Formaldehyde and benzene are not particulates, they are VOC’s - a very different kind pollutant.

But PM2.5 from, say, a frying pan could easily contain abundant formaldehyde and benzene as part of the oil particles.

Formaldehyde and benzene are to volatile to condense onto or absorb into PM2.5 particles. Cooking oil particles can contain other toxic compounds formed during heating, including polycyclic aromatic hydrocarbons (PAHs), acrolein, and various aldehydes and ketones. If formaldehyde or benzene react to form less volatile products, those reaction products might become part of particulate matter, but they're no longer formaldehyde or benzene at that point. So while cooking emissions do produce both harmful VOCs and harmful PM2.5 simultaneously, they remain distinct categories of pollutants.

"could easily"

I just asked ChatGPT: when using a fry pan, does the smoke contain formaldehyde and benzene?

    > Cooking at very high temperatures (over 450°F or 232°C), especially with oils or fats, could theoretically contribute to benzene formation.

That is a mighty hot fry pan. The hottest cooking that I know of in common practice is "wok hei"-style from China. When you start cooking, the food rarely exceeds 230C. When you are heating the pan, the oil may exceed 230C for a few seconds. If you use a fry pan, but cook in Mediterranean-style, the temperatures are much lower.

"could easily"? Hardly.

OK, but wood smoke is really bad for you even if the wood is completely natural.

yes but smoke from any urban area will have asbestos and numerous other potent toxins

Sure, but asbestos, lead, formaldehyde, benzene, etc particulate matters are all undoubtedly going to be more harmful than most types of wood smoke. An urban area will have both wood smoke (which is often treated, possibly with methyl bromide) and industrial smoke. Few would deny breathing in campfire smoke is less likely to cause more immediate harm than a fire at a waste site

Pollen fragments are really bad for some of us....

Of course! Different bodies have different sensitivities. But we're talking averages here. What's gonna cause the most social harm

Lumping all PM2.5 together is kind of like counting calories without considering whether they come from broccoli or corn syrup

They don't seem to have considered fungus spores as PM2.5 either. Seems like a single spore could cause more damage than many carbon particles.