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Compost Contaminated with Clopyralid
December 11, 2001
For the second year in a row, the persistent herbicide clopyralid has contaminated compost at two composting facilities in the U.S. state of Washington. Produced exclusively by Dow AgroSciences and available commercially under the name Confront, Clopyralid has recently contaminated compost in New Zealand and in the U.S. state of Pennsylvania, according to the U.S. Composting Council.
Confront is used on lawns to kill dandelions, clover and other broadleaf plants. Although most herbicides are considered to break down during composting, clopyralid and others in the pyridine carboxylic acid group break down extremely slowly, especially during composting.
In Washington, plants treated with Confront have contaminated compost at local composting facilities with levels of clopyralid high enough to cause damage to compost users' crops, including those at local gardens and nurseries. Publicly available studies show low acute toxicity to humans and animals, but no data on reproductive effects, developmental effects or cancer are available. Clopyralid is quite soluble in water, mobile in soil and extremely toxic to certain plants. Sunflowers, legumes, tomatoes and potatoes can be affected by clopyralid at levels of 10 parts per billion (ppb) or less.
Clopyralid contamination has prevented the Spokane Regional Composting Facility in Washington from selling compost to the general public this year, and 25,000 cubic yards of compost remain unsold from last year. Tests in May 2001 at the facility revealed clopyralid residue levels of 73 and 80 ppb. At Washington State University, loss of revenue, settling claims, testing and additional labor due to clopyralid contamination has cost the facility about US$250,000 over the past two years.
Critics charge that the contamination undermines the investment of millions of dollars in public and private composting facilities and threatens consumer confidence in composting facilities' reputation for providing quality products.
"Confront is totally contradictory to all of our goals for recycling, resource conservation and sustainability... Dow must follow the precautionary principle and withdraw Confront immediately until it can be proven safe for organics recycling," commented Ann Morse, president of GrassRoots Recycling Network in Georgia. "Dow must take full responsibility for damage caused by its products," she added.
In April 2001, the city and county of Spokane, Washington asked Dow to stop distributing clopyralid temporarily in their local area. The company agreed to do so for residential uses, but the herbicide will still be used on golf courses whose grass is not taken to composting facilities. The city has also begun a campaign to educate people about why herbicide treated grass cannot be composted. Washington State University has responded by certifying vendors of straw and hay--the main crops suspected of carrying clopyralid. Vendors will have to guarantee that their crops are herbicide free.
Fearing that the contamination may be more widespread than several isolated incidents, the Washington Organics Recycling Council has asked all composting facilities in the state to start monitoring for clopyralid.
Public utilities in the U.S. states of Washington and Oregon urged the U.S. Environmental Protection Agency (EPA) to reconsider its registration and re-registration criteria for herbicides to include the requirement that no residual herbicides remain after a normal 60 to 90 day composting cycle. The utilities emphasized that herbicide manufacturers, not composting facilities, should be held responsible for the residues.
The U.S. Composting Council and other groups have called for Dow to work with the EPA to develop clearer warning labels on clopyralid products. Currently, the labels warn not to use compost containing grass clippings that were sprayed with clopyralid during the same season as spraying occurred. However, the two cases in Washington show that contamination can persist beyond a single season.
The Council has called upon Dow to buy the contaminated compost, compensate organic growers for lost produce, compensate composters for costs of remediating clients' land and fund an independent study into the effects of clopyralid--including testing the amount of clopyralid that passes through to the urine of animals and humans who consume treated grain, asparagus, beets or their byproducts.
In 2000, Dow was the fifth largest agrochemical company in the world with sales of over US$2.2 billion dollars.
Sources: Bezdicek, David, Mary Fauci, Dan Caldwell, Rick Rinch and Jessie Lang, "One Year Later: Persistent Herbicides in Compost," BioCycle: Journal of Composting and Organics Recycling July 2001; Joe Truini, "Composting Council says Dow's Herbicide Product Poisons Compost" Waste News, November 12, 2001; Washington State University press release, June 13, 2001; Agrow: World Crop Protection News, Janurary 5, March 2 and April 13, 2001.
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