Air pollution linked to babies' ear infection risk

Babies and toddlers who live in areas with moderate air pollution have a higher risk of middle-ear infection than those breathing clean air.

Middle-ear infections, also called otitis media, are common among young children, with those younger than 2 years being most susceptible. They are caused by a viral or bacterial infection, and usually arise after a child has had a cold, sore throat or other upper-respiratory tract illness. Earlier studies have suggested that air quality plays a role in young children's vulnerability to middle-ear infections; exposure to second-hand smoke, for instance, has been linked to a higher risk. Researchers tracked doctor visits for middle-ear infections among 45,513 Canadian children followed from birth until age 2 years. All the children lived in an area of British Columbia with relatively good air quality. The researchers used data from government air-quality monitors to estimate each child's exposure to air pollutants, based on the family's home address. They then looked at the relationship between the children's ear infections and their air-pollution exposure in the two months prior to the infection.

Overall, 42 percent of the children visited the doctor for a middle-ear infection at least once in the first two years of life. When the researchers looked at air pollution levels, they found a correlation between ear infections and exposure to certain pollutants - even with factors such as the time of year (ear infections are most common in autumn and winter), neighbourhood income levels and whether mothers smoked during pregnancy. For example, when dividing children into four groups of exposure to nitric oxide, a traffic-related pollutant, those with the highest exposure were 10 percent more likely to have a doctor visit for middle-ear infection than those in the lowest.

Two other pollutants were also linked to moderately increased risks: particulate matter - the fine particles emitted via car exhaust, as well as power plants and other industrial sources - and smoke from wood burning. Children breathing the highest levels of wood smoke were 32 percent more likely to have doctor visits for middle-ear infections than those breathing the least. No other individual pollutants were linked to children's risk of infection.

The findings do not prove that air pollution itself was the cause. But if it is, that would allow parents to influence their child's risk of infection by moving to a place with better air.