Plastics linked to increasing rates of autism

Broadcast date: Week of August 5, 2022

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Scientists, doctors and activists are calling for more studies on autism that examine both genetics and toxic chemicals. (Photo: The Focal Project, Flickr, CC BY NC 2.0)

The CDC reports that 1 in 44 children are currently identified with an autism spectrum disorder, and that number is growing every year. In a commentary and study in the journal Pediatrics, scientists and clinicians urged that autism research should consider genetic interactions with synthetic compounds, including the hormone-disrupting class of chemicals called phthalates. Phthalates are common in plastics Dr. Irva Hertz-Picciotto, director of the University of California Davis Environmental Health Sciences Center and a co-author of this study joins host Steve Curwood to talk about the interaction between chemicals, genes, folic acid, and autism.


CURWOOD: From PRX and the Jennifer and Ted Stanley Studios at the University of Massachusetts Boston, this is an encore edition of Living on Earth.
I’m Steve Curwood.
The number of children diagnosed with autism spectrum disorder in the U.S. is growing at an astonishing rate, up about seven percent in recent years, according to the Centers for Disease Control.
And scientists point to a small body of studies linking plastic to the rise in autism, a condition often characterized by poor social and communication skills, as well as learning disabilities that require special help.
Phthalates are a group of chemicals used to make plastics more flexible and are found in a variety of products from shampoos to food packaging.
Phthalates have already been linked to several ailments, including obesity, heart disease, lowered IQ and birth defects.
And now half a dozen studies link phthalate exposure to the disruption of how our genes tell our bodies to curate folic acid, a compound for proper brain development.
The CDC announcement follows a commentary and study in the journal Pediatrics, in which scientists and clinicians urged that studying autism should also consider genetic interactions with toxic chemicals.
The good news is that even with the proliferation of plastics, there is a fairly simple and inexpensive public health solution that could reduce the rise in autism.
Supplemental folic acid for women.
For more information, we now turn to Dr. Irva Hertz-Picciotto, director of the University of California Davis Environmental Health Sciences Center, and a co-author of this study.
Welcome back to Living on Earth Irva!

HERTZ-PICCIOTTO: Thanks for having me.

CURWOOD: So, as I understand it, the CDC found the 7% increase in diagnosed autism among eight-year-olds over the course of the past two years. Boy, that’s a pretty high percentage. How worrisome is that?

HERTZ-PICCIOTTO: Sure, it’s worrying. I mean the number of children who need special education, special facilities can have all kinds of difficulties in school, but also in everyday life it is a remarkably high percentage. And because they often need a lot of special attention, special adjustments for their disabilities, it has economic consequences, it certainly has a lot of financial and social and emotional consequences for the families. So yeah, I agree it’s quite concerning.

Folic acid is critical for gross brain formation and the development of brain function of fetuses during pregnancy. Studies show that it plays an important role in preventing the development of autism when it is abundant in early pregnancy. (Photo: Tatiana, Flickr, CC BY 2.0)

CURWOOD: Now researchers have known about autism and some connection to genetics since the 1970s. But now we’re learning through studies like yours that chemicals like plasticizers and phthalates may play a role when it comes to neurodevelopment. So what do you think is the relationship, if any, between autism, genetics, genetic expression, and chemical exposure?

HERTZ-PICCIOTTO: Well, there’s an abundance of literature on genetics now. So we have a really good idea of ​​a lot of the genetic factors that can regulate how the body metabolizes, you know, chemicals that we’re exposed to, and how certain types of genes that regulate brain development can be affected. So there is a lot of potential for sensitivity during the prenatal period in particular and that is not a period where exposure to endocrine disrupting chemicals seems to have a strong influence on behavior, memory, cognitive skills and also mood problems such as depression and anxiety, all these seem to be influenced by phthalates in particular. I mention them because there is a growing literature on these compounds, the phthalates.

CURWOOD: One of the most interesting parts of your paper, which is actually kind of a meta-study looking at a number of different studies looking at autism, is the impact that folate, folate, this nutrient that’s in everything from kale to lentils. to all kinds of things. Well, tell me, what was the impact of people getting good amounts of folic acid in their diet?

HERTZ-PICCIOTTO: Some of our studies and studies by others have shown that folic acid is really important in autism and that mothers who didn’t have enough folic acid in the very early part of their pregnancy, and I mean just like the first month, had more chance of having a child who has developed autism, when they have reached the age at which autism can be diagnosed, let’s say the age of 2, 3, 4, 5 and so on. Thus, folic acid appears to be critical for more than just gross brain formation, but other aspects of brain function related to communication and social interactions, and so on.

CURWOOD: To what extent does adequate folic acid mitigate the impact of chemicals like phthalates implicated in this autism spectrum disorder, may I say, epidemic?

HERTZ-PICCIOTTO: Well, very interesting, what our studies and several other researchers found was that some mothers have a much higher need for folic acid and that’s because their genes don’t convert to folic acid very quickly and as a result they are a are at much greater risk of having a child with autism. It is therefore the combination of a low intake of folic acid and certain genetic variants that lead to a greater need for more folic acid and therefore a higher risk if they do not get it that their child will develop autism. And the moms who get enough folic acid and have the genes that are really beneficial to move that folic acid into folate and then into its methylated state, which makes it really effective, those are the moms least likely to have a child with autism. And if she has the right genes and so does her baby, there’s an even greater benefit with a 70% reduction in the risk of autism when combined with folic acid intake.

CURWOOD: Because brain development happens so early in pregnancy, actually in the first few weeks, this vulnerability is to folic acid deficiency. To what extent should women of childbearing age ensure that they always have a decent amount of folic acid in their diets, with the chance that they could one day become pregnant and may not understand that they are pregnant during this time when this important development is taking place?

HERTZ-PICCIOTTO: That’s exactly right. About half of the pregnancies are unplanned, and you know, we’re not going to change people’s behavior so that everyone plans their pregnancy. So being prepared by already taking folic acid supplements or prenatal supplements would probably be beneficial everywhere. And that could be a very easy public health intervention for women to be strongly encouraged to do.

According to the CDC’s 2018 report, one in forty-four children was identified with an autism spectrum disorder, compared to 1/54 in 2016. (Photo: Wall Boat, Flickr, Public Domain)

CURWOOD: This research you’re involved in is limited in the scope of the public health community. I think it’s less than a dozen studies that really look closely at environmental toxicity, and genetics and autism. Why is that?

HERTZ-PICCIOTTO: Well, I think scientists work in silos, and geneticists are interested in genetics, and the environmentalists are kind of busy, you know, studying the environment. It is shocking to me that research into the causes of autism is about 20 years old at this point. I mean, even in the 1990s there were genetic studies, I’d say the environmental studies really picked up in the mid to late first decade of this century. There’s a lot of work going on separately, but combining the two really requires special circumstances, you have to get bigger studies, bigger sample size, but the environment can take a lot more to be able to measure it and it changes, you know, the DNA code is constant throughout your life as the environment changes from day to day or sometimes hour to hour. And so it’s more difficult and I think having the brains from both fields combining their intellect and creatively finding the solutions to these challenges would really move that literature forward.

CURWOOD: Dr. Irva Hertz-Picciotto is director of the University of California Davis Environmental Health Sciences Center. Thank you so much for taking the time with us today.

HERTZ-PICCIOTTO: Thank you so much for having me.


Read the commentary in Pediatrics magazine entitled: Considering Toxic Chemicals in the Etiology of Autism

Learn more about the CDC’s data and statistics on autism spectrum disorders

CDC | “Prevalence and Characteristics of Autism Spectrum Disorder in Children Ages 8 – Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2018”

More information about Dr. Irva Hertz-Picciotto

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