Our environment is the sum total of all natural things such as air, soil, water, light, temperature, plants and animals around us and including us. We all live in our environment and are a part of it. All living and non-living things inside an environment interact with it and if all goes well, a healthy balance is maintained. But when something undesirable i.e. a contaminant or pollutant comes into the environment and upsets this natural balance adversely, it is called pollution. Such pollutants are usually either manmade (e.g. car exhaust, blaring horns), but can sometimes also come from natural disasters (e.g. volcanic gases, noise of volcano eruption).