If you believe Westvaco Corp. officials, the small quantities o dioxin their paper mill discharges into the Potomac River will have little or no effect on the fish that live there.
But if you believe most environmentalists, you would be foolhardy to fry up a bit of freshly caught trout and pop a morsel in your mouth.
Whom do you believe? Both sides can cite scientific evidence to support their positions.
Such is the confusion that now surrounds dioxin. Once thought to be the most potent cancer-causing chemical, dioxin has come under scrutiny recently as new evidence suggests it may not be as dangerous as was first believed.
MA The U.S. Environmental Protection Agency decided last week to
take a new look at the evidence and to use a new approach to figuring out the risk of exposure to human beings and the environment.
Dioxin was in the herbicide Agent Orange, blamed for the illnesses of many Vietnam veterans, and dioxin was one of the chemicals that forced the evacuation of Love Canal in 1978. It also was discovered in fish as far as 40 miles below Westvaco during EPA surveys several years ago, which led Maryland officials last June to advise fishermen not to eat fish they catch below the paper mill in Luke.
Based on research done in the 1970s and 1980s, the paper industry says it spent close to $1 billion to eliminate or reduce the amount of chlorine used to bleach paper products white. Westvaco alone spent $15 million and reduced its discharge of dioxin, the byproduct of the bleaching process, by 98 percent.
But today, the industry believes the EPA's re-evaluation, which is expected to take 12 months to complete, will show that dioxin is many times less potent.
"We wish this evaluation had occurred five years ago, but it didn't," said Red Cavaney, president of the American Paper Institute, a trade association of paper manufacturers. "We have done what we have done, and we are comfortable with it."
One of the first questions about dioxin was raised more than a year ago, when researchers reviewed slides from a key dioxin study in 1979, said Peter Preuss, with the EPA's office of research and development. During the research, mice and rats were exposed to dioxin. Sections of the tumors that developed in the rodents were examined under a microscope. Researchers had to decide whether the abnormal cells they saw
were malignant or fit into other categories.
However, in the past decade, pathologists have developed a more precise way of categorizing those tumors. When scientists went back to re-examine the slides, fewer tumors were categorized as malignant. Scientists then wrote the EPA to say they believed dioxin was a far less potent carcinogen than they had first believed.
The way in which the EPA uses animal studies to calculate the risk to humans also has come under review. Last fall, a conference of scientific experts in the field decided that a new model could be developed that would more accurately assess the danger. Currently, some federal and state agencies simply extrapolate the effect of small doses from experiments with large doses, but some scientists argue that small doses may have little effect.
"Some people believe [the new evaluation] will show the risk is much less. Others say it will be about the same," Mr. Preuss said. "Until we do the work, there is little
basis for speculating."
Environmentalists argue that even if the new EPA evaluation concludes dioxin is less potent, other factors must be considered when setting a safe limit.
For instance, said Robert Adler, a senior attorney at the Natural Resources Defense Council, the EPA must estimate how much fish the average American eats in a year and how much dioxin will accumulate in the fish from the water. Those estimates were first made a decade ago, before Americans began reducing the meat in their diet. In addition, he said, the estimates do not take into account the fact that people who live in coastal areas, such as Maryland, usually consume larger quantities of fish.
Although the latest scientific evidence may show the chemical to be less potent, the risk may be relatively the same when increased exposure is taken into account.
While the EPA studies the chemical further, the public controversy over what is safe will continue. Three federal agencies either regulate or evaluate the health risk of the chemical: the EPA, the Centers for Disease Control in Atlanta and the Food and Drug Administration. Each agency currently has a different evaluation of the risk dioxin poses.
As if that weren't confusing enough, each state has set different standards for what it considers a safe limit for rivers, streams and bays. Maryland and Virginia have the most lax standards in the nation. Delaware, however, has one of the most stringent.
Thus the Chesapeake Bay could have 100 times more dioxin than the waters of Delaware Bay, and both levels would be acceptable to the EPA. The Natural Resources Defense Council, which thinks these differences are absurd, has brought suit against the EPA, arguing that Maryland's standard is far too lax.
"How much protection you get shouldn't depend on what state you live in," said Mr. Adler. He said he is glad the EPA is reconsidering the issue because it could "perhaps eliminate the constant bickering over the standard."