Earlier this summer, a rule change at the Environmental Protection Agency essentially got rid of a rule that would have reclassified metro Phoenix’s air pollution status into a worse level.
Greg Blackie, deputy director of policy for the Arizona Free Enterprise Club, applauded the move.
“Eighty percent of the emissions in our area come from outside of this country. So, they’re coming from China and Mexico — completely outside of our control. And we don’t think that residents, business owners should be held accountable for emissions they can’t control,” said Blackie.
The U.S. Environmental Protection Agency earlier this year announced it will get rid of a policy that would have reclassified the Valley’s air pollution status into a worse level.
Blackie’s and other supporters of the change’s argument is essentially that since we didn’t cause the problem, we shouldn’t be punished for it. But critics of the change say while yes, ozone pollution is coming from elsewhere, it’s also causing health problems for people here.
JoAnna Strother, senior director of advocacy for the American Lung Association in Arizona, said not dealing with air pollution — even if it’s coming from somewhere else — will have negative impacts for Valley residents.
“We’re gonna get sicker as a community, and that’s why we need to invest now. We need to protect our health — again, that has a financial restraint on our economy as well,” Strother said.
Despite the differences of opinion over whether or not Arizona should be held responsible for ozone pollution that comes from outside the state — or whether we should do anything about it — both Blackie and Strother agree that some amount of that pollution does emanate from elsewhere.
So how exactly can we track that? How do we know where ozone pollution actually comes from?
It turns out, Ave Arellano has the answer. He’s a professor in the Department of Hydrology and Atmospheric Sciences at the University of Arizona, where he mainly works on air quality modeling and analysis.
Full conversation
MARK BRODIE: Ave, when I think about tracking something like this, the image that comes to mind is putting a chip on a bird’s wing or in a cow’s ear or something like that. How do you do that with particles?
AVE ARELLANO: So if we think about particles or even ozone, ozone is even harder to to track. Yes, it’s similar to tracking a bird or tracking a whale or tracking your flight, but we do this through models, rather than putting a chip in a bird. We do this through models because we could not really see how these particles move through from one to the other.
And it’s hard for ozone because there’s no single invisible source — unlike, for example, smoke from a chimney. You can easily track it, right? You can see this evolving, and you can actually track where it’s coming from.
However, ozone is not emitted directly in the atmosphere, so we really need to have the models figure out tracking molecules of this compound, of ozone from where it’s coming from, to where it’s going and where it’s removed from.
MARK BRODIE: Does that make it maybe a little more hypothetical or theoretical than, for example, tracking smoke out of a chimney or or tracking a bird as it migrates from one place to another?
ARELLANO: Absolutely. In fact, even this tracking of the smoke, we see this in some of these fires, of course, and we can look at the fire evolving or hurricane tracks, right? This is far harder because of the fact that it is modeled, and there’s chemistry involved, there’s weather involved, and so it is more of a theoretical tool. It’s actually a tool for us to find out where the sources of ozone are.
BRODIE: Given that, if you’re trying to figure out, for example, where ozone pollution in the Phoenix area is coming from, can you tell specifically where it is coming from? Or can you just, for example, “OK, we assume that this amount of it is coming locally and some amount of it is coming from elsewhere, even though we don’t know exactly from where”?
ARELLANO: We can actually know exactly where it is coming from, but obviously there is a lot of uncertainty associated with it because we don’t know how much it is emitted at that source. For example, emissions from California goes to us in Phoenix. We don’t know exactly how much it is emitted, so that way we have some uncertainties built into that.
But think about tracking this — or we call it tagging — we’re tracking this ozone as a mixing or a painting. So imagine ozone to be a color, for example. And you have several paints, let’s say coming from the cars, coming from the trees, coming from the smoke from the fires, coming from another country, or coming from the stratosphere — and each of those have colors as a molecule. And so that evolves in time, and the final result obviously is ozone.
So if you monitor, for example, ozone in Phoenix, you would only see that color, that ozone color, and you can’t really see where is it coming from unless you tag each of the sources, then you have some idea of the contributions for each of the sources. Remember, ozone is produced in the atmosphere chemically with three ingredients: nitrogen oxides, volatile organic compounds from plants and vegetations, but also sunlight. And so meteorology is important to consider here, the winds are also important to consider here, as well as what we emit — either from California, from Asia and from Phoenix.
BRODIE: Well, so given that, I mean, there’s obviously been so much discussion and debate about the amount of ozone pollution in the Phoenix area that is generated locally or that comes from here versus whether it comes from somewhere else and whose responsibility is to try to deal with that. Are you able to discern how much of the pollution in Phoenix is coming from Phoenix versus coming from somewhere else?
ARELLANO: We are trying, so we have advanced tools to do this. But again, as I said, there’s uncertainty built on each of these tools. It’s very hard to monitor, again, the sources of ozone because it’s a mixture of different colors, if you will. And so, yes, we can have, this is an advanced tool that we are actually developing to actually track each of these precursors — nitrogen oxides from California, from fires and so on.
But this has to be corroborated with other sources like or other sources of information like trajectory calculations or more observations of these compounds in Phoenix and upwind of Phoenix or downwind of Phoenix. So this is not an easy problem to solve, especially ozone. But you need more collaborations in order to actually pinpoint, identify with some accuracy, what are the contributions of fires, of local emissions and even international transport.
BRODIE: Have you found that there are other places that deal with ozone coming from elsewhere to the same extent that Phoenix does?
ARELLANO: This is a problem in West Coast, particularly in California and now in Arizona. Also the issue here is that the third ingredient of ozone is sunlight. And so we have a lot of sunlight here, and we have very high temperatures, and so that also exacerbates and even compounds the exceedance or the levels of ozone.
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