"A recent study found that a fireplace pumps out 58 milligrams of particles under 2.5 microns in diameter (PM2.5s) per kilogram of firewood burnt. This means that every hour you spend in a room with a fireplace burning wood reduces your lifespan by about 18 minutes, equivalent to smoking 1.5 cigarettes"
These kinds of stats really irritate me. Sure, smoking isn't great. Breathing in small particulates also isn't great. However, the 18 minutes is such a weird thing. There are so many people that have lived longer lives by smoking than people that work out all the time. There's just no real evidence this stat is true. You can't clone a person and sit one clone in the room with a fireplace, and then the other not in the room. Then watch which one dies first.
The only test I've seen with evidence of one doing something the other doesn't was the twin brother astronauts where one went to space and the other did not.
That's why they don't look at 1 person but at aggregates. If the world was made of twins and triplets and they lived identical lives (nutrition, stress levels, air quality, ...) besides the 1 factor you're interested in (fireplace yes/no), that would be great for learning from, but of course that's not the case, not even for that astronaut
I'd encourage you to open up one of these studies. The language in scientific papers is made to sound smart but it's still English (most of the time) and you'll see these sorts of things are established by looking at many people in many situations and then use maths to tease out how much each of the factors (living near a major road, for instance) contributes to the thing being investigated (such as longevity). Many of the factors, also depending on the number of people involved, will not turn out to be statistically significant, meaning that the error margins are too large to be sure. For smoking and woodfire particulates though, we're certain that it's unhealthy to within extremely low error margins. Whether that's precisely 18 minutes: probably not, but presumably that's our best guess, even if it has uncertainty associated with it. The paper is linked literally within the quote you gave, if you want to check how uncertain the value is: https://www.sciencedirect.com/science/article/pii/S235271022...
Skimming this one, they didn't establish the relation between particulate matter and lifespan themselves but they cite other studies that did this:
> correlating average PM2.5 levels during a shorter time interval and the average life expectancy during that same time period. In Taiwan, this method used data from 17 counties for the 2010 to 2017 period and resulted in a DLE factor of 0.798 years per 10 μg/m3-increase in exposure to PM2.5 [50]. Using data from 545 counties in the United States for between 2000 and 2007 [51] and data from 214 cities in China for between 2013 and 2017 [52], resulted in lower DLE factors: 0.14 and 0.18 years, respectively, per additional 10 μg/m3 of exposure to PM2.5.
If you doubt those methods, you should click through to sources 50, 51, and 52. This study just measured the amount of PM2.5 in three situations and then multiplied it with that value from the other studies (I didn't read far enough to see which one they ended up picking, that should be mentioned somewhere if you want to know/check it precisely), and that's how they get to this value
> There's just no real evidence this stat is true.
They don't just pull stats from thin air. If you think they made a mistake somewhere and arrived at the wrong number, I'm curious to hear where they went wrong, and the authors would probably be happy to be get an even better stat as well
These kinds of stats really irritate me. Sure, smoking isn't great. Breathing in small particulates also isn't great. However, the 18 minutes is such a weird thing. There are so many people that have lived longer lives by smoking than people that work out all the time. There's just no real evidence this stat is true. You can't clone a person and sit one clone in the room with a fireplace, and then the other not in the room. Then watch which one dies first.
The only test I've seen with evidence of one doing something the other doesn't was the twin brother astronauts where one went to space and the other did not.