ENVH 390 Construction Issues with Silica

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ENVH 390Construction IssueswithSilica
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Why Target Silica Exposure?

• Widespread Occurrence and use -
• Maritime
• Agriculture
• Construction
• General Industry
• Number of Related Deaths
• Number of exposed workers
• Health Effects

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Occurrence of Crystalline Silica

• Silicon Dioxide is basic component of sand,
  quartz, granite
• Quartz is second most common mineral in earths
  crust
• Silicone can be easily found in the earths crust
  in crystalline form or in amorphous powder form.
  Silicon and oxygen together are responsible for
  75 of the earths crust. Sand is Silicon Dioxide.

• Airborne silica is produced by, among other
  activities
• Sandblasting
• Rock Drilling
• Roof Bolting
• Foundry Work
• Stone Cutting
• Drilling
• Quarrying
• Tunneling

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According to OSHA These Industries Have
Significant Silica Exposure

• Electronics
• Foundries
• Ceramics, clay pottery, stone, glass
• Construction
• Agriculture
• Maritime
• Mining

• Railroad ( setting laying track)
• Slate flint quarrying flint crushing
• Use manufacture of abrasives
• Manufacture of soap detergents

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Number of Silica Related Deaths

• Total US deaths 1968-1990 where silica is
  reported on death certificate 13,744 people
• Deaths where silicosis is reported as underlying
  cause of death 6,322 people
• 68 of silica related deaths reported in 12
  states
• 10 of silica-related deaths reported from
  construction industry

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Number of Exposed Workers

• National Institutes for Occupational Safety and
  Health (NIOSH) Hazard Alerts estimate
• More than One Million Workers at Risk
• More than 100,000 sandblasters

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Health Effects

• Pulmonary fibrosis (silicosis)
• Acute silicosis (1 to 3 years)
• Accelerated silicosis (3 to 10 years)
• Chronic silicosis (5 to 25 years)
• Possible Lung Cancer
• Has high correlation to Tuberculosis

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What is Silica?
cristobalite
tridymite
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• Crystalline silica is a naturally occurring
  mineral that is white or colorless and found in
  the earth's crust
• It is a core component of quartz, sand, flint,
  agate, granite, and many other mineral rocks.
• Other types of silica include cristobalite and
  tridymite.
• Many of these mineral rocks are used to build
  homes, offices, and other structures.
• Silica is used to create materials such as glass
  and concrete.

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Silica

• Silica is the name which collectively describes
  various forms of silicon dioxide (SiO2),
  including both the crystalline and
  non-crystalline (amorphous) forms of silica.
• While amorphous silica can be transformed into
  crystalline forms such as tridymite and
  cristobalite by heating to high temperatures it
  is generally only the crystalline forms of silica
  which are fibrogenic (Inducing tissue injury and
  fibrosis (scarring).
• Quartz is the most common form of crystalline
  silica found in workplaces

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Silica

• The respiratory dangers posed by silica dust
  particles have been known for hundreds of years.
• Prior to the 1930s, Silica-related disease was
  referred to as
• "miners asthma" or
• "potters rot."

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Silica-Related Diseases

• Silicosis
• Acute
• Chronic
• Accelerated
• Lung Cancer
• Tuberculosis

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Silicosis

• Silicosis is a respiratory disease of the lungs
  that results from the inhalation of airborne
  crystalline silica dust.
• The dust contains the silica particles that can,
  over time, cause fibrosis (scar tissue
  formations) in the lungs.

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Silicosis

• When workers inhale crystalline silica, the lung
  cells and tissue gradually develop nodules (a
  clump or cluster of cells) and scars around the
  trapped silica particles. 

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Silicosis

• If the nodules continue to grow, at some point
  the respiratory functions of the lungs
  deteriorate.
• If the disease continues, it can eventually
  result in death.

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Healthy vs Silicosis Lung
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Silicosis X-rays
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Chronic Silicosis

• Chronic Silicosis usually occurs after 10 or more
  years of low-level exposure to crystalline
  silica.
• This is the most common form of the disease and,
  unfortunately, can go many years without
  detection.
• Often times, 20 years can pass from the initial
  exposure before an abnormality would appear on a
  chest X-ray.
• Symptoms would appear but may be mistaken for
  another condition.

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Accelerated Silicosis

• Accelerated Silicosis - This forms of Silicosis
  typically occurs with moderate to high levels of
  exposure over a 5 to 10 year period.
• Accelerated Silicosis is often triggered when
  workers have direct contact with split or
  fractured rocks that contain potent
  concentrations of silica dust particles

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Acute Silicosis

• Acute Silicosis the acute form of Silicosis is
  the most dangerous form because it involves the
  highest levels of exposure.
• The initial symptoms can begin as early as
  several weeks after the first exposure. However,
  it typically takes a few years before symptoms
  begin to develop.

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Silica and Lung Cancer

• A suspicion of lung cancer occurrence among
  workers exposed to crystalline silica evolved in
  the 1960s
• The link between silica exposure and lung cancer
  was generally considered impossible till the
  1980s (International Agency for Research on
  Cancer (IARC)
• The basis was that under laboratory conditions
  some quartz samples could be carcinogenic for
  rats, and this in spite of the fact that no other
  rodent species developed tumors.

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Silica and Lung Cancer

• Until 1996, the evidence that crystalline silica
  in itself could cause lung cancer in man remained
  according to the medical literature scanty and
  inconsistent and inadequate.
• The vast majority of the experts nevertheless
  agreed that an excess of lung cancer could be
  observed in silicotics, though a direct role of
  silica has not been established.
• We call this epidemiological inference

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Silica and TB

• Silica particles can destroy or alter the
  metabolism of the pulmonary macrophage, thereby
  reducing its capacity for anti-bacterial defense.
  
• Occupational exposure to silica dust renders a
  subject susceptible to developing pulmonary
  tuberculosis.

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Silica Exposures in U.S.

• At least 1.7 million U.S. workers are exposed to
  respirable crystalline silica in a variety of
  industries and occupations, including
• Construction
• Sandblasting
• Mining
• Pottery
• Glass Making

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Silica Exposures - Masonry
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Silica in Masonry
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Silica Exposures Abrasive Blasting of Concrete
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Silica Exposures Plumbers Sawing Concrete
Floors for Access
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Silica Exposures Building Site Preparation
Blasting and Drilling
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Silica Exposures Highway Construction
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Silica Exposures - Construction
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Silica Exposures Foundry and Sandblasting
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Silica Exposures Abrasive Blasting
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Silica Exposures - mining
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Silica Exposures Grinding Wheels
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Silica Exposures - Control

• Substitution Hydro and Hydro/Abrasive Blasting,
  Laser Cutting, Robotics
• Wet-methods and Personal Protective Equipment
  (PPE)
• Use of Blasting Booths and Cabinets
• Ventilation
• Good Practice and Education

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Required Warning Signs
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Improvement Hydro-BlastingEliminates Silica
Exposures
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Hydro/Abrasive Blasting Virtually Eliminates
Silica Exposure
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Respiratory Protection and Wet Methods
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Abrasive Blasting Cabinets-Rooms
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Portable Blasting Equipment for bridges and
other construction
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Equipment Modifications
Curtain, Downdraft Ventilation and Misting
Dust Control Room
Grinding Wheel w/Exhaust Ventilation
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Silica Good Work Practices

• Use a grinder that has local exhaust ventilation
  when possible.
• Do not use the grinder near another worker.
  Restrict some work areas to cut down exposures to
  other workers.
• Stand so that the dusty air will not blow on you
  and other workers.

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Good Practices continued

•  In poorly ventilated areas such as a courtyard
  or the inside corners of a building, use fans to
  blow out dusty air.
• Do not use compressed air to clean yourself, your
  clothes, or your equipment. Make sure the vacuum
  cleaners used for dust control and clothes
  cleaning capture at least 99 percent of the small
  particles that could be inhaled (0.3 micrometer
  diameter).

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Gauley West Virginia
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Gauley Bridge, West Virginia

• In 1935, approximately 1,500 workerslargely
  African Americans who had come north to find
  workwere killed by exposure to silica dust while
  building a tunnel in Gauley Bridge, West
  Virginia.
• Ordinarily, silicosis takes several years to
  develop, but these West Virginia tunnel workers
  were falling ill in a matter of months because of
  exposure to unusually high concentrations of
  silica dust.

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Gauley Bridge Tunnel (Hawks Nest)

• When the Rinehart Dennis, Co., contractors for
  the New-Kanawha Power Co., started tunneling
  through two mountains a mile east of Gauley
  Bridge, on a power project to cost millions, it
  knew the tunnel would go through silicate rock.
• It knew that men working in the tunnel would
  breathe in the dust.
• It knew that without protection they would get
  silicosis, deadly lung disease

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Gauley Bridge Tunnel

• The crisis over silicosis suddenly became a
  national issue.
• It has been called Americas Greatest Industrial
  Disaster
• In 1936 congressional hearings on the Gauley
  Bridge disaster, it was revealed that company
  officials and engineers wore masks to protect
  themselves when they visited the tunnel, but they
  failed to provide masks for the tunnelers
  themselves, even when the workers requested them.
  

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Gauley Bridge Tunnel

• 169 tunnel workers killed at Gauley Bridge were
  tossed into trenches to rot.
• Several workers each day, choked to death by
  silicosis, were hauled 40 miles to Summerville
  and dumped into the grave
• No identification, no coffins.
• The company paid the undertaker 50 a piece to
  bury them. Most often, they paid nothing to
  family
• A wife who came tearfully to claim the remains of
  her loved one was quietly driven away.

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Gauley Bridge Tunnel

• The local town of Gauley Bridge became known as
  the Village of the Dead or the Village of the
  Doomed
• Virtually every family in this small hamlet were
  directly affected by this tragedy
• Virtually all able-bodied men and boys worked on
  the tunnel and virtually all died or lived with
  crippling lung disease (quality of life was very
  poor)