Pollution — the undesirable change: the substance-or-energy introduced at harmful levels. Thetypes (the exam's list):
1. Air — the particulates-and-gases (the vehicles, the brick kilns, the industry; the indoor pollution — the firewood's toll; the Kathmandu's valley inversion — the winter's crisis).
2. Water — the domestic sewage, the industrial effluents, the agricultural runoff (the rivers' pollution — the Bagmati's story); the ground-and-surface waters' faces.
3. Soil/land — the chemicals, the solid waste (the municipalities' waste crisis), the e-waste.
4. Noise — the traffic, the industry, the construction (the urban soundscape).
5. Thermal-and-light — the modern additions.
6. The greenhouse gases' special face — the climate pollution (U5.8's world — the global commons' problem).