They're in nearly all candies and fruit-flavored snacks sold in conventional American grocery stores. They're on the ingredient list of hundreds of thousands of branded food items, from Fruit Loops and Trix Cereal to Gatorade and Skittles. And they may soon be banned in California public schools.

Artificial food dyes are the target of a growing number of state bills that would crack down on the chemicals in response to scientific studies that found a possible link between them and hyperactivity in children.

A "first-in-the-nation" measure that would bar schools from serving foods containing the chemicals passed in California's state legislature last month. AB 2316, or the California School Food Safety Act, would keep schools from serving six artificial food dyes that appear up and down the grocery aisle – Blue 1, Blue 2, Green 3, Red 40, Yellow 5, and Yellow 6.

The bill now sits on California Gov. Gavin Newsom's desk – he has until Monday to sign it into law, according to his office. It "will be evaluated on its merits," Brandon Richards, the governor's deputy director for rapid response, told USA TODAY in an email.

And similar legislation is taking off in at least 10 other states. A bill introduced in Pennsylvania's legislature in March seeks to classify the same six additives as "poisonous and deleterious substances."

"I'm constantly flipping labels over. It takes me four hours to grocery shop. It shouldn't have to," Pennsylvania State Rep. Natalie Mihalek, who introduced the bill, told USA TODAY.

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Do food dyes cause ADHD?

The California bill was prompted by a 2021 report from the state's Environmental Protection Agency that linked consumption of the dyes with "hyperactivity and other neurobehavioral problems."

"There's a strong suggestion that there is a relationship between intake of these materials and changes in behavior... particularly in children that are susceptible, that already have ADHD, or related behaviors," said Asa Bradman, a professor and chair of University of California Merced's public health department who worked on the California review. "Exposure to the dyes seems to exacerbate the symptom."

American kids consume artificial dyes more than ever before. Their per-capita use has increased more than five times since 1955, to more than 17 million pounds of dyes certified for use in 2015, according to a report from the Center for Science in the Public Interest, a nonprofit research and advocacy group. Food dye opponents point to a concurrent jump in ADHD diagnoses – from 6.1% in 1997 to 10.2% a decade later, one study found.

Bradman said some foods containing the dyes aren't eaten as frequently, like ice cream or candy. But the chemicals have made their way into other products that kids eat and drink daily, like juice and sodas.

"The reality is these have no nutritional or other benefits. They're totally aesthetic," Bradman said.

The Food and Drug Administration said in a written statement to USA TODAY that it has "reviewed the research on the effects of color additives on children’s behavior including the literature review cited by the Bill. The totality of scientific evidence shows that most children have no adverse effects when consuming foods containing color additives, but some evidence suggests that certain children may be sensitive to them."

Scientists can't say for certain that there is a proven link. According to Bradman and the report, some children were likely to be more affected than others.

Although more studies are needed to produce a definitive answer, "the state of the science really shows that, yes, there probably is some kind of link or effect," said Sarah Karalunas, an associate professor at Purdue University's department of psychological sciences.

"The better the study is, the larger the effect," she said, but even in well-controlled studies, the effect appears "very small," she said.

Karalunas noted that foods containing the dyes are also loaded with other additives, making it difficult to discern what negative health impacts can be solely traced back to them.

Bradman echoed that products with high levels of food dyes are often those that "we think of as junk food" and contain higher levels of refined carbohydrates, fats, and other additives.

More:Need after-school snack ideas? Healthiest options to add into your kid's routine.

State lawmakers go after food dye banned in cosmetics

Some legislation on the horizon takes specific aim at Red 3. Karalunas said, among color additives, red dyes, including Red 40, show a "particularly" strong link with hyperactivity in scientific research.

Red 3 has also been linked to cancer by some animal studies. The FDA banned the chemical's use in cosmetic products in 1990 in response to those concerns, but it remains in food products.

In the years since, advocates have launched numerous campaigns to regulate the chemical – last year, research nonprofit Consumer Reports sent a letter urging the maker of Peeps candies to stop using the dye, and launched a petition when the company did not respond.

California was also first out of the gate to ban the chemical. Last year, the state enacted a law dubbed the "Skittles ban" that gives manufacturers until 2027 to cut Red 3 out of their recipes.

Mihalek, whose bill targets Red 3, among other chemicals, called regulating the chemical "low-hanging fruit."

"We're talking about making something a pretty red color, with the risk of cancer and a whole other list of health risks associated with it," she said. "It doesn't make any sense."

More state lawmakers have introduced similar bills. The Illinois State Senate in April passed a bill that would ban Red 3, along with three other chemical additives, sending it next to the state House for consideration.

"The FDA doesn’t allow you to put it on your face for makeup. But yet kids are eating this in candy,” Illinois State Sen. Steve McClure told the Senate, according to local news reports.

Illinois State Sen. Willie Preston, who introduced the bill, said lawmakers have "a short window" to get the bill through a veto and lame duck session before the end of the year.

If they are successful, the bill will pass before Thanksgiving. If not, "I intend to refile that bill and continue to work that product through the process to make sure that we protect the food supply here in Illinois," he said.

Legislative efforts to restrict the chemicals have drawn the ire of food manufacturers and industry groups, who argue that they aren't science-based.

The National Confectioners' Association said in a news release responding to the Illinois bill, "It’s time to stop pretending that Illinois state legislators have the scientific expertise to make these very important regulatory decisions. Usurping FDA’s authority does nothing but create a patchwork of inconsistent requirements that increase food costs, create confusion around food safety, and erode consumer confidence.” The association did not return USA TODAY's request for comment.

Lawmakers pledge to reintroduce bills next year

In the last decade, bills targeting Red 3 and the six food dyes in the recent California bill have been introduced in Maryland, Missouri, New Jersey, New York, Pennsylvania, Rhode Island, South Dakota, Washington, and West Virginia, according to the Environmental Working Group, a nonprofit.

Some lawmakers say they'll keep pushing, even if the clock runs out to pass legislation this year.

With just a few months left in Pennsylvania's legislative session, Mihalek likely won't see her bill become law this year. If she is re-elected in November, she plans to reintroduce it next year, she said.

"First and foremost, the bill is creating awareness," she said.

The current regulatory framework, she said, puts it "on the consumer to stop buying these products that contain ingredients that have decades of evidence of cancer, behavioral issues," she said.

At least one bill for a nationwide ban is already on the table in Congress – in June, U.S. Rep. Anna Paulina Luna, who represents Florida's 13th congressional district, unveiled the "Do or Dye Act," which would deem "unsafe" any foods containing Red 40, Yellow 5, Yellow 6, and "substantially similar" additives.

"We knew that they were banned already in foreign countries because of the known health risks," Luna told USA TODAY. If the bill passes, she hopes producers "have to use alternatives, or just make it healthy, just not add it at all."

The legislation is important to Luna, who hopes to mirror it in amendments she's introducing to the farm bill, which has until the end of the month to pass Congress.

'Superficial way to make food appealing'

Thomas Galligan, principal scientist for food additives and supplements at the Center for Science in the Public Interest, said he anticipates California's movement on the issue will spur other states to act, although many advocates believe federal action is needed.

The center petitioned the FDA in 2008 to ban eight approved food dyes, force manufacturers to put a warning label on products containing the chemicals, and require new testing. The agency convened a meeting to revisit the issue in 2011, but determined that the link had not been established, and recommended further research.

Federal regulators have sometimes forced recalls of products that fail to disclose dyes. Two drink products were recalled earlier this summer for containing an undeclared amount of Yellow 5 and Red 40.

Galligan now hopes the California bill will force manufacturers to replace color additives with natural substances in products sold nationwide. "It's more challenging for them to produce a California-specific product than just to change their entire production line," he said.

European regulations produced a similar effect years ago. After two British government-funded studies in 2004 and 2007 reached similar conclusions to the California review, the European Union set stricter limits on the chemicals, including requiring producers to label foods with some dyes. In response, some food producers switched to using natural colors. Nestle, for instance, adopted annatto, made from the seeds of the achiote tree, to color the gooey centers of Butterfinger candy bars sold in Europe, according to the government of the Netherlands.

"The food industry clearly found them to be effective marketing tools, and that's really what they are," Galligan said. "It's really just there as a cosmetic, superficial way to make food appealing so that we spend our money on them."

The FDA completed its last exposure assessment of the six chemicals banned in the recent California bill in 2016, the agency told USA TODAY. The FDA will host a public meeting to take "a fresh look at the process" of assessing chemicals in food products after they hit the market.

Galligan believes new state-level bills, including California's, may have spurred the upcoming meeting.

"In some ways, the state action seems to be motivating both industry and FDA to act where, previously, they hadn't," he said. "You have a situation where evidence of harm emerges after approval, and nothing gets done for decades."

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her on email at [email protected]. Follow her on X @CybeleMO.