You also need protection against pollution when spending time outside. By car or by foot, be protected wherever you go.
Polluted air is full of particulate matters whose diameters are less than 2.5 micrometer. PM2.5 can greatly affect the air quality and visibility.
Pm2.5 is the most harmful air-pollutant and can enter straight into the bloodstream through the nose, throat, or lungs, causing detrimental effects to the immune system and other organs.
We cannot filter the outdoor environment as we can indoors. Instead, we must clean the air by usinga face mask, or an in-car purifier to avoid the adverse health effects.