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RESPIRABLE CRYSTALLINE SILICA

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RESPIRABLE CRYSTALLINE SILICA New Considerations for Sampling and Analysis SILICA IS A TOPIC IN THE U.S. SKC INC. is pleased to share the latest updates. – PowerPoint PPT presentation

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Title: RESPIRABLE CRYSTALLINE SILICA


1
RESPIRABLE CRYSTALLINE SILICA
  • New Considerations for Sampling and Analysis

2
SILICA IS A TOPIC IN THE U.S.
HOT
  • SKC INC.
  • is pleased to share the
  • latest updates.

3
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.

4
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.

5
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.

6
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.

7
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.

8
CRYSTALLINE SILICAWORKPLACE EXPOSURES
  • High Risk Jobs
  • Abrasive blasting
  • Foundry work
  • Stonecutting
  • Rock Drilling
  • Mining
  • Tunneling
  • Hydraulic Fracturing

9
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

10
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

11
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.
  • .

12
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)

13
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.

14
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.

15
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.

16
RESPIRABLE DUST SAMPLERS TO MEET ISO 7708
SPECIFICATIONS
  • OPTION 1
  • TRADITIONAL CYCLONES

17
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?)

18
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?
19
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
20
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.

21
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
22
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.

23
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.

24
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.

25
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.

26
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.

27
RESPIRABLE DUST SAMPLERS TO MEET ISO 7708
SPECIFICATIONS
  • NEW OPTIONS

28
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.

29
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.

30
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
31
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.)

32
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.

33
PPI SAMPLER PERFORMANCECOMPARED TO CRITERIA
34
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.)

35
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.

36
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.

37
THANK YOU FOR YOUR ATTENTION!
WWW.SKCINC.COM
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