- Air pollution is now the second leading risk factor for death worldwide behind high blood pressure, and ahead of tobacco and poor diet.
This is not even cutting edge stuff. Here’s a paper from 2010:
https://www.ahajournals.org/doi/10.1161/cir.0b013e3181dbece1
PM2.5 causes systemic oxidative stress, endothelial dysfunction, autonomic imbalance, and low-grade vascular inflammation
And aside from death, around 30% of childhood asthma is attributable to car exhaust NO2.
Up to 23 million annual asthma emergency room visits globally are attributable to ozone, and 5–10 million attributable to PM2.5.
And for cancer, PM2.5 was formally classified as a Group 1 human carcinogen way back in 2013. 370,000–450,000 lung cancer deaths per year are due to PM2.5, which is about 15–20% of global lung cancer mortality.
And more worryingly, https://pubmed.ncbi.nlm.nih.gov/37020004/ showed that PM2.5 promotes EGFR-mutant lung adenocarcinoma in never-smokers. It can explain around 15% of the lung cancers in never-smokers.
There are also links to diabetes: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(18)30140-2/fulltext That’s a paper about data from 2016, showing ~3.2 million T2D cases per year are attributable to PM2.5.
For kids, air pollution is associated with 2.7–3.4 million preterm births per year, and ~16% of low-birth-weight infants globally (https://www.sciencedirect.com/science/article/pii/S0013935123024416)
I suppose as somebody interested in longevity, you’re worried about dementia. Well https://www.bmj.com/content/381/bmj-2022-071620 showed that every 2 μg/m³ long-term PM2.5 increases all-cause dementia with a HR of ~1.04.
The evidence seems to weigh air pollution much more strongly than those. And especially water. If you live in a first-world country, your water is just fine. I asked Claude to integrate the findings, and it reckons that total deaths from chemicals in drinking water (lead, arsenic, PFAS etc) are responsible for 3-5% as many deaths as air pollution. Even if you take in total unsafe water (like bacterial contamination, poor sewerage etc), then it would be 20% of air pollution.
It also gives a nice explanation:
Dose and duration. You inhale ~11,000 liters of air per day versus ~2 liters of water. Even at modest PM2.5 concentrations, total delivered dose of particles and adsorbed toxicants to the alveolar surface is enormous, and the alveolar–capillary barrier is ~0.5 μm thick with no first-pass metabolism. Ingested chemicals pass through gut epithelium plus hepatic first-pass clearance, and most are excreted.
We can actually do some basic maths:
- Resting/sleeping adult: ~5–6 L/min
- Light activity (sitting, light office work): ~12 L/min
- Moderate activity (walking, housework): ~25 L/min
- Heavy activity (running, cycling): ~50–80 L/min
So let’s use 15 L/min as a representative number. Based on USA average levels of 9µg/m^3, it means yearly exposure of ~50mg/year. If you live in Dehli, that is 500mg/year.
During a wildfire, PM2.5 levels can rise to 300µg/m3, which will give you 4.5mg per day
The particles are tiny and don’t weigh much, so a better way might be to think about particle number. In the USA, that would be 10¹¹ to 10¹² ultrafine particles per day deep into your lungs.