Pollution refers to the introduction of harmful materials into the environment, which can cause damage to the natural world and human health.
There are several main types of pollution:
1. Air pollution - caused by vehicle emissions, industrial waste, etc.
2. Water pollution - caused by sewage, industrial discharge, etc.
3. Soil pollution - caused by pesticides, heavy metals, etc.
4. Noise pollution - caused by traffic, construction, etc.
5. Light pollution - caused by excessive artificial lighting.