Microbes in Smog

We’ve been hearing a lot about Microbes in Space. But what about Microbes in Smog?

Here in California, we know a thing or two about smog. To avoid it during the drought, we have been having a lot of Spare the Air Days lately to try to protect our air quality and reduce the amount of particulate matter in the air. Indeed small particulates have been linked to asthma, respiratory disease, emphysema, lung cancer.

With more than 20 million people living in Beijing, air quality has declined dramatically. You can find daily air quality forecasts for Beijing here and you can follow Beijing air quality on Twitter @BeijingAir. Poor air quality has become such a problem in Beijing that in 2013 tourism dropped significantly compared to 2012.

In a recent article, Cao et al. 2014 (sorry! paywall) used metagenomics to examine what microbes were found in smog before, during and after a massive, severe smog event that occurred from January 10-14, 2013 in Beijing. At the height of the smog event, particulate matter (PM) 2.5 measured 20 times higher than the WHO guideline value. They collected samples at a air quality monitoring site based at Tsinghua University, an area without nearby pollution sources. Particulate matter was separated by size into ≤ 2.5 um and ≤ 10 um. In all samples, Cao et al. detected 1315 bacterial and archaeal species; most species were terrestrial or fecal in origin and are harmless. A genus containing nitrogen fixing, filamentous bacteria, Frankia was the most abundant genus and the soil bacterium, Geodermatophilus obscurus was also abundant.

Several species increased dramatically during the smog event. Thermobifida fusca, a bacterial degrader found in decaying organic matter, showed a five-fold increase. The cause of community-acquired pneumonia, Streptococcus pneumonia showed a two-fold increase. A major fungal allergen, Aspergillus fumigatus increased by about four-fold. Human adenovirus also increased.

It’s unclear that these microbes are of as much concern to our health as the particulates themselves. Still most research on air quality focuses on particulates and neglects microbes. Researchers in the built environment are also starting to look at microbes in air, including this study by Robertson et al. 2013 that looked at bacteria in bioaerosols in the New York City subway.
Beijing Forbidden City Smog


Holly Ganz

Holly Ganz is a project scientist at UC Davis working with Jonathan Eisen on the microbiomes of built environments where animals live.

One thought on “Microbes in Smog

  1. It’s interesting that metagenomics, in opening the door to characterizing aerosol microbiomes in cities, also allows us to ask completely unexplored public health questions. I’m wondering if the authors of this study are collaborating with the scientists leading the “PathoMap” effort in New York? Given the cost of sequencing technology, would it be feasible to construct microbial “weather maps” for large cities such as Beijing?

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