Babies exposed to higher levels of air pollution during early pregnancy may experience delays in speech development compared to those with lower prenatal exposure, according to new research on Wednesday.

The study by researchers at King’s College London, conducted on 498 infants, showed babies exposed to nitrogen dioxide and fine and ultra-fine particulate matter in the first trimester may show delayed speech development by 18 months.

The effects were more severe in premature babies, who showed not only delayed speech development but also impaired motor skills.

Researchers said the findings highlight that air pollution disproportionately harms disadvantaged communities, exposing unborn babies to unequal health risks and underscoring the need for systemic change.

They said the study, the first in London to link prenatal pollution exposure with infants’ development, has global implications.

Nearly the entire world population breathes air exceeding World Health Organization limits, making pollution the leading environmental health risk.