posted 08-30-2002 08:55 AM            

WASHINGTON (Reuters) - The number of times unhealthy smog levels blanketed U.S. states rose 10 percent during the summer of 2001, and may double this year, according to a study released Thursday by the U.S. Public Interest Research Group.

Ground-level ozone, known also as smog, is worst during summer months when hot temperatures react with chemicals spewed by cars, trucks and power plants to form a gas which causes respiratory ailments.

The American Lung Association has estimated 141 million people -- or half of the U.S. population -- lives where smog levels are high enough to cause serious health problems such as asthma, eye and throat irritation and headaches.

During 2001 summer months, ozone levels exceeded federal health limits at least 4,634 times in 42 states and the District of Columbia, according to the new report by PIRG, an environmental advocacy group. That was up 10 percent from the number of unsafe days in 2000.

The trend appears to be worsening. Preliminary data for 2002 showed ozone levels for 21 states are already up 23 percent from 2001, PIRG said.

The smog data "should cause alarm bells to go off among state and federal policy makers," PIRG said in its report.

California, Pennsylvania and Texas were the smoggiest states in 2001, followed by Ohio, Maryland, New Jersey and North Carolina, PIRG said.

Regionally, levels in New England, the Mid-Atlantic and Midwest rose from 2000 to 2001, while those in the Southeast and West fell, PIRG said.

UTILITY POLLUTION RULES

PIRG offered the report as a reason for the Bush administration to reconsider a plan to relax pollution rules when U.S. utilities repair or expand their power plants -- the so-called "New Source Review" rules.

A Democratic-led Senate panel said it would hold a hearing next Tuesday to look at the White House plan to ease air pollution rules. Scheduled to testify are Christine Todd Whitman, the current head of the Environmental Protection Agency, and Carol Browner, the EPA administrator under the Clinton administration.

Cars and trucks generate about one-third of all nitrogen oxides, the precursor to smog. Other major sources are power plants, which contribute 23 percent, and off-road vehicles at 22 percent, PIRG said.

Ozone, an invisible, odorless gas, is formed when nitrogen oxides from power plants, cars and other sources mix with other chemicals in the presence of sunlight.

The highest health risk from smog is from early May to mid-August, when particulates in the air react most strongly to heat and sunlight.

The Edison Electric Institute, a utility lobbying group, said U.S. air quality has improved over the last three decades despite increases in power output and U.S. economic growth.

"We can't control the weather, which does contribute to ozone," said Dan Riedinger, a spokesman for the industry group. "But we can control our emissions, and they are coming down."

Utilities in the Midwest and Eastern U.S. will curtail their ozone emissions to achieve an industrywide 40 percent reduction by 2004 under existing regulations, he said.

The Clean Air Act required the Environmental Protection Agency to set nationwide standards for ozone. In 1997, the EPA adopted the current standard that ozone cannot exceed 0.08 parts per million over an eight-hour period, but the agency has said it will not apply the standard because of a number of court challenges.

In May, nearly a dozen U.S. health and environmental groups threatened to sue the EPA to end what they called "foot dragging" by the agency.

PIRG's report was based on data on eight-hour measurements from 1,121 stationary monitors gathered from the EPA and other state agencies.

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