Could "normal" human development lead to a sufficient air pollution to make gas masks mandatory?

Question

I'm starting a story taking place around 2080 AD/CE, and I'm wondering if the key element - global pollution - is plausible.

In my storyline, the XXIst century brings no huge technological advances (I mean nothing truly game-breaking). Mostly increased efficiency in computing power, a few new materials, and global switch to electricity.

Is there some kind of human-generated air pollution that could rise to dangerous levels, so that living outdoors without appropriate protection would be unsafe ? I'm thinking aerosol.

Assuming no big, coordinated action is taken for some decades (politics and global opinion react slowly at first), can such an omnipresent and impactful change occur, and will it take a long time to reverse ?

Living indoors with appropriate air filtering would be safe.

Answer 1

On a global scale, unlikely.

The major components of the "killer smogs" are fine particulates, sulfur dioxide, nitrogen oxides, and ozone. Sulfur dioxide has an atmospheric half-life of about 24 hours, so you'll only get buildups in the immediate vicinity of sources (volcanoes, coal-fired power plants). Atmospheric ozone tends to decompose into oxygen on timescales of about a day. Fine particulate matter in the lower atmosphere tends to settle out on a scale of a few days.

Your best bet is probably nitrogen oxides: nitrous oxide has an atmospheric half-life of about 50 days, but even then, getting a global buildup to hazardous levels will be hard.

The big problem with getting planet-wide deadly pollution is that the same properties that make it deadly (chemical reactivity) also make it short-lived: it tends to react with atmospheric moisture and either break down into stable compounds or fall out in the rain.

Answer 2

Yes, you can definitely get these effects although it may not be truly global.

Rising CO2 would have implications for global warming but is not directly life threatening at the sort of concentrations we are talking about.

Sulfer, particulates, carbon monoxide, lead (before we phased it out of petrol) and many more though are dangerous and are already rising to toxic levels in some areas.

Particularly in China and areas burning dirty coal this can get seriously bad already.

One way this could happen is if the corporate powers managed to sidestep oversight and neutralize or shut down anti-pollution laws. They could then run their factories and generators as dirty as they liked, while rich people live in isolated islands or air conditioned and filtered areas far away from the consequences.

Even now this is already starting to happen, for example in Hong Kong:

The mortality rate from vehicular pollution can be twice as high near heavily travelled roads, based on a study conducted in the Netherlands at residences 50 metres from a main road and 100 metres from a freeway. Since millions of people in Hong Kong live and work in close proximity to busy roads, this presents a major health risk to city residents. The Hong Kong Medical Association estimates that air pollution can exacerbate asthma, impair lung function and raise the risk of cardio-respiratory death by 2 to 3 percent for every increase of 10 micrograms per cubic metre of pollutants. Studies by local public health experts have found that these roadside pollution levels are responsible for 90,000 hospital admissions and 2,800 premature deaths every year.

And elsewhere in China:

Chinese scientists have warned that the country's toxic air pollution is now so bad that it resembles a nuclear winter, slowing photosynthesis in plants – and potentially wreaking havoc on the country's food supply.

Essentially all you need is for people to increase burning the dirtier kinds of fossil fuels (coal in particular) without sufficient safety in place and while increasing production and you don't need to extrapolate much beyond what we already have.

Keep in mind also that things don't need to be immediately harmful for people to wear masks. Asbestos can get in the lungs for a long time before you show symptoms, but people still wear breathing masks to work with it.

Now, these would still not be completely global, for example out at sea or a long way from industrial centers there would still be smog free areas - and as a result extremely expensive homes - but you could easily cover the vast majority of the available land areas, and certainly all major cities.

Answer 3

Release of large amounts of fine dust that releases alpha radiation, from a Chernobyl-like disaster.

The radiation is easily stopped, unless it's coming from inside the body. The dust is very hard to clean up, but fortunately has a moderate half-life; in a decade or so everyone can take the masks off again. Plutonium is also chemically toxic (as a heavy metal).

(Something to consider in any "global pollution" scenario: what happens to farm animals?)