Researchers in Italy have examined how short-term exposure to air pollution can affect the nasal microbiota of school children in Milan during winter and spring.
Nasal microbiota refers to the community of microorganisms – mostly bacteria – inside the nose and upper respiratory tract which form part of the body’s first line of defence against airborne pathogens and play a key role in respiratory health.
The researchers monitored 95 children in winter and 74 in spring (with 68 participating in both seasons), equipping them with personal monitors that measured exposure to a mix of air pollutants, over roughly 16 hours. Nasal microbiota samples were analysed to identify links between pollution levels and microbial composition.
The research revealed that both air pollution and seasonal changes significantly influenced the nasal microbiota. In winter, when pollution levels were two to three times higher, microbial diversity was lower, and a single bacterium called Moraxella dominated. Moraxella is common in the airways but can increase the risk of respiratory infections and inflammation if there’s too much of it.
In contrast, samples taken from spring showed greater microbial diversity and a higher presence of Staphylococcus, which is generally harmless.
It was also found that exposure to specific pollutants, such as black carbon and benzene, was linked to increases in potentially harmful bacteria like Streptococcus and decreases in protective ones like Corynebacterium.
These seasonal differences are thought to result from both environmental conditions and human behavior, such as spending more time indoors in winter, which limits exposure to a diverse range of microbes. Additionally, air pollution may trigger inflammation in the airways, disrupting the balance of microbiota and the immune system’s interaction with them.
Indoor pollutants such as limonene (from cleaning products) were also seen to affect the microbiota.
The study is the first to examine this issue using personal exposure data in children, offering a more accurate picture than previous studies relying on general environmental monitoring. The findings suggest that even short-term and peak exposures to pollution – especially from traffic and indoor sources – can significantly alter children’s respiratory microbiota, potentially impacting health.
The full research can be read here.
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