Babies exposed to higher levels of air pollution during early pregnancy take longer to learn to speak than those exposed to lower levels in the womb, new research suggests. A study by researchers from King’s College London found that exposure to nitrogen dioxide and fine and ultra-fine particulate matter during the first trimester delayed speech development at 18 months.
For premature babies, the impact was even more severe: not only was their speech development delayed, but they also exhibited impaired motor skills. Tyrone Scott, head of campaigns at War on Want, commented: "This research should act as a wake-up call, because air pollution is not just an environmental issue, it’s a matter of justice and equality from the very start of life."
The researchers believe this is the first study to investigate pollution exposure and development in London by measuring the language and motor skills of infants whose mothers were pregnant in the capital. However, the implications are global. Almost the entire world population breathes air containing pollutant levels that exceed World Health Organization guideline limits, making air pollution "the world’s largest single environmental health risk."
Disproportionate Impact on Marginalized Communities
Scott emphasized that in cities like London, working-class and marginalized communities are disproportionately forced to live near busy roads and toxic air. "That means the harm is not shared equally, it is concentrated on those already facing the greatest inequalities," he said. Agnes Agyepong, chief executive of Global Child and Maternal Health, added: "We have to be honest that exposure to polluted air is not randomly distributed, but shaped by longstanding inequalities in housing, planning and power."
Study Details and Findings
The King’s College London team studied 498 infants born at St Thomas’ Hospital between 2015 and 2020, including 125 born prematurely. Using mothers' home postcodes, they estimated pollution exposure during each trimester. At 18 months, infants underwent standard clinical tests measuring cognitive, language, and motor skills.
Infants exposed to high pollution in the first trimester scored five to seven points lower on language tests compared to those with low exposure. Premature babies with the highest pollution exposure across pregnancy scored an average of 11 points lower on motor skills. Lead author Dr. Alexandra Bonthrone noted that it is too early to determine if these babies will catch up, and further studies are needed.
Roy Harrison, professor of environmental health at the University of Birmingham, called the study "well-planned and executed" and said its findings came as no surprise, citing research estimating a collective loss of around 65 billion IQ points globally due to air pollution.
