A map has revealed America’s autism hotspots for the first time.
Rates of the disorder have nearly tripled in children and young adults in the last decade, which is in part due to doctors being better at diagnosing it.
But that doesn’t explain the full story — a review earlier this week highlighted air pollution as a major possible driver.
Now, a study has revealed how American rates of autism in children are disproportionately high in the northeast and southeast.
Worchester County in Massachusetts and Chesterfield County in South Carolina, there were up to 8.1 percent of children with autism, or one in 12. There were also clusters of hotspots around major cities like Los Angeles and Chicago.
Researchers say these differences mainly are due to hotspot areas having better access to hospitals or research centers, making it easier to diagnose.
But there may be environmental and demographic factors too. Many of the hotspot counties also had higher minority children and low-income families, who are more likely, in recent years, to be diagnosed with the disorder.
The researchers took data from roughly 70,000 kids and applied what they found to each county across the US. They then estimated higher levels of autism as hotspots, designated in red and estimated lower levels of autism as cold spots, designated in blue
Your browser does not support iframes.
Autism spectrum disorder is a developmental condition that affects how people interact with others, communicate, learn and behave. National reports say about one in every 36 children have autism.
Understanding which regions of the country have a higher amount of people with autism could help researchers understand what outside influences are contributing to the diagnoses.
In 2023, the researchers from the University of South Carolina looked to this topic in their paper published in the Journal of Autism and Developmental Disorders.
They estimated the autism rates in every county across the US by looking at data from 700,000 children.
The researchers gathered their information from the National Survey of Children’s Health, which askes parents to report on the health of their kids between five and 17 years old.
The survey randomly selected homes within each state and called them, asking them, amongst other questions, if their child had been diagnosed with autism.
They also took down information about their race, sex, age and other health conditions, like ADHD.
After getting this dataset, the researchers used small area estimation to apply the patterns they observed to the whole country.
They found that 3.29 percent of US children may have autism, slightly higher than a 2023 model by the CDC which put the rate at 2.8 percent.
The American Lung Association ranked the top cities that suffer from the worst air quality in the US – affecting roughly 131 million Americans
They found that girls had lower rates of autism boys, with 1.38 percent of girls diagnosed and 4.58 percent of boys diagnosed.
Meanwhile, 3.82 percent of black children were diagnosed, compared to 3.36 percent of Hispanic children and 2.87 percent of white children.
They found hot spots in the Southeast, East coast and Northeast. Rates were specifically high in New Jersey, ranking between 2.6 and 8.1 percent of the total population of children.
Though as a whole region the Southwest was considered low in autism the researchers said there were small clusters of high diagnoses around Los Angeles and Las Vegas.
Rates of autism were especially low in the Texas Panhandle and in Oklahoma, where access to healthcare is notoriously difficult.
The researchers found that in areas around California, the rates corresponded to trends of autism diagnosis based on family income.
In general, overall rates of autism in affluent white children has been decreasing, while rates of autism in poorer or middle-class white children has been increasing.
This could have to do with increased healthcare opportunities for less-affluent families, or increased awareness, according to the researchers.
Poorer families are also more likely to suffer pregnancy complications and be exposed to air pollution – two factors which may raise the risk.
According to a 2024 report from the American Lung Association, some of the most polluted cities include like Los Angeles and Long Beach in California, Phoenix and Mesa in Arizona and Denver and Aurora in Colorado.
Some of the cities flagged as hotspots by the University of South Carolina researchers also have high autism rates, like Los Angeles but not all do.
Dr Haitham Amal, the head of the department of Laboratory of Neuromics, Cell Signaling, and Translational Medicine at Hebrew University of Jerusalem, recently published a paper trying to explain this increase.
It’s thought between 40 and 80 percent of autism cases are linked to inherited genetic mutations, but Dr Amal’s new research has suggested a complex interplay of both genetics and environment as contributors to autism diagnoses.
The paper found people with genes linked to autism are more likely to develop it if they are exposed to pollution in the womb or early childhood.
Scientists have not concluded that air pollution can lead to autism. However, the topic has been increasingly studied as the rates of autism increase globally.
Your browser does not support iframes.
Dr Amal’s new research, which focused on four different types of air pollutants – including natural gases and those produced from manufacturing and burning fuel – can get into the blood stream when inhaled.
From there, they may cause changes to the developing brain in a number of ways – leading to inflammation that affects how the brain develops, or blunting the amount of chemicals that the brain produces, Dr Amal and his team said.
Likewise, older research from Harvard University’s school of public health has linked an exposure to an air pollutant called particulate mater to autism.
In these kinds of studies, it’s hard for researchers to rule out the influence of other factors that could skew the data, like diet, smoking or exercise habits.
This is a problem behind many similar studies linking autism to air pollution, Amy Kalbrenner an environmental epidemiologist at the University of Wisconsin, told Scientific American.
Dr Kalbrenner said: ‘It’s the same weakness as other studies [on environmental pollutants and autism]. They’re using an EPA model, which estimates what’s coming out of factories and traffic and spits out a pollution estimate’.
However, scientists also caution that the uptick in autism diagnoses can be partially attributed to an increased awareness about the disease.
