In addition, the report, using 1990 data (the latest available), pointed a finger at some surprising sources of the chemical compounds. Instead of toxic- waste incinerators and paper mills, targets of environmental protests, the report said medical-waste and municipal-waste incinerators produce about 88 percent of all dioxin air emissions.
Environmentalists promptly embraced the report as proof of dioxin's ''devastating effects." Peter deFur, a scientist with the Environmental Defense Fund, said: "We have to take a long-term approach at the prevention level."
But critics, including industry scientists, pointed out that, despite voluminous research and rigorous analysis, the EPA had been unable to find any direct links between dioxin and human health problems.
"There is an awful lot riding on dioxin," said John Whysner, a toxicologist and the vice president of Washington Occupation Health Associates, a consulting firm. "The government has caused . . . industry to do a lot of things. It would be difficult for the government to say, 'OK, dioxin doesn't need to be regulated so extensively.' "
This month, the EPA proposed tougher dioxin standards for new and existing trash incinerators. In February, it will issue new dioxin standards for medical-waste incinerators.
Dioxins are a family of 210 chemical compounds incidentally created when chlorinated chemical products are made, and when fuels, refuse and wood are burned.
Only 17 dioxin compounds are toxic, and each year just 30 pounds of these potentially dangerous materials are produced, according to the report. Nevertheless, the chemicals are found in trace levels just about everywhere.
Each day, the EPA estimated, Americans ingest the equivalent of 42 trillionths of an ounce of toxic dioxins. Most of that comes from eating beef, dairy products, chicken, pork, fish and eggs. Dioxins are not soluble in water, so that is not a significant source. Cattle, pigs, chickens and fish ingest the dioxin from grass, grain, soil and sediments.
Once in the body, dioxins are absorbed by the blood. According to the EPA, they can show up in a wide variety of organs, but the highest concentrations have been found in the liver and fatty tissue.
The background dioxin exposure in the average American's body is about 18 trillionths of an ounce. While that does not appear dangerous, the study did not say what a safe level might be. The EPA did express concern, however, about infants receiving dioxins from their mothers' milk.
One problem in assessing risk is that dioxin, unlike toxic lead or radioactive radon, does not pose a direct threat but triggers complex cell mechanics that may or may not lead to problems.
"A concentration of (dioxin) that elicits a response in one individual may not do so in another," the study said. "These differences . . . may reflect genetic variation."
The EPA estimates that dioxins and related compounds may play a role in less than half of 1 percent of all cancer cases.
While dioxins are now ubiquitous in the environment and found in human and animal tissues, the EPA report also found that, as a result of a series of regulatory and industry initiatives, dioxin levels are already dropping.
An analysis of sediment cores found that there was a buildup of dioxins between 1920 and the late 1970s but that then the levels started declining. Similarly, between 1982 and 1987, a study of dioxins in humans noted reductions in toxin levels ranging from 9 percent to 96 percent.
Dioxins, however, remain in the body for decades. Half of a dose consumed today will still be there in 9.7 years, the study said.
Bans on dioxin-tainted pesticides and leaded gasoline, as well as tighter controls on incinerators and the reduced use of chlorine by pulp and paper
mills, have contributed to the declines in dioxin levels, according to the EPA.
Still, the EPA is continuing to go after dioxin sources. And if there was any surprise in the EPA's report, it was the identity of the main culprits strewing dioxin about.
For the better part of 10 years, after all, environmental activists and community groups have hissed at their two favorite villains in the dioxin drama: paper manufacturers and hazardous-waste incinerators. Their hands, though, are clean, or at least relatively so, according to the report.
Of the known 30 or so pounds of dioxin produced yearly, pulp and paper
mills disgorge less than one-tenth of an ounce, according to the EPA's figures. And facilities burning hazardous wastes emit a relatively measly 1.2 pounds.
The real heavies are hospital-waste and municipal-waste incinerators, which together produce approximately 28 pounds of dioxin a year - about 88 percent of the total dioxin created.
But those figures cry out for careful scrutiny, representatives of the two industries say.
The 10 major Northeastern states, including Pennsylvania and New Jersey, have tough air-emission standards requiring sophisticated incineration, elaborate monitoring, and top-of-the-line pollution-control equipment, according to Bill Jones, a West Chester incineration consulting engineer.
And that means that dioxin emissions in this part of the country are far less than those from incinerators in such places as Maryland and Delaware, where, Jones said, "you can put in an incinerator without pollution control or monitoring."
Not that incinerator operators in states with lax laws can breathe easy. The EPA, heeding requirements in the 1990 Clean Air Act Amendment, has been whipping up tough new anti-dioxin regulations.
The municipal-waste incinerator rules issued this month are designed to reduce dioxin emissions by 95 percent to 99 percent, according to the EPA. Dioxin emissions from new plants would be cut by 99 percent.
"Within the next three years, dioxin emissions from incinerators will go
from 5,000 grams to 60," said Margaret Ann Charles of the Integrated Waste Services Association in Washington.
The EPA will have to have similarly stringent regulations in place for the 5,000 medical-waste incinerators around the country by April 1995.
The bad news, of course, is that none of this will be cheap.
Many waste incinerators - including the Westinghouse incinerator in Chester, the Montenay Power Corp. burner in Montgomery County, and the
Wheelabrator facility in Bucks County - will need little or no changes to reduce their dioxin emissions to meet the new regulations, according to industry experts.
But at least 60 percent of the nation's 180 municipal-waste incinerators will have to undergo major changes to bring them into compliance with new dioxin regulations, according to Dave Gatton, senior environmental adviser to the U.S Conference of Mayors.
Said Gatton: "We're talking big bucks. Your larger facilities, depending on age, could be looking at retrofit costs of $30 million to $50 million per facility."
Expense is a worry for the hospital industry, too.
Many hospitals, including Hahnemann University and Thomas Jefferson University Hospitals, do not have incinerators and turn their waste over to commercial outfits for disposal.
Others, including about 20 in New Jersey, "grind, crush, sterilize and chemically treat wastes to render them harmless (so they) don't have to be burned," said Keri Ellerbroek, a representative of the New Jersey Hospital Association.
The 5,000 facilities that still burn their own waste may have to spend between $1 million and $2 million each to bring their incinerators up to grade. Nationally, that could mean outlays of as much as $1 billion, according to the American Hospital Association.
Some hospital executives worry about whether "Medicare will allow them to recoup the enormous costs" of upgrading their waste-disposal facilities, said Richard H. Wade, senior vice president of the hospital association.
But others are likely to simply close down their incinerators and let commercial outfits dispose of the stuff for them. That, too, would cost.
Burning medical waste on hospital grounds costs about 10 cents a pound, according to Kurt Bresser, Temple University Hospital's energy manager. Shipping it out for disposal can run from 20 to 30 cents a pound.
For Temple, which burns about 40 percent of its waste and uses a commercial hauler to get rid of the rest, that could mean yearly expenses of about $200,000.
The question that the EPA's 2,000-page report does not answer is whether the cost is justified by the risk.
"There is no known safe level of dioxin, and there is no level at which dioxin does not affect cells," said the Environmental Defense Fund's deFur.
But industry consultant Whysner said: "My concern is that the general public believes this could be a cause of cancer, and I don't think it is. It is a diversion."