Portland’s Harriet Tubman Middle School sits right next to I-5 and may sit even closer if plans to expand the freeway move forward. What does this mean for the air that Tubman students breathe when they’re at school?
Brett Stinson, mechanical engineering student and a junior in PSU’s Honors College, tackled that question as part of his Honors thesis project, part of a larger partnership between Portland Public Schools and PSU.
Stinson worked with Elliott Gall, assistant professor of mechanical and materials engineering and head of the Healthy Buildings Research Laboratory, to study a type of air pollutants called VOCs inside and outside of Harriet Tubman Middle School. Gall and his students helped the school select the most effective high-tech air filters, and studies like Stinson’s are measuring how well these filters work.
Besides continuing this work, Stinson is tackling another issue of increasing interest to Oregonians: how to clean indoor air during wildfires.
What are VOCs and why are they important?
Stinson: VOCs are called volatile organic compounds. Many of them are highly reactive, and the reason that people study them so closely is because they can cause cognition issues in humans at high exposures. They vary in that some are harmless and some are harmful. They come from everywhere, including humans themselves. In this study, we studied human VOC emissions as well as the emissions from cars.
Why did you measure VOCs at Harriet Tubman Middle School?
Stinson: Harriet Tubman Middle School closed down in 2012 and stayed closed until 2018. The problem is that it's built near I-5 so Portland Public Schools (PPS) chose PSU to run a campaign when it reopened in fall 2018. The campaign was to assess the effectiveness of a renovated air handler that they installed. In my work, we took the data set and ran in a different direction because there's so much there; it's such an interesting, unique data set.
What did you do and what did you find?
Stinson: Before I was there, the original PPS field campaign had them running what's called a PTR-TOF-MS, which is an instrument that can measure the concentrations of VOCs. They had it set up at three different locations around the HVAC handler [inside and outside the building].
We took data collected on two days. We got really lucky because one of the days the school was unoccupied. It was Memorial Day 2019. That's how we figured out the background VOC emissions. Then we used data from the day after.
One of the big things that I found is they were unable to analyze air flows on site, which is really important. When you're trying to run the numbers, you need equations that include air flows. So basically, I took a little bit from all of the indoor air quality knowledge that my advisor teaches in one of his classes and back calculated air flows.
We used VOC concentrations [from the PTR-TOF-MS] along with the airflows that I calculated to [analyze] emission rates. How much of it was coming from the building itself? How much was coming directly from supply air (after the air is cleaned)? How much was coming from the occupants within the building themselves? We were able to construct a pretty neat source apportionment which told you where each VOC was coming from.
What are the main takeaways from this project?
Stinson: The air handler is really effective, that's one of the big human health takeaways. But I think the other takeaway is people probably don't assign enough importance to per person VOCs. The concentrations are really high.
The real big takeaway from this is 15% of schools are located within 250 meters of a freeway. There are recommendations where you can time it so you don't have kids outside during rush hour, for instance. There are simple fixes, but I think any school in this situation should at minimum have the sort of air handler that Harriet Tubman Middle School has installed...very, very few schools probably in the entire country have an air handler like this installed. The most vulnerable population you can think of is young children. This should be standard procedure, I think, but it's really expensive and that's the reason why it's not installed everywhere.
ODOT is considering expanding I-5, which would place the road even closer to Harriet Tubman Middle School. What impact do you think that might have on air quality at the school?
Stinson: I personally think it's a bad idea for a million reasons. It's going to increase [VOC] concentrations outside. This is just one building out of 1,000s of buildings—homes, residential areas, businesses—located near the highway, and I think the less traffic pollution, the better.
Was there anything that surprised you while working on your Honors thesis project?
Stinson: When I started, I never really thought about indoor air quality. On top of that, I never really thought about [statistics] like this: 40% of urban populations live within 500 meters of a roadway. I just never really considered that so the whole thing was kind of surprising to me. And now that I'm into it, it’s one of those things that once you see it you cannot not see it. I think about it all the time.
What’s next?
Stinson: We’ve expanded the study to 250 compounds [from 11]. Now we’re looking at everything, and I think this is going to open a lot of doors.
I want to take a deep dive on the compounds with the largest indoor strength. I want to get into the chemistry, try to tell the story, try to figure out why they're being emitted at these levels and see where their emissions typically come from. I think there are 250 questions to be answered here.
Another thing I'm working on is air cleaning and wildfires. The EPA issued a challenge to make your own air cleaner out of household materials. The lab submitted to that and we're waiting to see if we won.