Study links air pollution before pregnancy to childhood obesity risk

With rapid urbanization and industrial growth, air pollution levels are rising globally, posing serious risks to public health. From respiratory diseases to cardiovascular conditions, the adverse effects of polluted air are well-documented. However, emerging research suggests that air pollution may also have more subtle but long-term consequences—especially on early childhood development.

A new study now reveals that exposure to air pollution in the three months before pregnancy could increase the risk of childhood obesity. The study, conducted on more than 5,000 mothers and their children, raises concerns about children's body mass index and obesity risk factors up to age two. 

The research, supported by the National Institute of Environmental Health Sciences and published in Environmental Research, reveals the potential impacts of environmental exposure before conception.

While previous studies have connected air pollution during pregnancy to various childhood health issues, including respiratory problems and increased risks of obesity and heart conditions, this research specifically examined the preconception period. The study focused on the final stages of egg and sperm development when environmental factors can influence reproductive cell health.

Researchers from the Keck School of Medicine of USC, Duke University, and Fudan University conducted one of the largest studies to date on preconception environmental exposures. The team analyzed 5,834 mother-child pairs recruited from 28 maternity clinics across Shanghai, examining the relationship between pre-pregnancy exposure to different types of air pollution and childhood body mass measurements.

"These findings imply that the three months before conception are important and that people who plan to bear children should consider taking measures to lower their air pollution exposure to reduce their children's risk for obesity," said Jiawen Liao, postdoctoral research associate in population and public health sciences at the Keck School of Medicine and the study's lead author.

The research team developed advanced machine learning models to assess daily pollution exposure at participants' residences. Led by Jim Zhang of Duke University, they incorporated satellite data, pollutant simulations, and meteorological factors to measure levels of PM2.5, PM10, and nitrogen dioxide, primarily produced by vehicles.

The study tracked children's weight and height through electronic medical records every three months until age two. Researchers compared participants exposed to lower pollution levels (25th percentile) with those exposed to higher levels (75th percentile) to evaluate connections between air pollution and child development outcomes.

Results showed that higher PM2.5 exposure before conception correlated with a 0.078 increase in child BMIZ, a standardized score comparing body mass index to children of the same age and sex, at age two. Similarly, increased PM10 exposure was linked to a 0.093 kilogram per square meter rise in BMI at the same age. After six months, children with greater preconception exposure to all three pollutants demonstrated higher weight, BMI, and BMIZ growth rates.

Zhanghua Chen, assistant professor of population and public health sciences at the Keck School of Medicine and senior study author, noted the broader implications: "The magnitude is small, but because air pollution is widespread and everybody is exposed, the risk of air pollution exposure on children's obesity risk may be substantial and may start before their mothers' pregnancy."

While the observational nature of the study necessitates additional research to establish direct causation between pre-pregnancy air pollution exposure and childhood obesity risk, researchers recommend precautionary measures. These include wearing masks during poor air quality conditions, minimizing outdoor exposure, and using air purifiers indoors. The recommendations apply to both women and men planning to conceive.

The research team at the Keck School of Medicine plans to continue investigating this connection through a new study monitoring preconception air pollution exposure in Southern California. They are also evaluating the effectiveness of indoor air purifiers in reducing heart and metabolic problems among the general population.