Researcher Michael Snyder, Ph.D., started asking questions about the exposome five years ago. On Jan.16, he came to NIEHS to discuss the approach he and his team took to address those questions. At his seminar "Exposing the Human Exposome," he talked about a device called the MicroPEM that captures particulates in the air.
Taking a leisurely stroll in the park, stopping by a busy coffee shop, or lounging at home exposes a person to an assortment of small bits of matter floating in the air. Wearable devices can detect pollen, smoke, and other particles. Now, scientists are beginning to understand how these specific environmental exposures may affect individuals’ health during their lifetime.
Known as the exposome, exposure measurements are a big part of personalized medicine and are poised to reveal the long-term effects of daily life.
The MicroPEM was developed by RTI International, with support from NIEHS and the Genes, Environment, and Health Initiative, a collaboration between geneticists and environmental scientists, and funded by the National Institutes of Health (NIH).
David Balshaw, Ph.D., and Lisa Chadwick, Ph.D., both members of the NIEHS Division of Extramural Research and Training (DERT), co-hosted the seminar. "When we were discussing who to invite that would be of interest to everyone, and who is doing really innovative stuff in exposure biology, our first thought was Michael Snyder," said Balshaw.
Personal air monitoring
Snyder, who is the Stanford W. Ascherman Professor and chair of the Department of Genetics at Stanford University School of Medicine, also directs the university’s Center for Genomics and Personalized Medicine. When Snyder started the project, he wondered how vast the exposome was and what drove it.
His team re-engineered the RTI MicroPEM to hold two types of filters, one that collects RNA or DNA from biological samples, called biotics, and one that captures chemicals, or abiotics. After sampling, scientists perform mass spectrometry on the material from the filters to see what each individual was exposed to.
"The filters sample a portion of our airborne exposures, and linking to GPS helps inform where those exposures occur," Snyder said.
Snyder contributes to the work by wearing a personal air monitor as he travels around the country and the world. He even wears a camera, especially on the weekend, so he can better correlate what he is doing while the monitor is on.
When it came time to analyze the data, Snyder had worn the monitor for a little over two years. Another volunteer did one year of monitoring, and a third wore a monitor for three months. Taken together, the efforts provided deep data sets, corresponding to approximately 300 filter samples.
The three individuals were exposed to more than 2,500 different species of living organisms. Snyder alone interacted with 2,000 species. He was able to determine that some days were dominated by fungi, while on other days he was exposed to mostly plants or bacteria. More importantly, the types of species floating in the air varied by location.
'Tis the season
Snyder said that the location of a person drives the variation of species, and the time of year is probably the second most important factor for the kinds of species in the air. Strikingly, the study found the insecticide DEET in almost every sample, and trips to agricultural areas generated a spike in pesticide exposures.
The team identified 60 different associations between biotics and abiotics. For example, in one interesting correlation, a high concentration of a particular chemical in paint detected on a filter occurred alongside a decrease in the number of fungal species in the sample. If the paint was designed to be an antifungal, it apparently did its job.
"This talk really illustrated how important it will be for environmental health researchers to also think about exposures at the level of the individual, and how they might vary as a result of lifestyle,” said co-host Chadwick.