Why is wildfire smoke so bad for kids? What should I do if mine were exposed?

Jun 02, 2023

New York City is no stranger to less-than-fresh air, but this week, the city reached historical levels of bad. Thanks to climate change–fueled Canadian wildfires and a stubborn weather system that pinned toxic air to the city surface, Wednesday's daily average dwarfed the worst daily average in San Francisco at the peak of the 2018 wildfire season. A safe one-day level of PM2.5 particles, the lung-penetrating culprits that can wreak havoc on our health, is 35 micrograms per cubic meter of air. This Wednesday, the average was more than tenfold, with at least one sensor logging a literally breath-taking 868. Now, this unholy blanket of pollution is moving south, with Washington, D.C., bracing for a similar experience.

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Children, particularly susceptible to air pollution, have been at the forefront of concerns. In New York City, school systems canceled field trips, moved recesses indoors, and handed out masks. Playgrounds were shuttered to discourage outdoor activity. Many of us parents on the East Coast, unaccustomed to wildfire-induced pollution, were caught off guard. I’ll admit, I was one of them, strolling leisurely with my kid through air pollution levels that would trigger lawsuits in an industrial setting.

Now, as the smoke starts to clear, we’re left questioning: What toll did this week take on our children's health? And how can we be better prepared next time?

To understand more about the dangers of wildfire smoke, especially to kids, I reached out to Stephanie Holm. She's a pediatrician, an occupational environmental medicine doctor, and an environmental epidemiology scholar. Holm directs the Western States Pediatric Environmental Health Specialty Unit, based at the University of California, San Francisco—which is a long way to say she leads an outreach effort in the Southwestern U.S., educating health professionals about children's environmental health. Plus, she's a West Coast parent, armed with practical advice for us East Coast parents on navigating these new challenges.

We discussed the actual impact of wildfire smoke on children, whether to stress over masks, and if some of us made a serious misstep by not hunkering down as soon as warnings were issued. Our conversation has been condensed and edited for clarity.

Tim Requarth: We know wildfire smoke is bad for you. So how bad is it?

Stephanie Holm: It's pretty bad. Air pollution in general can have a number of health effects for adults and kids. I focus a lot on kids because of my background and particular interest in them. But we know that a lot of the common air pollutants from industry and traffic, such as PM2.5 or nitrogen dioxide, can cause breathing problems, and problems with growth, and problems with learning and development. And wildfire smoke not only has all of those things, but there's some evidence it contains other types of pollutants that might irritate the body in even worse ways.

That doesn't sound great for anyone, but why would wildfire smoke be so bad for kids in particular? In the warnings to stay inside, we hear children singled out as a "vulnerable group." Why is that?

Kids are vulnerable for three main reasons. One is that there are differences in their body and in their physiology such that they get a higher dose of pollution. What I mean by that is if I am sitting next to a child and we’re breathing the exact same air, the kid gets a higher dose of the pollution relative to their body size than I do. Kids just breathe more air relative to their body size than adults. So that's one reason.

The second is that kids have behavioral differences that make it so that they also get more exposure. Kids run and play a lot more than we adults do sitting at a desk for large chunks of the day. And that's a really good thing, right? We want to encourage that play. But when you’re active, you are also breathing more. And so that's also going to increase the dose of the air pollution that you get.

The third reason is that kids really have unique windows of growth and development. And if you affect a pattern of growth, you can have lifelong effects that are very different from what might happen to an adult. This is because the smoke has disrupted this dynamic growth pattern, as opposed to just perturbing a more stable system like an adult. This is especially true during periods of really rapid change, like in utero, early infancy, or puberty.

How do we know it's so bad? What kind of data do we have?

There's a lot that we don't know about wildfire smoke and kids. There just really hasn't yet been a generation that is as exposed to wildfire smoke as the generation growing up now. My daughter here in California has had "smoke days" as part of her school year every year. Like, that's a normal part of her childhood. That shouldn't be normal.

I don't yet know of any studies that have looked at repeated short, high wildfire smoke exposures and longer-term outcomes in kids over the years. We just have to take what we know from the studies that have been done with wildfire smoke in adults, what we know from studies that have been done looking at health outcomes for children and air pollution more broadly. And, you know, that's where critical thinking comes in. We pull those things together to provide folks with the best knowledge that we have from a combination of sources.

One thing I’m curious about is exposure patterns. When we talk about something like traffic pollution, kids are exposed to airborne pollutants for long periods of time. I remember when we talked for an article about gas stoves and child brain health , we discussed how stoves are different because you’re exposed to really high doses of pollutants, but for relatively short bursts of time. So gas stoves are a real concern, but maybe not as concerning as you would think reading about the slew of pollutants they expel, because it's over quickly.

It strikes me that wildfires are somewhere in the middle. You’re exposed to it for longer than cooking, but it's only intermittently throughout the year, unlike traffic. So what do we know about this intermittent exposure to wildfires and long-term effects in children?

That's a really great question, and I get asked a lot actually about why I do cooking-related pollution work and wildfire work. People comment, not incorrectly, that those seem somewhat unrelated. But I find the exposure patterns can be very similar between the two. Wildfire smoke exposures do tend to have these very large peaks, they can be fast, and they can change very quickly. The wind can change directions. One moment you have smoke blowing right downwind at you, and an hour later, none. But it can also be more prolonged.

We do know that there are very short-term health effects of short exposures. We don't really have hardly anything, though, where we’re looking at very high, short exposures and then we’re following up with people for health outcomes years later. And part of that is just a logistics issue. That would be a very difficult study to do, especially in a world like the current one where nearly all kids are having some repeated exposures to airborne pollutants. How exactly do you quantify just how much wildfire smoke exposure your kid got today? Or my kid got today? Those are really tricky things.

Speaking of how much smoke exposure my kid got, I want to talk about New York City, where I live. Most of us really weren't expecting this or prepared for it. On Tuesday everyone was going about their business, and on Wednesday it was an apocalypse. I talked to one parent who was surprised to see a lot of people, kids even, in masks on Wednesday, and she was like, "I guess I didn't get the memo." To be honest, I wasn't totally up on all of this until yesterday, and on Tuesday I walked my kid home from a friend's house and we marveled at the Martian sun and the weird smoke. On Wednesday it occurred to me, maybe that was, like, a big mistake. Did I really fuck up?

In general, I try to never make parents feel guilty for decisions that they’ve made for their kids because parenting is hard enough.

That's nice of you to say, but really, what did I expose my kid to? Like, in terms of absolute risk?

I’m going to crunch some really, really rough numbers for you, to be taken with a grain of salt. But they’ll give you an idea. Being in the "unhealthy" air quality range for a day is, in terms of particulate matter, somewhere in the ballpark of smoking three or four cigarettes. Being in the hazardous range for a day is like smoking 15 cigarettes. But that's being in unhealthy or hazardous air for a full 24-hour period.

Oh my God, I basically gave my 4-year-old a cigarette on Tuesday.

I wouldn't panic. It's true that research suggests that there is no threshold below which air pollution is safe. And we know that two minutes in unhealthy air is marginally worse than one minute, and so on. But it's hard to say how much worse. And what we don't have a good answer to is: How does two minutes at hazardous levels compare to 10 minutes at unhealthy levels?

It is really important that we remember that minimizing air pollution exposure is not the be-all, end-all. You don't necessarily want to do things like cancel all kid activities, which can really affect a kid's mental health, in the name of getting them to zero air pollution exposure. Life is a balance. So, I wouldn't necessarily say something you did yesterday was a mistake. It's more a question of what can you do today?

OK, so what can I do today?

We have a number of resources on our Western States Pediatric Environmental Specialty Unit webpage for families about what they can do to try and decrease smoke exposure. And you know, anything that you can do to decrease your exposure but especially the exposure of your kids, or kids in your care, is good. So if your kid had a little more exposure yesterday, I’d try to work extra hard to decrease their exposure today.

Things that you can do include creating a cleaner indoor air space. So if you have central air or central heat, if you’re able to, you really want to get a MERV 13 filter that helps to filter out a majority of these very small particles. If you don't have central air, or if you have a large space and need some extra on top of the central, you can also get portable air filters. You want a HEPA filter, which are better than the ones that have things like ionizers and electrostatic methods. The ion-based filters can have their own bad health effects.

What about masks?

If you have to be outdoors, there are some kinds of masks that can help both adults and kids. The best ones are NIOSH certified, the N95s, which I think people are more and more familiar with because of the pandemic. The reason those are so helpful is that they seal really tightly to your face and they have really high quality material. It's much better to do a NIOSH certified N95 than any of the other kinds.

Meg Duff

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Wait, I’m confused. The Centers for Disease Control and Prevention doesn't recommend masks for children for wildfire smoke. And you can find experts in newspaper articles saying there's no point. But you’re saying they can help? It seems like nothing about masks is ever straightforward. Why is there all this conflicting advice again? Can you provide some clarity for us?

I think the reason that there's a lot of conflicting advice about masks for kids is that we don't have a lot of direct data for kids. So what you’re seeing is a number of experts trying to take the information that we do have, and use some critical thinking and figure out what the answer is. So I’ll tell you what my answer is. And it is different from what some people will say, and I can give you a perspective on why that is. I mentioned before that I’ve been really active in wildfire research. And I’ve been particularly really active in respiratory protection for kids. I serve on some national advisory councils as the pediatric expert for the country. That's not to say that I’m necessarily always right, but that's sort of the background that I’m bringing to this. I’ve spent a lot of time talking to a whole bunch of experts in respiratory protection, and in pediatrics, and thinking about how we can merge the two. Part of the confusion comes from the fact that there is not a certification process for respirators in this country for children. And in fact, you know, sort of more broadly, there is not currently a structure for respiratory protection, certification, and standardization for the public more generally. So we have a system that's set up for workers, but we do not currently have a similar certification system for the general public, let alone children.

So part of the message from government agencies about masks and children is because they haven't officially tested and certified them, so they can't recommend them?

Exactly. But we have data that show respirators can be really helpful for the public who are not fit tested. And there are respiratory manufacturers who have done work looking at kids in other countries. And there's some work looking at facial shape characterizations. Many children can fit in the so-called "NIOSH grid," the profile of face shapes and face sizes that is used to develop respirators. But it's not perfect. If there's leakage around the face, if you’re a little kid who's pulling at it, because it's annoying you, it's itchy, and you’re getting more airflow coming in around the sides, it won't be perfect. And it's hard to tell people exactly how much protection they’re getting from an imperfectly fitted N95. I can't tell you whether your kid's N95 is reducing their exposure by 95 percent, or 80 percent, or 75 percent. It could be somewhere in that ballpark, but you wouldn't want to rely on that entirely as your only way of protecting yourself or your kids.

Does your daughter wear a mask outside during smoke days?

Yes, she has a NIOSH-certified N95 that she wears. I’ve found for her, the ones that work best are ones that don't have sort of a rigid cup shape but are a little bit more flexible. So there's the duckbill style, and ones that have the more flexible trifold kind of shape. But you know, it's really a question of the individual kid and what seals well on their face. On our Western States webpage, we’ve got some info about performing a user seal check with a kid and getting a sense of whether it's fitting as well as it could.

This is all good advice, but also I’m getting overwhelmed.

One of the tough things about all of that advice is that that's all really useful if you’ve been able to prepare ahead of time. But when the smoke day hits, you know—and I certainly have had the experience of going to the local hardware store, and there are no N95s, and there are no HVAC filters, and there are no portable air cleaner filters. That's frustrating. I think more and more we as a society need to be moving towards a model of being what folks like to call "smoke ready." And so as you get towards the summer, that's your time to do a tune-up on your heating and air conditioning system and make sure you’ve got a filter and a backup one if you need it, and make sure you’ve got some N95s that fit your family, so that when the smoke event happens, you’ll have those supplies for you and your children. Because it's no longer if, it's when.