Since 2008, the EPA has been criticized for failing to prevent Dow Agrosciences from contaminating the public compost supply with persistent herbicides. The aminopyralid herbicide, Milestone, is part of a group of related herbicides known as pyralids. These powerful weed killers are sold to farmers to spray on their pastures and hayfields. When animals graze on treated pasture or hay, the chemicals persist in the manure for several years, even if the manure is processed into compost. As a result, gardeners unknowingly use contaminated hay or compost on their crops, which causes a slow death to plants such as carrots, lettuces, potatoes, beets, spinach, tomatoes, beans, and peas.

The problem is not minor, nor is it isolated. Soil samples from 17 Montana counties have confirmed pyralid toxicity, and several Pennsylvania reports of contamination have been received. The impact on organic farms and community gardens in Whatcom County, Washington, has been estimated to cost hundreds of thousands of dollars.

These toxic herbicides are so potent that residues can damage sensitive crops at levels as low as 10 parts per billion, and their effects can be apparent immediately or take weeks to manifest. The EPA approved Milestone/aminopyralid with “conditional” approval in 2005, despite inconsistencies in Dow's Environmental Fate and Ecological Risk Assessment. The EPA scientists also noted the risk to endangered native plants and that aminopyralid kills legumes, including wild species that contribute nitrogen to the soil, thus crippling nature's fertility cycle.

At the time of approval, lab tests were not available to identify pesticide residue levels in soil, and today, such tests are costly. Recently, the EPA asked Dow to make the environmental risks of aminopyralid more prominent on labels, but Dow has failed to provide precautionary information on its website.

Persistent herbicides will continue to pollute gardens until the EPA reevaluates aminopyralid, with data completion scheduled for 2014. Meanwhile, it is up to individuals to raise awareness about the dangers of these herbicides, and to demand greater protection from the EPA.

Eliminating persistent herbicides from our food supply chain is essential for sustainability and conservation. By taking action to reduce the use of toxic herbicides, we can protect our environment, and ensure that our crops are safe for consumption. Gardeners can opt for natural methods of weed control, such as mulching or hand-pulling, while farmers can explore non-toxic alternatives. With collective action, we can transform our food supply chain, and eliminate persistent herbicides once and for all.