be ionising or non-ionising. Ionising radiation includes ultraviolet rays, radon gas and X-rays. Too much exposure to ionising radiation can be harmful, leading to increased risk of cancer. Non-ionising radiation includes visible light, radio waves and microwaves. This type of radiation is less risky to health because it contains less energy, but it can still be harmful at high levels for a long time. A rich soil-like material produced from decayed plants and other organic matter, such as food and animal waste, that decomposes naturally. Most food waste can be put into compost, but you should not include meat, bones, cheese, cooking oils and fish. These may take a long time to break down and attract unwanted pests. A source of fuel made from living and recently-dead plant materials such as wood, leaves and the biodegradable part of industrial and municipal waste. An illegal method of getting rid of household waste, possibly in an attempt to save on bin charges, that releases levels of pollutants into the air, so harming air quality and risking the health of those burning the waste and of their neighbours.