Exposure to common air pollution may cause childhood obesity because it affects children’s ability to control impulse, new first-of-its-kind peer-reviewed research finds.

Particular matter 2.5 (PM2.5) is a neurotoxin that has been linked to obesity, and Mt Sinai researchers say they have for the first time identified impulse control as a potential pathway. The study found that babies exposed to higher levels of PM2.5 during their first year of life were more likely to develop difficulties with controlling impulses later in childhood.

Those behavioral changes were then linked to higher body fat and higher BMI in children between four to eight years old.

“A lot of the obesity research primarily focuses on – and is being shaped by – diet and physical activity, and a lot may not include environmental exposures, including air pollution,” said Jamil Lane, a co-author with Mt Sinai’s Icahn School of Medicine.

“Our study is novel in that we are showing that high levels of air pollution early in life may cause more difficulty with self-regulation, which contributes to weight gain.”

PM2.5 is a pollutant composed of microscopic solid or liquid particles that are suspended in the air. Among its common manmade sources are traffic emissions and the burning of fossil fuels.

It is considered a probable carcinogen and linked to a range of health problems from dementia to strokes. Previous research has shown how PM2.5 has obesogenic properties that can disrupt the metabolism and is associated with weight gain.

Meanwhile, about 42% of American adults were estimated to be obese in 2018.

It is well-established that poor inhibitory control is linked to obesity, and Bob Wright, a study co-author and environmental epidemiologist at Mt Sinai, said the authors wondered if the substance’s neurotoxic effects and obesity were “part of the same processes”.

They looked at data from a group of 434 children born largely between 2007-2008 in Mexico City who are part of a longitudinal health study. The authors modeled ambient PM2.5 levels during pregnancy and the children’s first year of life, which Lane said is a “very sensitive window” for brain development. The children were later checked for impulsivity and obesity measures.

The group with the highest levels of PM2.5 exposure showed a pattern of high impulsivity, reflecting significant deficits in inhibitory control.

“Our study shows that greater early exposure to PM2.5 in the first year of life is associated with alterations in inhibitory control function in childhood,” the study’s authors wrote. “The effect is likely due to altered eating behaviors related to inhibitory control that are programmed early in life.”

The study acknowledges some limitations, including a small population size and limited covariates. Cecilia Moura, a clean transportation scientist with the Union of Concerned Scientists, who was not involved with the study, said the research was sound and the novel findings “indicate there is sufficient evidence supporting the correlation to motivate policies and regulations that mitigate exposure to PM2.5”.

People can take steps to protect themselves and their kids. Home Hepa air filtration systems are effective at removing PM2.5, while furnace filters rated at Merv 13 or higher also capture much of the substance. DIY filtration systems using a box fan, cardboard, tape, and pleated air filters have been shown to be effective at reducing particulate matter. The authors advised that parents avoid high congestion areas as much as possible, and stay indoors if there is heavy wildfire smoke in the air.

However, individuals cannot fully protect themselves, and the findings highlight the need for policy solutions and to raise awareness, Wright said.

“There is not going to be change if people are not aware and lobbying for it, but policy change takes a long time and there are things we can do to protect ourselves,” Wright said.