The HEAP interview – Allison Zhang on Personal Exposome Monitors (PEMs)

We talk to Allison Zhang, a postdoctoral scholar who is working on a HEAP project to pilot continuous personal exposome profiling of 100 volunteers during their pregnancies. She is part of a team at Stanford University, led by Michael Snyder, that has been focusing on improving the design of wearable Personal Exposome Monitors (PEMs) and multi-omic profiling. 

Q:  How did you come to be working on the HEAP Exposome Monitoring project?

Our lab previously worked on a two-year study that used a device to track the environmental exposures of 15 people. The device that we used was a precursor of the Personal Exposure Monitor (PEM), and we succeeded in using it to capture over 2000 different species and 1000 chemical features. We found that people’s exposures varied significantly with the seasons and between locations, and also that the exposome is highly personalized. Even while based in the same geographical area, people’s exposures showed wide variations.

This study led our team to get involved in the HEAP project, which aims to extend exposome monitoring to a wider group, and then link it to results of health screening and a particular life point, in this case, pregnancy.

Q: Tell us more about the improved Personal Exposure Monitor.

Over the past eighteen months or so, we have redesigned the Personal Exposure Monitor (pictured below) to make it suitable for a larger-scale project. The battery now lasts long enough for the device to be carried around all day, and has twice the airflow rate of the old device, with the potential to reach a quadruple airflow rate. Other improvements we have devised include integrating a customized 3D printed cartridge with a filter that can capture both chemical and biological exposures.

What’s more, the device only costs half of the price as the previous one, and can also record GPS location, temperature and humidity. Overall, it will be is a great help in carrying out longitudinal exposome studies such as this one.

Q: One of your aims is to pilot “personal exposome profiling”. What is this, and how will the project achieve this?

A: Personal exposome profiling is achieved by monitoring and measuring day-to-day environment exposures. Using the PEM, our volunteers will collect air samples as they go about their daily lives, in each place they visit. After taking a minimum of two samples per week, they will store the samples in their home freezer at -20 degrees, from where they will be delivered to the lab every month, and stored in a 80-degree freezer. This monitoring will be the next stage of the project, to start in 2021.

Q: What data will the project generate?

A: There will be a wide range of data, relating to patient consent, geolocation, environmental parameters such as temperature, humidity, airflow rate, analysis of airborne particles and toxins. There will also be metabolomics data gathered as part of the project. This will be high-resolution mass spectrometry coupled with liquid chromatography, and sequence analysis. We expect the baseline data from the devices to be between 10-50GB, while the sequence data and metabolomics analysis data will be in the terabyte range.

Q: What is the most exciting thing about this project, from your perspective?

A: It’s most exciting to me to fully characterize the pregnancy exposome. Pregnancy is a special period as the body goes through unique changes and exposures that affect both mother and child. What’s unique about this project is that it aims to depict both the external exposome, or environmental exposures, and the internal exposome, or the metabolome, which shows how the body reacts to these exposures. Bringing the two together will provide valuable insight into how the exposome affects pregnant women and their babies.

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