Trace emissions from fossil-fired power plants pose nearly imperceptible health risks to people living near them, a comprehensive study by the Electric Power Research Institute shows.

The study, performed over the last decade by EPRI and completed late last year, is the most thorough assessment to date of the possible health risks posed by U.S. power plants. It covers 600 plants, including all of The Southern Company’s fossil steam-generating plants larger than 25 megawatts.

The EPRI study modeled the effects of emissions of 16 trace substances —including arsenic, chlorine, mercury, lead, and radionuclides — on people living within 50 kilometers (about 31 miles) of a plant. For a person experiencing reasonable exposure through inhalation near any plant in the study, the lifetime chance of suffering cancer caused by the power plant’s emissions was well below one in 1 million. And the risk of noncancerous health effects — such as disorders of the respiratory, cardiac, renal, or nervous systems — was zero for all plants.

At all but two plants in the study, the cancer risk was less than one in 10 million. About 85 percent of the plants had risks below one in 100 million. EPRI has not identified risks for individual plants.

“We’ll continue to closely monitor our emissions. But judging from this exhaustive study, it’s very safe to live near a power plant,” said Bryan Baldwin, manager of Southern Company Services’ environmental assessment department.

EPRI even calculated risks for the “maximally exposed individual” — for example, someone who lived next door to a power plant for 70 years, sitting outside all the time and never leaving the property. Such a person’s risk increased to only a fraction more than one in 1 million at only three of the 600 plants. None of those plants was Southern Company plants.

To put that in perspective, consider this: The lifetime risk you’ll contract some form of cancer is nearly one in three (in other words, one out of three people will develop some form of cancer). The added risk for “porch sitters” living near those three plants is 0.000003 in three. The added risk for normal people living near Southern Company plants would be far, far less than that.

EPRI also performed case studies at four plants to determine risk levels for all types of exposures — inhalation, ingestion, or skin contact. Even in the worst case scenario of the lifelong porch-sitter, the risk remained less than one in 1 million.

The case studies also indicate exposure to mercury, which comes primarily through consumption of fish, is not a problem near coal-burning power plants. Individuals near the studied plants had been exposed to only 30 percent of the highest level the Environmental Protection Agency has deemed safe.

“There had been lots of claims that the coal-burning industry was contributing to mercury problems in fish,” Baldwin said. “The EPRI report shows we’re not large contributors.”

The EPRI study is similar to one the EPA must perform under a mandate by the 1990 Clean Air Act Amendments, and EPRI results will go to the EPA. The EPA study will determine if there is a basis for regulating trace substance emissions at 25-megawatt or larger units at fossil-fired plants.