Pub Health 4310 Health Hazards in Industry

Pub Health 4310Health Hazards in Industry John Flores Lecture 22 Minerals

Lecture 22:Minerals • Chapters 25-32 • Minerals • Quarrying • Mining • Smelting • Asbestos Products • Asphalt Products • Abrasive Products • Glass Products • Ceramic Products PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Introduction: • The term “quarrying” refers to the open pit removal of a wide range of mineral rock • Can be removed in bulk by drilling, blasting, and then transferring the rubble using earth moving equipment to a crushing facility for sizing and packaging • Ex: traprock, crushed stone, kaolin clay, limestone, and mica • Can also be removed dimensionally in slabs or block for architectural or construction purposes • Ex: slate, marble, and granite • All minerals present dust exposure while being quarried • The dust can also contain a significant amount of quartz depending on the quarried mineral and its deposit bed • The presence of quartz is the chief health hazard among quarrying operations leading to silicosis • One of the most hazardous operations is rock drilling which creates significant dust exposures and it is done in all quarrying operations whether bulk or dimensional PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Rock Drilling • Rock drilling is done with air-powered percussion drills that deliver power to the drill bit by a combination of rotation, impact, and thrust • Drill operation: • To cut deep holes, steel rods are used to connect the power conversion unit (drifter) to the drill bit • Compressed air causes the drill mechanism to rotate while rapid impact blows are driven by a piston onto the striker bar and transmitted through the “string” of drill steels to the bit • A separate air motor using a chain drive to the drifter or by hand in the case of hand held drills like jack hammers, provides the thrust • Cuttings are blown from the hole by blow air supplied through the center of the drill steel and bit • Sinker drills (jackhammers) • Are only designed to drill holes 0.5 to 2.5 inches in diameter and are used mostly for secondary drilling to break up boulders, general excavation, and any other jobs in which require only small diameter holes • Jackhammers can break up about 20 cubic inches of rock per minute PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Rock Drilling (cont.) • Track drills • Consist of larger drills mounted on self propelled crawler carriers that can travel over very rugged terrain • Most blast hole drilling operations are done with this type of drill • Power is supplied by a flexible hose from an air compressor that is towed behind the drill • Most track drill are designed to cut holes about 4.5 inches in diameter, but larger equipment is available that can drill at 6 inch diameter holes • These drills can pulverize 50-250 cubic inches of rock per minute • After drilling, ammonium nitrate-fuel oil (an-fo) is added to the hole in preparation for blasting • Unlike underground mining, the an-fo does not present a significant exposure in open pit operations • Dust control • The most common dust control technique used with track drills is water mist injection • Water alone or with a wetting agent such as a detergent is introduced as a mist into the blow air • The dust collected by the water mist forms small pellets that drop out at the edge of the hole • Too much water will create a “mud collar” or a bridge between the steel and the sides of the hole, whereas not enough water will not control the dust PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Rock Drilling (cont.) • Dust control (cont.) • Water mist injection systems (cont.) • Advantages of a water mist injection systems • This system has no parts that are exposed to the dust abrasion so its efficiency is constant throughout the life of the system and is often more economical than other methods • Disadvantages of water mist injection systems • This system needs a water supply, the drill rate is slower, and antifreeze is needed in freezing weather • Lubricants are displaced by the water causing increased wear and tear, • The wet drill slurry can harden and form “collars” around the drill bit which must be broken before the bit can be removed • All of these disadvantages can result in higher operating costs for extra rigs and operators • Mechanical (dry) collectors • Air ejectors or mechanical blowers have been developed and use either a reverse airflow through the drill or an exhaust hood around the drill steel at the hole collar • Systems are also available that use small air-cleaning packages for small drills and large track drills • Advantages of Mechanical (dry) collectors • Require less attention than wet methods • Penetration rate and bit life are better • Air alone is more effective in cleaning and stemming blast holes PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Rock Drilling (cont.) • Dust control (cont.) • Mechanical (dry) collectors (cont.) • Disadvantages of mechanical (dry) collectors • Mechanical problems of freezing and transport of water are eliminated • The installation costs are much higher than wet methods • Internal parts are subject to wear and tear from abrasion, leading to decreased efficiency and higher maintenance costs • Noise and vibration • In 1917, Alice Hamilton identified Vibration White Finger (VWF) in stonecutters using pneumatic drills in limestone quarries in Indiana, in 1978 Burgess visited the same quarries and found 24 of 30 stoner cutters with VWF • Great advances have been made in the design of air compressors and drills to reduce worker exposures to noise and vibration • Still noise may exceed 90 dBA and VWF is still possible in this industry, so good IH practice is necessary to eliminate chronic injury PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Bulk Mineral Quarrying • Open quarries resemble small version of open pit metal and coal mines • Often heavy burden (unneeded dirt or rock) as deep as 100-ft must be moved to establish quarry face heights of 30 to 200-ft • Loose gravel can be removed with earth moving equipment associated with heavy construction • Health and safety issues with these operations include noise, vibration, heat, and dusts (quartz silica??) • Bulk materials are either processed directly at the quarries as in the case of crushed stone for roadways or to a mill for more crushing and subsequent milling • The mill • The mill receives the quarried rock and processes it through a primary and secondary crusher • The crushed rock is then sized by passing through screens of various sizes, any oversized rock is transported back the the crusher • The principle problem with this type of plant is dust control at the crusher, screens, storage hoppers, and at transport points between the buckets to the conveyors • Initial attempts at ventilation control required enclosing hoods with face velocities at open areas in the range of 150-200 fpm PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Bulk Mineral Quarrying (cont.) • The mill (cont.) • A subsequent design approach by the ACGIH vent manual requires face velocities at open areas in the range of 350-500 cfm/ft of conveyor belt width, 0.5 cfm/cubic ft of bin volume, or 50 fpm/square ft of screen area • Many of the installations based on this criteria were not adequate because air induced due to falling rock was not adjusted for • Hazards • Crystalline quartz remains the primary hazard causing chronic injury in this industry PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Dimensional Stone Quarrying • In the early quarrying of dimensional stone, the material was removed by drilling and blasting resulting in much waste • A variety of new techniques were developed to reduce this waste, with some of them creating more serious health hazards • As stated before, the characteristic of the parent rock and the free silica content determine the toxicity of the dust created • In the early 1900’s, core drilling was used to block out an island of rock for subsequent removal • Now, a channel burner is used, which is essentially a large blow torch on a long handle fueled by compressed air and diesel oil • The operator moves the tip of the burner over the rock and the hot flame spalls the rock generating a kerf of a few inches • Channel Burner Noise • The noise generated when the cutting is started and the burner is operating in open air can be as high as 118 -122 dBA • The minimum noise generated is about 114 -116 dBA and occurs when the burner is immersed deeply into the cut PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Dimensional Stone Quarrying (cont.) • New techniques (cont.) • Channel Burner Noise (cont.) • Even with a 20 dBA reduction with muff-type ear protection, the worker is still exposed to over 100 dBA, so OSHA in 1990 recommended the following • Operating with oxygen at lower pressure reduces the noise by 5 dBA – not adequate • Use of automated burners, which allows the worker to operate the burners further away • Use of high pressure water jets to cut the stone is another possible alternative • Channel burner generate a particulate cloud consisting of: • crystalline respirable dust, • a submicrometer rock fume, and • fused micrometer-sized spheres • After the channel cuts have been made, a fluted flat wire saw is used to cut the stone into slabs or blocks • Holes are drilled into the slab or blocks to serve as lifting eyes to remove the finished product from the quarry, if this drilling is done dry, a significant dust exposure can occur PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Dimensional Stone Quarrying (cont.) • Dimensional stone milling • The mill is usually located very close to the quarry • In small shop operations, the quarry stone is cut to shape using a diamond or a small wire saw • These saws can cut using wet methods to control dust exposures • In high production (large) shops quarry stone is cut to shape by • Guillotine for curbstone, which can be vary dusty so requires localized ventilation • Small wire or diamond saws, which can be done using wet methods • Finishing operations in mills includes surfacing with pneumatic tools, small fuel oil-oxygen burners, and polishing tables using various wet abrasives • Sculpting is completed with burners, pneumatic tools, and abrasive blasting • All finishing and sculpting operations, with the exception of polishing, requires local exhaust • Crushing plants • Dimensional stone quarries usually have crushing plants for recovery of scrap • As with bulk quarrying, crushers, transfer points, hoppers, and screening operations require ventilation control • Bagging operations are usually the dustiest, but new technology uses integral exhaust hoods on equipment PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Quarrying • Workplace Evaluation • In evaluating dust exposures in quarries it is extremely important that personal monitoring be conducted • Relationship between fixed monitoring and personal monitoring is often nil • For silica containing dust, which is commonly found in granite and slate quarries, silica dust should be measured for the respirable mass on personal air samples • It is not uncommon for parent rock to contain 30% free silica but the respirable samples only contain 10% free silica PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Introduction • Diverse minerals are mined in both underground, open pit, or surface mines • Mining has a huge array of health hazards including • the dusts of the mineral sought, • the associated rock or substrate, • natural and man made gases and vapors, • and a gamut of physical hazards • It is convenient to class mines as coal, metal, and non-metal • The total number of miners in the 1980’s was about 465,000, with the largest sector in coal mining, employing about 208,000, about 93,000 in non-metal mining, about 57,000 in copper and iron mining, and about another 107,000 serving as support personnel • It would not be a surprise to find the total number of miners today is somewhat the same due to: • Some mining sectors are cyclic, • Some mining areas continue to produce, close down, re-open, • New mines being started, and • Competition outside of the US where many of the environmental laws that US mines must abide, other countries do not. PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Introduction (cont.) • Other than coal, few minerals are mined underground and most of those are of low tonnage as compared to coal • Antimony, lead, and tungsten are almost exclusively mined underground • 62% of molybdenum is mined underground • About 60% of silver is mined from underground • 95% of all metallic ores come from surface mining • 75% of crude non-metallic ores come from surface mining PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Types of Mines • Surface mines may be developed in 3 ways • Area mining • The simplest and most efficient method of mineral removal • The mineral may be just below the surface or 100-200 feet overburden must be removed to reach the target seam, like many of the coal mines in Wyoming • Contour mining • A surface mining technique commonly found in the hills of West Virginia in which a coal seam outcropping is mined by notching or cutting away a portion of the contour as you would when building a road • The exposed coal seam which can be anywhere from 2-12 feet high is removed • Often a large auger is used to follow the seam up to 150 feet into the hillside • Open pit mining • Similar to a large earth moving work, in that blast holes are drilled, the earth is blasted, and the rubble is picked up with large ore movers, and the ore is trucked to a crushing plant • Kennecott Copper Mine is a good example of an open pit mines • Most open pit mines are used to mine copper or gold as the primary ore PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Types of Mines (cont.) • Underground mining • Drift mining • Are used to mine outcroppings on the sides of mountains by following the seam horizontally into the mountain • Slope mining • In this method, a tunnel is dug into the ground slanting downward from the surface to the ore • This method can be used when the ore body is below grade, but at a distance in which it is economical to tunnel an access way to the ore • This method allows direct access by truck or rail into and out of the mine, eliminates the need for an elevator and hoist to access the mine • Shaft mining • A vertical shaft is dug vertically into the ground to the depths of the ore, then a series of tunnels spread out from the shaft to mine the ore • These shafts can be up to a mile in depths as is the case of many metal mines in Colorado • A hoist and mine elevator is needed to enter the mine, and to bring equipment in and out of the mine • Shafts have to be constructed to personnel and equipment entry and exit and a separate shaft to bring ore out of the mine PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Mining Health Issues • In surface mining, the equipment and processes are identical to those found at a very large construction site, exposures include: • roadway dusts, dust from the ore body and the supporting material, • noise, • vibration, and • ergonomic stressors • In underground mining hazards can be classed as naturally occurring or generated by mining activity • Natural hazards include: • Oxygen deficiency, called “black damp” in common mining terms • is a potential hazard in old mine workings when a reducing ore exists or an organic is decomposing and using up the existing oxygen • Radon progeny (daughters) concentrations are found not only in uranium mines but can be found in many hard rock mines areas that are not being adequately ventilated • Extremes temperature and humidity (naturally occurring caves stay at about 57-60 ºF), but for every 100 m of depth into the ground the temperature increases 1 ºC (1.8 ºF) and a lot of water is added for roadway dust suppression • In some mines, like the deep mines of South Africa, air conditioners are installed underground to deliver cool air to the workers PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Mining Health Issues (cont.) • In underground mining hazards (cont.) • Man-made hazards include • Poor lighting, noise, vibration and ergo issues including working postures and repetitive motion • Generation of toxic vapors from the use of ammonium nitrate prills saturated with fuel oil (an-fo) and fired with dynamite caps produces carbon monoxide (whitedamp) and nitrogen dioxide (afterdamp) • Use of diesel fuels to operate machinery produces particulate and gases containing aldehydes, nitrogen dioxide, and carbon monoxide • Scrubbers can be used on diesel to remove exhaust gases and particulate • Use of drills, miners, and other compressed air tools creates serious noise hazards • Hearing loss has always been a chronic problem in the underground mining industry • Silicosis is not a major health issue in coal mining, but hard rock metal miners do have significant exposures • In 1915 the prevalence rate of silicosis was 65.5% • A 1960 study showed the prevalence rate of 3.4% PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Underground Coal Mining • Coal workers pneumoconiosis (CWP), commonly called “black lung,” is a chronic lung disease caused by the inhalation of coal dust • In 1930, England deemed this a compensible disease • A 1963-1965 survey in US coal mines showed CWP in 9.8% of working miners and 18.2% of nonworking miners in the Appalachia Fields • The Federal Mine Health and Safety Act of 1969 and the Federal Mine Safety and Health Amendments Act of 1977 have made the prevention of CWP a major objective • These acts also set a respirable mass coal dust standard of 2 mg/m3 based on the respirable mass sampling with a personal sampler • The acts also provides compensation for miners disabled from CWP and for the survivors of CWP victims • Since the act was passed, nearly half a million miners have received compensation at a total cost in excess of 12 billion dollars • It is estimated that 55% of currently working coal miners have a non-disabling stage of CWP PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Coal Mining Techniques • Conventional Mining • Although the room and pillar setting is being replaced by other techniques it still produces about 10-15% of the underground coal mined in the US • Process steps • In conventional mining the first step is to cut a slot about 6-in high and about 10-ft deep at the base of the seem with a cutter machine • A cutter machine looks like a very large chain saw that is positioned to make only horizontal cuts • A number of holes for ammonium nitrate are drilled into the coal face with a track mounted drill • The area is cleared, the charge is detonated, and about 50 tons of coal are pulverized and drop to the mine floor • A loading machine is then moved in place to start loading the coal for transport onto a conveyor belt • Once the rubble is cleared from the floor a roof bolter moves in to bolt the roof to prevent rock falls • Once the area is safe for entry, rock dusting is done to keep dusts down, and subsequently improve visibility PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Coal Mining Techniques (cont.) • Continuous Mining • The continuous miner (drum miner) does everything conventional mining does, but it is all done with one piece of equipment • Continuous mining accounts for 2/3 of all coal mined in the US • The cutting head (drum) is a rotating cylinder about 2 ft in diameter and 2-10 ft long, covered with sharp picks • The continuous miner head starts at the top of the coal seam and makes a downward sweep cutting out a swath of coal which is then gathered by sweeping arms and directed to a conveyor mounted at the other end of the miner, this continues until the room is mined, then the miner backs out and moves to another room • Once the continuous miner moves out the roof bolter and rock duster move in to do their work PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Coal Mining Techniques (cont.) • Long Wall Mining • As of 1995, this method accounted for approximately 10-12% of US underground coal production, today it probably accounts for more • It is extremely efficient and can be used if the seam to be mined has an acceptable geometry • The long wall shear requires quite a bit of set up time • A continuous miner is used to cut 2 roadways 800 ft apart on each side of the block to be mined and at a distance 1-2 miles deep (shorter distances may be warranted) • The long wall equipment consists of hydraulic roof support shields, face conveyor, and a cutting machine with 2 counter rotating shearers • The miner is set up to travel and cut the the 800 ft face • As the coal is cut, it drops onto the conveyor to be transported to the main haulage conveyor • After each cut is completed, the roof supports move forward towards the face for the next cut • The previously supported roof collapses behind the supports • The long wall miner requires at least 2 operators • Dust control is very difficult to achieve possibly requiring respiratory protection during operation PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Coal Mining Techniques (cont.) • Support Activities • Roof falls causing deaths were a common practice at one time • The first solution was to shore up the roof using wooden timbers • This inefficient and dangerous practice has been replaced by roof bolting • Roof bolting • After the room is mined the roof bolter enters under the existing bolted roof and begins drilling vertical holes 4 ft on center from the last set of roof bolts, and drilled 4-6 ft deep • Roof bolts that are 4-6 ft long are inserted into the holes and held in place by expansion shells, similar to a molly bolt, or with a polyester resin • Once positioned the roof bolts bond with the rock strata and support the roof as a continuous member • Since the rock overburden may contain significant concentrations of quartz, roof bolting must be either done wet or it must be equipped with an exhaust to limit the respirable exposures • Rock dusting • After the roof is bolted and becomes stabilized, rock dusting is done to prevent coal dusts from being suspended in the event of a methane flash • The rock dust is made from limestone which is inert, when it covers the coal dust it mixes with it so that if it is re-suspended it will not sustain an explosion PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Coal Mining Techniques (cont.) • Support Activities (cont,) • Rock dusting (cont.) • Rock dusting is needed because when coal is cut it releases methane (firedamp) from the coal face, if methane reaches a range of 5-15% it can become explosive • If the mine is not dusted and a methane explosion occurs, then the coal dust will be suspended and a secondary lethal explosion of the mine will occur and result in a tremendous amount of CO • Methane control is done with • Ventilation to keep concentrations below their explosive limits, • By removing ignition sources from the mine, and • installing sensors on electrically powered equipment so that it will auto shut down if concentrations of methane exceed a certain limit PH 4310 - Health Hazards in Industry, Lct 22

Minerals - Mining • Dust Control • The dust the chief hazard in mining whether from toxic mineral dusts or from the host rock must be controlled • Using wet methods with equipment and to wet down loose rock has proved effective • Wetting agents are used to improve the effectiveness of existing wet methods • The principle dust control method continues to be ventilation since it not only removes dusts but it dilutes hazard gases • Brattice or line cloth, a heavy plastic curtain material is used in mines to define the air flow path of the ventilation to keep the miner upstream from the exhaust and dust generation • Brattice can be set up in so that it blows air across the working face where a continuous miner would be working • It can also be set up so it is exhausting from the face removing any dust or toxic gases • For long wall mining, dust control is much more difficult to control with ventilation, so the use of wet methods is much more important PH 4310 - Health Hazards in Industry, Lct 22

Pub Health 4310 Health Hazards in Industry