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Introduction | |

This guideline summarizes pertinent information about coal dust for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.

|Recognition |

SUBSTANCE IDENTIFICATION

* Formula

Not applicable.

* Structure

(For Structure, see paper copy)

* Synonyms

Sea coal, coal facings, ground bituminous coal, anthracite coal dust, lignite coal dust

* Identifiers

1. CAS No.: None.

2. RTECS No.: GF8281000

3. DOT UN: 1361 32

4. DOT label: Flammable solid

* Appearance and odor

Coal dust is an odorless dark brown to black dust created by the crushing, grinding, or pulverizing coal. The coal dust covered by this document contains less than 5 percent free silica.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

The physical properties of this coal dust vary depending on the specific type of coal.

1. Molecular weight: Varies.

2. Boiling point: Varies.

3. Specific gravity: Varies.

4. Vapor density: Not applicable.

5. Melting/Freezing point: Varies.

6. Vapor pressure: Not applicable.

7. Solubility: Varies.

8. Evaporation rate: Not applicable.

* Reactivity

1. Conditions contributing to instability: Heat, sparks, open flame, or other ignition sources.

2. Incompatibilities: None reported.

3. Hazardous decomposition products: None reported.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has not assigned a flammability rating to coal dust. Other sources rate coal dust as a fire hazard and consider the airborne dust an explosion hazard when these substances are exposed to heat or open flame.

1. Flash point: Data not available.

2. Autoignition temperature: >601 degrees C (>1114 degrees F)-cloud; >200 degrees C (>392 degrees F)-layer

3. Flammable limits in air: >0.05 oz./ft(3)

4. Extinguishant: For small fires use dry chemical, sand, earth, water spray, or regular foam. Use water spray, fog, or regular foam to fight large fires involving coal dust.

Fires involving coal dust should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. For a massive fire in a cargo area, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from the area and let the fire burn. Emergency personnel should stay out of low areas. Containers of coal dust should be moved from the fire area if it is possible to do so safely. If this is not possible, cool fire exposed containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving coal dust.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for the respirable fraction of coal dust (less than 5 percent silica) is 2.4 milligrams per cubic meter (mg/m(3)) time-weighted average (TWA) concentration.

* NIOSH REL

* The National Institute for Occupational Safety and Health has not established a recommended exposure limit for coal dust.

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned the respirable fraction of coal dust containing less than 5 percent crystalline silica a threshold limit value (TLV) of 2 mg/m(3) as a TWA for a normal 8-hour workday and a 40-hour workweek.

* Rationale for Limits

The ACGIH limit is based on the risk of pneumoconiosis [ACGIH 1991, p. 326].

 

|Evaluation |

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to coal dust can occur through inhalation, ingestion, and eye contact.

* Summary of toxicology

1. Effects on Animals: Coal dust is a tumorigenic agent in experimental animals. Coal dusts were shown to be equivocal tumorigenic agents associated with lymphomas and, at the higher dose, adrenal cortex tumors in rats exposed to either 6.6 or 14.9 mg/m(3) for 6 hours/day intermittently for 86 weeks [NIOSH 1991]. The American Conference of Governmental Industrial Hygienists (ACGIH) considers the toxicity of coal dust with greater than 5 percent silica to be similar to quartz [ACGIH 1991].

2. Effects on Humans: Coal dust causes pneumoconiosis, bronchitis and emphysema in exposed workers. Coal dust causes coal workers' pneumoconiosis (CWP) [Hathaway et al. 1991]. Simple CWP is characterized by development of coal macules, a focal collection of coal dust particles with a little reticulin and collagen accumulation. These lesions may be visible as small opacities (less than 1 cm in diameter) on X-rays [Hathaway et al. 1991]. Complicated CWP is characterized by lesions consisting of a mass of rubbery well defined black tissue that is often adherent to the chest wall. This is associated with decrements in ventilatory capacity, low diffusing capacity, abnormalities of gas exchange, low arterial oxygen tension, pulmonary hypertension, and premature death. The disease may progress after the cessation of exposure. In X-ray examinations, opacities greater than 1 cm in diameter may be observed [Hathaway et al. 1991]. Coal dust is also recognized as a cause of chronic bronchitis [Rom 1992]. Exposure to coal dust is associated with an increased risk of focal emphysema, which is usually associated with the presence of pneumoconiosis and centrilobular emphysema, which can occur in the absence of pneumoconiosis [Rom 1992]. Workers with rheumatoid arthritis and the simple coalworkers' pneumoconiosis may also have Caplan's Syndrome which involves rapidly developing lung damage [Genium 1990]. ACGIH considers the toxicity of coal dust with greater than 5 percent silica to be similar to quartz [ACGIH 1991].

* Signs and symptoms of exposure

1. Acute exposure: Symptoms of inhalation of excessive amounts of coal dust include coughing, wheezing, and shortness of breath [Genium 1990].

2. Chronic exposure: Chronic exposure to coal dust may result in symptoms of bronchitis and emphysema [Rom 1992].

EMERGENCY MEDICAL PROCEDURES

* Emergency medical procedures: [NIOSH to supply]

Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve coal dust and lead to worker exposures to this substance:

• The mining and transportation of coal

• Use of coal during operations involving grinding, crushing, or pulverizing

Methods that are effective in controlling worker exposures to coal dust, depending on the feasibility of implementation, are as follows:

• Process enclosure

• Local exhaust ventilation

• General dilution ventilation

• Personal protective equipment

Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].

Good sources of information about control methods are as follows:

1. ACGIH [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

MEDICAL SURVEILLANCE

OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to coal dust are required to implement medical surveillance procedures.

* Medical Screening

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to coal dust, a licensed health care professional should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the respiratory system. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American

Thoracic Society.

A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to coal dust at or below the prescribed exposure limit. The health care professional should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the respiratory system.

* Periodic medical evaluations

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to coal dust exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of coal dust on the respiratory system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

* Termination medical evaluations

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population. Because occupational exposure to coal dust may cause diseases with prolonged latent periods, the need for medical surveillance may extend well beyond the termination of employment.

* Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. No biological monitoring test acceptable for routine use has yet been developed for coal dust.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to the airborne respirable fraction of coal dust containing less than 5 percent silica is made using a tared low ash polyvinyl chloride (LAPVC) filter (5 microns), preceded by a 10 mm cyclone. Samples are collected at a maximum flow rate of 1.7 liters/minute until a maximum collection volume of 816 liters is reached. Analysis is conducted by gravimetric analysis (weighing). This method is described in the OSHA Computerized Information System [OSHA 1994] and is fully validated. NIOSH has also published a similar method (Method No. 0600) for respirable sampling of nuisance dusts [NIOSH 1994b].

|Controls |

PERSONAL HYGIENE PROCEDURES

If coal dust contacts the skin, workers should wash the affected areas with soap and water.

Clothing contaminated with coal dust should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of coal dust.

A worker who handles coal dust should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, using toilet facilities, applying cosmetics, or taking medication.

Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where coal dust handled, processed, or stored.

STORAGE

In the event coal dust requires storage, it should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of coal dust should be protected from physical damage and ignition sources and should be stored separately from oxidizing agents.

SPILLS AND LEAKS

In the event of a spill or leak involving coal dust, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Do not touch the spilled material.

2. Notify safety personnel.

3. Remove all sources of heat and ignition.

4. Use non-sparking tools.

5. Water spray may be used cautiously to wet down the coal dust to reduce raising dust.

6. Collect the spilled material and place the material into a covered metal container for disposal or reclamation.

SPECIAL REQUIREMENTS

U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Coal dust is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.

* Reportable quantity requirements for hazardous releases

A hazardous substance release is defined by EPA as any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of contaminated containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required to notify the proper Federal, State, and local authorities [40 CFR 355.40].

Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of coal dust; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of coal dust emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although coal dust is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S.

Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of coal dust exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

PERSONAL PROTECTIVE EQUIPMENT

Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with coal dust. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to coal dust. There are no published reports on the resistance of various materials to permeation by coal dust.

To evaluate the use of PPE materials with coal dust, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.

Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve coal dust.

Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, or other toxic substance may be splashed into the eyes.

In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.

Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.

Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.

|References |

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ATS [1987]. Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 136:1285-1296.

CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

DOT [1993]. 1993 Emergency response guidebook, guide 32. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Genium [1990]. Material safety data sheet No. 491. Schenectady, NY: Genium Publishing Corporation.

Hathaway GJ, Proctor NH, Hughes JP, and Fischman ML [1991]. Proctor and Hughes' chemical hazards of the workplace. 3rd ed. New York, NY: Van Nostrand Reinhold.

Mickelsen RL, Hall RC [1987]. A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.

Mickelsen RL, Hall RC, Chern RT, Myers JR [1991]. Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public

Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-116.

NIOSH [1987b]. NIOSH respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108.

NIOSH [1991]. Registry of toxic effects of chemical substances: Coal, ground bituminous. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

NIOSH [1994a]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-116.

NIOSH [1994b]. NIOSH manual of analytical methods. 4th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113.

NIOSH [1995]. Registry of toxic effects of chemical substances: Coal, ground bituminous. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

OSHA [1994]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

Rom WN [1992]. Environmental and occupational medicine. 2nd ed. Boston, MA: Little, Brown and Company.

Sittig M [1991]. Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.

USC. United States code. Washington. DC: U.S. Government Printing Office.

|Introduction | Recognition | Evaluation | Controls | References |

Black Lung Disease - Topic Overview

What is black lung disease?

Black lung disease is a common name for any lung disease developing from inhaling coal dust. This name comes from the fact that those with the disease have lungs that look black instead of pink. Medically, it is a type of pneumoconiosis called coal workers' pneumoconiosis. There are two forms: simple, which is known as coal workers' pneumoconiosis (CWP); and complicated, which is known as progressive massive fibrosis (PMF).

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[pic]The inhalation and accumulation of coal dust into the lungs increases the risk of developing emphysema and chronic bronchitis. Coal dust can also increase the risk of developing chronic obstructive pulmonary disease (COPD).

What causes coal workers' pneumoconiosis?

The inhalation and accumulation of coal dust causes coal workers' pneumoconiosis (CWP). This stems from working in a coal mine, coal trimming (loading and stowing coal for storage), mining or milling graphite, and manufacturing carbon electrodes (used in certain types of large furnaces) and carbon black (a compound used in many items, such as tires and other rubber goods). Because CWP is a reaction to accumulated dust in the lungs, it may appear and get worse during your exposure to the dust or after your exposure has ceased.

The severity of CWP depends on the type of coal mine and the dust conditions in the work environment.

Is CWP the same thing as chronic obstructive pulmonary disease (COPD)?

No. Although CWP may share many of the symptoms of emphysema and/or chronic bronchitis (which are also known as COPD), CWP is not COPD and is not treated like COPD.

What is the course of CWP?

CWP starts with the inhalation and accumulation of coal dust in the lungs. For many, there are no symptoms or noticeable effect on quality of life. There may be a cough and sputum (mucus) from inhalation of coal dust, but this may be more a matter of dust-induced bronchitis. As CWP progresses and becomes PMF, a cough and shortness of breath develop, along with sputum and moderate to severe airway obstruction. Quality of life decreases. Complications of CWP include cor pulmonale.

Smoking does not increase the prevalence of CWP, nor does it affect the development of CWP. But it may add to lung damage and contribute to the development of COPD. Coal workers who smoke are at much greater risk of developing COPD than nonsmoking coal workers.

How does CWP affect my lungs?

When coal dust accumulates in the lungs, a coal macule may form. A coal macule is a combination of coal dust and macrophages. As the disease progresses, macules can develop into a coal nodule, an abnormality of the lung tissue. In time, a type of emphysema and fibrosis may develop.

Lung nodules wider than 1 cm (0.4 in.) have been accepted as evidence of progressive massive fibrosis (PMF), although some organizations say a minimum width of 2 cm (0.8 in.) is necessary. Nodules may grow to a large size and hinder or stop the airflow in the lungs' airways.

How is CWP diagnosed?

CWP is diagnosed through an occupational history and chest X-rays. Lung function tests may be used to determine how badly the lungs are damaged.

Occupational history is very important to the diagnosis of CWP-if a person has not been exposed to coal dust, he or she cannot have CWP. The occupational history should include not only recent and past full-time employment, but also summer jobs, student jobs, military history, and short-term jobs.

The diagnosis of CWP has legal public health implications, since some states require that all cases be reported.

Can I prevent CWP?

The only way to prevent CWP is to not inhale coal dust. This could mean quitting your job.

How do I treat CWP?

There is no proven effective treatment for CWP, although complications can be treated.

There are several U.S. laws regarding CWP and its treatment, and the government may help pay for treatment. But to be eligible, you must be totally and permanently disabled by this disease. Most miners are not eligible for federal black lung benefits. For information on organizations dealing with mining and black lung disease, see the Other Places to Get Help section of this topic.

Coalworker's pneumoconiosis

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|Coalworker's pneumoconiosis |

|Classification and external resources |

|[pic] |

|Coal |

|ICD-10 |J60 |

|ICD-9 |500 |

|DiseasesDB |10145 |

|MedlinePlus |000130 |

|eMedicine |med/398 |

|MeSH |D011009 |

Coal workers' pneumoconiosis (CWP), colloquially referred to as black lung disease, is caused by long exposure to coal dust. 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 worse cases, necrosis.

Coal workers' pneumoconiosis, severe state, develops after the initial, milder form of the disease known as anthracosis (anthrac - coal, carbon). This is often asymptomatic and is found to at least some extent in all urban dwellers[1] due to air pollution. Prolonged exposure to large amounts of coal dust can result in more serious forms of the disease, simple coal workers' pneumoconiosis and complicated coal workers' pneumoconiosis (or Progressive massive fibrosis, or PMF). More commonly, workers exposed to coal dust develop industrial bronchitis[2], clinically defined as chronic bronchitis (i.e. productive cough for 3 months per year for at least 2 years) associated with workplace dust exposure. The incidence of industrial bronchitis varies with age, job, exposure, and smoking. In nonsmokers (who are less prone to develop bronchitis than smokers), studies of coal miners have shown a 16%[3] to 17%[4] incidence of industrial bronchitis.

|Contents |

| [hide]  |

|1 History and prevention efforts |

|2 21st century |

|3 Research |

|4 Pathogenesis |

|5 Appearance |

|6 Diagnosis |

|7 See also |

|8 References |

|9 External links |

[edit] History and prevention efforts

Black lung is actually a set of conditions and until the 1950s its dangers were not well understood. The prevailing view was that silicosis was very serious but it was solely caused by silica and not coal dust. The miners' union, the United Mine Workers of America, realized that rapid mechanization meant drills that produced much more dust, but under John L. Lewis they decided not to raise the black lung issue because it might impede the mechanization that was producing higher productivity and higher wages. Union priorities were to maintain the viability of the long-fought-for welfare and retirement fund, and that required higher outputs of coal. After the death of Lewis, the union dropped its opposition to calling black lung a disease, and realized the financial advantages of a fund for its disabled members. In the Coal Mine Health and Safety Act of 1969, the U.S. Congress set up standards to reduce dust and created the Black Lung Disability Trust. The mining companies agreed to a clause, by which a ten-year history of mine work, coupled with X-ray or autopsy evidence of severe lung damage, guaranteed compensation. Equally important was a "rate retention" clause that allowed workers with progressive lung disease to transfer to jobs with lower exposure without loss of pay, seniority, or benefits. Financed by a federal tax on coal, the Trust by 2009 had distributed over $44 billion in benefits to miners disabled by the disease and their widows. A miner who spent 25 years in underground coal mines has a 5-10% risk of contracting the disease.[5]

[edit] 21st century

There are currently about 130,000 underground coal miners actively working in the United States. The mining and production of coal is a major part of the economy in several developed countries. In the past ten years, over 10,000 American miners have died from CWP. Although this disease is preventable, many miners are still developing advanced and severe cases.

In 1966 Doctors I.E. Buff, Hawey Wells, and Donald Rasmussen started studies on effects of working in coal mines. They soon had the first miner who would allow experimental tests to find out how his lungs were affected, Earl Stafford, then a 48 year old miner who had been forced to leave the mines due to his lung condition.

In the following years, Doctors Buff, Wells, and Rasmussen, and Mr. Stafford, continued to lobby for action to provide help and develop preventive measures to eliminate this disease. Mr. Stafford along with a group of disabled miners lobbied congress. Mr. Stafford later testified before the U.S. congress about the conditions to which miners were subjected. He later lead this band of miners to conduct local strikes and work stoppages to bring attention to miners suffering from Black Lung, its effects and possible preventative measures. In addition he lectured at several universities, including Berea College in 1974.

By January 1986, Mr. Stafford was considered a lay expert on the cause and effect of the disease.[citation needed] Less than 20 years after being forced to leave the industry he loved, at the age of 68, Earl Stafford passed away quietly as a result of black lung.

In the 40 years since the Federal Coal Mine Health and Safety Act of 1969 became law, the proportion of miners with black lung disease has gone down by about 90%. But the downward trend of this disease in coal miners has not continued. 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.[6] [7]

The National Institute for Occupational Safety and Health (NIOSH), with support of the Mine Safety and Health Administration (MSHA), has started a Mobile Health Screening Program. This Mobile Unit travels to mining regions around the United States. Miners who participate in the Program receive health evaluations once every five years, at no cost to themselves. Chest x-rays can detect the early signs of and changes in CWP, often before the miner is aware of any lung problems. The screening program is only available to current miners.[8]

[edit] Research

Pioneering work to investigate the relationship between respirable dust exposure and coal worker's pneumoconiosis was carried out in Britain by the Institute of Occupational Medicine. This research was known as the Pneumoconiosis Field Research (PFR). The research underpinned the recommendations for more stringent airborne dust standards in British coalmines and the PFR was ultimately used as the basis for many national dust standards around the world.

Following observations on industry workers in Lucknow (India), experiments on rats found that jaggery (a traditional sugar) had a preventive action against the harmful effects of coal dust[9].

[edit] Pathogenesis

Coal dust is not as fibrogenic as is silica dust[10]. Coal dust that enters the lungs can neither be destroyed nor removed by the body. The particles are engulfed by resident alveolar or interstitial macrophages and remain in the lungs, residing in the connective tissue or pulmonary lymph nodes. Coal dust provides a sufficient stimulus for the macrophage to release various products, including enzymes, cytokines, oxygen radicals, and fibroblast growth factors[11], which are important in the inflammation and fibrosis of CWP. Aggregations of carbon-laden macrophages can be visualised under a microscope as granular, black areas. In serious cases, the lung may grossly appear black. These aggregations can cause inflammation and fibrosis, as well as the formation of nodular lesions within the lungs. The centres of dense lesions may become necrotic due to ischemia, leading to large cavities within the lung.

[edit] Appearance

Simple CWP is marked by the presence of 1-2mm nodular aggregations of anthracotic macrophages, supported by a fine collagen network, within the lungs. Those 1-2mm in diameter are known as coal macules, with larger aggregations known as coal nodules. These structures occur most frequently around the initial site of coal dust accumulation - the upper regions of the lungs around respiratory bronchioles[1]. The coal macule is the basic pathological feature of CWP, and has a surrounding area of enlargement of the airspace, known as focal emphysema[12].

Continued exposure to coal dust following the development of simple CWP may progress to complicated CWP with progressive massive fibrosis (PMF), wherein large masses of dense fibrosis develop, usually in the upper lung zones, measuring greater than 1 cm in diameter, with accompanying decreased lung function. These cases generally require a number of years to develop. Grossly, the lung itself appears blackened. Pathologically, these consist of fibrosis with haphazardly-arranged collagen and many pigment-laden macrophages and abundant free pigment. Radiographically, CWP can appear strikingly similar to silicosis. In simple CWP, small rounded nodules (see ILO Classification) predominate, tending to first appear in the upper lung zones. The nodules may coalesce and form large opacities (>1 cm), characterizing complicated CWP, or PMF.

[edit] Diagnosis

There are three basic criteria for the diagnosis of CWP:

1. Chest radiography consistent with CWP

2. An exposure history to coal dust (typically underground coal mining) of sufficient amount and latency

3. Exclusion of alternative diagnoses (mimics of CWP)

Symptoms and pulmonary function testing relate to the degree of respiratory impairment, but are not part of the diagnostic criteria. As noted above, the chest X-ray appearance for CWP can be virtually indistinguishable from silicosis. Chest CT, particularly high-resolution scanning (HRCT), are more sensitive than plain X-ray for detecting the small round opacities.

Dust explosion

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A dust explosion is the fast combustion of dust particles suspended in the air in an enclosed location. Coal dust explosions are a frequent hazard in underground coal mines, but dust explosions can occur where any powdered combustible material is present in an enclosed atmosphere.

|Contents |

| [hide]  |

|1 Conditions for dust explosion |

|1.1 Sources of dust |

|1.2 Sources of ignition |

|1.3 Concentration |

|2 Mechanism of dust explosions |

|3 Terminology |

|4 Protection and Mitigation from dust explosions |

|5 See also |

|6 References |

|7 External links |

[edit] Conditions for dust explosion

There are four necessary conditions for a dust explosion or deflagration:

1. A combustible dust

2. The dust is suspended in the air at a high concentration

3. There is an oxidant (typically atmospheric oxygen)

4. There is an ignition source[1]

[edit] Sources of dust

[pic]

[pic]

1878 Stereograph rendering of the Great Mill Disaster.

Many materials which are commonly known to oxidise can generate a dust explosion, such as coal, sawdust, and magnesium. However, many otherwise mundane materials can also lead to a dangerous dust cloud such as grain, flour, sugar, powdered milk and pollen. Many powdered metals (such as aluminium and titanium) can form explosive suspensions in air.[2]

The dust can arise from activities such as transporting grain and indeed grain silos do regularly have explosions. Mining of coal leads to coal dust and flour mills likewise have large amounts of flour dust as a result of milling. A gigantic explosion of flour dust destroyed a mill in Minnesota on May 2, 1878, killing 18 workers at the Washburn A Mill. A similar problem occurs in saw mills and other places dedicated to carpentry. Thermobaric weapons, depending upon their fuel, are also a potential and intentional source of dust.

To support combustion, the dust must also consist of very small particles with a high surface area to volume ratio, thereby making the collective or combined surface area of all the particles very large in comparison to a dust of larger particles. Dust is defined as powders with particles less than about 500 micrometres in diameter, but finer dust will present a much greater hazard than coarse particles by virtue of the larger total surface area of all the particles.

[edit] Sources of ignition

There are many sources of ignition and a naked flame need not be the only one: over one half of the dust explosions in Germany in 2005 were from non-flame sources.[3] Common sources of ignition include

• electrostatic discharge

• friction

• arcing from machinery or other equipment;

• hot surfaces, including e.g. overheated bearings

• fire

However it is often difficult to determine the exact source of ignition post-explosion. When a source cannot be found, it will often be cited as static electricity. Static charges can occur by friction at the surfaces of particles as they move against one another, and build up to levels leading to a sudden discharge to earth.

[edit] Concentration

Below a certain value, the lower explosive limit (LEL),[3] there is simply insufficient dust to support the combustion at the rate required for an explosion. A figure 20% lower than the LEL is considered safe. Similarly, if the fuel/air ratio increases above the upper explosive limit there is insufficient oxidant to permit combustion to continue at the necessary rate.

[edit] Mechanism of dust explosions

Dusts have a very large surface area compared to their mass. Since burning can only occur at the surface of a solid or liquid, where it can react with oxygen, this causes dusts to be much more flammable than bulk materials. For example, a 1 kg sphere of a material with a density of 1g/cm3 would be about 27 cm across and have a surface area of 0.3 m2. However, if it was broken up into spherical dust particles 50µm in diameter (about the size of flour particles) it would have a surface area of 1600 m² This greatly increased surface area allows the material to burn much faster, and the extremely small mass of each particle allows it to catch on fire with much less energy than the bulk material, as there is no heat loss to conduction within the material. When this mixture of fuel and air is ignited, especially in a confined space such as a warehouse or silo, a significant increase in pressure is created, often more than sufficient to demolish the structure. Even materials that are traditionally thought of as nonflammable, such as aluminum, or slow burning, such as wood, can produce a powerful explosion when finely divided, and can be ignited by even a small spark.

[edit] Terminology

Dust explosions may be classified as being either primary or secondary in nature. Primary dust explosions occur inside process plant or similar enclosures and are generally controlled by pressure relief through purpose-built ducting to atmosphere. Secondary dust explosions are the result of dust accumulation inside the factory being disturbed and ignited by the primary explosion, resulting in a much more dangerous uncontrolled explosion inside the workplace. Historically, fatalities from dust explosions have largely been the result of secondary dust explosions.

[edit] Protection and Mitigation from dust explosions

[pic]

Mount Mulligan mine disaster in Australia 1921. These cable drums were blown 50 feet (15 m) from their foundations following a coal dust explosion.

Much research has been carried out in Europe and elsewhere to understand how to control these dangers, but explosions still occur. The alternatives for making processes and plants safer depend on the industry. In the coal mining industry, a methane explosion can initiate a coal dust explosion, which can then engulf an entire pit working. Stone dust is spread along mine roadways, or suspended from trays in the roof, so as to dilute the coal dust raised ahead of the combustion zone by the shock wave, to the point where it cannot burn. Mines may also be sprayed with water to inhibit ignition. Some industries exclude air from dust-raising processes, known as "inerting". Typically this uses nitrogen, carbon dioxide or argon, which are incombustible gases and so inhibit combustion. The same method is also used in large storage tanks where inflammable vapours can accumulate. Usage of oxygen-free gases however brings a risk of asphyxiation of the workers.

Good housekeeping practices, namely eliminating the build-up of deposits of combustible dust that may be disturbed and lead to a secondary explosion, also help mitigating the problem.

Best engineering control measures which can be found in the National Fire Protection Association (NFPA) Combustible Dust Standards include:

• Oxidant Concentration Reduction

• Deflagration venting

• Deflagration pressure containment

• Deflagration suppression

• Deflagration venting through a dust retention and flame-arresting device

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