from the article
Infants whose mothers were exposed to higher levels of tiny air pollution particles during pregnancy are much more likely to develop asthma, according to research.
The study analysed the impact of ultra-fine particles (UFPs), which are not regulated by governments. These are thought to be even more toxic than the larger particles that are routinely monitored and have also been linked to asthma.
Sources of UFPs include vehicles and wood burners, and tens of thousands of particles can be found in each sugar cube-sized volume of city air. They are thought to pass through the expectant mother’s lungs and into her bloodstream, causing damaging inflammation. They are also likely to cross the placenta into the foetus’s circulation.