Radiation exposure
Coal also contains low levels of uranium, thorium, and other naturally occurring radioactive isotopes which, if released into the environment, may lead to radioactive contamination. Coal plants emit radiation in the form of radioactive fly ash, which is inhaled and ingested by neighbours, and incorporated into crops. A 1978 paper from Oak Ridge National Laboratory estimated that coal-fired power plants of that time may contribute a whole-body committed dose of 19 µSv/a to their immediate neighbours in a 500 m radius.The United Nations Scientific Committee on the Effects of Atomic Radiation’s 1988 report estimated the committed dose 1 km away to be 20 µSv/a for older plants or 1 µSv/a for newer plants with improved fly ash capture, but was unable to confirm these numbers by test.
Excluding contained waste and unintentional releases from nuclear plants, coal-plants carry more radioactive wastes into the environment than nuclear plants per unit of produced energy. Plant-emitted radiation carried by coal-derived fly ash delivers 100 times more radiation to the surrounding environment than does the normal operation of a similarly productive nuclear plant. This comparison does not consider the rest of the fuel cycle, i.e., coal and uranium mining and refining and waste disposal. The operation of a 1000-MWe coal-fired power plant results in a nuclear radiation dose of 490 person-rem/year, compared to 136 person-rem/year, for an equivalent nuclear power plant including uranium mining, reactor operation and waste disposal.
Dangers to miners
Historically, coal mining has been a very dangerous activity, and the list of historical coal mining disasters is long. The principal hazards are mine wall failures and vehicle collisions; underground mining hazards include suffocation, gas poisoning, roof collapse and gas explosions. Chronic lung diseases, such as pneumoconiosis (black lung) were once common in miners, leading to reduced life expectancy. In some mining countries black lung is still common, with 4,000 new cases of black lung every year in the US (4 percent of workers annually) and 10,000 new cases every year in China (0.2 percent of workers).Rates may be higher than reported in some regions.
In the United States, an average of 23 coal miners per year died in the decade 2007–2016.Recent U.S. coal-mining disasters include the Sago Mine disaster of January 2006. In 2007, a mine accident in Utah’s Crandall Canyon Mine killed nine miners, with six entombed. The Upper Big Branch Mine disaster in West Virginia killed 29 miners in April 2010.
However, in lesser developed countries and some developing countries, many miners continue to die annually, either through direct accidents in coal mines or through adverse health consequences from working under poor conditions. China, in particular, has the highest number of coal mining related deaths in the world, with official statistics claiming that 6,027 deaths in 2004. To compare, 28 deaths were reported in the US in the same year. Coal production in China is twice that in the US, while the number of coal miners is around 50 times that of the US, making deaths in coal mines in China 4 times as common per worker (108 times as common per unit output) as in the US.
The Farmington coal mine disaster kills 78. West Virginia, US, 1968.
Build-ups of a hazardous gas are known as damps:
- Black damp: a mixture of carbon dioxide and nitrogen in a mine can cause suffocation. The anoxic condition results of depletion of oxygen in enclosed spaces, e.g. by corrosion.
- After damp: similar to black damp, after damp consists of carbon monoxide, carbon dioxide and nitrogen and forms after a mine explosion.
- Fire damp: consists of mostly methane, a highly flammable gas that explodes between 5% and 15% – at 25% it causes asphyxiation.
- Stink damp: so named for the rotten egg smell of the hydrogen sulphide gas, stink damp can explode and is also very toxic.
- White damp: air containing carbon monoxide which is toxic, even at low concentrations
Firedamp explosions can trigger the much more dangerous coal dust explosions, which can engulf an entire pit. Most of these risks can be greatly reduced in modern mines, and multiple fatality incidents are now rare in some parts of the developed world. Modern mining in the US results in approximately 30 deaths per year due to mine accidents.