State and national environmental groups have filed a lawsuit against the Environmental Protection Agency hoping to reverse a decision allowing the use of two blood-thinning poisons to kill prairie dogs.

The lawsuit was filed Wednesday in U.S. District Court in Washington, D.C., by Defenders of Wildlife and Audubon of Kansas. Both have been actively involved in prairie dog issues, specifically because of efforts to reintroduce the black-footed ferret.

Audubon of Kansas has been a key player in the reintroduction of ferrets in Logan County, where the controversy over prairie dogs has been rampant.

The federal lawsuit claims EPA failed to follow its own rules when it allowed the general use of Rozol Prairie Dog Bait to target black-tailed prairie dogs in 11 states, including Kansas. The EPA has also allowed special local needs registrations for the use of Kaput-D to target prairie dogs, also in Kansas.

Rozol, which contains the blood-thinning chemical chlorophacinone, was approved for use on prairie dogs on May 13.

"Somebody at EPA decided 'let's make it available for general use,' " Ron Klastaske, Audubon of Kansas's executive director, said of Rozol. The rodenticide has been used in Kansas to kill prairie dogs, but its use had been allowed under the special local needs registrations.

Kaput-D contains diphacinone, another blood-thinning chemical, and its use is governed by the local needs rule, which is first advanced by the Kansas Department of Agriculture and then the EPA.

In the lawsuit, Defenders is asking for an order reversing the general registration of Rozol as well as the localized use of Kaput-D.

The suit claims EPA did not announce the application to register chlorophacinone for general prairie dog use and failed to solicit public comment on the application prior to its registration.

Defenders also claims that EPA's determination that the use would have no unreasonable adverse effects on the environment was flawed.

One of the biggest reasons, however, came earlier this month when the U.S. Fish and Wildlife Service sent a six-page letter to EPA objecting to the registration of Rozol.

"We recommend that EPA withdraw the registration for Rozol and not issue a registration for prairie dog control for Kaput until EPA completes a formal consultation with the (Fish and Wildlife) service on the use of rodenticides to control black-tailed prairie dogs."

FWS also sought to implement rules requiring agencies to confer on issues affecting endangered species, such as the black-footed ferret or eagles.

The Western Association of Fish and Wildlife Agencies -- a consortium of Canadian provinces and 23 states, among them Kansas -- also voiced its concerns over the chemicals in a 2008 letter. That group urged a full review of the use of both chemicals and the immediate suspension of any existing permits and a prohibition against issuing future permits.

EPA's registration of Rozol followed several months after the WAFWA made its comments.

Defenders and Audubon had filed a notice of intent to sue in the wake of the rodenticide registration.

"This concern about Rozol has been discussed here for a couple years," Klataske said.