Originally Published: 13 JUL 23 07:01 ET

Updated: 13 JUL 23 09:28 ET

By Abby Turner and Andrew Kaczynski, CNN

(CNN) — Democratic presidential candidate Robert F. Kennedy Jr. has a history of repeatedly sharing unfounded conspiracies that man-made chemicals in the environment could be making children gay or transgender and causing the feminization of boys and masculinization of girls.

Experts dispute the claims from Kennedy, an environmental lawyer and anti-vaccine activist, and told CNN’s KFile his theories that “sexual identification” and “gender confusion” among children could be from their exposure to “endocrine disruptors” found in the environment are completely unfounded.

“I want to just pursue just one question on these, you know, the other endocrine disruptors because our children now, you know, we’re seeing these impacts that people suspect are very different than in ages past about sexual identification among children and sexual confusion, gender confusion,” Kennedy said on his podcast in June last year. “These kinds of issues that are very, very controversial today.”

Endocrine disruptors are chemicals that interfere with the body’s hormones and endocrine system, according to the Environmental Protection Agency. Such chemicals are commonly found in pesticides and plastic, and can affect reproductive functions and increase the risk of obesity. Kennedy on multiple occasions misconstrued endocrine disruptors’ studied ability to cause some male frogs to become female and produce viable eggs, suggesting that these chemicals could have similar effects on children and change their sexuality.

CNN spoke to multiple experts who said there is no link between endocrine disruptors and children’s gender and sexuality. While sex in in frogs is determined by environmental factors such as temperature and chemicals, Dr. Andrea Gore, professor of pharmacology and toxicology at University of Texas at Austin, said the sex of humans is determined at the moment of conception, and cannot later be altered by endocrine-disrupting chemicals.

The baseless claim that chemicals – particularly in tap water – could turn people gay has gained popularity with conspiracy theorists over the years, most memorably with conservative radio host Alex Jones, who said chemicals in the water were “turning the friggin’ frogs gay.”

“Mr. Kennedy’s remarks are being mischaracterized. He is not claiming that endocrine disruptors are the only or main cause of gender dysphoria,” a Kennedy campaign spokesperson said in a statement to CNN. “He is merely suggesting that, given copious research on the effects on other vertebrates, this possibility deserves further research.”

CNN’s KFile reviewed dozens of appearances from Kennedy, both on his podcast, and in other media in recent years where he occasionally discussed the topic. Kennedy has been polling around 19% among Democratic voters in his bid to challenge President Joe Biden for the Democratic nomination.

Kennedy made the comments multiple times between March 2022 and June 2023.

“If you expose frogs to atrazine, male frogs, it changes their sex and they can actually bear young. They can lay eggs, fertile eggs,” Kennedy said in the June 2022 episode of his podcast.

“And so the capacity for these chemicals that we are just raining down on our children right now to induce these very profound sexual changes in them is something we need to be thinking about as a society,” he added.

Atrazine, one of the most common herbicides, is an endocrine disruptor, though Gore said there is no link between these chemicals and gender and sexuality in humans.

“I don’t think people should be making statements about the relationship between environmental chemicals and changes in sexuality when there’s zero evidence,” she said.

A study Kennedy discussed on multiple podcast episodes exposed male African clawed frogs to atrazine in a lab, castrating 75% of the male frogs and turning one in 10 males into females.

On an episode of Jordan Peterson’s podcast, a video of which was removed from YouTube, Kennedy said children are “swimming through a soup of toxic chemicals.” He further discussed how atrazine can “chemically castrate and forcibly feminize” frogs, saying “if it’s doing that to frogs, there’s a lot of other evidence that it’s doing it to human beings as well.” Kennedy did not offer any proof of similar changes happening in human beings.

Dr. Linda Kahn, assistant professor in the departments of pediatrics and population health at New York University, added that comparing frogs to humans is an “apples and oranges thing, it’s not appropriate.” For humans, atrazine is metabolized and excreted from the body within 12 hours, she said.

During Kennedy’s June appearance on Joe Rogan’s podcast, he discussed atrazine’s effect on male frogs but did not make a direct link between chemical exposure and sexuality as in previous comments.

“Nobody knows. Cause we know what it does to frogs,” he said. “But nobody knows what that does to, what it’s doing, those kinds of persistent exposures would do to our children.”

Kennedy also said on a 2022 episode of his podcast that the Midwest’s entire water supply is “coated” with atrazine, and boys and girls in these areas have delayed puberty. But later he contradicted himself in a March episode of his podcast, when he said endocrine disruptors are causing early menstrual cycles in girls.

Kahn said while general studies on endocrine disruptors have shown effects on puberty, no study has proven if atrazine, the chemical Kennedy often cites, specifically affects puberty in humans.

Gore added that, while general studies on endocrine disruptors have shown a trend in early onset puberty and a decreased sperm count in men, these effects are part of a multitude of factors affecting children’s development. Endocrine disruptors’ effects on puberty and reproduction functions are not linked to sexuality and gender expression in children.

While Kennedy’s claims that chemicals are causing sexual dysphoria in children are false, Gore said there is legitimate concern over endocrine disruptors’ proven effect on diabetes, obesity, thyroid disease and more.

But both Gore and Kahn said that routine exposure to endocrine disruptors is just one factor that can affect a person’s risk for disease.

“It’s not as dramatic on an individual level as it might, he might be making it out to be,” Kahn said.