Smog was cited as a major factor that contributes to global warming.
Most people who live in or near a large city are familiar with the look of smog that appears as a thick, gray blanket of air pollution that covers the city.
However, sunlight is not always the most effective source for the vitamin, depending on geographic latitude, seasonal changes, cloud cover, smog and sunscreen.
Noxious gases, as they're released into the air, cause chemical changes in the atmosphere which result in the formation of smog and acid rain.
In a city, this has the added benefit of providing cleaner air and reducing the air pollution and smog that is a problem in many large cities.
Vitamin D deficiency is also slightly more common in inner city areas, because environmental factors, such as smog, can block the necessary ultraviolet (UV) component of sunlight.
Not a grain of smog anywhere.
It would be nice getting away from the smog and traffic for a while.
The Atlanta night was muggy and dark; a thin layer of smog trapped the city's light and made the sky glow an eerie yellow-orange.
He waved a hand at the smog and all that caused it.