Pollution is a game concept in Civ2. Pollution reduces the productivity of terrain squares. It can be caused by buildings such as Factory, Power Plant, or Manufacturing Plant. The chances of a square becoming polluted increase after the invention of the automobile. Nuclear pollution can be caused by meltdown of a (fission) nuclear power plant or the detonation of nuclear weapon.
Pollution can be prevented by city improvements such as recycling center or mass transit, and can be cleaned up by settlers. High productivity is still possible with minimal pollution by using solar plants, hydro plants, or nuclear plants. (Fission plants do not produce pollution unless they melt down.)
Pollution also reduces the score at the end of the game.
Pollution is most commonly caused by the excessive production of Shields in a city; however, it may also be caused by large city populations (after the discovery of the Automobile), nuclear attacks, or the meltdown of a Nuclear Plant. When a city poses a potential pollution problem, skulls on yellow triangles appear in the Information Box of the City Display. The more skulls a city generates, the higher the city's chance of polluting a terrain square within the city radius each turn. When world pollution reaches sufficiently critical levels, there is a chance that global warming can occur.
Pollution can be cleaned up by moving Settlers or Engineers into the polluted square and pressing the "P" key, or choosing the "Clean Up Pollution" command from the Orders menu. Pollution production of cities can be reduced through the construction of certain City Improvements, or by reducing the city's Shield production.