There's a microbial, particulate, and chemical cloud surrounding each one of us that is like the one around Pig Pen in the Peanuts comics. It's called the exposome. Researchers from the Stanford University of Medicine found that we each have our own distinct personal cloud - which is everything we're exposed to both indoors and outdoors (pets, rain, household chemicals, air pollution, pesticides, etc.), and what we use on our bodies. It is influenced by geographical regions of where a person lives, works, and travels, as well as a person's lifestyle.
The study followed the personal exposomes of 15 individuals for varying times and over 66 geographical locations (one of the researchers was followed for more than 2 years, during which time he traveled extensively). This was done by having the individuals wear a sensitive air filtering device - which collected what was in the air (environmental airborne exposures). The results showed that each person is exposed to thousands of species (plant pollen, bacteria, fungi, viruses, etc.) and chemicals. From Science Daily:
We are all exposed to a vast and dynamic cloud of microbes, chemicals and particulates that, if visible, might make us look something like Pig-Pen from Peanuts.
Using a re-engineered air-monitoring device, scientists from the Stanford University School of Medicine have peered into that plume and discovered a smorgasbord of biological and chemical minutia that swirl in, on and around us. Their findings show, in unprecedented detail, the variety of bacteria, viruses, chemicals, plant particulates, fungi, and even tiny microscopic animals that enter our personal space -- a bombardment known as the human "exposome."
"Human health is influenced by two things: your DNA and the environment," said Michael Snyder, PhD, 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."
The study's findings also reveal information about geographic- and household-chemical spikes and weather-related patterns, and likewise show the wide range of chemical and biological particulates that can be found between individuals -- even within a relatively small geographic region, such as the San Francisco Bay Area.
For two years, the scientists collected data from 15 participants who traversed more than 50 different locations. Some people were monitored for a month, some for a week, and one (Snyder) for two full years. To capture bits of each individual's exposome, a small device that straps snuggly to the participant's arm "breathes" in tiny puffs of air -- about one-fifteenth the volume of an average human breath.
The device, about the size and shape of a large matchbox, accompanies participants everywhere and is equipped with a sub-micron filter that traps particulate matter in the device. The data -- bacteria, viruses, chemicals, fungi and anything else sucked up by the device -- is brought back to Snyder's lab and extracted for DNA and RNA sequencing, as well as chemical profiling to identify all the collected organisms and chemicals that the person is exposed to.
"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," Jiang said. It includes information on bacteria, viruses, fungi, animals, plants and more, all organized in a single searchable database. "We sequenced these samples in incredible detail," said Snyder, who is also the Stanford W. Ascherman, MD, FACS, Professor in Genetics. "No one has ever done a study this deep before. We ended up with about 70 billion readouts."
Between participants, Snyder and Jiang found that exposomes could be vastly different, even in a reasonably tight geographic region -- in this case, the San Francisco Bay Area. Snyder cited an especially well-controlled portion of the study, in which four participants, including Snyder, were closely monitored over one month, as a case in point.
Each person lived in a distinct region of the San Francisco Bay Area: Palo Alto, Sunnyvale, Redwood City and San Francisco (though the person who lived in Redwood City commuted across the bay to his job). "It turns out, 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 that are consistently seen on or around a single person, but that vary between people. 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're schlepping around and spewing out," Snyder said.
Specific and unique signatures were captured for every individual (although Snyder added that DEET, an insect repellant, along with several carcinogens were found in just about every chemical sample). For example, the resident from San Francisco showed high rates of "sludge bacteria," or bacteria typically found in wastewater and sewage treatments. Snyder had consistently high fungal exposures at home due to what he suspects is the use of "green" paint. "The guy who painted my house was a really environmentally friendly, green person. And he avoided using paints with a substance called pyridine in it," Snyder said. Pyridine, which used to be a popular additive to house paints, has an inverse relationship with fungus, meaning the less pyridine, the more fungus.