The U.S. Environmental Protection Agency has spent the past decade considering adding warnings to herbicide product labels against applying the chemicals in ways that can result in drift, but has yet to mandate the change.

The federal government regulates herbicides under the 1947 Federal Insecticide, Fungicide and Rodenticide Act. Initially administered by the Department of Agriculture, the law focused on the effectiveness of new chemicals that promised to make life easier by killing weeds and insects.

In 1972, the EPA took over enforcement and shifted the focus to guarding human health and the environment. The EPA tries to do that by requiring labels that tell how to use the chemicals.

The agency relies on users to follow label instructions.

Spray drift has long been a sore point. Any stray wind can push spray droplets away from their target. Also, some herbicides that have landed where they were intended can volatize and become airborne as fine droplets that are blown off site.

Enforcement varies from jurisdiction to jurisdiction. Also, some jurisdictions, such as California, have imposed additional restrictions.

In California, the state Department of Pesticide Regulation has delegated some enforcement authority to agricultural commissioners in each of its 58 counties.