Monsanto officials strongly deny the accusations, but environmentalists and some cancer patients say the company’s top selling weed killer is a carcinogen.

It’s one thing for a presidential candidate to support and defend a company that is responsible for genetically engineering organisms (GMOs) that have been banned in 38 countries.

But it’s quite another for a candidate to defend, invest in, or take hundreds of thousands of dollars from a company whose most successful product is the target of lawsuits that claim it causes cancer.

Democratic presidential nominee Hillary Clinton has enjoyed a long, profitable relationship with Monsanto.

The St. Louis-based agribusiness giant is a world leader in GMOs. It also manufactures Roundup, the popular weed killer that multiple studies have linked to cancer.

Republican nominee Donald Trump also has a vested interest in Monsanto.

He reportedly owns as much as $50,000 worth of Monsanto stock in one of his two wealth management accounts with Deutsche Bank, according to a story on The Motley Fool website.

Meanwhile, Monsanto has been busy this year defending itself against dozens of lawsuits from people with cancer who say they’ve been sickened by Roundup.

The product’s main ingredient, glyphosate, is a “probable human carcinogen,” according to the International Agency for Research on Cancer (IARC). The agency is the cancer wing of the World Health Organization (WHO).

The IARC’s conclusion last year that glyphosate can cause cancer in humans was based largely on studies of exposure to glyphosate in nations across the globe.

The findings were strongly disputed by Monsanto officials, who posted a detailed response on the company’s website.

Read more: Vice report on genetically engineered crops stirs debate »

Roundup has been around since the 1970s.

But its popularity soared in the 1990s when Monsanto introduced “Roundup Ready” crops, which are genetically engineered to resist the herbicide so that farmers can spray it liberally on entire fields.

Monsanto reportedly took in revenue of nearly $5 billion for Roundup products in 2015.

That’s the same year the IARC reported that glyphosate caused cancer in lab tests on animals, and concluded the chemical damaged DNA in human cells.

Monsanto, which continues to insist that Roundup is safe and does not cause cancer, got a boost this year when the United Nation’s Food and Agriculture Organization (FAO), and the WHO Joint Meeting on Pesticide Residues (JMPR), concluded that glyphosate is “unlikely to pose a carcinogenic risk to humans from exposure through the diet.”

After this second report was released, Monsanto released a statement on its website.

“We welcome this rigorous assessment of glyphosate by another program of the WHO, which is further evidence that this important herbicide does not cause cancer,” Phil Miller, Monsanto’s vice president for global regulatory and government affairs, said in the statement.

But multiple scientific studies in the United States and worldwide have linked exposure to glyphosate to cancer.

And critics of the UN/JMPR declaration that glyphosate is an “unlikely” cancer risk have raised questions about whether this conclusion was influenced by industry ties.

In a press statement, Greenpeace, the global environmental organization, noted that at least two experts involved in the decision, Alan Boobis and Angelo Moretto, have ties to the International Life Sciences Institute (ILSI) in Europe.

That organization “receives a majority of its operating and research funding from private companies, including glyphosate producers Dow and Monsanto.”

Greenpeace also pointed out and that ILSI’s Health and Environmental Sciences Institute (HESI) is primarily funded by private companies, including Monsanto.

Read more: Wide range of pesticides contribute to dwindling bee populations »

While politicians court Monsanto, an increasing number of Americans are taking Monsanto to court.

At least 25 lawsuits have been filed in federal court by plaintiffs alleging that Roundup more likely than not caused their non-Hodgkin lymphoma, a common and potentially deadly blood cancer.

When Maria Pichardo, 41, a married mother of three from Texas, was 12 years old, she started making annual summer trips with her family from her home state to Maryland and Minnesota to work in farm fields.

It was during those years as a migrant worker picking fruits and vegetables that she was first exposed to Roundup.

In an exclusive interview with Healthline, Pichardo said that in early 2000, she began using the pesticide at her house and on her surrounding property to control weeds.

Since then, she’s routinely used Roundup to kill weeds.

In August 2014, Pichardo said she was diagnosed with non-Hodgkin lymphoma.

In August 2015, several months after completing chemotherapy, she was diagnosed with the cancer again and underwent chemo a second time.

“I was exposed to Roundup from the time I was a young girl, and for many years after that,” said Pichardo, who is still undergoing treatment. “After I was diagnosed with cancer, when I heard on the radio that there could be a connection between Roundup and non-Hodgkin lymphoma, I called the number and spoke to attorneys.”

Pichardo’s attorney, Christopher Dalbey of Weitz and Luxenberg, an environmental law firm with offices in New York, New Jersey, and Los Angeles, told Healthline his firm has four active cases in federal court against Monsanto, with a total of seven plaintiffs.

“Our federal cases are in Fresno [Mendoza], Los Angeles, Chicago, and Nebraska. We also have a case in Delaware state court with three plaintiffs,” said Dalbey.

He added the lawsuits’ goal, in addition to rewarding plaintiff damages, is to force Monsanto to stop the use of glyphosate “or at the very least make Monsanto post more accurate warnings. One of the things we allege is that there is no warning of any carcinogen. The suggested safety measures are inefficient.”

Read more: The lingering health effects of Agent Orange »

Clinton’s relationship with Monsanto dates back to when she worked at the Rose Law Firm in Arkansas, where Monsanto was a client.

Monsanto reportedly gave between $500,000 and $1 million to the Clinton Foundation, which has been in the news this week after critics said the organization traded donations for access to the State Department.

In 2013, the New York Daily News reported that State Department officials under Clinton were using taxpayer money to globally promote Monsanto’s GMO seeds.

In 2015, Monsanto Chairman and Chief Executive Officer Hugh Grant spoke at the Clinton Global Initiative conference, along with many other high-powered people.

And in 2014, Clinton was paid $335,000 to give the keynote address to a Monsanto lobbying group, Biotechnology International Organization (BIO), in San Diego.

In the speech, she reportedly coached the lobbyists on how to develop “a better vocabulary” to improve the largely negative image of GMOs.

An Organic Consumers Association report on the speech noted that Clinton received a “standing ovation” from the lobbyists for her encouraging advice on how to get more people to support GMOs.

“‘Genetically modified’ sounds Frankensteinish. ‘Drought-resistant’ sounds like something you’d want,” Clinton reportedly said in the speech. “Be more careful so you don’t raise that red flag immediately.”

Read more: Indoor pesticide use linked to childhood cancers »

As for Trump’s platform on environmental issues, his promises include saving the coal industry and canceling the Paris Agreement on climate change that was approved by more than 190 countries around the world.

But he hasn’t said much about Monsanto.

His reported stock holdings in the company may or may not have influenced him to delete a tweet that slammed Monsanto.

Last fall, after it was announced that Ben Carson was leading Trump in the Iowa primary polls, Trump retweeted a message slamming Monsanto.

Trump retweeted, “’@mygreenhippo #BenCarson is now leading in the #polls in #Iowa. Too much #Monsanto in the #corn creates issues in the brain? #Trump #GOP.’”

But the tweet was quickly deleted, perhaps because most of Iowa’s corn and soybeans are genetically engineered.

Trump said he didn’t post the remarks, tweeting, “the young intern who accidentally did a Retweet apologizes.”

Read more: Consumers concerned about pesticides, GMO foods »

Monsanto’s chemical-based herbicides and other concoctions over the past half-century have been blamed by some for killing and harming humans across the globe.

Monsanto co-developed Agent Orange, the deadly herbicide that was used by the Department of Defense during the Vietnam War to flush out the enemy.

As the Department of Veterans Affairs now acknowledges, Agent Orange causes non-Hodgkin lymphoma and many other types of cancer and other diseases, including Parkinson’s disease and diabetes.

Agent Orange has killed and harmed more than half a million Vietnamese and also hundreds of thousands of U.S. war veterans.

Monsanto also developed polychlorinated biphenyls (PCBs), which were used as hydraulic fluid and an engine lubricant. PCBs were banned in the 1970s after being linked to cancer and birth defects.

As Reuters reported last year, Monsanto is still embroiled in multiple court cases over PCBs, which the WHO also labeled as carcinogenic.

At least 700 lawsuits against Monsanto or Monsanto-related entities are reportedly still in the courts, Reuters noted. The plaintiffs in these cases are people who insist their non-Hodgkin lymphoma was caused by exposure to PCBs.

Monsanto also marketed dichlorodiphenyltrichloroethane (DDT), the highly toxic herbicide that was ultimately banned in the United States in 1972.

Monsanto is also the world’s leader in producing genetically modified seeds, which have been banned in more than two dozen countries.

Read more: Common chemicals may cause more cancer than previously thought »

The debate over whether Roundup’s glyphosate can cause cancer in humans continues.

A few months after IARC said glyphosate probably causes cancer in humans, the European Food Safety Authority (EFSA) said glyphosate was “unlikely” to cause cancer in humans.

But there are many other studies in the United States and globally that link glyphosate to non-Hodgkin lymphoma and other cancers.

This includes a 2016 study from researchers in Italy and Brazil that concluded exposure to glyphosate “increases the risk for cutaneous melanoma.”

A 2013 study concluded that glyphosate fuels breast cancer by increasing the number of breast cancer cells through cell growth and cell division.

The study, published in the journal Food and Chemical Toxicology, found that glyphosate fuels cancer cell lines that are hormone dependent.

There are several recent studies that show glyphosate’s potential to be an endocrine disruptor, which are chemicals that can interfere with the hormone system in mammals. These disruptors can cause cancer tumors.

And a 2013 peer-reviewed report in the journal Entropy, co-authored by Stephanie Seneff, Ph.D., at the Massachusetts Institute of Technology (MIT), noted that glyphosate residues “enhance the damaging effects of other food-borne chemical residues and toxins in the environment to disrupt normal body functions and induce disease.”