We all take a lot of breaths every day – it's sort of essential to living – so the science of what we're actually taking into our lungs is hugely important. That air might contain two to three times more in the way of fungal spore fragments than previously thought, according to a new study.
Not only could these fungal cell nanoparticles contribute to asthma and allergic reactions, they could also be significant in cloud formation – particularly clouds made up of ice crystals, which are known to form around similar particles.
"These fragments are most likely bits of fungal spores that have burst after swelling with water," says chemist Michael Lawler, from the University of California, Irvine (UCI). "It was unexpected to identify them as fungal fragments.
"The appearance of large numbers of atmospheric nanoparticles is usually ascribed to reactions of gases in the atmosphere, growing up from molecules rather than breaking down from larger particles."
At their sample site in Oklahoma, the team used a device that collected ambient particles measuring 20-60 nanometres in diameter, then placed them on a thin platinum filament. After a vaporisation process, a high-resolution mass spectrometer was used to analyse the resulting gases.
The fungal cell fragments measured about 30 nanometres in size – incredibly small, when you consider a piece of paper is some 100,000 nanometres thick. The researchers think previous studies may have missed these fragments because they weren't working at a small enough scale.
Intact cells floating through the atmosphere can be thousands of nanometres in size, and that means the biological 'shrapnel' from these fungal spores are able to penetrate much deeper into the lungs. That's a potential problem for asthma and allergies, and might help explain why rainfall affects asthma in some.
Then there's cloud formation. Based on previous studies, these nanoparticles are likely to be excellent candidates for ice nuclei – capable of turning into ice crystals in the atmosphere and contributing to the creation of clouds, a crucial factor in short-term weather forecasts and long-term climate predictions.
"Large, intact biological cells are extremely rare in the atmosphere, but we've identified fungal nanoparticles in orders-of-magnitude higher concentrations, so if some or all of these are good ice nuclei, they could play a role in ice cloud formation," says Lawler.
It's worth noting that the sampled air was collected from one spot in northern Oklahoma, over the course of a month in 2016 – this is a picture of air composition that doesn't necessarily apply everywhere else, although the team notes in their paper that the events they recorded "show similarities to unclarified events reported previously in the Amazon".
One this is for sure, the findings were rather surprising, and researchers deem them definitely worthy of more investigation.
The next step is to further analyse the relationship between these cell pieces and cloud formation, which should lead to more accurate climate modelling, as well as a better understanding of how the air we breath could change as the climate does.
The research has been published in Science Advances.