Coal dust is a fine powdered form of coal, which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. Blasting at mountaintop removal (MTR) sites also expels coal dust and fly-rock into the air, which can disturb or settle onto nearby communities. The dust contains sulfur compounds, which corrodes structures and is a health hazard.
Coal dust is highly explosive and both accelerates and spreads smaller ignitions underground. It has been linked to several coal mining explosions.
Coal dust suspended in air is explosive -- coal dust has far more surface area per unit weight than chunks of coal, and is more susceptible to spontaneous combustion. As a result, a nearly empty coal store is a greater explosion risk than a full one. The worst mining accidents in history have been caused by coal dust explosions, such as the disaster at Senghenydd in South Wales in 1913 in which 439 miners died, the Courrières mine disaster in Northern France which killed 1099 miners, the Luisenthal Mine disaster in Germany, which claimed 299 lives in 1962, and the worst: the explosion at Benxihu Colliery, China, which killed 1549 in 1942. Such accidents were usually initiated by firedamp ignitions, the shock wave of which raised dust from the floor of the mine galleries to make an explosive mixture. The problem was investigated by Michael Faraday and Charles Lyell in the explosion at the colliery at Haswell County Durham of 1844, but their conclusions were ignored at the time.
The 1907 Monongah Mine Disaster of Monongah, West Virginia, which claimed the lives of 362 men and boys and is known as the worst mining disaster in American History, is thought to have been caused by the ignition of methane, which in turn ignited the highly flammable coal dust.
The main attempts at prevention include using safety lamps, adding stone dust coffers to mine galleries, watering workings, and ensuring efficient ventilation of all the workings. US federal mine safety rules require removal of accumulated coal dust and the use of crushed limestone or "rock dust" to neutralize the combustibility of fine particles of coal that naturally cling to mine equipment, floors, pillars and roofs.
Upper Big Branch Disaster
In September, 2010, it was reported that the search for a cause of April 2010's deadly Upper Big Branch Mine Disaster in West Virginia had turned up evidence of excessive coal dust in the Upper Big Branch Mine. Analysis of 1,803 dust samples collected by investigators after the blast showed that 79 percent were not in compliance with federal coal dust standards, according to Kevin Stricklin, director of the coal mine division of the federal Mine Safety and Health Administration. The finding, Stricklin said in a press briefing, suggests coal dust has "more potential to be involved in the explosion."
The sample results followed earlier reports that week stating excessive coal dust was seen in areas of the mine hit by the explosion a half-hour before the blast. Handwritten logs kept by two "fire bosses" - mineworkers who check for dangerous conditions before and after work shifts - noted excessive coal dust along conveyor belts as little as 30 minutes before the explosion. The logs were first obtained and reported by The Associated Press. Excessive coal dust is considered important in the investigation because the explosion traveled more than two miles, turning corners and spreading in opposite directions, suggesting the blast was fed, directed, and accentuated by an accelerant.
Massey Energy continues to insist that the explosion was likely caused by a sudden and massive infusion of methane gas through cracks in the mine floor. But a recent lawsuit filed by Massey challenging the MSHA from preventing the company in doing its own investigation was dismissed by an administrative law judge. Two hundred thirty-five witnesses have been interviewed by MSHA, and investigators have 20 more people they'd like to question. But some are Massey managers who have objected to subpoenas issued by the West Virginia Office of Miners' Health, Safety and Training. Federal investigators do not have the power to compel testimony except in public hearings. Massey did not respond to requests for comment about its managers' resisting subpoenas. And Ron Wooten, the director of the West Virginia mine safety agency, said through a spokeswoman he had no comment.
A federal criminal investigation is also under way and a federal grand jury in Charleston, W.Va., has also been issuing subpoenas and taking testimony.
September 21, 2010: New compliance rules on coal dust issued
On September 21, 2010, MSHA director Joe Main announced plans to require underground mines to do more to control explosive coal dust under an emergency rule. The announcement came amid mounting evidence that coal dust played a role in the Upper Big Branch mine explosion in April. The change will raise to 80 percent the amount of pulverized stone or other inert material mines use to dilute coal dust in air intake tunnels, the same amount already required in return tunnels. Currently intakes need just 65 percent. Main says MSHA's change is based on federal research that shows decreasing the amount of coal dust in air intakes can prevent explosions.
May 2011 report: Most Upper Big Branch miners had black lung
In May 2011, the first comprehensive state report on the 2010 Upper Big Branch Mine Disaster faulted Massey Energy, concluding that Massey had “made life difficult” for miners who tried to address safety and built “a culture in which wrongdoing became acceptable.” The report also noted that most of the miners killed had black lung disease, or coal workers’ pneumoconiosis (CWP). The report stated: "Of the 29 victims, five did not have sufficient lung tissue available to make a determination relating to CWP: two due to massive injury and three due to autolysis. The remaining 24 victims had sufficient tissue for examination. Seventeen of the 24 victims’ autopsies (or 71 percent) had CWP. This compares with the national prevalence rate for CWP among active underground miners in the U.S. of 3.2 percent, and the rate in West Virginia of 7.6 percent."
Chronic exposure to the coal dust stirred up during mining can lead to black lung disease, or pneumoconiosis. It is a common affliction of coal miners and others who work with coal, similar to both silicosis (from inhaling silica dust) and to the long-term effects of tobacco smoking. Inhaled coal dust progressively builds up in the lungs and is unable to be removed by the body; that leads to inflammation, fibrosis, and in the worst case, necrosis, or the premature death of cells and living tissue.
Federal U.S. regulations of coal dust did not exist until the Coal Mine Health and Safety Act of 1969, in which the U.S. Congress set up standards to reduce dust and the Black Lung Disability Trust Fund (BLDTF), which pays health benefits to coal miners afflicted with black lung. A miner who spent 25 years in underground coal mines has a 5-10% risk of contracting the disease.
According to journalist Ken Ward Jr.: "When Congress passed the [Coal Mine Health and Safety Act of 1969], the black-lung protection provisions were supposed to be flexible. Things like the legal dust limit, the testing procedures, and the enforcement scheme, were to change over time as experts learned more about the disease and how to prevent it. But the intent was clear: Congress wanted black lung to end." Regardless, efforts to institute tougher dust limits and more rigorous sampling requirements than the 1969 law have been repeatedly stymied by the coal industry and supporters.
The BLDTF was instituted in 1978, and is funded through an excise tax on coal to support a trust fund covering health costs of affected workers. However the tax is not sufficient to cover all costs, and the BLDTF was given “indefinite authority to borrow” from the U.S. General Fund. By the end of FY 2008, the BLDTF had accrued nearly $13 billion in debt. In 2008, Congress partially “bailed out” the BLDTF.
2012 US coal dust violations
In 2012 federal regulators with the MSHA announced the results of a September inspection blitz targeting 13 coal mines in seven states "previously cited for violations regarding respirable dust sampling ... inadequate dust control ... and hazard complaints" involving excessive coal dust. More than 120 new violations were found, including failures to maintain adequate ventilation and water-spraying equipment underground, which work together to suppress coal dust and minimize its inhalation by coal miners.
Black lung took the lives of an estimated 10,000 miners worldwide over the last decade. Rates of black lung are on the rise, and have almost doubled in the last 10 years. The US National Institute for Occupational Safety and Health (NIOSH) reported that close to 9 percent of miners with 25 years or more experience tested positive for black lung in 2005-2006, compared with 4 percent in the late 1990s.
From 1968 through 2007, black lung caused or contributed to roughly 75,000 deaths in the United States, according to government data. In the decades following passage of the 1969 miner safety law, rates of the disease dropped, but the trend reversed in the 1990s. There are theories about why. Public health experts and industry experts point to a combination of outdated coal dust regulations, insufficient oversight/enforcement, and miners working longer hours. Another likely explanation: Miners are breathing a more potent mix of dust, as companies are increasingly turning to thinner and thinner coal seams surrounded by more silica rock. When ground up, silica is more toxic to the lungs than coal dust and can cause faster-progressing disease. Comparing miners’ X-rays taken from 2000 to 2008 with those taken during the 1980s, researchers found that the proportion bearing the markers of silica had nearly quadrupled and, in central Appalachia, had increased almost eight times over.
2011 US study finds lung diseases from legal coal dust levels
A 2011 study, "Severe Occupational Pneumoconiosis Among West Virginia Coal Miners: 138 Cases of Progressive Massive Fibrosis Compensated Between 2000-2009" by researchers at West Virginia University in the peer-reviewed journal Chest, concluded that "Contemporary occupational dust exposures have resulted over the last decade in rapidly progressive pneumoconiosis and massive fibrosis in relatively young West Virginia coal miners, leading to important lung dysfunction and premature death." Coal miners working in currently legal dust levels were found to still be contracting and dying from serious lung diseases caused by the exposure to legal levels of coal dust.
The study looked at 138 miners with progressive massive fibrosis whose claims were approved by the West Virginia State Occupational Pneumoconiosis Board between January 2000 and December 2009, and found that progressive massive fibrosis (PMF) developed in 138 West Virginia coal miners at a mean age of 52.6 years after an average of 30 years work tenure.
Brayton Point Station
On more than one occasion, coal dust from the Brayton Point Station has covered the nearby neighborhoods of Somerset, Massachusetts. The cities of Fall River, MA, New Bedford, MA, Brockton, MA, and Providence, RI are also within a thiry-mile radius of both Dominion's Brayton Point Station and NRG Energy's Somerset Power Generating Station. The coal dust has been carried from the Station while deliveries of coal were unloaded from ships on windy days. On October 29, 2008, coal dust covered nearby Ripley Street where residents reported having coal dust in their homes despite the windows being closed. A 45,000 ton shipment of coal was unloaded overnight and the community woke up to the dust the following morning.
The most recent of these incidents was early November 2009, when thirty-six homes were covered. This was another occasion when residents woke up in the morning to find their neighborhood covered in coal dust. In a news interview, resident David Gasperini said, "I can clean stuff, but I can't clean our children's lungs, our animals’ lungs and stuff like that. Who knows if 20 or 30 years from now if anybody is going to end up getting any kind of diseases or anything from this stuff." Dominion blamed an extra-dry shipment of coal combined with winds. The company said it would no longer unload coal in winds over 15 miles per hour. Dominion sent insurance adjusters to the affected neighborhood and said they would reimburse the residents for the clean up.
In 2010, an independent laboratory analysis of coal dust wipe samples taken by the Pittsburgh Post-Gazette found soot, arsenic, lead, coal ash, and other materials and compounds associated with coal combustion byproducts and emissions at Pennsylvania homes and other residential locations around and downwind from industrial operations and utilities. Additional testing is needed to determine if those substances are related to local or distant industrial or vehicle pollution and if concentrations are high enough to pose a health risk: "While there are no specific health-based standards for toxic heavy metals in soot or dust, some of the metals that turned up in the wipe samples -- lead in particular -- were detected at levels that are a concern and warrant additional inspection, testing and assessment."
Articles & resources
- Coal mining accidents
- Health effects of coal
- Longwall mining
- Mine Safety
- Monongah Mining Disaster
- Sago Mine Disaster
- Upper Big Branch Mine Disaster
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