RESPIRABLE CRYSTALLINE SILICA

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RESPIRABLE CRYSTALLINE SILICA

• New Considerations for Sampling and Analysis

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SILICA IS A TOPIC IN THE U.S.
HOT

• SKC INC.
• is pleased to share the
• latest updates.

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BUT FIRST CONSIDERSILICA THE COMPUND

• Look at chemical formula for silica (SiO2), and
  consider
• this
• Oxygen is the most abundant element in the
  Earths crust and silicon is the second most
  abundant.
• Quartz, the most common form of crystalline
  silica, is the second most common mineral on the
  earths surface.
• Amorphous silica such as diatomaceous earth is
  not particularly toxic to humans unless heated to
  high temperatures.

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CRYSTALLINE SILICAWHERE ITS FOUND

• Crystalline silica is naturally occurring in
  sand, gravel, and mineral ores.
• Quartz, the most common form, is found in almost
  every type of rock.
• Nearly all mining and quarrying activities
  involve exposures to crystalline silica.

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CRYSTALLINE SILICAWHERE ITS USED

• Due to its chemical and physical properties,
  crystalline silica is a prized mineral with a
  number of industrial applications.

• Major ingredient in building materials such as
  concrete, bricks, and stone
• Used as a molding material for metal casting in
  foundries.
• Filler in plastics, rubber, and paint.
• Raw material for glass manufacture along with
  porcelain and fine china.

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APPLICATION IN THE HEADLINESFRACKING

• Silica sand is used to hold open the fissures
  created by hydraulic fracturing (fracking) so
  natural gas or oil can flow out of the shale and
  into the well.

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CRYSTALLINE SILICAWORKPLACE EXPOSURES

• U.S. OSHA reports that 2.2 million workers are
  exposed to respirable crystalline silica.
• The majority (1.85 million) are in the
  construction industry.
• Exposures occur when workers cut, grind, crush,
  or drill silica-containing materials.

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CRYSTALLINE SILICAWORKPLACE EXPOSURES

• High Risk Jobs
• Abrasive blasting
• Foundry work
• Stonecutting
• Rock Drilling
• Mining
• Tunneling
• Hydraulic Fracturing

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NEW PROPOSED RULE FROM U.S. OSHA

• In September 2013, U.S. OSHA published a
• Notice of Proposed Rulemaking (NPRM) for
• Occupational Exposure to Respirable Crystalline
• Silica.
• This is the first update since the original
• Permissible Exposure Limit (PEL) was adopted
• in 1971.
• See this 757-page document at
• https//www.osha.gov/silica/nprm.pdf

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SUMMARY OF ISSUES IN THE NPRMAFFECTING SAMPLING
ANALYSIS

• New Permissible Exposure Limit
• New Specifications for Respirable Dust Samplers
• Guidance on Sample Times required to exceed limit
  of quantification at the proposed levels
• Guidance on Analytical Methods that are sensitive
  enough to measure silica at proposed levels

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PERMISSIBLE EXPOSURE LIMITEXISTING

• CONSTRUCTION AND
• SHIPYARDS
• A formula based on obsolete
• method of collecting dust into
• impingers with analysis by
• particle counting.
• PEL is approximately
• equivalent to 250 ug/m3.

• GENERAL INDUSTRY
• A formula based on the silica
• in the air sample. Example
• _____10____
• Quartz 2
• PEL is equivalent to 100 ug/m3
• when the material is pure
• quartz . PEL approaches 5
• mg/m3, (the PEL for Particulates
• Not Otherwise Classified) with a
• low percentage of quartz in the
• sample.
• .

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PERMISSIBLE EXPOSURE LIMITPROPOSED

• 50 ug/m3 as an 8-hr TWA for all forms of
• silica including quartz, cristobalite, and
• trydymite for all industry sectors covered by
• the rule.
• 25 ug/m3 action level (same as current TLV)

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SPECIFICATIONS FOR SAMPLERS EXISTING

• Existing specs for respirable dust samplers were
• promulgated in 1971 and are listed in 29 CFR
• 1910.1000 Table Z-3 for mineral dusts.
• A respirable dust sampler with a 50 (median)
• cut-point of 3.5 um is specified.
• The Dorr-Oliver (nylon) cyclone is the only
• sampler used by federal OSHA inspectors to meet
• the existing specifications.

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U.S. OSHA IS TRYING TO UPDATE TO CURRENT AEROSOL
SCIENCE

• Page 539 OSHA acknowledges that the existing
• collection efficiency specifications for
  respirable dust
• samplers (50 cut-point of 3.5 um) are obsolete.
• Page 542 OSHA states that crystalline silica
• measurement should be determined by a sampling
• device designed to meet the characteristics for
  particle-
• size-selective samplers specified in ISO
  77081995 Air
• Quality-Particle Size Fraction Definitions for
• Health-Related Sampling.

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ISO 77081995

• This is the standard that ACGIH, NIOSH, CEN, and
  most countries around the world have already
  adopted.
• The collection efficiency curve for respirable
  dust samplers in this standard includes a 50
  (median) cut-point of 4 um which is more
  conservative than the existing OSHA specification
  of 3.5 um.

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RESPIRABLE DUST SAMPLERS TO MEET ISO 7708
SPECIFICATIONS

• OPTION 1
• TRADITIONAL CYCLONES

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CYCLONE SAMPLERS TO MEET SPECS IN ISO 7708

• NYLON DORR-
• OLIVER CYCLONE
• Listed in OSHA SILICA NPRM on page 267
• Listed in NIOSH respirable dust methods
• Designated flow rate is 1.7 L/min (same as that
  used for previous criteria?)

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DORR-OLIVER CYCLONEADVANTAGES AND DISADVANTAGES

• Advantage Long history of use in the U.S. by
  compliance officers.
• Disadvantage Nylon construction creates static
  electricity concerns.
• Disadvantage Orientation bias. (AIHA Journal
  56, November 1995).
• Disadvantage Dust sticks to cassette top with
  closed-face operation. (ASTM, STP 1565, 2013)

A BETTER WAY?
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CYCLONE SAMPLERS TO MEET SPECS IN ISO 7708

• SKC ALUMINUM
• CYCLONE
• Listed in NIOSH respirable dust methods
• Published performance
• (J. Aerosol Science, 29, 1998).
• Designated flow rate is 2.5 L/min

SKC 225-01-02
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ALUMINUM CYCLONEADVANTAGES AND DISADVANTAGES

• ADVANTAGES
• Metal construction eliminates static electricity
  concerns.
• Open-face sample collection enhances collection.
  
• Calibration adapter offers user convenience.

• DISADVANTAGE
• Aluminum can not be used in underground mines due
  to spark hazard.
• Users frequently make the mistake of removing the
  red cap (grit pot) on the cyclone during sampling.

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CYCLONE SAMPLERS TO MEET SPECS IN ISO 7708

• SKC G(S)-3
• Listed in OSHA SILICA NPRM on page 267
• Published performance
• (J. Aerosol Science, 28, 1997).
• Designated flow rate is 2.75 L/min
• .

SKC 225-100
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GS-3 CYCLONEADVANTAGES AND DISADVANTAGES

• ADVANTAGES
• Designed to overcome orientation bias of
  Dorr-Oliver
• Conductive plastic construction eliminates static
  electricity concerns.
• Not a spark hazard for underground mines.
• Open-face sample collection enhances collection.
  

• DISADVANTAGES
• No calibration adapter like with aluminum
  cyclone. Requires calibration jar or the easier
  jarless calibration methods.

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CYCLONE SAMPLERS TO MEET SPECS IN ISO 7708

• BGI GK 2.69
• Listed in OSHA SILICA NPRM on page 267
• Designated flow rate is 4.2 L/min
• Now available from SKC as 225-269-37 or -25 for
  25-mm version.

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BGI GK 2.69 CYCLONEADVANTAGES AND DISADVANTAGES

• DISADVANTAGES
• May not be suitable for use in underground mines.
• No calibration adapter like with aluminum cyclone.

• ADVANTAGES
• Metal construction eliminates static electricity
  concerns.
• Higher flow of 4.2 L/min allows users to sample
  only 4 hours to collect enough sample for
  quantitative analysis of even cristobalite at the
  action level.

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IMPORTANT NOTE ON FLOWRATE

• All cyclones are not created equal!
• Each cyclone has different operating
  specifications and performance criteria.
• Be sure you know the flow rate specified to
  achieve the desired cut-point before using any
  cyclone.

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TECH TIP CASSETTE MATERIAL

• In a March 2013 JOEH article by NIOSH, cassette
  wall losses were noted when using cyclones with
  typical cassettes made of styrene.
• NIOSH recommends the use of 37-mm black
  conductive cassettes made of polypropylene.
• Ashley Harper (2013) Analytical Performance
  Issues, Journal of
• Occupational and Environmental Hygiene, 103.

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RESPIRABLE DUST SAMPLERS TO MEET ISO 7708
SPECIFICATIONS

• NEW OPTIONS

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NEW SAMPLERS TO MEET SPECS IN ISO 7708

• Page 539 of OSHA SILICA NPRM states
• Adoption of this (ISO) definition by
• OSHA would allow for workplace sampling to
• be conducted using ANY particulate sampling
• device that conforms to the ISO definition i.e.
• collects dust according to the
• particle collection efficiency curve specified in
  
• the ISO standard.

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NEW SKC SAMPLERS TO MEET SPECS IN ISO 7708

• Impaction based PPI samplers also available for
  respirable dust.
• Designed to precisely match the
  ISO/CEN/ACGIH/NIOSH criteria.
• Available in reusable or disposable options.

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SKC RESPIRABLE PPIFLOWRATE OPTIONS

• Single-use, disposable PPI models are available
  for use at either 2, 4, or 8 L/min.
• Available empty or pre-loaded with filters.
• A calibration adapter is available for disposable
  models.

2 L/min 225-385
8 L/min 225-384
4 L/min 225-387
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WHY THE HIGHER FLOW RATE RESPIRABLE PPI SAMPLERS?

• NIOSH reported that for a working environment
  with
• an airborne concentration of respirable silica
  near
• the current TLV of 25 ug/m3, the amount of sample
  
• collected with current respirable dust samplers
  (at
• typical flow rates of 2 L/min ) might not be
  enough
• for quantitative analysis. (Harper, et. al. Ann.
  Occup. Hyg., 2010.)

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PUMP PARTNERSHIGH FLOW PPI SAMPLERS

• Respirable PPI
• 4 L/min model can be partnered with SKC XR5000.
  
• 8 L/min model can be partnered with the SKC
  Leland Legacy pump.

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PPI SAMPLER PERFORMANCECOMPARED TO CRITERIA
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PPI DATAOSHA DOCKET

• SKC submitted comments to the OSHA
• docket on the silica NPRM with data on
• the PPI. (Electronic copies are available upon
  
• request).
• The data which was published in the Journal
• of Physics shows that the collection efficiency
  of
• the PPI is a close match to the ISO standard
• and the bias is more acceptable than the HD
• cyclone (listed in the NPRM.)

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SAMPLE TIMES REQUIREDFOR QUANTIFICATION BY LAB

• 4 HOURS
• PER OSHA NPRM
• Using respirable dust
• samplers at flows of
• approx. 2-4 L/min in
• workplace concentrations
• of quartz down to the
• proposed action level of
• 25 ug/m3. (TLV levels)

• 2 HOURS
• PER SKC SCIENTISTS
• Using respirable dust
• samplers at flows of
• 8 L/min at these same
• workplace concentrations.

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ANALYTICAL METHODSSENSITIVITY CONCERNS

• U.S. OSHA concluded that both X-Ray diffraction
  (XRD) and Infrared Spectroscopy (IR) methods are
  sensitive enough to quantify silica in workplace
  concentrations at the proposed PEL and action
  levels. (But precision is lacking at 25 ug/m3)
• Visible absorption spectrophometry (VIS) methods
  are NOT sensitive enough.

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THANK YOU FOR YOUR ATTENTION!
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