The designation of the popular weed-killer, Roundup, as a potential cancer causing agent could change how the chemical is used by school districts and municipalities.

The state Office of Environmental Health Hazard Assessment announced Monday that Roundup, or more precisely the chemical glyphosate, will be "added to the list of chemicals known to the state to cause cancer for purposes of Proposition 65,” according to information on the agency’s website.

Monsanto, the manufacturer of Roundup, denies the chemical causes cancer and will "aggressively challenge” the state Superior Court ruling that cleared the path for Monday’s decision, according to the Los Angeles Times.

San Juan Unified School District and Sacramento City Unified School district both report using Roundup on school campuses for weed control. Although the herbicide is still approved for weed-control on school campuses, both districts indicated they use it sparingly. Use of chemicals on school campuses is governed by state law.

“Roundup is considered an herbicide and users must follow the regulations applicable to pesticides under the California Healthy Schools Act (HSA) which was enacted in 2000,” said Maria Lopez of Sacramento City Unified School District in an email. “That means there are regulations around notice to the school community, time restrictions, record keeping, etc. are required under the act. Roundup is not on the list prohibited from use in schools and child care facilities. The proposed regulation would not ban the use of Roundup but require the manufacturer, Monsanto, to add a warning.”

Should state guidelines for use of the chemical change, San Juan Unified School District will alter its practices accordingly, said Raj Rai, communications coordinator for the district.

Placer County uses it mainly alongside roadways for fire prevention purposes, said Ken Grehm, director of public works and facilities. He said it is possible that it is used in county parks, but other weed-control measures like use of sand and bark in landscaping are also used for weed management, so use of Roundup is probably very limited.

As with the school districts, the county will revise policies on its use should guidelines for it change, Grehm said.

The City of Sacramento and counties of Sacramento and Yolo did not immediately respond to requests for information on their use of the chemical.