Anthropogenic hazards are hazards caused by human action or inaction. They are contrasted with natural hazards . Anthropogenic hazards may adversely affect humans, other organisms, biomes and ecosystems . The frequency and severity of hazards are key elements in some risk analysis methodologies. Hazards may also be described in relation to the impact that they have. A hazard only exists if there is a pathway to exposure. Industrial hazards Industrial accidents resulting in releases of hazardous materials usually occur in a commercial context, such as mining accidents . They often have an environmental impact but also can be hazardous for people living in proximity. The Bhopal disaster saw the release of methyl isocyanate into the neighbouring environment seriously affecting large numbers of people. It is probably the world's worst industrial accident to date. Engineering hazards Engineering hazards occur when structures used by people fail or the materials used in their construction prove to be hazardous. This history of construction has many examples of hazards associated with structures including bridge failures such as the Tay Bridge disaster caused by under-design, the Silver Bridge collapse caused by corrosion attack or the original Tacoma Narrows Bridge caused by aerodynamic flutter of the deck. Failure of dams was not infrequent during the Victorian era , such as the Dale Dyke dam failure in Sheffield , England in 1864, causing the Great Sheffield Flood , which killed at least 240 people. In 1889, the failure of the South Fork Dam on the Little Conemaugh River near Johnstown, Pennsylvania , produced the Johnstown Flood , which killed over 2,200. Other failures include balcony collapses , aerial walkway collapses such as the Hyatt Regency walkway collapse in Kansas City in 1981, and building collapses such as that of the World Trade Center in New York City in 2001 during the September 11 attacks . Waste disposal In managing waste many hazardous materials are put in the domestic and commercial waste stream . In part this is because modern technological living uses certain toxic or poisonous materials in the electronics and chemical industries. Which, when they are in use or transported, are usually safely contained or encapsulated and packaged to avoid any exposure. In the waste stream, the waste products exterior or encapsulation breaks or degrades and there is a release and exposure to hazardous materials into the environment, for people working in the waste disposal industry, those living around sites used for waste disposal or landfill and the general environment surrounding such sites. Power outage A power outage is an interruption of normal sources of electrical power. Short-term power outages (up to a few hours) are common and have minor adverse effect, since most businesses and health facilities are prepared to deal with them. Extended power outages, however, can disrupt personal and business activities as well as medical and rescue services, leading to business losses and medical emergencies. Extended loss of power can lead to civil disorder, as in the New York City blackout of 1977 . Only very rarely do power outages escalate to disaster proportions, however, they often accompany other types of disasters, such as hurricanes and floods , which hampers relief efforts. Electromagnetic pulses and voltage spikes from whatever cause can also damage electricity infrastructure and electrical devices.