California to Put Four Pesticides on Cancer List

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By David Schultz

Sept. 8 — California's impending decision to place on its list of carcinogenic chemicals four widely used pesticides—including Monsanto's glyphosate, the most widely used pesticide in the country—has uncertain ramifications for the state's agriculture industry.

If the state's Environmental Protection Agency, also known as CalEPA, places the four pesticides on its list, any knowing discharges of the chemicals into drinking water would become illegal. Also, farmers, pest control companies and any other businesses that want to use the pesticides would first have to provide “clear and reasonable warnings” to the public, according to state law.

Sam Delson, a deputy director in CalEPA's scientific review office, told Bloomberg BNA he was unsure if the drinking water restrictions would apply to runoff of pesticides from farms.

CalEPA will accept comments from the public for the next 30 days on whether to list the four pesticides: glyphosate, malathion, parathion and tetrachlorvinphos.

However, a formal listing of these chemicals is all but certain, Delson said. “It’s fair to say that it’s very likely that this will become final.”

Automatic Decision 

Delson can speak with confidence on this because of the process California uses for listing potentially cancer-causing chemicals.

The process was created in 1986 by the state's Proposition 65, also known as the Safe Drinking Water and Toxic Enforcement Act. The voter-approved measure required the state to maintain and to update at least annually a list of carcinogenic chemicals. Chemicals on the list are subject to drinking water restrictions and use notification requirements.

There are several ways for a chemical to get on California's list; one of those ways is if a chemical is found to be carcinogenic to humans or animals by an “authoritative body.”

These bodies include various federal agencies, such as the U.S. Environmental Protection Agency or the Food and Drug Administration, as well as the World Health Organization's International Agency for Research on Cancer.

Earlier this year, the IARC issued a finding that the four pesticides at issue here are probably carcinogenic to humans based off of several studies of lab animals exposed to the chemicals.

As a result, the IARC's findings triggered an almost automatic decision by California to place the four pesticides on its list. In a sign of just how automatic this decision is for the state, Delson said CalEPA will only consider comments on whether the IARC did or didn't find the pesticides to be carcinogenic, not on whether the IARC's findings are correct.

Safe Harbor 

After the pesticides are listed, California businesses will have 20 months to come into compliance with the drinking water restrictions and 12 months to begin notifying the public when they use the pesticides.

Businesses with fewer than 10 employees are exempt from complying with these rules. Also, businesses that use the chemicals at levels below a state-developed threshold are exempt.

That threshold is called in California regulations a “safe harbor.” Delson said CalEPA has established safe harbor levels for less than half of the more than 800 chemicals on its cancer-causing list. Dozens more chemicals are prioritized on a wait list.

Despite this, Delson said CalEPA will “definitely” establish safe harbor thresholds for glyphosate and for malathion, the two more widely used of the four pesticides, within one year of their formal listing. If the agency fails to do this, no amount of these pesticides would be permitted in drinking water, and the use of any amount would trigger the public notification requirements.

“We do have limited resources, but that’s a priority,” Delson said.

Depending on how high the state sets its safe harbor levels, tens of thousands of farms and other businesses many find themselves unaffected by CalEPA's listing.

Public Perception 

While it's still unclear how the listing of these chemicals will affect industry, it's already having a negative impact in the court of public opinion. News stories about California's move, which it announced Sept. 4, circulated widely online, briefly making Monsanto a trending topic on Facebook over the Labor Day weekend.

Monsanto developed the herbicide glyphosate in the 1970s and currently sells the weed killer under the trade name Roundup. However, the company's patent on the chemical has long since expired, and it is now widely used in numerous products produced by dozens of pesticide companies, including Dow AgroSciences, Syngenta, Bayer CropScience and many others.

Many of these companies also produce genetically modified crops that are engineered to withstand glyphosate, which allows farmers who plant them to spray the chemical broadly without inadvertently killing their crops. As a result of the widespread adoption of these GM crops, glyphosate use has skyrocketed over the past 20 years.

Glyphosate's Effect on Humans 

Another reason for its wide adoption was the belief that glyphosate posed almost no toxicity risk to humans. It kills plants by preventing them from internally synthesizing certain vital proteins; humans, however, get these proteins externally through food.

However, since the IARC findings were announced in March, many are beginning to take a second look at how glyphosate affects humans.

Charla Lord, a Monsanto spokeswoman, said her company “continues to join with the agricultural industry in strongly disagreeing with IARC’s classification.”

“Glyphosate is an effective and valuable tool for farmers and other users, including many in the State of California,” she told Bloomberg BNA in an e-mail. “We will provide detailed scientific information to [CalEPA] about the safety of glyphosate and work to ensure that any potential listing will not affect glyphosate use or sales in California.”

To contact the reporter on this story: David Schultz in Washington at

To contact the editor responsible for this story: Larry Pearl at

A notice of intent to list the four pesticides as carcinogenic from the California Environmental Protection Agency is available at