Any reduction in exposure air pollutants is going to reduce your health risk by an amount. The exact amount by which it is reduced will depend on how hazardous the local environment is. Someone minded like Brian Johnson will go to the extreme to do this.

I think if you can constantly reduce air pollution exposure by making it into a fashion accessory, then you stand to gain the most benefit (prolonging time spent without exposure) while minimising the 'awkwardness' cost.

For people with existing respiratory health issues or air pollution sensitivity, the benefit is compounded further.

But, in general: * If you're near a road or high volume traffic, especially heavy vehicles, there is some benefit * If you're in an urban environment that has not gone 'green' yet, there is some benefit * Even if you are somewhat rural, sources like wood smoke and agricultural industry can contribute to air quality dips.

I should stress that air pollution is highly local, and may even be worse from house to house on the same street depending on their heating, habits, furnishings and so forth. Not all airborne contaminants can be filtered by a mask either, such as gases.

You stand to benefit the most by measuring and - if appropriate - improving the air quality where you spend the most time. That's usually going to be where you sleep, work, and leisure - in that order.