Air pollution coming from farming operations contributes an estimated 26 percent of all air pollution in the Central Valley, leaving one out of every six children in the Fresno air afflicted with asthma.

Agricultural air pollution comes from diesel irrigation pumps, farming equipment, and livestock waste from giant dairy, poultry, and beef factory farms. The Central Valley of California has three of the nation's four metropolitan areas with the worst ozone pollution: Fresno, Bakersfield, and Visalia-Tulare-Porterville.

Earthjustice and the Environmental Law and Justice Clinic representing Medical Advocates for Healthy Air, Sierra Club, Natural Resources Defense Council, Our Children's Earth Foundation and Communities for a Better Environment, intervened in the Ninth Circuit case to defend EPA's authority to regulate air pollution from agricultural operations. The Center on Race, Poverty and the Environment also intervened on behalf of the Association of Irritated Residents.

The lawsuit, filed by the California Farm Bureau Federation, challenged EPA's authority to regulate major agricultural sources of air pollution in California until the State adopts new legislation dropping the agriculture exemption from air permit requirements. The Ninth Circuit held that EPA's decision to disapprove California's permitting program was "not only reasonable, but mandated by the plain language of the [Clean Air Act]." The Court noted "the California Legislature had been on notice since 1995 that full approval of [its state permit program] hinged on the repeal" of the agricultural exemption from air permit requirements.

Legislation (SB 700) removing the exemption is currently pending in the State Legislature.