More than a dozen Southern Arizonans are suing agrichemical giant Monsanto, claiming they developed cancer after long-term exposure to a substance likely found in many Tucson garden sheds.

The local lawsuits over Roundup, the world’s most widely used weedkiller, are part of a wave of similar cases nationwide that some are comparing to past legal fights against tobacco companies and asbestos manufacturers.

The surge in lawsuits follows a March 2015 finding by the World Health Organization’s International Agency for Research on Cancer that glyphosate, the active ingredient in Roundup, is “probably carcinogenic to humans.”

Monsanto promised, but did not provide, a response to the Arizona Daily Star’s request for comment.

The company’s website says the firm “strongly disagrees” with the 2015 finding. It says most scientists support the company’s position that Roundup isn’t harmful when used as directed.

Even so, a handful of countries, including France, the Netherlands, Bermuda and Sri Lanka, have banned glyphosate-based herbicides, either for personal or commercial use or both .

In the U.S., California recently added the substance to its list of chemicals that can cause cancer.

It isn’t clear how many Roundup lawsuits have been filed nationwide, but a Google search shows several law firms actively soliciting business from those who believe they were harmed.

Some have established websites with names like and

The local cases, filed by David Diamond, a Tucson attorney with the injury law firm Goldberg & Osborne, claim area residents developed non-Hodgkin’s lymphoma after long-term use of the herbicide.

The plaintiffs include the owner of a Sierra Vista landscaping firm, the manager of a ranch in Sonoita and several longtime backyard gardeners in the Tucson area.

The suits claim Monsanto “has led a prolonged campaign of misinformation to convince government agencies, farmers and the general population that RoundUp is safe.”

Plaintiffs are seeking unspecified damages for seven civil counts including negligence, failure to warn, breach of warranty and violations of Arizona’s consumer fraud act.

Contact reporter Carol Ann Alaimo at 573-4138 or On Twitter: @StarHigherEd