Smoke and stuff from factories, cars and trucksThis is the pollution everybody sees and knows about. You can't miss it, can you? Every time you go anywhere in a car or walk in the street, you smell the stink of exhaust fumes. Sometimes the exhaust fumes get so thick they form a sort of fog. People call this 'smog' ('smoke' + 'fog' = smog). It's particularly bad in cities like Los Angeles, Mexico City and Delhi. People get sick because of it. Why? Because the smoke, fumes and gases that make up the smog are poisonous. You might even be surprised to know that smoke from barbecues, grills (you know, restaurants and fast food places) and lawnmowers is also pretty bad and makes smogs even worse.
What you don't see in this sort of pollution are the poisonous but invisible gases like carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), nitrogen oxides (NOx) and ozone. Ozone is a poisonous form of the gas we animals all breathe: oxygen. CO, SO2 and NOx are also poisonous. CO2 is a special problem all of its own. This is the gas which is mostly responsible for what people call the 'greenhouse effect'. It is mostly this gas that is making our planet heat up (see my guide to global warming).
thing you don't see so easily which comes out of factories, farms and
cities is the liquid pollution. This is the stuff
Flushed away, yes, but where to? This is a huge problem for humans. Because people make so much waste, they have to dump it somewhere. Up to now, as long as no-one could see the waste (Not In My Back Yard, shortened to NIMBY), everyone thought it was okay. "Out of sight, out of mind." The planet is only so big and people make so much mess that the whole planet gets dirty. The transport that the flowing rivers, tidal seas and ocean currents provide for human pollution means that it really does get everywhere.
The same applies to the air which is why factories have big smoke stacks to dump smoke and fumes into the flowing wind. Then it blows away... but where to?