After I began to learn about herbicides from Dow Chemical remaining active in composted matter & killing gardens that it is used on, I posted a couple of times on the issue (http://backyardorganic.wordpress.com/category/pesticides-herbicides/). I also got curious enough to write to the EPA asking about the issue. Today I finally received a response.
My original email
Hello Richard & Peter,
I’m writing because I’ve recently found a lot of information about herbicides such as clopyralid and aminopyralid finding their way into compost. I was going to get free compost from my city, but after learning that they ship organic matter to a processing facility that handles multiple cities, the chances of getting herbicide laced compost increase significantly.
What, if anything, is the EPA doing to address this problem? If you can’t safely use compost from city programs, that is a disincentive for people that would otherwise participate in community composting programs to begin with, which in turn increases the amount of waste going into landfills.
As a result of this problem I can’t trust the free compost from my municipality and must compost in my yard as much as possible to ensure that only clean compost goes into my vegetable garden.
What is the EPA doing about this problem?
The response from the EPA
Dear Mr. Carleton–
Thank you for your email of October 30, 2009, expressing concern about herbicides such as clopyralid and aminopyralid finding their way into compost and the potential for this contaminated compost to damage or kill garden plants. You ask what EPA is doing to address this problem.
Federal law requires that before selling or distributing a pesticide in the United States, a person or company must obtain a registration from EPA. Before registering a new pesticide, EPA must first ensure that there is reasonable certainty that no harm to human health and the environment will result from use of the pesticide according to label directions and precautions. If EPA later receives new data or information indicating a risk of concern, the Agency works to mitigate that risk by modifying the way the pesticide can be used, or by eliminating use completely if the risk cannot be mitigated.
Residues of the pyridine-containing herbicides clopyralid, aminopyralid, and picloram may remain in treated plant material or in manure from animals that have grazed in treated pastures or have been fed hay or forage harvested from treated pastures or crops. EPA is aware that these pesticide residues may remain active in composted plant material or animal manure for a period of time. The Agency is working with the manufacturer, Dow Chemical Company, to change the use of these pesticides as needed to address the contaminated compost problem.
Clopyralid was previously registered for use on residential lawns. In the western U.S., centralized programs collect lawn clippings and put them through an accelerated 90-day composting process, after which the material is sold as compost. Crops treated with this compost were being damaged. To address this problem, Dow has voluntarily cancelled the residential use of clopyralid. Our understanding is that incidences of clopyralid-contaminated compost are declining, as a result.
Aminopyralid was registered in 2005 and is effective in controlling noxious weeds in the western U.S. Currently some grazing restrictions exist when aminopyralid is used on pasture and rangeland. In the eastern U.S., horses have been allowed to graze on treated pastures, and third parties may collect the horse manure and market it as compost. When applied to certain vegetable crops, this compost has caused damage. EPA is currently working with Dow to address this problem. Dow has stopped selling aminopyralid in the eastern U.S. while the company is developing and implementing a stewardship program.Meanwhile, negotiations are ongoing regarding further label restrictions.
Picloram is considered very useful in controlling invasive weeds in the western U.S. While EPA is aware of an isolated incident several years ago (2000) in Washington State that involved picloram-contaminated compost, the invasive weed control use generally has not resulted in compost problems. However, run-off and ground water problems in the southern U.S. and use of these contaminated waters for irrigation purposes has resulted in damage to treated crops due to picloram’s persistence in water and phytotoxicity. In response, many of the crop uses of picloram have been cancelled. Dow has lowered the application rate for the remaining uses from 12 pounds per acre to 1 to 2 pounds per acre. Dow has also changed the formulation of picloram from a pellet to a liquid, resulting in improved calibration and less potential for over-application. Finally, picloram also has been classified as a restricted use pesticide, so it may be used only by or under the direct supervision of trained, certified applicators. The registrant has initiated a stewardship program providing education to users. As a
result of all of these actions, there have been few reports of picloram contamination of irrigation water in recent years.
If new information becomes available indicating that additional mitigation is warranted, EPA will continue to take steps to reduce the potential for clopyralid, aminopyralid, and picloram to contaminate garden compost. These three pesticides are scheduled to begin registration review in 2014. Through this program, the Agency periodically reviews registered pesticides to make sure they meet the statutory standard for registration; that is, each pesticide can still perform its intended function without posing unreasonable risks to human health or the environment. We encourage interested members of the public to participate in this open, transparent process. For further information, please see the Agency’s Registration Review Web page,
http://www.epa.gov/oppsrrd1/registration_review/ .
I hope this information is helpful and will be glad to be of any further assistance.
Rick Keigwin
Director, Pesticide Re-evaluation Division
Office of Pesticide Programs
US Environmental Protection Agency
Phone: 703-308-8000
FAX: 703-308-8005
Keigwin.Richard@epamail.epa.gov
http://www.epa.gov/pesticides
