We are bombarded by thousands of species and various chemicals | Information Center

The device, the size and shape of a large box of matches, accompanies participants everywhere and is equipped with a sub-micron filter that traps particles in the body. ;apparatus. Data – bacteria, viruses, chemicals, fungi and other objects aspirated by the device – are brought back to Snyder's laboratory and extracted for DNA and RNA sequencing, as well as chemical profiling to identify all organisms and chemicals collected. exposed to.

This idea – of siphoning parts of a person's exposome and systematically classifying it – is pretty new, Snyder said. And Jiang needed to put together an entirely new database.

"Scientists have collected separate databases on bacteria, viruses or fungi, but to completely decode our environmental exposures, we have created a pan-domain database covering over 40,000 species," Jiang said. It includes information about bacteria, viruses, fungi, animals, plants and others all organized in a single searchable database.

"We have sequenced these samples with incredible detail," said Snyder, who is also Professor Stanford W. Ascherman, FACS, professor of genetics. "Nobody has ever done a study as thorough before. We finished with about 70 billion reads.

Particle analysis

Between the participants, Snyder and Jiang found that the exposures could be very different, even in a relatively small geographic area – in this case, San Francisco Bay. Snyder cited a particularly well-controlled part of the study, in which four participants, including Snyder, were closely monitored for a month, for example.

Each person lived in a separate area of ​​the San Francisco Bay Area: Palo Alto, Sunnyvale, Redwood City and San Francisco (although the person who lived in Redwood City crossed the bay for his work). "It turns out that, even at very close distances, we have very different exposure profiles or signatures," Snyder said. These personal signatures are essentially traces of specific fungi, plants, chemicals and bacteria, visible regularly on or around a single person, but which vary from person to person. Many environmental aspects contribute to this microscopic amalgam: pets, household chemicals, flowers in bloom and even rain.

"The bottom line is that we all have our own microbiome cloud that we are reducing," Snyder said.

Specific and unique signatures were captured for each individual (although Snyder added that DEET, an insect repellent, as well as several carcinogens were found in just about every chemical sample). For example, the San Francisco resident has shown high levels of "slime bacteria" or bacteria that are commonly found in sewage and sewer treatments. Snyder constantly had fungal exposures at home because of what he suspected was the use of "green" paint. "The guy who painted my house was a green and green person. And he avoided using paints containing a substance called pyridine, "Snyder said. Pyridine, which was a popular additive for indoor paints, has an inverse relationship with fungi, that is, less pyridine, plus there are fungi.

Snyder's profile was the most diverse, as he took the camera everywhere he went, nationally and internationally, for two years, trading his filters for each new location. Apart from exhibits of his pet (Snyder has a cat, a dog and a guinea pig), his signature also showed signs of eucalyptus in early spring, providing nuanced information about what could cause his allergies d & # 39; in April.

Connect to human health

In addition to the four highly controlled participants, a dozen participants were added at different times of the year, helping Snyder to grasp the exposures brought by weather, seasons and location.

"There are many results that have not been described before – all kinds of seasonal patterns of fungi, bacteria and plants," Snyder said. The device can even capture viral / bacterial signatures and carcinogenic particles in the air. Although the devices have detected potentially pathogenic viral and bacterial sequences, it can be difficult to distinguish a threatening pathogen from one of its near innocuous relatives.

The bottom line is that we all have our own microbiome cloud that we are reducing and spitting.

Carcinogens are also more complicated than simply detecting them in the device. "We measure individual exposures, not absolute levels," he said. "So, at this point, the data is not generalizable enough to make general statements."

But that does not mean that one day it will not be the case. Snyder said the study only scratches the surface of human exposure data and its link to health, and that his team's future goals are to better understand exposure to human health. "We want to measure more people in more diverse environments," said Snyder. "We also want to simplify the technology, ideally to the point that everyone can measure their personal exposures, maybe something like an exposure-sensing smartwatch."

The work is an example of Stanford Medicine's focus on health accuracy, which aims to anticipate and prevent disease in healthy people and accurately diagnose and treat disease in patients.

The other author of the Stanford study is postdoctoral scholar Qing Liu, PhD.

Snyder is a member of Stanford Bio-X, Stanford Cardiovascular Institute, Stanford Children's Health Research Institute, Stanford Cancer Institute and Stanford Neurosciences Institute.

The study was funded by funding from the National Institutes of Health (grant U54DK102556) and a pilot grant for the health of the Stanford Spectrum population.

The Stanford Genetics Department also supported the work.