Intervale Compost sales halted

By Candace Page, Free Press Staff Writer • January 30, 2009

Chittenden Solid Waste District will temporarily suspend sales of its Intervale Compost products today as the result of tests that found tiny amounts of a cancer-causing compound in the compost.

The compound, benzo(a)pyrene poses no immediate health risk. It has been found in compost across the country.

State toxicologist Bill Bress said Thursday that he would not worry about using Intervale Compost on gardens and lawns. Benzo(a)pyrene is a product of incomplete burning and is found in everything from tree leaves to the blackened crust of a barbecued steak.

On the other hand, the compost last month flunked commonly used federal guidelines for soil remediation at residential brownfield sites.

In an interview, he said, “I understand the risk of over-reacting, but this product and our credibility are really important to me.”

He said he hopes to resume sales of the compost, which this time of year are slow, after either “getting some guidance from the state of Vermont or from an independent risk assessment.” CSWD has about 5,000 tons of compost waiting to be sold when spring planting season arrives.

He said one solution might be to put labels on the compost alerting buyers to the presence of the carcinogen.

Chittenden Solid Waste District recently took over the state’s largest composting operation from the nonprofit Intervale Center.

‘You can’t avoid them’

Benzo(a)pyrene is one of a family of compounds known as polycyclic aromatic hydrocarbons, PAHs, created when a fire does not burn all the carbon in a fuel.

PAHs become part of the char on a piece of barbecued meat; they are released into the air by volcanoes; forest fires; tobacco smokers; and most commonly, by automobile exhaust pipes, furnaces and wood stoves.

The compound ends up in compost — particularly compost made from the leaves of urban trees — because trees filter PAHs from the air and store them in the leaves.

Benzo(a)pyrene is a proven carcinogen. Humans are exposed when they breath smoke, eat grilled meats, drink contaminated water or work in heavily contaminated soil.

“You have to understand they are ubiquitous. There is no way you can go through your day and avoid them,” Bress, the state toxicologist, said of PAHs.

A national expert on compost analysis, Will Brinton of Woods End Laboratories of Mount Vernon, Maine, said that’s certainly true of composts.

He said an analysis of 100 composts from across the United States found none that was free of benzo(a)pyrene. Levels ran up to 700 parts per billion; Intervale Compost tested in December at 192 parts per billion.

The California office of the U.S. Environmental Protection Agency set a goal of 15 parts per billion for soil used to rehabilitate brownfields — polluted industrial sites — for residential use. Vermont’s brownfields guideline is even lower, 10 parts per billion.

There’s no standard for PAHs in compost. Moreau learned about the PAH problem only when a private contractor tested Intervale Compost because he wanted to use it on a brownfields site in Burlington. That company alerted CSWD to its findings of higher-than-accepted levels.

‘A very tiny risk’

If benzo(a)pyrene is ubiquitous and found in all urban compost, what’s the worry? Any substance proven to cause cancer after long exposure is a concern to regulators and businesses.

“I have to think about product liability,” Moreau said.

Vermont’s standard of 10 parts per billion for soil is based on keeping the risk of additional cancers to less than one in a million over 70 years: That is, if a million people were exposed to benzo(a)pyrene every day for 70 years, only one of those million would get cancer as a result. (Massachusetts’ regulatory level for soil is 2,000 parts per billion; New York’s, 1,330, Moreau said.)

“It’s a very tiny risk, it’s very conservative,” Bress said of Vermont’s guideline.

At the state Department of Environmental Conservation, solid waste regulator Cathy Jamieson said, “This took us quite by surprise. ... We need more information before we can make a thoughtful decision. We have to consider our public health protection goal as well as our environmental goal of diverting leaves from landfills.”

She raised the possibility that the department might require leaves to be excluded from compost.

“A possible option is, is there another use for this material?” she said. “But we’re not there yet. People are exposed to leaves in their backyard, too. We need to put this in perspective.”

‘Should we all drive less?’

Brinton said the question of PAHs in compost is a new one. It was the subject of a scientific conference in Europe last year, where governments are also considering what, if any, standards to set.

He noted that the EPA guideline is for soil. Compost typically is mixed with garden or lawn soil at a dilution rate of 100 to one, so using the EPA guideline does not make sense, he said.

“As far as I know, from the papers I’ve read, nobody is trying to regulate below 1 or 2 parts per million,” as opposed to billion, Brinton said.

“I’m not against regulating PAHs, and we have to find ways to reduce loading in compost, but we have to look at society as a whole. Should we all drive less?” he asked, to reduce PAH pollution.

Contact Candace Page at 660-1865 or This email address is being protected from spam bots, you need Javascript enabled to view it To have Free Press headlines delivered free to your e-mail, sign up at www.burlingtonfreepress.com/newsletters.

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