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


Air Date: Week of

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A new study by the National Academy of Sciences criticizes the EPA for using outdated science to evaluate the safety of using sewage sludge as fertilizer. Ellen Harrison, head of Cornell University’s Waste Management Institute, discusses the study with host Steve Curwood.


CURWOOD: For years, sewage sludge has been used to fertilize soil in everything from parks and golf courses to home gardens. The Environmental Protection Agency created standards for sludge processing and application. But a recent critical review by The National Academy of Sciences says those standards may not adequately protect public health.

Ellen Harrison directs The Waste Management Institute at Cornell University and was a member of The National Academy Review Panel. She says the EPA is using outdated science that allows too many toxic chemicals to remain in processed sludge.

HARRISON: We have so little information about the contents of our sewage sludges. Right now, the rules require people who want to land apply sludges to test for nine metals. And we know that there are hundreds of chemicals, probably thousands of chemicals that are used in industry and homes that go down the drain, and will end up in sludges.

And, it is this combination of wastes that generate an incredible mix of contaminants and pathogens that go into the sewage treatment plant where the plant is designed to clean the water. That's its objective. And, many of the contaminants and pathogens are concentrated then, in the sewage sludges.

CURWOOD: So, pathogens, that's a fancy word for germs, things that can make people sick from infectious disease. In terms of pathogens, how safe is sludge when it's applied to land?

HARRISON: The treatment of sludge before land application can be done at sort of two different levels. The first level of treatment is designed to reduce pathogen levels, but not eliminate pathogens. And, that Class B, so-called, sludge is the main kind of sludge that's applied around the country.

We have very little information on the pathogen content of those Class B sludges. They're tested only for a couple of pathogens that are supposed to be sort of an indicator of how well the treatment process has taken place.

CURWOOD: My understanding is a number of people are making complaints about getting sick from sewage sludge being applied to land in their neighborhood or their locality. What are the nature of these complaints and how valid might they be?

HARRISON: The symptoms include headaches, nosebleeds, nausea, vomiting, coughing, heavy mucus. A number of people have gotten lesions, boils on various parts of their bodies. I have been struck by the sort of commonality amongst symptoms at different sites. Actually, these people who call themselves sludge victims call it sludge syndrome.

And, I have become convinced, even though these are anecdotal reports, in looking through them, and the commonality of what I'm seeing, I believe that there are cases in which people are getting sick. So we don't know what's happening. It may be a combination of chemical contaminants and pathogens moving off the site, either via air-- because if anybody's been to an ag field, they know that things tend to blow around if it's been dry. And, anything that was in that Class B sludge, if it's blowing off the site, will be arriving at neighbors' properties. Or it may be going in runoff, water runoff from the site. And those are two pathways that were not evaluated in developing the federal rules.

CURWOOD: The Environmental Protection Agency says that current standards do protect human health. But, they do say there's a need to strengthen and update the science behind these standards. What's your response?

HARRISON: EPA has been both the regulator of land application, and it's also been a promoter of land application. And I think that's a very dangerous position to be in, to try and have both those hats. Unfortunately, what that means is, to some extent, they forfeited the ability of people who have concerns to trust them. Because the sense is that they're looking to find an answer that makes land application okay.

In terms of doing further science, I think that there is additional science that's needed that the National Academy report points that out. We talked about the need to do a new survey of what's in sludges, both pathogens and chemicals. We talked about a real need to investigate these health incidents. And I'm not sure that EPA can do that investigation, but somebody needs to. And there are other scientific questions that need to be addressed. But I'm a bit fearful that there are also policy questions that need to be addressed. And I would hate to see those put off while we spend another ten years looking at the science.

CURWOOD: Ellen Harrison is a geologist and the director of Cornell University's Waste Management Institute. Thanks for taking this time with us today.

HARRISON: Thank you for concentrating on this important issue.



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