SAN FRANCISCO—Activists have filed another petition to force federal regulators to set safety standards that protect children from pesticides that drift from farm fields into nearby communities.

Pesticide Action Network, the United Farmworkers of America and other groups filed the petition Wednesday in San Francisco federal court.

It asks a judge to force the Environmental Protection Agency to answer a petition from 2009, which demanded the agency evaluate children's exposures to pesticide drift and adopt no-spray buffer zones around homes, schools, parks and daycare centers.

Plaintiffs say in the four years since the initial petition was filed, the EPA hasn't responded or taken action.

EPA spokesman Bill Keener said the agency couldn't comment, because it hasn't seen the petition yet.

In 1996, Congress required the EPA to set standards to protect children from pesticides.