TCS Daily


Harvard's George Gray Brings Science And Sense To Chemical Risks

By Kenneth Green - March 12, 2001 12:00 AM

Environmental problems generally revolve around the concept of risk - where something, whether human, animal, or ecosystem, is held to be at risk from exposure to some potentially harmful force. Environmental policy usually focuses on risks of human origin, though sometimes, as with the risk of foreign species invading a cherished ecosystem, risk management can involve one non-human species harming another non-human species.

Of the many environmental risk issues that pop up in the news or popular media, one of the most volatile is the debate over pesticides and other environmental chemicals. A steady drumbeat of newspaper stories, magazine articles, or advocacy group reports lay the blame for a variety of diseases on environmental chemicals and call for chemical bans. Regulations banning pesticides or other chemicals are becoming more common, and chemical-risk issues sometimes move beyond the news in movies such as Erin Brokovich.

But some experts observe that the public's perception of risk is increasingly at odds with reality. They observe that agencies and advocacy groups often overstate the degree of risk that people, animals, and ecosystems face from manmade chemicals and pesticides. These experts, such as noted toxicologist Bruce Ames and others, argue that a new approach to risk management is needed - one that puts more emphasis on targeting the biggest risks before putting limited public-safety resources into attacking small or insignificant risks.

To get the straight scoop on the risks of pesticide and chemical exposures, I talked to George Gray, director of the Program on Food Safety and Agriculture at the Harvard Center for Risk Analysis. The Harvard Center for Risk Analysis is a leading voice in environmental risk studies.

Ken Green: Let's get straight to an environmental concern that's frequently in the news, and where you've done a lot of research at the Harvard Center. Do people's normal exposure to pesticides pose a health to their risk?

George Gray: No, Ken, I don't think they do. And I actually act on this belief. For example, I am the grocery shopper in my family and I buy conventionally grown fruits and vegetables and foods for my wife and kids, and have no concerns about the risks of pesticides and residues on those foods.

Green: But from all the hype over "organic" produce, the public seems very concerned about chemicals. What do you think is the origin of the public's concern? Do you think it is misinformation or do you have other ideas why the public is so concerned about pesticides?

Gray: Well, part of it is, I think I have an advantage over the rest of the public. I am a toxicologist and a risk analyst. I know the science. I know the exposure. I know what the risks are and what they are not. And I know that the science tells us that the risks of pesticide exposures are extremely low if they exist at all. Other folks hear only about the fact that they are being exposed to pesticides. They only focus on the hazard part of the equation that says there's something there that could do something bad, and so it must be doing something bad. I think it's simply a case where people don't have all the information they would need to really understand how low these risks are.

Green: Right, but these are chemicals that can hurt laboratory animals in high doses, isn't that right?

Gray: Yes, they can; but I just got back from teaching my toxicology class that the dose makes the poison and it's the exposure that matters. The level of exposure that a person gets, for example, from many of these chemicals ... well laboratory animals get as much in a day as a person will get in a lifetime, and they get that day after day after day. So if adverse effects are found at those levels in animals, it does not necessarily tell us that the same adverse effects will be found in people exposed to much lower levels.

Green: What about other chemicals besides pesticides? There are other chemicals in the environment. Some people are concerned with so-called persistent environmental chemicals, things that don't break down easily, like for example, PCBs. What is the bottom line on those chemicals? Do you think people should be concerned about exposure to them, for instance, when they're working with the dirt in their gardens or when they are out swimming at the shore?

Gray: Well, no, not really, except for situations that might provide a pretty significant exposure, and those are pretty hard to come by in this country, in this day and age. In general, most chemicals in the environment pose a very small risk for people, if there is any risk at all. But all chemicals are not the same and one can't lump chemicals into a box of "just all chemicals." We do have to remember that different chemicals have different potentials to be dangerous. Still, you need a significant exposure in order for a chemical to be a concern and there are very few situations in which people's environmental exposure to chemicals are high enough to really be of concern.

Green: You mentioned that it is hard to assume all chemicals are the same and yet the gold standard of safety that U.S. agencies use is that if a chemical hurts an animal during laboratory tests, a human is assumed to be at risk when exposed to even one one-hundredth of that exposure. Do you think that a guideline like that is a good policy or a good way to manage risk and if not, what would you replace it with?

Gray: The first thing to remember is that the agency gold standard isn't one-one hundredth of a harmful dose, it's one one-hundredth of a harmless dose. They start from a dose given to animals that does not even do anything. So this is a dose that is completely safe for animals and humans are usually exposed to far less than one-hundredth of that dose. This approach to assessing potential harms or assessing risks is an old approach. It grew up in the fifties and it might have worked, sort of, in the old days when we were setting standards and costs and feasibility were not big concerns. But now, when we want to use risk assessment to do things like weigh benefits and costs or evaluate alternative risk management strategies, this kind of safety-factor approach is less useful. It's also less useful when we're trying to rank and prioritize risks to help people understand the big risks in their lives and what things they should really be worrying about.

Green: What are those risks that should really worry people? If you were the environmental risk czar, where would you focus your efforts?

Gray: Well, again, I think it depends very much on the specific chemical mix, the exposure situation. There could be places in which people in occupational settings or even home settings, such as people with exceptionally high radon levels in their homes, face situations to be concerned about. But in general, when we look at actuarial data about the things that really harm people, it's awfully hard to put environmental chemical exposures and the health effects that they might pose very high on that list.

Green: Then what is high on that list?

Gray: High on that list are things like accidents and diseases, the sorts of things we have known about for very long time. And there are plenty of involuntary risks. Six thousand pedestrians are killed every year by cars. That's a risk that we can clearly do more about, and yet it receives so much less attention than chemicals in the environment.

Green: Is that because people are more frightened by invisible risks or mysterious risks with unfamiliar chemical names?

Gray: Sure. The field of risk perception tells us that there's lots of things that would influence people, that makes people's concern meters go up; and it's quite clear that chemicals, for a variety of reasons, do that. The fact that people can't see them, that they are not familiar with them, and that they have kind of scary names seems to make people react more strongly. People also may react strongly because chemicals get a lot more attention than other risks do. There are a lot more column inches in newspapers devoted to chemical risk than there is to the risk of pedestrians crossing the street. When someone is killed by a car, it might get a little mention in the corner in the back page, on page H-55 or something, but when a report comes out claiming that a chemical is harmful to people, it's a front page story.

Green: So what about people who attribute every malady under the sun to chemicals in the environment?

Gray: Erin Brokovich. You make a movie out of it.
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