Pub Health 4310 Health Hazards in Industry

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Pub Health 4310Health Hazards in Industry

• John Flores
• Lecture 26
• Mills and Textiles

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Lecture 26Mills and Textiles

• Chapters 33-34
• Mills and Textiles
• Pulp and Paper
• Textile Fibers Cotton and Rayon

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Mills and Textiles Pulp and Paper

• Introduction
• The major producers of pulp are the US, Canada,
  Japan, Sweden, and Finland
• Although wood pulp was originally only used for
  paper it is now used in a variety of chemical
  processes
• The US workforce in pulp, paper, and paperboard
  is about 160,000 strong
• Pulp production in dominated by
• the sulfate (Kraft) process (60),
• the sulfite process (10),
• and 40 of other techniques including the ground
  wood processing
• Discussion will be based on the sulfate and
  sulfite processes as they make up about 70 of
  the industry and represent the bulk of the
  occupation health challenges
• Although only a few comprehensive studies have
  been done within this profession it appears that
  paper dust and working in pulp and paper has an
  impact on lung capacity and that it is possible
  that this industry may cause restrictive or
  obstructive lung disease

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Mills and Textiles Pulp and Paper

• Chemical Pulping
• Pulp can be produced by mechanical and chemical
  processes
• The chemical process produces more than 70 of
  the pulp used today
• Exposures in chemical pulping are much more
  serious than those of the mechanical pulping, so
  we will discuss chemical pulping
• The sulfate (Kraft) process
• Chipped wood is digested with steam in tanks
  using a solution of sodium sulfide and sodium
  hydroxide (white liquor)
• The digestion builds gases, so must be
  periodically vented off
• When digestion is complete, the load is dumped to
  the blow tank and any gases will vent from the
  pulp and digestion liquid
• The spent cooking liquid (black liquor) is
  drained off to the evaporators, and the pulp is
  washed, screened, and bleached
• The black liquor is processed through
  multiple-effect evaporators to concentrate
  chemicals
• Salt cake (sodium sulfate) and the recovered
  chemicals are sprayed into a recovery furnace
  where water is removed, the liquor is burned, and
  chemicals are recovered
• Recovered chemicals are dissolved in a smelt
  tank, quicklime is added to convert the sodium
  carbonate to sodium hydroxide and leave calcium
  carbonate
• The calcium carbonate is converted to calcium
  oxide in the lime kiln, then slaked with water to
  produce calcium hydroxide which is used in the
  caustic tank (part of process to produce white
  liquor)

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Mills and Textiles Pulp and Paper

• Chemical Pulping (cont.)
• Soda pulp process
• Is the original chemical pulp process, of which
  the Kraft process is an advance of this
• Similar to the Kraft (sulfate) process except
  that sodium carbonate is the chemical used in the
  furnace to make sodium hydroxide
• Unlike the Kraft process, only sodium hydroxide
  cooking liquor is used in the digester
• Sulfite process
• This process is often called the acid sulfite
  process because it uses high-acid cooking liquor
  and requires a substantial chemical plant and
  recovery process for the sulfur dioxide released
• The digester liquor is an aqueous solution of
  sulfurous acid mixed with lime or another base to
  form bisulfites
• Sulfur dioxide is obtained either as a compressed
  gas, from the burning of sulfur, or from the
  roasting of pyrite ores
• The relief gases from the digester contain high
  concentrations of sulfur dioxide, which must be
  recovered for air quality reasons
• The sulfur dioxide is processed using a
  combination of separators and coolers

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Mills and Textiles Pulp and Paper

• Paper Production
• The paper making process usually occurs at a site
  adjacent to the pulp mill
• The process starts with bleaching of the pulp
• Pulp bleaching is done by
• Mixing the pulp with chlorine to remove colored
  degradation products
• Extracting it and mixing it with sodium
  hydroxide, then exposing it to calcium or sodium
  hypochlorite to remove any remaining lignin, and
  a chlorine dioxide final treatment to brighten
  the pulp
• Exposures from the pulp bleaching process include
  chloride hydrates which form when gaseous
  chlorine mixes in the vat and seeps to the
  surface releasing chlorine byproducts
• Generally the chlorine is well controlled with
  local exhaust ventilation
• After the pulp is bleached, it goes through a
  series of beating and refining steps, additives
  are blended with the pulp which is determined by
  paper end use
• Chemicals that make up the additives are
  extensive but fall into 7 major categories
• Filler pigments
• Lubricants, plasticizers, and flow modifiers
• Humectants and viscosity modifiers
• Barrier coatings
• Coating pigments
• Sizes
• Foam Controls

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Mills and Textiles Pulp and Paper

• Paper Production (cont.)
• The paper making process (cont.)
• The pulp consistency is adjusted by adding water,
  this pulp slurry is then pumped to a wire sieve
  where some of the water is drained away
• The pulp leaves the sieve and processes through a
  press to increase solids content
• A heated cylinder is then used on the pulp to
  reduce the water content to 5-8
• The paper may be coated with clay, mica, talc,
  casein, soda ash, dyes, plastics, gums,
  varnishes, linseed oil, and organic solvents
• Exposures
• Principle exposures occur during operations in
  which acrlolein and other aldehydes are formed
  from the oxidation of linseed oil and solvent
  vapors from coating and drying operations

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Mills and Textiles Pulp and Paper

• Exposure Profile
• The principle exposures to operators in the pulp
  and paper industry include
• Raw wood preparation exposes employees to
• Wood volatiles
• Wood dusts
• Spores and Fungi
• Sulfate (Kraft) and soda process digester
  preparation
• Lime
• During Kraft pulping, opening the digester and
  dumping the product releases the following gases
• Hydrogen sulfide,
• Methyl mercaptan
• Dimethyl sulfide
• Dimethyl disulfide,
• Sulfur dioxide
• From operation of the recovery furnaces, effluent
  contains
• Organic mercaptans and sulfides
• Hydrogen sulfide, and
• Sulfur dioxide

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Mills and Textiles Pulp and Paper

• Exposure Profile (cont.)
• The principle exposures to operators in the pulp
  and paper industry (cont.)
• Bleaching operations exposures include
• Chlorine
• Chlorine dioxide
• Boron compounds
• Neoabietic acids
• Paper rolling, sizing, dying, drying, glazing,
  coating exposures include
• Urea and melamine formaldehyde
• Paper dust
• Coating and pigment dusts
• Maintenance
• General plant exposures

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Mills and Textiles Pulp and Paper

• Controls
• Worker exposure controls
• Lime exposures can be excessive in both the
  sulfate (Kraft) and soda processes so handling
  practices to limit dust and inhalation exposures
  may be necessary
• Digestion pits should be ventilated to remove and
  control sulfur dioxide, hydrogen sulfide, and
  mercaptans
• Serious exposures to sulfur dioxide can be
  released through out the entire sulfate process,
  so controlling emissions at the sulfur burners
  provides the best control since this also puts
  the rest of the system under negative pressure
• Ventilation provided to the digester controls
  build-up of gases which removes most of them
  prior to opening the digester
• Remote operation of blow down valves allows for
  the operation to occur without the worker being
  president
• Air pollution control
• Most significant effort to control air emission
  involves the oxidation of the black liquor (used
  liquor) before it enters the multiple-effect
  evaporators, this occurs by
• Sulfur compounds are oxidized which reduces their
  volatility
• Incineration of sulfur off-gases has also been
  effective, this is done by
• The gases are collected in a gas holder then
  burned off in the furnace

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Mills and Textiles Textile Fibers

• Introduction
• There are many natural and artificial fibers that
  are able to be used in the textile industry
• Natural
• Cotton (plant)
• Silk (silkworm)
• Wool (sheep)
• Linen (flax plant)
• Hemp (plant)
• Artificial
• Rayon (cellulose treated with various chemicals)
• Nylon (diamines and dicarboxylic acids)
• Polyester (ethylene glycol and terephthalic acid)
• Vinyl (ethylene)
• Polyacrylonitrile (from natural gas, oxygen, and
  nitrogen)
• For discussion purposes, only the natural fiber,
  cotton, and the artificial fiber, rayon will be
  discussed
• Both of these materials have a range of
  manufacturing processes and health hazards that
  span the textile industry

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Mills and Textiles Textile Fibers

• Cotton
• First of all, concerning cotton, there is disease
  related to the cotton textile industry
• Byssinosis is a disease characterized by
  shortness of breath, coughing, and a tight chest
• This disease occurs in workers handling cotton,
  but is also found in workers handling other
  organic fibers such as flax and hemp
• Symptoms occur when returning to shift from
  extended time away, such as returning to work on
  a Monday after a weekend off
• Symptoms are strongest at beginning of shift and
  subside as the week moves on, then returns upon
  returning to work
• Since the disease is prevalent in the cotton
  industry, OSHA has a standard for cotton dust
• Extracts of cotton dust and specific cotton
  components cause bronchoconstriction (asthma) and
  are contaminated with gram-negative bacterial
  endotoxin that can cause acute respiratory
  symptoms and pulmonary decrement
• Prior to entering the cotton mill it must be
  picked
• Cotton is now picked almost entirely by machine
  in the US
• Seed cotton is processed a local cotton gins in
  which the seed and trash are separated from the
  cotton lint (fiber)
• After ginning, the cotton lint is cleaned and
  baled
• Biologically active materials are still present
  in the cotton bales , which are sent to the
  textile plant

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Mills and Textiles Textile Fibers

• Cotton (cont.)
• Cotton processing operations
• The processing of cotton into textiles involves a
  large number of specific operations common to
  textile plants, understanding these operations is
  necessary to understand
• Opening
• When cotton reaches the textile plant, it is
  first opened so that compressed fibers can be
  loosened
• Heavy and bulky impurities are removed making the
  cotton fiber suitable for processing
• Dust producing equipment includes
• Bale breaker
• Automatic feeders
• Separators and openers
• Mechanical conveyors
• Dust producing equipment are enclosed and
  supplied with local exhaust to control dust
  emissions
• Picking
• A picker includes a feed hopper, beaters, screen
  sections, and calendar roll section
• This equipment opens and cleans cotton and forms
  a continuous web (lap) for the carding machine
• This equipment creates a lot of dust so should be
  equipped with an exhausted enclosure

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Mills and Textiles Textile Fibers

• Cotton (cont.)
• Carding
• The cards are a major source of dust because they
  handle the cotton in such a way that dust,
  debris, and trash are released from the fibers,
  generally the machine is enclosed and ventilated
• The lap formed by the picker is a loosely bound
  layer of cotton that consists of unopened tufts
  and tangled fibers which the card is designed to
  remove
• This lap contains a large amount of trash or
  non-lint material that must be removed
• The lower the quality of cotton, the higher
  amounts of trash and debris
• Along with removing unwanted debris, the card
  also takes the cotton lap and forms it into a
  thin lacy mat with parallel fibers that will
  eventually be converted to a continuous filament
• The card process
• The lap (mat) is positioned on the feed roll and
  fed between the lickerin (small cylinder
  covered with wire teeth) and the feed roll
• The rotating lickerin finger the lap to open
  the tufts of cotton releasing trash out of the
  lap (dusty work)
• The continuous mat is processed across a rapidly
  rotating card cylinder which is covered with wire
  teeth
• Flats contain a wire cloth which slowly passes
  over the card cylinder moving in the opposite
  direction to open and straighten the cotton
  passing between them and the cylinder (dusty
  work)
• The fibrous mat is removed from the card cylinder
  by the doffer (small cylinder with needle
  surface)
• The web is then compressed by rolls and fed
  through a round opening to transform the 100 cm
  (39 in) wide web into a 2.5-cm (1-in) diameter
  rope-like sliver which is coiled into a can for
  the next operation

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Mills and Textiles Textile Fibers

• Cotton (cont.)
• Drawing and Roving
• The drawing process consists of feeding several
  cotton slivers into a drawing frame which
  compresses them into one dense sliver that is
  coiled again for the next operation
• This process pulls the fibers together and
  orients them all in the same direction and
  improves the uniformity of the sliver
• Although this operation is usually enclosed and
  ventilated it does not generate a lot of dust
• Roving involves combining many slivers into one
  sliver, again providing additional uniformity to
  the cotton product
• During continuous roving, the product is also
  given a twist that improves the product strength
• The roving process is also not a major source of
  dust
• After drawing and roving the sliver is wound on a
  bobbin for spinning
• Spinning and Winding
• Spinning takes the large diameter roving and
  processes it into a small-diameter twisted yarn
• Since the spinning process occurs at high speeds,
  any trash left in the cotton will be released
• To provide long yarn lengths, cotton is removed
  from small bobbins and spun onto cones or tubes
  at high speeds which can become dusty
• By the time the cotton is ready for weaving,
  little trash or dust is left in the cotton so
  additional hazards are minimal

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Mills and Textiles Textile Fibers

• Cotton (cont.)
• Control
• NIOSH (1975) recommends the following controls
• Treat raw cotton to remove or minimize the
  offending agents
• Change the process that is the source of dust
• Remove dust from the workplace air
• Ventilation continues to be the principle measure
• A study of airborne cotton dust in a large
  textile plant showed much of the re-circulated
  air contained respirable cotton dust (Hammad and
  Corn, 1971), requiring the following
  recommendations
• Re-circulated air must be curtailed or use of
  better filtering be implemented
• Local exhaust ventilation should be used with
  enclosures
• Better work procedures and housekeeping to remove
  settled dust
• A major source of cotton dust is due to blowdown
  by air lines or blowers
• This is done to remove deposited lint and dust
  which can become a fire hazard and must be
  removed
• Vacuuming is considered inadequate to remove the
  lint and dust, so blowdown tasks in conjunction
  with the use of respiratory equipment is
  recommended

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Mills and Textiles Textile Fibers

• Rayon
• Rayon making process
• Pads or sheets of cellulose made from wood pulp
  are soaked in sodium hydroxide to form a soda
  cellulose
• The sheet material is then shredded, aged, and
  mixed with carbon disulfide in an xanthating
  churn (mixer with xanthic acid)
• The mixture becomes a cellulose xanthate, which
  is a brown syrupy liquid known as viscose
• After filtration, aging, and deaeration, the
  viscose if forced through small holes in a nozzle
  (spinnerette) submerged in a sulfuric acid bath
• When the stream of viscose contacts the bath, the
  cellulose is regenerated into a continuous fiber
• Tension (stretching) on the fiber is controlled
  with godgets which operate at slightly
  different speeds to orient the yarn fibers

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Mills and Textiles Textile Fibers

• Rayon
• Exposure and controls
• Exposures to carbon disulfide are widespread in
  this industry
• Carbon disulfide has a range of toxic effects
  that are very serious
• Overexposures can lead to a Parkinsonism like
  syndrome, psychosis, and suicide
• Repeated exposures have been linked to coronary
  heart disease
• Has a wide explosive range and can autoignite at
  120 ºC (250 ºF), about the surface temperature of
  a light bulb
• Potential vapor exposures occur during
• The xanthation process
• Can usually be controlled because it is an
  enclosed operation
• Spinning process
• The open spinning baths release carbon disulfide
  and hydrogen sulfide and should be monitored and
  controlled with ventilation
• Godget and cutter operations
• During the stretching of the fiber, carbon
  disulfide is released, if the fiber breaks, it
  must be pulled by hand to get it started again,
  exposing the employee to the off-gasing carbon
  disulfide
• This operation must be controlled by local
  exhaust ventilation with an enclosing hood
• Complete range of controls must be utilized to
  protect employees from overexposure
• If engineering and procedural controls are not
  adequate, a complete respiratory program is needed