Every day our bodies come into direct contact with whatever is in our environment, and new work has shown that we're exposed to a vast number of chemicals, particles, and microbes. The cloud of biological and chemical bits, called the exposome, has now been described by scientists at Stanford University. Researchers modified a device used to monitor air so that it could assay the viruses, bacteria, fungi, molecules and even minuscule animals that we encounter. They want to know more about the stuff that different people come into contact with and how it may vary through seasons or geography.
“Human health is influenced by two things: your DNA and the environment,” said Michael Snyder, Ph.D., professor and chair of genetics at Stanford. “People have measured things like air pollution on a broad scale, but no one has really measured biological and chemical exposures at a personal level. No one really knows how vast the human exposome is or what kinds of things are in there.”
Over two years, the researchers followed participants that moved around 50 locations; volunteers in the group of 15 were monitored for a week, a month, or in Snyder’s case, for the entire two years. The device collected air samples near the participants’ arm. About the size of a box of matches, the device could trap any kind of microbe, which the lab would then analyze in a database they created.
“Scientists had assembled separate bacteria, viral or fungi databases, but to fully decode our environmental exposures, we built a pan-domain database to cover more than 40,000 species,” postdoc Chao Jiang, Ph.D. explained.
“We sequenced these samples in incredible detail,” said Snyder. “No one has ever done a study this deep before. We ended up with about 70 billion readouts.”
Reporting in Cell, the team led by Snyder found patterns in exposure, like spikes in household chemicals or patterns linked to the weather. They determined that even though the participants were all living in the San Francisco Bay Area, their exposomes were all very different.
“It turns out, even at very close distances, we have very different exposure profiles or ‘signatures,’” Snyder revealed. Those signatures contain traces of everything we interact with, from the rain to our pets to household cleaning products.
“The bottom line is that we all have our own microbiome cloud that we’re schlepping around and spewing out,” Snyder said.
Every person had a unique signature, although the insect repellant DEET and some carcinogens were present in nearly every sample. Because Snyder used his device everywhere he went for two years, his sample was the most diverse. It reflected parts of his life, like changes in the seasons or that he was a pet owner. It may have also provided some insight into why he gets allergies in April.
To be sure their findings covered different weather conditions and every season, they followed different people at various times of the year.
“There are a lot of findings that haven’t been described before — all kinds of fungal, bacterial and plant seasonal patterns,” Snyder said. Although many different microbes were picked up by the devices, it’s not easy to tell from the genetic sequence alone whether or not any were dangerous.
While carcinogens were also detected, the technology is not yet sophisticated enough to tell us much more than that they were present. “We’re measuring individual exposures, not absolute levels,” explained Snyder. “So at this point, the data isn’t generalizable enough to make broad claims.”
It may be possible to engineer a device like that one day. Snyder’s team is just beginning their work on the exposome and want to continue to investigate its impact on human health.
“We want to measure more people in more diverse environments,” Snyder said. “We also want to simplify the technology, ideally to the point that everyone can be out there measuring their own personal exposures — perhaps something like an exposome-detecting smartwatch.” Check out the video above to hear more from Snyder about how wearable devices might improve human health.