It is common knowledge that air pollution is bad for the health of the eyes and lungs but indoor and outdoor pollution can cause serious problems for the skin.
One of the biggest culprits that can ruin your skin is cigarettes, whether it is through direct inhalation or through passive smoking. Smoking causes more premature aging than sun exposure, due to reducing vitamin A and moisture levels in the skin. There is also the narrowing of blood vessels (vasoconstriction). Which reduce the blood supply to the skin and causes changes in the skins elastic fibres and results in loss of collagen which brings about wrinkles and sagging skin.
The most common pollution found in the outdoors consists of smog and particulate matter made up from burning fossil fuels and industry waste such as car exhaust and smoke from factories. How this effects the skin, is that topically applied substances can get absorbed through the skin into the blood stream and tissues of the body. The particulate matter that is found in pollution and smug can also irritate the skin, resulting in increased sensitivity. But sensitivity is not the only skin condition that can result from pollution; rashes, eczema, and acne can also be expected due to pollution.
So the pollution you are inhaling and walking around in can accumulate in the body and form free radicals. Free radicals are molecules that have lost an electron due to oxygen, and once this happens the free radicals wreak havoc on the cells in the body which cause the skin to age. The free radicals do this by breaking down the collagen and elastin fibres leading to wrinkles and sagging skin.