address ozone pollution on even an individual basis, like taking the bus to work or walking,” Bell said.

Proportional to its size, Bell said, New Haven’s air pollution is considerably bad. She said it is becoming more common for not only large, but moderate-sized cities to have high levels of air pollution. Bell said lowering current ozone levels by roughly a third could save a total of about 4,000 lives a year in the 95 cities studied and would decrease the number of fatalities resulting from long-term exposure to elevated ozone levels.

Dr. Mark Mitchell, the president of the Connecticut Coalition for Environmental Justice, said New Haven’s air pollution is worse than the state average, but the city has taken steps to improve the situation. He said Yale-New Haven Hospital and the University have switched their power plants’ fuel from the highly polluting number-six oil to the cleaner-burning number-two oil, and his organization is pushing for St. Raphael’s Hospital to follow suit. In addition, Mitchell said CCEJ has collaborated with city officials to decrease emissions from public vehicles.

“This year we have worked with the city to reduce diesel emissions from school buses,” Mitchell said. “Diesel emissions in the air are a lot more toxic than previously thought and have been shown to increase many health problems like asthma, in addition to being a large source of global warming.”

Mitchell said the city should retain control over efforts to prevent water — as well as air — pollution. The proposed regionalization of New Haven’s Water Pollution Control Authority, discussed earlier this fall by city officials, could jeopardize New Haven’s voice in local sewage treatment, he said.

“We are very concerned about that, particularly that the city might lose control of the facilities,” Mitchell said. “Our fear is that the residents of New Haven might suffer the environmental consequences of pollution but lose control to correct mishaps.”

In September, New Haven Mayor John DeStefano Jr. and other local officials said their initial plans to establish a joint agency for sewage treatment for New Haven, East Haven, Hamden and Woodbridge could cut costs and improve services.

Heather Blankenstein, the director of education for the Connecticut marine education organization Schooner, said she often sees seasonal oxygen fluctuations in the water of New Haven Harbor and other parts of the Long Island Sound, but one of biggest concerns for local communities is sewage runoff.

“There is a huge misconception that it’s the water coming out of sewage treatment that is bad,” Blankenstein said. “When there is high rain activity — on days there is overflow — that contributes the most to water pollution.”

Blankenstein said local sources are not the only contributors to water pollution in the New Haven area. She said runoff from as far away as Canada and Vermont could eventually reach the sound. While new regulations have reduced emission volumes, Blankenstein said, the changes must be maintained over the long term to rid the amount of pollution that has accumulated over hundreds of years.

Other issues confronting the city include frequent proposals to place regional waste facilities in New Haven, Mitchell said. These facilities would overextend the city’s resources and increase pollution, he said.

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