Caltech students and some of their children were unknowingly exposed to a chemical listed by a state agency as a probable carcinogen, according to emails obtained by this news group.

A generic version of the weed-killer Roundup, which contains glyphosate as the main ingredient, was sprayed on planters within a courtyard and on artificial turf in a playground at a Caltech graduate student housing complex on Villa Street in Pasadena, the university wrote in a notice to residents.

Applications of the herbicide occurred at several off-campus Caltech housing properties, the university reported.

Listed as toxic by state

Glyphosate is listed by the California Office of Environmental Health Hazard Assessment among other chemicals know to cause cancer in adherence to Proposition 65, a measure passed in 1986 requiring the listing of toxic chemicals used in the state.

Glyphosate’s inclusion followed a 2015 classification by the International Agency for Research on Cancer, an arm of the World Health Organization, which labeled the herbicide as “probably carcinogenic.”

However, the U.S. Environmental Protection Agency said in a draft assessment that the chemical is not likely carcinogenic.

Notification not provided

In California, members of the public must been notified if a Prop. 65 chemical is used. In this case, the residents said they did not learn of the herbicide’s use until months after the fact.

“We are sorry that advance notice of the spraying was not provided,” Caltech’s Director of Housing Maria A. Katsas wrote in an email to the residents Wednesday.

Katsas’ email said a landscape contractor sprayed the herbicide in the courtyard of the Villa Street apartments on several occasions, including June 6 in the planters and on the artificial turf. Residents said the area sprayed includes playground equipment used by little children.

Application of the generic Roundup, known as Ranger Pro, was also applied on April 12, she wrote.

Vendor told to stop spraying

In a June 21 email to a student who complained, Katsas said the university directed the vendor to stop spraying any herbicides at the student housing complex on Villa Street. Her recent mass email said Caltech directed its vendors not to use Roundup, Ranger Pro “or any other herbicide at or around Caltech student housing or other residential facilities.”

Riley Galton, 27, a Ph.D. candidate studying developmental biology, lives at the complex and complained about the use of the herbicide to Caltech. She said she and her 10-month-old son, Indigo, often spent time at the courtyard and the playground.

Galton witnessed the spraying of the playground area that contains fake grass and play equipment, she said.

“There were three or four weeds in between the turf and the sidewalk. It would have been so easy just to pick them,” Galton said.

Galton said she’s read about glysophate’s correlation to some cancers and is worried about exposure to her son, who often played on the surface that was treated. She said she no longer takes her son to the playground.

“I am very concerned about the effects of chemicals on my baby’s development. I feel very unsafe,” Galton said.

She said her complaints fell on deaf ears for several weeks. Only this week, after the university received media calls, did the graduate students receive a mass email.

“We take this situation seriously and are continuing to investigate the matter,” Caltech Chief Communications Officer Shayna Chabner wrote in an emailed response.

Massive lawsuits, jury awards

Roundup, made by chemical giant Monsanto, purchased by Bayer for $63 billion, has been the subject of multiple lawsuits from plaintiffs who allege their cancers were a result of exposure to the herbicide. Recently, a jury awarded a Northern California man who was diagnosed with non-Hodgkin’s lymphoma in 2014 $80 million. Edwin Hardeman used the herbicide for many years on his property.

Earlier this week, a judge reduced the jury award to $25.27 million but still called the conduct of Monsanto “reprehensible.”

It is estimated there are 13,400 plaintiffs who have sued Monsanto and now Bayer, alleging the product’s main ingredient, glyphosate is unsafe under certain exposures.

In a multipage response on its website, Bayer said glyphosate has been studied hundreds of times and is safe. Bayer and Monsanto dispute the International Agency for Research on Cancer finding as an anomaly, saying the “IARC is not a regulatory authority and conducted no independent studies.”

“There is no evidence that local municipalities who choose to move away from glyphosate for amenity weed management are enhancing safety, given there is an extensive body of research on glyphosate and Bayer’s glyphosate-based herbicides, including more than 800 rigorous studies submitted to EPA, European and other regulators in connection with the registration process, that confirms that these products are safe when used as directed,” Charla Lord, Bayer spokesperson, wrote in an emailed response on Wednesday.

Studies disputed

Jennifer Sass, a senior scientist with the Natural Resources Defense Council, a national environmental group, said a new, 257-page study by the federal Agency for Toxic Substances and Disease Registry supports the International Agency for Research on Cancer conclusion.

“When you look at it, you can see a preponderance of evidence of studies linking it to cancer,” she said during an interview Wednesday. “And that is a concern from a public health perspective.”

The Agency for Toxic Substances and Disease Registry review of past studies found some studies showed no link as well, she said, in essence agreeing with the U.S. EPA. “Half a dozen studies show a link to cancer and half a dozen studies show they don’t,” Sass said.

While the debate rages and jury awards pile up, some continue to ask the herbicide not be used in public places.

Stopping glyphosate in L.A. River

In June, U.S. Rep. Adam Schiff, D-Burbank, asked for an amendment to a funding bill that would curtail the use of glyphosate by the U.S. Army Corps of Engineers along the banks of the Los Angeles River.

The House Rules Committee did not include his amendment in the bill.

Recently, the L.A. County Department of Public Works stopped using Roundup or any glyphosate-based herbicide in the clearing of nonnative brush and debris from behind Devil’s Gate Dam in Pasadena.

Sass said the issue is difficult because the product has been widely used in agriculture and backyard gardening for decades, and studies are not always conclusive.

Natural alternatives encouraged

She suggested landscapers use natural alternatives, such as concentrated acetic acid, a form of vinegar, or just pick the weeds by hand.

“I would say it is more important to not poison people in playgrounds than to have it look completely green with no dandelions,” she said.

The Associated Press contributed to this story.i

EDITOR’S NOTE: This article has been updated to correct the spelling of Riley Galton.