Next week, Monsanto and California's Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) will face off over the agency's plan to list the herbicide glyphosate as a carcinogen. The outcome of this legal battle could have major ramifications to California's long-established regulatory program.

It all started back in Sept. 2015 when the OEHHA issued a notice of intent to list the chemical as known to the state to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986, commonly known as Proposition 65. The OEHHA determined that glyphosate met the criteria under the "Labor Code" listing mechanism, which directs the office to add a chemical or substance to the Prop 65 list of known carcinogens if it meets certain classifications by the World Health Organization's International Agency for Research on Cancer (IARC). The France-based IARC concluded that glyphosate is "probably carcinogenic to humans (Group 2A)" in March 2015.

Monsanto then filed a lawsuit against the OEHHA in January 2016 to prevent the listing, arguing that the Labor Code listing mechanism is unconstitutional because the office delegated law-making authority "to an unelected and non-transparent foreign body that is not under the oversight or control of any federal or state government entity."

Glyphosate happens to be the main ingredient in Monsanto's Roundup, the world's most popular herbicide. The chemical is applied onto "Roundup Ready" crops that are genetically modified to resist applications of the spray. The agribusiness giant has long maintained the safety of their flagship product and has vehemently denied glyphosate's link to cancer and has also demanded a retraction of the IARC's report. The company's lawsuit also cited the OEHHA's own 2007 study concluding that the chemical was unlikely to cause cancer.

In response, the OEHHA filed a motion to dismiss Monsanto's lawsuit. The office asserted in its motion that the listing mechanism "simply provides a way for OEHHA to make the most of scarce resources." According to the motion, IARC's scientific determinations are "the gold standard in carcinogen identification," and are trusted and relied upon by state governments, the federal government and foreign governments alike.

At the upcoming Jan. 27 hearing in Fresno Superior Court, both sides will make their arguments before a judge decides whether to dismiss the case or allow it to proceed.

"Monsanto's lawsuit is significant for a number of reasons," Kevin Haroff and Marina Cassio of Marten Law wrote in a blog post. "It raises fundamental issues over how scientific health assessments can appropriately be used as the basis for governmental actions, with broad-reaching implications for both consumers and the overall economy. As a practical matter, it also challenges a key element of a unique California regulatory program that has now been in place for three full decades."

The OEHHA's Labor Code listing mechanism using IARC's classification scheme has been tested in court before. In 2013's Styrene Information & Research Center v. Office of Environmental Health Hazard Assessment (SIRC v. OEHHA), the trial court and appeals court determined that the OEHHA could not just rely on the IARC's classification scheme to list a chemical as a known carcinogen in the state. Rather, the court decided that a listing must always be supported by a finding that the chemical in fact is known to the state to cause cancer. In the end, the OEHHA was required to reevaluate four listed substances and six substances under consideration for listing.

"Put another way, an IARC Group 1 or 2A classification decision could create a presumption that a chemical must be listed as a known carcinogen under Proposition 65; however, court decisions construing the application of the Labor Code listing mechanism and similar provisions suggest that at least in some circumstances the presumption should be a rebuttable one," Haroff and Cassio point out.

"This may be important to how the courts will respond to Monsanto's legal challenge to OEHHA's proposed glyphosate listing," the authors continue. "Monsanto's argument that Proposition 65 improperly delegates lawmaking power to IARC assumes that OEHHA plays no independent role in identifying chemicals known to the state to cause cancer using the Labor Code listing mechanism. OEHHA could counter that that it does play an independent role, since under SIRC v. OEHHA, it has an independent obligation to find that there is evidence sufficient to establish that a chemical is 'known to the state of California' to cause cancer."

On the same day of the hearing, environmental lawyer Robert F. Kennedy, Jr. and the law firm of Baum, Hedlund, Aristei & Goldman will hold a press conference in Fresno in support of the OEHHA. The press conference will take place outside the courthouse at Noon PST and EcoWatch will stream the event live on Facebook.

Kennedy and Michael L. Baum, senior partner at Baum Hedlund, will speak in support of the state of California's motion to dismiss the lawsuit. Arturo S. Rodriguez, president of the United Farm Workers of America, will speak in support of protecting farm workers from harmful herbicides and pesticides.

Several of Baum Hedlund's and Kennedy's California Roundup cancer clients will also be speaking at the press conference.

Since Monsanto's lawsuit was filed, a number of organizations have intervened on both sides. The organizations that support California's OEHHA include the AFL-CIO, Center for Food Safety, Sierra Club, Canadian Labor Congress, Natural Resources Defense Council and the Environmental Law Foundation.

The organizations supporting Monsanto include California Citrus Mutual, California Cotton Ginners & Growers Association, California Grain and Feed Association, Almond Alliance of California, Western Plant Health Association and Western Agricultural Processors Associations.

The OEHHA has received more than 9,300 written comments in response to the listing. The comments are mostly from individuals and groups supporting the proposed listing. Monsanto, chemical producers and industry groups have also submitted comments opposing the listing. The public comment period is now closed, and OEHHA has yet to take final agency action on the listing.