A new paper in Canadian Medical Association Journal has linked irregular heartbeats in 322 Chinese cities to small-micron particulate matter, invisible pollution that needs an electron microscope to visualize. Given its minute size, PM_2.5 is one-fourth the size of real pollution, PM10, there is four times as much of it, so the paper could have used PM₁₀ and achieved the same statistical significance. It just would have been less dramatic

So they go for drama, because everyone already knows smog is harmful. After over 12,000 died in a short period in London in the 1950s, a deadly confluence of PM₁₀ and natural atmospheric events keeping the pollution at street level, developed countries began to cut down.

Today, air in developed countries is cleaner than at any time in the last 100 years so epidemiologists and activists began to 'define clean air down' and write papers about PM_2.5.

The good news for public health is that they are reduced to using epidemiology, so no one is being harmed. There are no deaths from PM_2,5 and even ancillary effects like on asthma patients are less than people would get walking through the perfume department in stores. A rudimentary air filter in any home or business keeps things worry-free. The big problem for public health is still PM₁₀, like from wildfires.(1)

China is a much different story. The government self-reported their own emissions and western nations had to pretend the giant rivers of CO2 and pollution emanating from there didn't exist. When it was finally too much to ignore, China immediately became recognized as the world's top polluter. During the Beijing Olympics they banned cars for everyone but communist party officials and visiting athletes.

That means, if virtual pollution is actually a "modifiable risk factor" for atrial fibrillation and flutter, they should be having far more heart attacks. Yet they are not. Data from 2025 hospitals in 322 cities overlaid with pollutant levels reported by monitoring stations found 190,115 patients reported symptoms but the only really interesting correlation they found was to nitrogen dioxide (NO2).

PM_2.5 is now Big Business in the US - California and 12 other states rely on it to control automobile manufacturers - so activist epidemiologists and the attorneys they ally with may note that since these are hospital cases, the real numbers may be much higher. Yet it may a distinction without a difference, because Chinese people don't have more heart disease. Or more heart attacks. Or anything else.

That is the problem with epidemiology; it does not care about biology, chemistry, toxicology, or any field of science. So they will always note in papers their findings are not able to show cause - but in press released they always claim they found a smoking gun. In this case, a smokestacking gun. And call for more government involvement, and higher costs and penalties on the poor. Without ever showing it will help save anyone from anything.

The top way to reduce heart disease is to lose weight. Obesity is the top cause of type 2 diabetes and that is a risk factor for heart disease that is meaningful. But instead of touting weight loss, epidemiologists write papers about "processed" food. Like with PM2.5 concerns, that shows public health is not the real goal.

NOTES:

(1) Even car pollution is down to where further action makes no sense. During the COVID-19 pandemic, when few were driving, Los Angeles, which is naturally prone to high pollution because it is in a basin, had no decrease in air quality. The only way to go lower is to force all the residents of LA to move to Fresno.