Between eating bacon, hot dogs on white buns, drinking beer, and riding in high AQI, I had better get my affairs in order. At my age, it’s probably a good idea anyway.
Ozone is a reactive molecule that’s gone once it reacts. Particulates can hang around for a long time.
Again, I’m quite happy for people to decide to not ride outside with high AQI values. The information I am trying to share though is that the absolute health risk of riding outside on a bad day is trivial.
Very happy to share more information on this, as I don’t want people to rely on the claimed credentials and academic background of an anonymous person on the internet.
First of all, just think critically about this for a moment to put things into perspective. There are hundreds of millions of people (actually close to over a billion!) around the world living their entire lives in cities where the average AQHI for years on end is above 50 every day.
These people obviously have an increased risk of cardiovascular and respiratory diseases and cancer… but the average life expectancy in Henan province in China for example is actually the same as in the US!
For scientific data… there is an overwhelming amount of info on this. An approachable and relatively paper I have on hand is [this one](https://www.thelancet.com/pdfs/journals/lanwpc/PIIS2666-6065(23)00226-2.pdf), where the data suggests that unless you I have long term (many years) daily exposure to PM2.5 values above ~50, there is no significant increase in any disease. That includes asthma.
You can find many many more using pubmed, or doing a google search restricted to the site:nih.gov domain.
Again, I completely support your decision to not go outside on bad air quality days. But I also completely support people who want to go ride their bike for hours outside on a bad air quality day (provided they don’t have any acute symptoms), because the absolute health risk of this is extremely low to nonexistent.
AQI reading are fundamentally about predicting risk of acute symptoms. If you feel unwell when outside on bad days, then don’t go out when it’s bad. If you feel fine, then it’s not a huge issue to ride outside if you choose to.
Inland Empire, Southern California.
And conveniently, the air is sparkling clear right now to prove me wrong 
Here’s a new study from Stanford on the hazards of PM2.5. In the Denver area we only had a week or two of bad particulates this year. Some recent years have been much worse.
https://sustainability.stanford.edu/news/us-faces-rising-death-toll-wildfire-smoke-study-finds
I usually avoid it over 100 as I’m someone who enjoys a trainer ride if necessary. The first 4 hours of Leadville this year were 150. I had a horrible cough as soon as I crossed the finish line. I’m sure that was partly due to elevation and breathing in dust all day though.
You’ve made a fundamentally unsupported assumption, which is that all PM2.5 has equal effects on health. PM2.5 is literally just measuring the size of the pollutants in the air, nothing else. But it does matter what those particles are if we are to evaluate the health risk.
In fact, the very paper you referenced calls this out:
In this study, we found that the C-R functions differed by cause of death. The possible explanation is that within the PM2.5 concentration range from 17 to 102 ug/m3 the physical and chemical composition of the atmosphere may change, resulting in different distribution of PM2.5 components responsible for health effects across the exposure range. Previous studies have shown that the health effects caused by PM2.5 are related to its chemical components. For example, components such as organic carbon, elemental carbon, and chloride ions are associated with blood pressure; components such as zinc, cobalt, and manganese are associated with cardiovascular biomarkers. Therefore, due to the spatial variation in PM2.5 components, a single-shape C-R function is unlikely to be applicable to deaths from different causes. More studies are needed to clarify the health effects of specific components, so as to obtain a more comprehensive understanding of the C-R functions between PM2.5 and cause-specific mortality.
So in other words, the actual pollutant chemicals matter when trying to determine the health impacts. So their study is only relevant to the pollutants those people experienced, which seem to be mainly industrial air pollution like NOX.
This meta review of wild fire health risks discusses points:
So don’t be too confident in any of the data so far.
I will say that the effect sizes seen in studies so far haven’t been huge. It’s not a clear and present danger type of thing. But when the AQI gets above 100 I certainly want to avoid high intensity exercise or long moderate exercise. Instead I run a HEPA filter in my trainer room.
Agree with basically everything you say. Again though, as you put it yourself:
>I will say that the effect sizes seen in studies so far haven’t been huge. It’s not a clear and present danger type of thing.
If you’re out there and feel fine with no acute symptoms, it’s not something I would think twice about.
The effect size is very, very, very small. Even with daily exposure for many many years.
There are other things in your life that you are exposed to on a near daily basis that are much more problematic than this.
If you wanna avoid it, I completely support that. But I also completely support people going out and riding in this stuff if they want to.
Emitters