Bacteria are feeding and multiplying in the severe smogs that regularly blanket Chinese cities. The microorganisms could pose a threat in themselves and may also change the composition of the haze.
China鈥檚 capital Beijing is regularly smothered in a thick, toxic haze that forms as a result of coal burning, vehicle exhausts and other sources. It is worst in winter, when weather patterns trap pollution over the city. China has cracked down on emitters, and , but there is a long way left to go.
Many other cities, like Delhi in India, have similarly severe air pollution. Western countries like the UK tend to have cleaner air but it is often still more polluted than is thought safe. The World Health Organization says, because it worsens the risk of episodes like heart attacks and strokes, which can prove fatal.
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Most of the focus on air pollution has looked at the chemicals that make up smog and how they interact. But at Peking University in Beijing, China, is one of several researchers who suspect there is another factor involved: microorganisms like bacteria.
In , Yao鈥檚 team showed that tiny clumps of bacteria were common during severe hazes in Beijing. The bacteria made up a significant fraction of the particulate matter in the smog.
Life in the smog
Now they have taken a closer look. They collected air samples during four haze episodes in 2017 and 2018 and examined the particles of bacteria present. They were far more numerous and larger when the haze was bad than at other times.
Of these bacteria, up to 70 per cent of the bacteria could survive and multiply in the lab, suggesting they were alive and thriving in the smog. The bacterial community changed when the smog got worse, with some species becoming less common and others becoming more common. 鈥淭his is the first time that I鈥檝e actually seen information like this,鈥� says at King鈥檚 College London in the UK.
A different team recently examined the bacteria living in smogs in Guilin: a tourism-focused city with no heavy industry that has nevertheless started to experience hazes in winter, probably due to car use and the burning of coal. Like Yao鈥檚 team, they found that .
Yao suggests that the bacteria are feeding on some of the pollutant chemicals, such as sulphates and nitrates. 鈥淭here are so many nutrients for bacteria in the air and also very high humidity levels,鈥� he says, all of which is favourable for the microbes.
Clearing the haze
It might seem like good news that the bacteria are eating the pollution, but Yao and Kelly say it is not so simple. For one thing, the bacteria release volatile organic chemicals as waste, so they may simply replace one pollutant with another. It鈥檚 possible airborne smog bacteria may also cause disease and affect allergies.
By clumping together into microscopic lumps, the bacteria may also form more particulate matter, which is one of the most dangerous forms of pollution.
鈥淲e don鈥檛 fully understand the biological basis for the toxicity of particulate pollution,鈥� says Kelly. It could be the physical size and shape of the particles that cause harm, or it may be the chemicals or biological components they contain 鈥� or several of these factors in concert.
As to where these bacteria come from, Yao鈥檚 team traced many of the species back to a local wastewater treatment plant, which uses bacteria to process waste, and a pharmaceutical plant that uses engineered bacteria to make drugs. He says it may be necessary to control the industrial use of bacteria to help limit air pollution.
鈥淲e鈥檙e introducing these various bacteria into the environment, maybe for the first time, without fully understanding the implications,鈥� says Kelly.
搁别蹿别谤别苍肠别:听产颈辞搁虫颈惫,听顿翱滨:听
