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Public Radio's Environmental News Magazine (follow us on Google News)

Dangerous Dioxin: An Update

Air Date: Week of

Host Steve Curwood previews a forthcoming 2,000 page E.P.A. report on the harmful effects of dioxin. The new research compiled by hundreds of scientists contains findings which suggest that dioxin is even more hazardous than previously thought. Others, in the chlorine industry, say there is no need to be alarmed.


CURWOOD: This is Living on Earth. I'm Steve Curwood. Dioxin has been called the most toxic chemical compound ever produced. The presence of tiny amounts has been enough to empty entire towns. And for many environmental activists, it's Public Enemy Number One. But in recent years, some scientists and interested businesses have questioned the dangers of dioxin, claiming that public fear of the substance and government efforts to eliminate it are overreactions. Now, a new draft report by the Environmental Protection Agency is reaffirming the dangers of dioxin, and suggesting that it could be even more harmful than had been thought. And it contains a chilling warning. It says that many of us may already harbor enough dioxin in our bodies to affect our health. Possible problems, the draft says, range from cancer to reducing our ability to fight disease, to disrupting our ability to have healthy children.

BIRNBAUM: Levels that are fairly close to levels that the average person in the US or in Europe or in Canada might have in their bodies are very close to the levels where adverse effects have actually been reported in experimental animals, and even in some human studies.

CURWOOD: Linda Birnbaum is Director of Environmental Toxicology at the Health Effects Research Laboratory of the EPA, which has just completed a 3-year reassessment of dioxin. Hundreds of scientists were involved in producing the 2,000-page document. The findings are dramatic. Dr. Birnbaum says the report affirms the risk of cancer from exposure to dioxin. But it goes much further. It suggests, for instance, that minute amounts of dioxin, its chemical relatives, and related compounds like furans and PCBs, may cause a drop in the male hormone testosterone, which is necessary for normal sexual development. Other possible effects include the aggravation of age-related diabetes and the weakening of our ability to fight diseases.

BIRNBAUM: It's clear that we need to pay more attention to these non-cancer effects. Some of the effects that we're seeing in experimental animals at levels that are not very different from the background level in the population are effects on the immune system and effects on the developing reproductive systems.

SCHWARTZ: That's, I think, the most intimidating piece of the reassessment.

CURWOOD: Joe Schwartz is Director of Policy for the group Physicians for Social Responsibility.

SCHWARTZ: What this reassessment shows is none of us, whether we live in a major city, whether we live near a factory, whether we live in the North Pole, we've been exposed to dioxin in the environment. And the current background levels of dioxin are not that far removed from the levels at which we are already seeing harmful effects. This is not some problem that we might face in the future. This is a problem that we're already facing now.

CURWOOD: But Bill Carroll of the Chlorine Chemistry Council says we should not be alarmed.

CARROLL: It's not an emergency, it's not time for panic in the streets. It's time for some serious evaluation and some work on the problem.

CURWOOD: Dr. Carroll's industrial employers are especially interested in the EPA's reassessment of dioxin. Dioxin is produced as a by-product in many industrial processes which use chlorine, especially the manufacture of paper products. Chlorine is also used in making pharmaceuticals and plastics. Dr. Carroll calls the EPA's reassessment important, but says it's too early to draw conclusions from it.

CARROLL: Most of this stuff is very new, and most of the study of the effects is very new. And so there's probably more that we don't know about this than what we do. What we're relatively sure of, I think, is that the dose still makes the poison.

CURWOOD: In other words, Dr. Carroll says, it's the exposure level that's key. But Linda Birnbaum of the EPA says government scientists have found biological effects of dioxin even at the smallest detectable levels.

BIRNBAUM: These can be very, very potent chemicals. And you don't need much of a potent chemical to bring about an effect. The amounts, for example, which are currently regulated in fish or food supplies are in the parts per trillion range.

CURWOOD: But Bill Carroll of the Chlorine Chemistry Council says there may be a difference between finding a biological response in the laboratory and an actual health risk in people.

CARROLL: The discussion that the EPA has is that they feel that doses that are as small as they can measure show some biochemical response. Whether that response is harmful or not is another story.

CURWOOD: So, no matter how small the dose, there is a biochemical response to dioxin.

CARROLL: That's what the EPA suggests. But whether there is a direct cause and effect relationship at low doses to those effects is still unshown.

CURWOOD: One of the reasons for the hair-splitting on the cause and effect is that the EPA assessment of dioxin uses a relatively new and controversial method of calculating its risk. It's called TEQ, the Total Equivalency Approach. Traditionally, the EPA determines the hazards for one chemical at a time. But since there are dozens of chemicals with dioxin-like properties, Linda Birnbaum of the EPA says the report deals with them as a group.

BIRNBAUM: That's one of the major new steps in this risk assessment. That instead of looking at a single chemical, we are looking at a family of chemicals. And we are basically saying that if there's concern with one, there needs to be concern with all. Since they all do the same thing. Basically, some of these other compounds are really dioxins in disguise. Very few of them are as toxic as dioxin; but while some of them aren't as toxic as dioxin, there may be a lot more of them out there in the environment.

CURWOOD: Scientists believe that the banning of dioxin-like PCBs, tighter pollution controls, and changes in manufacturing processes, have already cut dioxin production over the last 20 years. But the draft EPA report is likely to prompt a new round of calls for tighter restrictions, or even outright bans on dioxin. For now, EPA officials will open the document up to public comment and scientific review over the next few months. Any new regulations that do emerge would likely focus on getting dioxin out of our food. It's estimated that 95% of our exposure to dioxin comes from what we put in our mouths. It accumulates in the food chain and becomes more concentrated at every step. Even if it's too early for the government to make new recommendations, Joe Schwartz of Physicians for Social Responsibility says there are things people can do to minimize the dangers of dioxin. Chief among them is cutting down on fat.

SCHWARTZ: Reducing the amount of fat in people's diet would be a good idea, because fat is where dioxin bioaccumulates in the environment. And reductions in fat in the diet should have some impact on reducing the average human's exposure to dioxin from the food chain.

CURWOOD: The final version of the EPA's dioxin reassessment is scheduled to be released next spring.



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