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Air Pollution and Asthma
This is part 2 of a 4 part series about air pollution and how it could harm you. Today, we talk about how different types of air pollution can affect you. Most people in the US think they need not worry much about air pollution, owing to the fact that we are in the top 5% for clean air worldwide. Yet air pollution is likely one of the largest causes of asthma, and outdoor pollution in the US regularly kills off an estimated 200,000 people per year* (or ~0.06% of the population).
We've focused in prior posts on particulate matter pollution in developing countries. We haven't focused on invisible chemical pollution in developed countries.
So let's focus on the fact that one in twelve kids will get asthma in the US. This year in the US, asthma will kill an average of 10 people per day, and cost $56 billion to manage. This is more than Apple makes in profit each year (the money, not the number of deaths).
There is significant research to suggest NO2 pollution from traffic, specifically, is linked with higher asthma rates. These articles, respectively, indicate that up to 6x asthma rates are associated with 1/3 legal max US NO2 levels, and 3x asthma rates associated with up to 1/4 legal max NO2 levels. Later research shows that the effect persists when living up to 500m from major highways (1/3 a mile). These results show when children are exposed to pollution from 0-2, they have these increased chances of lifelong asthma at age 8. These strong relationships are not demonstrated in relation to PM when you account for NO2 pollution. In other words, it's the pollution you can't see that is harming your kids in the US. Keep in mind that in developing countries, this NO2 pollution problem is worse, but it typically also has visible PM.
Why this is important:
Infants lungs are one of the only organs that change in more than size after they are born. In other words, they are the only organ that really develops outside of the womb, and this persists until age 8. Infants are most vulnerable to lifelong effects of air pollution.
What about older children?
Research from California shows that the average female lung capacity increases by 0.876L from age 11 to 15 (to 3.15L), and the average male lung capacity increases by 1.5L (to 3.8L). For each 25% increase in NO2 exposure relative to legal maximum, the study showed a ~0.1L decrease in this lung capacity growth. In other words, 25-50% of total lung capacity growth could be decreased by exposure to NO2 pollution within legal limits. What about PM2.5 pollution? The research shows that it takes an increase in PM2.5 pollution equal to the full legal limit of PM2.5 pollution to have a .06L decrease on lung capacity in this time. In other words, NO2 exposure is far more associated with decreased lung capacity growth in older children.
So pretty much, traffic is not good for children.
One thing to make very clear: these studies are not prognostic. They compare changes in lung capacity both latitudinally (ie for different pollution exposures happening in the same year to differing populations) and longitudinally (it for the same population types exposed to differing pollution levels in different sets of years). So we can say there is a very strong link between the air pollution and the findings. Why can we not say air pollution caused the results? Because we didn't do tests whereby we actively reduced pollution exposure to one set of people, and did nothing with another set of people in the same area. Until we carry out these tests, we won't have a 100% sure link (instead we can be like.... 90% sure, given the preponderance of data. But ask any data scientist, 90% isn't enough to make people change their habits. Or ask any smoker, where 100% certainty of knowledge isn't enough). There are no currently available ways to reduce exposure to NO2 pollution (literally give us 6 months and you'll have one), so the only way to do tests would be to increase exposure of air pollution to some populations, and this would be extremely immoral.
The other option would be to filter air pollution for individuals, and then show a difference to general population. I bet you can guess where I'm going with this!
What about adults?
Who do you think the 200,000 people dying per year are? More seriously, here is a very in depth report about PM pollution (a much larger problem in the 3rd world, but a not-terrible proxy for NO2 pollution), and health. No one expects you to read this entire report, cause it's long and dense. And it literally refers to cities as "Human Settlements." The take-away is that nearly all the deaths that occur in the US from air pollution come as the result of heart attacks or stroke. You know who gets heart attacks and strokes? Hint: it is not infants and children. Air pollution exposure in infancy and childhood can cause lifelong respiratory disease, or just decrease your lung capacity for your entire life, and thus later increase your chances of stroke and heart attacks. In other words, exposure to air pollution in the US, particularly traffic pollution, is a lot worse for you and your family than you ever thought.
What about raising kids abroad?
This is a far cry from it's like in Beijing, with 4.5x higher PM2.5 and 2-3x higher SO2 and NO2 than in the US. Or in parts of India, where PM2.5 is 10x higher than in the US, and people have only 70% the lung function of other countries, and up to half of people pretty much have asthma.
Conclusion: Try to reduce your children's exposure to traffic pollution. It's actually really bad.
What about indoor pollution?
This is an entire other can of worms. Indoor pollution can be dust, cigarette smoke, or droppings and dander from cockroaches, mice, and other pests. Getting rid of cigarette smoke is easy. Stop smoking. If you live in low-income housing and have mold or pests, do a web search for organizations to help remove these harmful things, or speak with your child's pediatrician about what to do about this. Fixing smoking or mold is more important that controlling outdoor pollution exposure, cause your infant will spend 90% of time inside. For dust, just get a HEPA filter. For indoor NO2 from gas stoves, pretty much Blue Skies (my company) has the only effective NO2 filter, so sign up there (more on this in the post two weeks from now).
Thanks for reading!
- Jason Munster
*This study has some serious caveats. They don't look at NO2 pollution from traffic, and as we discussed in our last post, NO2 pollution from traffic is the dominant type. They also don't look at the effect of SO2.