Anyone who lives in north China understands that the air quality that they endure is potentially hazardous. There are other environmental hazards to health that have been less obvious or less widely understood, but that emerge in patterns of illness among populations in certain areas: the cancer villages that can be identified, particularly around chemical industry installations, for example, or elevated levels of lead that are found in children in certain areas, as a result of battery production or simply proximity to coal fired power generation. Lead poisoning can cause damage to the liver and kidneys, as well as permanent intellectual and development disabilities, and children up to the age of seven are particularly vulnerable because of their immature central nervous systems.