Natural pollutants

Some substances are created by nature in sufficiently large quantities to temporarily throw an ecosystem out of balance. These include volcanic dust and ash, sea salt, sulphur dioxide from volcanoes, smoke from forest fires and the like. Some say that these cannot strictly be called pollutants because their impact is always short-term, and can be seen as a part of natural systemic regeneration. In the short term, however, they are definitely experienced as pollutants.
(C) Cross-sectoral problems