What is the hazy film that accumulates on the inside of windshields and are we breathing all of that stuff into our lungs? Is that bad?
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If it’s cold outside the humidity in your warm breath can condense on the cold glass. In that case it’s just water.
Sometimes you’ll also get a fine layer of dust on the interior surfaces of the car if your cabin air filter isn’t doing a great job. Pollen, blown dirt, volcanic ash, shed skin, car exhaust…
You’re breathing all that stuff in all the time. Most of it is harmless, some of it is not.
Do you vape? Vaping tends to leave a film of glycol on the window that’s kind of a pain to take off.
Only asking because I’ve had this issue, and the other comment adequately explains the condensation thing. Note, if its real bad, its possible your heater core is leaking, adding excess moisture to your cabin and a lot more condensation; repairs are good, but you can keep some kitty litter to dehumidify a bit. The air conditioner (even on a warmer setting, so long as its on) will remove some humidity too.
Are you smoking cigarettes or weed in the car? If so then there’s a residue that smoke leaves behind on glass. So yeah, you’re definitely breathing that in if you’re smoking it first
**Outgassing**
I had an older car, where the kind of plastic in the dashboard was known to break down in sunlight. This process took years.
The byproduct of this breakdown was some gasses, which (I’m told) was the cause for the film/residue on the inside of the windshield.
My take on this is that outgassing from.plastics in the car is the biggest culprit.
But organic material in your breath, and from the air plays a role too.
Pollen, dust, small droplets of spit and mucus from coughing and breathing, oil vapor and exhaust from the other cars on the road.
I imagine all this stuff condensing in to the oily film that I habitually have to clean off my own windshield from time to time.
[Plasticizers](https://en.wikipedia.org/wiki/Plasticizer) are a collection of chemicals that change the properties of plastics (and other things), generally to make them more flexible. They are used in the dash, vinyl fabrics, gaskets, wires, couplings, and more.
They naturally move out of the plastic over time, often in the form of a gas or vapor called “off-gassing” and accumulate on all surfaces of the car but, most annoyingly, on the windshield. If you’ve ever noticed something plastic getting gummy, brittle, or changing color over time, this is sometimes caused by plasticizer migration. Heat, light, and other environmental factors can increate the movement of these molecules directly (eg they “evaporate”/off-gas) or damage the plastic itself causing the plasticizers to sort of seep or collect like a very thin coat of oil.
Some plasticizers can interact with your hormone system so are considered toxic. I suspect that the level of most plasticizers in most cars is less toxic than lots of other things in life, including other things that off-gas (like cooking on over-heated teflon.) There are other plastic additives like BPA that can also migrate out of plastic and might also be among the things coating your windshield that have been found to be bad enough they are being removed from some consumer goods.
Broadly speaking, plastic is an amazing invention that has revolutionized the world but, the same properties that make it useful make it persist in the environment, transport small, maybe dangerous chemicals, and cause lots of long-term environmental problems. Despite this, practically speaking, the off-gassing in your car or any other “normal” plastic exposure is unlikely to be all that bad for you, as an individual.
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