A large swath of the West Coast is dealing with wildfires. Although things seem to be improving in some areas for this year, the impacts of climate change mean this problem is not going away any time soon.
On top of worries about physical safety, evacuation and property destruction in the immediate area of the fires, a much larger population is experiencing significant concerns about air quality. The particular concern from wildfires is a high concentration of particulate matter, particularly PM 2.5. Home air quality monitors can be used to map out just how bad the air is. Areas right in the midst of the fires are above 400, but even more distant areas have seen numbers in the 150 to 200 range. By contrast, less affected areas even within California are in the single digits. (And most of the East Coast is under 10).
How dangerous is this? And, in particular for the readers of this newsletter, the question I get on repeat: what does the evidence say on risks to pregnant women and children?
For young infants or children (or anyone) with respiratory conditions (notably, asthma) particulate pollution can exacerbate existing problems. Evidence from 2007 fires near San Diego showed more than a doubling in ER visits for respiratory ailments among children. This is also true for adults. If you or your children are in a high risk group, you should do your best to avoid going outside when particulate matter is high.
But this isn’t quite the question people are asking. What they want to know is: for healthy adults and children, with no asthma or pre-existing conditions, are there risks? It’s unpleasant to be outside, for sure. But is it okay to go for a walk? Can the kids play in the backyard occasionally? Weeks inside are difficult to manage, especially during a pandemic.
These question are harder to answer.
One issue is we are looking for smaller impacts. Admission to an emergency room is not a likely outcome for healthy pregnant women and children, even with more sustained exposure. But there are concerns about more subtle, longer-term effects. These may be very important, but they are much more difficult to detect. Finding smaller effects requires a large sample size, and finding long term effects requires the ability to follow-up. Both are hard.
Some of the most striking evidence I’m aware of on this comes from Indonesia. Seema Jayachandran, an economist at Northwestern, published a paper in 2009 about the impacts of the 1997 Indonesian wildfires on pregnant women and young children. She looks in the 2000 census in that country, and uses the number of children by age group to infer whether pregnant women and children were affected by wildfires. The evidence she observes suggests that miscarriage, stillbirth, infant and child mortality were all increased by wildfire exposure. She calculates almost 16,000 child, infant and fetal deaths occurred as result of the wildfires.
Obviously, this is is extremely scary.
But before we panic, there are a few limitations to taking this evidence to the US. For one, the level of particulate matter in Indonesia was extremely high — above 150 for very long periods, and ranging up to 1000. Perhaps more important for interpretation, the effects are largest in groups with the most exposure to indoor air pollution (mostly from indoor cooking). Indoor air pollution is a major health issue in much of the developing world, and particulate levels can be as high as 5000. This evidence suggests risks interact: if you are already at risk due to a lot of exposure to indoor air pollution, adding a high risk outdoor environment seems especially bad.
There is relatively little indoor air pollution of this type in the US. Extrapolating, we would expect any effects of wildfires on pregnancy and children to be smaller. Which they are, although they do not seem to all be zero.
Most convincing is the data on wildfires and pregnancy. There are several studies of the impact of wildfires in California and Colorado on birth weight and preterm birth. The evidence suggests there are small impacts on both outcomes. The evidence on California shows that second and third trimester exposure to the 2003 fires in Southern California (particulate levels in the range of 100 to 200) reduced birth weight by 7 to 10 grams. First trimester exposure had no significant effect. These effects are significant but, again, they are really small. Average weight for a full term baby is about 3500 grams, so 7 to 10 grams isn’t likely to be very important.
Evidence on children in the US is more limited. We simply do not really know much about long term health impacts on kids (the data is more challenging than for pregnancy and it is less clear what outcomes should be measured).
One thing we do know is that even if kids physical health isn’t affected, their mental health may be. Wildfires are scary. They are probably scarier on the back of a pandemic. When you search Google Scholar for “wildfire children” the first papers that come up are on the psychological stresses associated with these events. There is, as we are all learning through COVID, more of a tension than we might realize in protecting physical and mental health in children.
Where does this leave us, other than with the general sense that we need to understand these impacts better? My read is that the evidence does suggest the value for some caution for both pregnant women and children. Lengthy exposure to significant air pollution seems risky. However: this can probably go too far. Given the generally good air quality we enjoy, the evidence suggests negative effects are likely to be small. And there are always tradeoffs. Staying inside for a month with a small child may be unhealthy — for both adult and child — in other ways. There is no perfect answer. Is there ever?
