You are surrounded by thousands of microbes and chemicals

You will never walk alone.

As you wrap yourself around, you'll discover a vast menagerie of microbes and other details – inventoried and cataloged for the first time by scientists at the Stanford School of Medicine.

The result is surprising: in just one week, the average person is exposed to about 800 different species of bacteria, viruses, chemicals, plant pollen, fungi and tiny microscopic animals.

The Bay Area volunteers, each equipped with a suction device on their arm, gathered a tiny zoo as unique as a fingerprint, influenced by where they went and what they got. fact. There was also seasonal variation in their exhibits.

"We wanted to know exactly what was happening and what impact it could have," said lead researcher Michael Snyder, professor and president of genetics. He wore his camera for five years, carrying it only for swimming, showering and sleeping.

Human health depends on our environment, but the diversity and variation of our exposure to the wild side of life is poorly understood.

There is no need to be paranoid, Snyder said. Our immune systems protect us largely by detecting and rejecting the most dangerous intruders.

But the Stanford team hopes to find out if such shows influence our health. They are now studying blood samples to find changes related to peak levels of microbes and chemical exposures.

According to other leaders in the field, the new strategy – siphoning invisible parts of our landscape and systematically identifying them using chemical profiles and genetic sequences – will deepen our understanding of this invisible landscape.

"This is a detailed, neat and beautiful analysis of the immediate physical world around us," said Stanford's famous microbiologist, David Relman, who did not participate in the research.

"This highlights, for me, the degree to which humans have given a chemical and biological signature to the environment, the individualized nature of our daily environmental encounters and the role that personal decisions and lifestyle choices play for determine these individualized exposures "Relman, professor of microbiology and immunology.

Pieter Dorrestein, a specialist in the use of mass spectrometry to understand the chemistry and ecology of the microbes around us, compared it to "the first series of finches that allowed Darwin to develop the theory of evolution".

"This is a very useful survey of exposures," said Dorrestein, a professor at Skaggs School of Pharmacy and Pharmaceutical Sciences. "If we do not monitor all these shows, we will never be able to understand their impact on people."

Snyder's personal exposome – a total of 2,378 species spanning two years – ranged from exotic bacteria caught on international voyages to the daily detritus of her daughter Diana's guinea pig at her home in Palo Alto.

Other volunteers, traveling to 68 locations, experienced various microscopic safaris. In total, 15 individuals were studied. One was monitored for a year; from others, for weeks.

They each carried a small battery-powered device, costing about $ 2,700 each, firmly attached to their arms. The device breathed tiny gusts of air, about one fifteenth of the volume of a medium human breathing. Inside each device, a filter was brought back to Snyder's laboratory and analyzed.

The team's microbe hunters counted 2,560 different species, as well as many chemicals. The device was so sensitive that it detected a virus carried by bees, responsible for recent mortalities.

The device detected potentially pathogenic bacteria and viruses, but the team failed to distinguish a threatening virus from one of its inoffensive close cousins. It has also detected carcinogenic particles. But because it measures individual exposures rather than absolute levels, it is not possible to assess risks.

Just as a physical landscape confers a unique taste and flavor to fine wines, they found that the microscopic soil of your BART course is different from the terroir of your yoga class, with different species and chemicals in each.

The exposures were influenced not only by location, but also by the presence of household chemicals and insect repellents like DEET, according to the team. Weather, like rain, also makes the difference.

There are seasonal fluctuations – not just in familiar levels like pine, eucalyptus and fungi, but also in more mysterious microbes.

The most disgusting, the team found, were the volunteer exhibits based in San Francisco. His camera captured high levels of "slime bacteria" commonly found in wastewater or sewage treatment – or perhaps faecal dust from pets, pigeons and people.

"There are more rude things in the city," said Snyder.

But even our healthiest activities are shared with uninvited guests, he concluded.

Snyder celebrated the Thanksgiving holiday with a football match, a holiday decoration and rotifers. They are strangely small telescopic creatures that grow in the thin film of water around the ground and leaf litter.

The diversity of its exhibits has also exploded during an annual family camping trip to the Santa Cruz Mountains, near the beach, with a roaring campfire.

It has also shown consistently high exposure levels to mushrooms, because of what it suspects is the use of nontoxic "green" paint, free of organic solvents, when used in the kitchen. a recent renovation.

Snyder made peace with his mushroom: "It's a good thing, if you stink."

Previous research in this area has taken different approaches. We searched inside and immediately around the human body, where billions of bacteria and viruses live. We emit them every time we cough, wave to a friend, or scratch our heads.

Remember Walt Whitman's great poem "Leaves of Grass"? When he wrote, "I am great, I have multitudes," he told us.

We also measured our environment using more stationary tools – for example to detect pollution.

This study uses a larger strategy, studying our exposures during our lifetime.