Linda Bonnar, age 11 of Ottawa, Ontario, or her question:

What is smog?

When the wash is on the line, Mother keeps her eye on it, At the first sign of rain, she scurries out with the clothes basket. Wet or dry, in come the sheets, T‑shirts and dish towels, Why not leave them outdoors until the sun comes out and dries them again? Mother knows best. After a pouring shower, those could be as dirty as when they went into the washer.

The raindrops fall quite a distance through the airy And the air is full or dirt, dust and fine particles of smoke, Not only in the city. There is dust and dirt even in fresh country air. There are fine particles of dust in the clean air high above the oceans, This invisible floating, debris tends to cling to moisture. Lots of it is gathered by the falling raindrops, Rainwater will dry out from the damp clothes., But it leaves, its quota of dust behind to make them dirty again.

Smog is really a dirt ‑ ladened cloud, The cloud is sitting on the ground. When this happens, we call it a fog or mist. This fog is the basic ingredient of smog. The word smog is coined from two words ‑fog and smoke, However, the dirt in the smog is not necessarily particles of smoke,

The fog, of course, is caused by air temperature. Air is always thirsty, Dry air always drinks up as much moisture as it possibly can. Water is always being evaporated from the surface of the ssa, from rivers, streams, puddles and lines of wet laundry. This evaporated mixture becomes vapor, which is a gas. It is invisible and floats off with the other gases in the air,

Warm air can hold more water than cool air, The smiling sun heats the ground and the ground heats the air above. it, This warm air takes up all the vapor it can hold. Then the sun is hidden or along comes a chilly wind, The air is cooled off. This cooler air now has more than its quota of vapor, This must be unloaded. The extra water collects in tiny water droplets ‑small enough to float in the air, They form a mist ‑ a cloud aloft in the air or a fog sitting on the ground,  ‑

Fine dust and dirt in the air is trapped among tiny droplets of water, The dirt sticks to the moisture and the clear droplets of water become grubby and grimy, The clean white mist becomes a blanket of smog. Sometimes chemicals mix with fog to make smog, They may come from automobile exhaust gases or from the chimneys of factories and refineries.  In any case, if most of the impurities are removed from the air' fog cannot turn into grimy,, choking smog.

There is never smog over the clean oceans. The smog regions are around big cities and busy industrial areas. Household chimneys add a certain amount of smog‑making smoke particles to the airs but not enough to blind a big city like London in peasoup smog or choke a big cities.