Air pollution from fossil fuels and wood burning can directly affect the behaviour of bacteria, in some cases making them more likely to cause illness, a series of studies has shown.
鈥淭his is at an early stage, but it鈥檚 something that we need to look into more,鈥� says at the University of Leicester in the UK. 鈥淭his could be affecting health, because it is potentially affecting microbiomes and infectious disease microbes.鈥�
Air pollution has many adverse effects on our health, including making us more vulnerable to respiratory infections. It has long been assumed that such infections are a result of damage to the tissues in our airways and lungs. A few years ago, however, a conversation with a colleague made Morrissey wonder if air pollution could also affect bacterial behaviour directly. Her team has now amassed substantial evidence suggesting that this is the case.
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Many people have potentially dangerous bacteria living harmlessly inside their airways. When these bacteria sense an opportunity, they may collectively decide to launch an attack, causing an infection. Morrissey鈥檚 findings suggest that the presence of some pollutants can trigger this change in behaviour.
In one of the latest studies, her team grew a strain of MRSA 鈥� an antibiotic-resistant 鈥渟uperbug鈥� 鈥� for a few days in the presence or absence of a kind of particulate pollution called black carbon. 鈥淚t鈥檚 like soot,鈥� says Morrissey.
When the MRSA bacteria were then put in the noses of mice, those that had been exposed to black carbon were more virulent. After a week, there were five times more of the black-carbon-exposed bacteria in the respiratory tract of the mice.
The team then added MRSA bacteria to human cells growing in the lab. Two hours later, the microbes that had been exposed to black carbon were also more likely to stick to the human cells and invade them.
Further studies showed that exposure to black carbon was switching on a whole set of genes associated with these bacteria becoming more virulent, including genes for toxins and for evading the immune response.
Other studies by the team suggest the behaviour of a wide range of bacteria is directly affected by black carbon and by at least one other pollutant: brake dust from automobiles.
鈥淚 think it鈥檚 something that needs to be investigated further,鈥� says Morrissey. If it turns out that specific pollutants are responsible, it gives more insight into their health effects and more reason to control their levels, she says.
While there is growing evidence of the harmful effects of air pollution, it is still important to understand the reasons why it is harmful, says at Queen Mary University of London, who wasn鈥檛 involved in the study.
鈥淚t does matter. It strengthens the epidemiological evidence by providing biological plausibility,鈥� he says. 鈥淚 think we are significantly underestimating the health effects of air pollution.鈥�
The finding might also lead to treatments for protecting vulnerable individuals on high pollution days, for example, to prevent them developing infections, Grigg says.
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