1. SAMPLING FOR RESPIRABLE CRYSTALLINE SILICA
TO MEET THE 2016 U.S. OSHA FINAL RULE

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

3. BUT FIRST LE’TS LOOK AT SILICA THE COMPOUND
Given the chemical formula for silica (SiO2), it is
interesting to note:
Oxygen is the most abundant element in the Earth’s crust and silicon is the second most abundant.
Quartz, the most common form of crystalline silica, is the second most common mineral on the earth’s surface.
It’s no wonder that exposures to respirable crystalline silica are widespread throughout the world.

4. CRYSTALLINE SILICA: WHERE 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 SILICA: WHERE 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. A NEW USE FOR SILICA: FRACKING
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 SILICA: WORKPLACE 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 SILICA: OTHER WORKPLACE EXPOSURES
Abrasive blasting
Foundry work
Stonecutting
Rock Drilling
Mining
Tunneling
Hydraulic Fracturing

9. ACTIONS BY U.S. OSHA ON CRYSTALLINE SILICA
In September 2013, U.S. OSHA published a
Notice of Proposed Rulemaking (NPRM) for
Occupational Exposure to Respirable Crystalline
Silica.
This was the first update since the original
Permissible Exposure Limit (PEL) was adopted
in 1971.
On March 25, 2016, OSHA published the
long-awaited final rule.

10. WHAT’S NEW FOR SAMPLING IN THE SILICA FINAL RULE
New Permissible Exposure Limit (PEL)
and Action Level
New Specifications for Respirable Dust Samplers
Guidance on Sample Times to Meet the Limit of Quantification for Lab Analysis
Guidance on Analytical Methods that are sensitive enough to measure silica at the new, lower levels

11. ORIGINAL PELs FROM 1971 WERE CALCULATED FORMULAS
PEL FOR
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.
PEL FOR
GENERAL INDUSTRY
A formula based on the % silica
in the air sample. For quartz:
_____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. NEW OSHA PEL PASSED IN 2016 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. OSHA’S 1971 SPECIFICATIONS FOR RESPIRABLE DUST SAMPLERS
U.S. OSHA originally specified the use of a respirable dust sampler whose collection efficiency curve had a 50% (median) cut-point of 3.5 um.
NOTE: The 50% cut-point is the size of the dust that the sampler collects with 50% efficiency.
U.S. OSHA has historically used the 10-mm nylon Dorr-Oliver cyclone to meet this 1971 criteria.

14. NEW SAMPLER SPECIFICATIONS PASSED IN 2016
In their proposed and final rules, OSHA
acknowledges that the 1971 specifications for respirable dust samplers (50% cut-point of 3.5 um) are obsolete.
OSHA now requires that respirable crystalline silica
sampling be done using a device that meets the
specifications in ISO Standard 7708 entitled Air Quality
Particle Size Fraction Definitions for Health-Related
Sampling.

15. ISO STANDARD 7708
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.

16. COMPARISON: NEW AND OLD OSHA SPECIFICATIONS
Samplers with a 4 um cut-point collect more contaminant mass than those with 3.5 um cut-point.
So they are more conservative/protective of worker health.
A simple explanation:
If you were collecting particles 3.5 um and smaller in the past and then change to collecting particles 4 um and smaller, you will collect more particles.
Also you will collect bigger particles which weigh more. Thus more contaminant mass.

17. RESPIRABLE DUST SAMPLERS: TO MEET ISO/CEN & OSHA CRITERIA
OPTION #1:
TRADITIONAL CYCLONES

18. CYCLONE SAMPLERS: TO MEET ISO & OSHA CRITERIA
10-mm NYLON DORR-
OLIVER CYCLONE:
Listed in OSHA Final Rule on page 16439
Listed in NIOSH respirable dust methods
Designated flow rate is 1.7 L/min (This seems strange because it is the same flowrate as that used for 1971 criteria).

19. DORR-OLIVER CYCLONE ADVANTAGES 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?

20. CYCLONE SAMPLERS: TO MEET ISO & OSHA CRITERIA
SKC ALUMINUM
CYCLONE:
Listed in OSHA Final Rule on page 16439
Listed in NIOSH respirable dust methods
Published performance
(J. Aerosol Science, 29, 1998).
Designated flow rate is 2.5 L/min
SKC

21. SKC ALUMINUM CYCLONE DESIGN FEATURES
Metal construction eliminates static electricity concerns.
Open-face sample collection enhances collection.
Calibration adapter offers user convenience.
IMPORTANT NOTE FOR MINING:
Aluminum is considered a spark hazard in underground mines. So choose another sampler such as the GS-3 cyclone for this application.

22. CYCLONE SAMPLERS: TO MEET ISO & OSHA CRITERIA
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

23. GS-3 CYCLONE DESIGN FEATURES
Developed at West Virginia University
to overcome problems evidenced with
10-mm nylon cyclone:
Conductive plastic construction eliminates static electricity concerns.
3-inlet slits overcome orientation bias
Open-face sample collection using
3-piece cassette enhances collection and eliminates particles sticking to the top of a 2-piece cassette. .
SKC /103

24. 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 before using any cyclone.

25. 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 clear styrene*.
NIOSH recommends the use of 37-mm black conductive cassettes made of polypropylene.
3-piece polypropylene cassettes are available from SKC as SKC
*Ashley & Harper (2013) Analytical Performance Issues, Journal of
Occupational and Environmental Hygiene, 10:3.

26. RESPIRABLE DUST SAMPLERS: TO MEET ISO 7708 & OSHA CRITERIA
NEW OPTIONS

27. NEW SAMPLERS: FOR ISO 7708 & OSHA CRITERIA
On Page 16439, OSHA notes:
The new silica rule “will permit
employers to use ANY sampling device that
conforms to the ISO/CEN convention”.

28. NEW SAMPLERS: FOR ISO 7708 & OSHA CRITERIA
Page goes on to say that in addition to traditional cyclones:
“There are also personal impactors available for use at flowrates from 2 to 8 L/min that have been shown to conform closely with the ISO/CEN convention”.

29. PERSONAL IMPACTORS FROM SKC: PPI SAMPLERS
Shown here are SKC PPI samplers designed to precisely match the ISO 7708/CEN/OSHA collection efficiency curve for respirable dust with a 4 um median cut-point.

30. SKC PPI DESIGN: 4 INLETS OF DIFFERENT SIZES
Each of the 4 inlets is uniquely sized to achieve a designated cut-point. As such, each inlet functions as a separate impactor.
The performance of each impactor matches part of the collection efficiency curve.
Dust collected on final filter closely matches the entire curve.
Inlet
Impaction
Plate
Exhaust with
Final Filter

31. USERS ASKED SKC DELIVERED
SKC originally produced the PPI only in reusable aluminum.
But users asked SKC to produce the PPI sampler in a single-use plastic model.
This design eliminates the need for sampler assembly and cleaning.
Filters in either model should be pre- & post-weighed by the lab if necessary.
Reusable Aluminum
Disposable Anti-Static Plastic

32. PPI SAMPLER PERFORMANCE COMPARED TO CRITERIA

33. SKC RESPIRABLE PPI: FLOWRATE 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:
8 L/min:
4 L/min:

34. PPI FUNCTIONALITY
The disposable PPI looks like a traditional 37-mm filter cassette.
But the inlet section has 4 internal, pre-oiled impactor plates that scrub out larger particles.
The respirable dust is then collected onto the filter in the outlet section for analysis.

35. 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.)

36. PUMP PARTNERS: RESPIRABLE PPI SAMPLERS
2 or 4 L/min models can be partnered with SKC XR5000 or new AirChek Touch pump.
8 L/min model can be partnered with the SKC Leland Legacy pump.

37. GUIDANCE ON SAMPLE TIMES FOR QUANTIFICATION BY LAB
Page of the OSHA Final Rule includes a handy chart for guidance on sample times that will result in collection of at least 10 ug which is the limit of quantification for quartz by OSHA Method ID 142.
EX: Using the SKC Aluminum Cyclone at 2.5 L/min
If sampling at PEL levels of 50 ug/m3 for 4 hours, 30
ug of quartz will be collected (3 x the limit of
quantification). If sampling at the action level of 25
ug/m3 for 4 hours, 15 ug of quartz will be collected.

38. ANALYTICAL METHODS: OSHA SPECIFICATIONS
U.S. OSHA reports on page that both X-Ray diffraction (XRD) and Infrared Spectroscopy (IR) methods can detect and quantify crystalline silica in amounts below the final rule’s 25 ug action level.
Visible absorption spectrophometry (VIS) methods are NOT sensitive enough and are no longer used.

39. THANK YOU FOR YOUR ATTENTION!
Please with technical queries or contact your local SKC office for silica sampling equipment!