WASHINGTON — Health Secretary Robert F. Kennedy Jr. said Wednesday that the agency will announce, within three weeks, a series of studies aimed at identifying “environmental toxins” he claims are responsible for a dramatic rise in autism rates in children in the U.S.

Kennedy spoke a day after the Centers for Disease Control and Prevention released a report that found in 2022, 1 in 31 kids in the U.S. were diagnosed with autism spectrum disorder by their 8th birthday — up from 1 in 150 kids in 2000, when the agency began collecting data.

Autism diagnoses among 4-year-olds in the new report were estimated at 1 in 34.

Pediatricians and other health experts have attributed the increase largely to greater awareness and better surveillance of the disorder. Autism’s definition has also broadened to identify milder cases, which has contributed to more diagnoses.

Despite evidence that suggests there is no one single cause of autism, Kennedy is vowing to uncover an underlying reason by September.

During a news conference Wednesday, Kennedy claimed, without evidence, that environmental exposures — such as the nation’s food supply, water or medicine — are likely contributing to rising autism rates in kids. He called autism a “preventable disease,” an assertion pushed back on by health experts.

“We know what the historic numbers are,” Kennedy told reporters, “and we know what the numbers are today, and it’s time for everybody to stop attributing this to this ideology of epidemic denial.”

He also dismissed conclusions from the CDC report’s authors, who attributed the rise to more awareness and better surveillance. The report also reaffirmed evidence suggesting that genetics likely plays a role.

“We know it’s an environmental exposure. It has to be,” Kennedy said. “Genes do not cause epidemics. It can provide a vulnerability. You need an environmental toxin.”

Kennedy said the agency will look at mold, food additives, pesticides, water, medicines, ultrasound and obesity.

He didn’t provide guidance as to which outside groups, if any, would support the agency’s research or how the studies would be conducted and when.

A spokesperson for the Department of Health and Human Services did not immediately respond to a request for comment.

Alison Singer, the president of the Autism Science Foundation, a nonprofit group for families with autism, said the CDC’s report Tuesday “is the most convincing evidence yet that changes in factors like access to services and de-stigmatization” are leading to the increases in prevalence of autism.

Singer said Kennedy made a series of false assertions about autism during Wednesday’s news conference, including that the disorder is caused by something in the environment.

An overwhelming amount of evidence points to a genetic cause, Singer said, adding that in about 20% of autism cases, one genetic variant can explain the disorder.

In other cases, she said, there may be multiple genetic mutations interacting to cause autism.

At the same time, most researchers acknowledge that genes don’t explain every case of autism and when people develop autistic traits, it may be due to a combination of genetics and environmental exposures. Some research has indicated that a mother’s exposure to air pollution may be linked to an increased risk of autism in children.

The health secretary’s remarks on environmental exposures echo his previous comments about the disorder.

Kennedy has repeatedly suggested that vaccines are linked to autism — a connection that has been widely debunked.

Dr. Paul Offit, the director of the Vaccine Education Center at Children’s Hospital of Philadelphia, said he isn’t persuaded that Kennedy’s studies will uncover anything new, saying that the health secretary has already come to a predetermined conclusion.

“What’s going to happen is you’re going to hear from him that he’s looked behind the curtain at the FDA, looked behind the curtain at the CDC, and he has found things that are shocking to him, shocking about the degree to which Big Pharma has influenced those people,” Offit said.