From the minute we're born, we're surrounded by a swarm of things not visible to the human eye — dangerous pathogens, harmless microbes, and a wide assortment of chemicals. A new study out of Stanford University seems to illuminate this hidden world, and the results are admittedly both cool and terrifying.
Typically, when scientists want to know what's floating around us in the air, they use stationary devices in a single room or location. Then they use that data to predict what the average person gets exposed to in a given day. But Michael Snyder, a geneticist at the Stanford University School of Medicine, and his team decided to try a different approach.
They constructed an air-monitoring device so that it could be attached to a single person all day. The device took in puffs of air and was equipped with a tiny filter that could trap microscopic bacteria and aerosol particles as small as 25 micrometres across. Every few days, the device was emptied out, allowing their lab to analyse the chemicals and living things collected in a sample.
Over the course of two years, the team recruited 15 volunteers to wear the device, including Snyder himself. Some wore it for a week, others for a month, and in Snyder's case, for the entire two years.
By the end of the study, the volunteers had travelled to 66 distinct locations. And along with the countless chemicals they found in these samples, the team documented and sequenced the genetics of more than 40,000 different bacteria, fungi, plants, and animals. All of these airborne passengers found in our personal space make up our "exposome," a term coined by Snyder and his team.
The team's findings were published Thursday in Cell.
"This is allowing us, for the first time, to categorise what we get exposed to, on a personal level," Snyder told Gizmodo. "You are just exposed to a vast array of organisms, and a vast array of chemicals."
Even in people who wore the device the shortest amount of time, he pointed out, the team collected as many as 800 species. In Snyder's case, they collected more than 2000.
Most of what the team found was harmless, but they did pick up some interesting and possibly worrying exposures. The pesticide DEET was ubiquitous in almost every sample, as were several known carcinogens (DEET is thought to be safe for people to use on their skin, though we know less about the risks of long-term exposure). And depending on where the person lived and visited, as well as the time of year, some kinds of exposures were much more common.
In the San Francisco bay area, for instance, there were more traces of bacteria typically found in sewer sludge.
"That further illustrates that your environment does have these signatures that are presumably affecting your health," Snyder said. "Over time, we'll need to figure out what it exactly means to be exposed to sludge bacteria. Do people get more sick as a result? We just don't know that yet."
Snyder is also quick to point out that the device can't quantify these exposures right now. So there's no way to tell just how much of something people are breathing in, at least currently. But the device might have already solved one mystery for Snyder personally.
"I had assumed that I was allergic to pine, but looking at the correlations, it's more likely that it's actually eucalyptus," Snyder said. "So there's this potential to better inform you of your environment so you can take steps to control it."
The team plans to refine the device, making both it and the filter smaller, so it can trap even tinier things like viruses (the current device is about 8cm high, 5cm wide, and 5cm thick). And the team would want to make it so that the device could someday analyse a person's exposome in real time. Getting even more in the realm of Star Trek science fiction, Snyder envisions a future where the device could warn people of the presence of potentially dangerous chemicals or allergens, possibly via their smartphone.
For now, Snyder hopes his research can make us think a little more about the immediate world around us.
"We take things for granted — air is air and it's all fine. But I guess my point is that there's a lot of stuff out there," he said. "So let's figure out what's good stuff and bad stuff and get rid of the bad and keep in the good."