41.   The pollution is caused by smoke from fires in neighboring Indonesia, where forest is being burnt to clear land.

42.   The pollution is caused by a deadly combination of salt, selenium and clay in the soils west of the San Joaquin River, south of Kesterson.

43.   The pollution is caused by smoke from fires in neighboring Indonesia, where forest is being burned to clear land.

44.   The pollution is caused by smoke from fires in neighboring Indonesia, where plantations are clearing land.

45.   There is also the problem of agricultural runoff, which causes water pollution even in normal times.

46.   They consume less energy than cars and trucks, cause less pollution, and take up less space than roads.

47.   A former Shell official says the oil giant ignored repeated warnings from its own environmental department that its production operations in Nigeria were causing pollution.

48.   As part of the project, the miners will be encouraged to use other means of searching for gold that cause less pollution.

49.   As part of the project, the porknockers will be encouraged to use other means of searching for gold that cause less pollution.

50.   But some environmental activists, particularly in Europe, are concerned that excessive fertilizer use could cause serious pollution.