the niosh 7500 analytical method and osha pels … the niosh 7500_shannon arlauckas.pdfthe niosh...

The NIOSH 7500Analytical Method

and OSHA PELs for Crystalline Silica

PALMS II Advanced Environmental Workshop at MTA

2 Broadway, NYC

December 2, 2014

Shannon Arlauckas

What is Silica?

• Family of materials consisting of silicon dioxide (SiO2)– crystalline or amorphous material

• Crystalline Silica–

– a solid formed by a repeating framework of (Si and O) atoms in 3 dimensions, which have fixed distances between them (d-spacing)

2RJ Lee Group

Crystalline Silica Polymorphs Regulated by OSHA

Quartz TridymiteCristobalite

Exposure to Crystalline Silica

• Rock – an aggregate of minerals– Igneous – granite, other felsic igneous rocks

– Sedimentary – sandstone, shale, carbonates

– Metamorphic – schist, gneiss, quartzite, etc.

• Many industries exposed– Mining

– Construction

– Railroads

• Delayed health effects:– Silicosis

– Lung cancer

– Chronic obstructive pulmonary disease (COPD)

– Kidney disease

3RJ Lee Group

How Do We Monitor Crystalline Silica?

• Gravimetric Analyses

– NIOSH 0500, Total Dust

– NIOSH 0600, Respirable Dust

• NIOSH 7500, Crystalline Silica by XRD

– Analytes: respirable quartz, cristobalite, tridymite

– Instruments: Microbalance, X-ray Diffractometer

– Sampling: cyclone + cassette

4RJ Lee Group

Cassette Assembly – Performed by the lab

• Filters Used:

– 5 µm pore size

– 37 mm diameter

– Polyvinyl chloride (PVC)

• Filters are conditioned

• Pre-weights:

– Weighed in sets of 10

– Every 10th weight is re-weighed to ensure that the balance did not drift during weighing of the set

5RJ Lee Group


• Pre-weighed filters are placed into cassette housing on top of a backing pad that has been stamped with a unique tracking number

6RJ Lee Group


7RJ Lee Group

• Cassettes capped, closed and taped

• Labeled again with the unique tracking number

• Shipped to clients for air sampling

Cassettes can be 2 piece or 3 piece

Grit pot

Air Flow

Direction

Sampling – Performed by the Client

Cyclone

10-mm nylon cyclone (Dorr-Oliver)

Higgins-Dewell (HD) cyclone

Aluminum cyclone + 5 µm PVC filter

Flow Rate

1.7 ± 5 % L/min

2.2 ± 5 % L/min

2.5 ± 5 % L/min

8RJ Lee Group

Tips from the lab:

• Ensure the cassette is loaded into the cyclone properly

• Do not invert sampler assembly while using the cyclone

Outlet-side of Cassette

(connect tubing here)

TubingOutlet

Sample for an

8 hour shift

(480 min, ~ 816 L)

Sample Preparation – preformed in the lab

• Samples received

• Dried in a desiccator

• Cassettes are carefully opened to remove filters

• Filters are post-weighed, recorded

• Total respirable dust mass is calculated

9RJ Lee Group

‘Gravimetric Analysis’

NIOSH 0600

Reporting Limit: 0.100 mg


• Removal of the filter

– Low temperature plasma ashing (beaker)

• 1 hr

– Muffle furnace ashing(crucible)

• 2hr @ 600°C

– Filter dissolution

• Tetrahydrofuran (THF)

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• 15 mL of 2-Proponal is added to each beaker

• Cover and sonicate

• Obtain a silver membrane filter

– 25 mm

– 0.45 µm

• Attach funnel

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• Pour suspension into the funnel

• Walls of beaker are rinsed well

• Apply vacuum

• Remove the silver filter with the sample deposited on it

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• Mount into XRD holder

• Place in tray

• Ready for analysis

13RJ Lee Group

X-Ray Diffractometer

14RJ Lee Group

PANalytical Cubix3 Diffractometer

X-raySource

Detector

Goniometer

Sample

XRD Basics

• Bombardment of X-rays results in scattering of the X-rays off of atomic planes

• X-Ray diffraction produces patterns that are indicative of the atomic planes in a material, which serve as a fingerprint for individual minerals

15RJ Lee Group

d

Incident X-ray

beam

Diffracted beam

q

qAtomic Planes

λ

λ = 1.54 Å, CuKa

nλ=2dsinΘ

XRD Data

16RJ Lee Group

Position [°2Theta] (Copper (Cu))10 20 30

Counts

0

40000

160000

360000

XRD Data

17RJ Lee Group

Quartz

Silver

Silver Chloride

Position [°2Theta] (Copper (Cu))10 20 30

Counts

0

40000

160000

360000

Primary Quartz Peak

Secondary Quartz Peak

Primary

Silver

Peak

NIOSH 7500 - External Standard Method

• Create a Calibration Curve

– Create a set of standards using a pure mineral of various concentrations

• Compare unknown sample data to results from known standards to determine silica mineral concentrations

18RJ Lee Group

Pure Mineral Standards Used in Calibration

19RJ Lee Group

100 µg Qtz

20 µg Qtz

10 µg Qtz

50 µg Qtz

Blank

500 µg Qtz

100 µg Qtz

Quartz Detection Limit (0.005mg)5 µg Qtz

Calibration Curves – External Standard Method

20RJ Lee Group

y = 0.0007x - 0.4596R² = 0.9995

0

50

100

150

200

250

0 100000 200000 300000 400000

Act

ual

Qu

artz

Co

nce

ntr

atio

n (

ug)

Area Under the Curve (counts)

Calibration Curve forQuartz 26.6° 2Θ

y = 0.0032x + 3.6198R² = 0.9952

0

50

100

150

200

250

0 20000 40000 60000 80000

Act

ual

Qu

artz

Co

nce

ntr

atio

n (

ug)

Area Under the Curve (counts)

Calibration Curve forQuartz 20.8° 2Θ

Quality Assurance Practices in the Lab• Balance

– Calibration – daily

– Gravimetric test samples

• Calibration Curve

– Reanalyze and re-measure standards (every 3 mos.)

– CCV – Continuing Calibration Verification – Set of standards run after every 10th sample

• To ensure the calibration curves remain accurate

– RL – Reporting limit – Set of standards run daily

• To ensure that tube intensity is strong enough to see the RL (0.5µg)

• Sample Preparation

– Blanks – every day

• To check for cross contamination between samples during preparation

• Analysis

– 10% of unknown samples are re-measured by a second analyst

– 10% of CCVs and RLs are re-measured by a second analyst

• Audits

– AIHA audit – every 2 years

– Internal audits – annually

21RJ Lee Group

Common Mineral Interferences

• Mica*

• Potash

• Feldspars*

• Zircon

• Graphite

• Aluminosilicates

22RJ Lee Group

Best way to determine interferences: collect a bulk settled dust sample or send the bulk material in question for XRD analysis for

phase identification.

RJ Lee Group, Inc.

350 Hochberg Road, Monroevi l le, PA 15146

Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way

Pittsburgh, PA 15200 REPORT DATE June 4, 2014

ATTENTION: Crystal N. Silica SAMPLES RECEIVED May 30, 2014

TELEPHONE: 724-XXX-XXX RJ LEE GROUP JOB NO. PA30052014001

CLIENT JOB NO. N/A

ANALYSIS: Respirable Dust and Crystalline Free Silica Dust on 5 µm PVC Air Filters PURCHASE ORDER NO: N/A

METHODS: Gravimetry, NIOSH 0600 and X-Ray Diffraction, NIOSH 7500

LOD: 0.005 mg Quartz , Cristobalite, and Tridymite 0.100 mg Respirable Dust

Air* Respirable Masses of Free Weight Percentages of Airborne Dust

Sample Identification Volume Dust Mass Silica Minerals (mg/filter) Crystalline Silica Minerals Concentrations (mg/m3)

Client I.D. RJ Lee Group (liters) (mg/filter) Quartz Cristobalite Tridymite Quartz Cristobalite Tridymite Respirable Quartz Cristobalite Tridymite

Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004

Blank 006 N/A < 0.100 1.050 < 0.010 < 0.010 N/A N/A N/A N/A N/A N/A N/A* Supplied by the client.

N/A Not Applicable

Standard Report

23RJ Lee Group

RJ Lee Group, Inc.


Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way




CLIENT JOB NO. N/A







Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


N/A Not Applicable

Standard Report

24RJ Lee Group

Air volume during a worker’s

shift

RJ Lee Group, Inc.


Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way




CLIENT JOB NO. N/A







Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


N/A Not Applicable

Standard Report

25RJ Lee Group

Mass of material on filter from

micro-balance


shift

RJ Lee Group, Inc.


Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way




CLIENT JOB NO. N/A







Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


N/A Not Applicable

Standard Report

26RJ Lee Group


micro-balance


shift

Mass of each mineral determined by XRD

measurements using the calibration curves derived

from standards

RJ Lee Group, Inc.


Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way




CLIENT JOB NO. N/A







Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


N/A Not Applicable

Standard Report

27RJ Lee Group


micro-balance


shift



from standards

Mass of mineral

Mass of total dust× 100

RJ Lee Group, Inc.


Tel : (724) 325-1776 | Fax: (724) 733-1799

LABORATORY REPORT

ABC Company

1 Industrial Way




CLIENT JOB NO. N/A







Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


N/A Not Applicable

Standard Report

28RJ Lee Group



from standards


micro-balance


shift

Mass

Air Volume× 1000Mass of mineral

Mass of total dust× 100

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100

Re

spir

able

Du

st P

EL m

g/m

3

Quartz Concentration (wt. %)

Current OSHA Personal Exposure Limits (PEL)

29RJ Lee Group

𝐏𝐄𝐋 =𝟏𝟎

𝐦𝐠𝐦𝟑

%𝐐𝐮𝐚𝐫𝐭𝐳 + 𝟐

The OSHA PEL for Respirable Dust is not a

number, but a function that is dependent on

the percentage of crystalline silica in the dust

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 10 20 30 40 50 60 70 80 90 100

Re

spir

able

Du

st P

EL m

g/m

3


Dust containing no quartz:

PEL = 5 mg/m3

or

5000 µg/m3

Dust containing all quartz:

PEL = 0.1 mg/m3

or

100 µg/m3


30RJ Lee Group


𝐦𝐠𝐦𝟑


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 20 40 60 80 100

Re

spir

able

Du

st P

EL m

g/m

3





Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004

Blank 006 N/A < 0.100 1.050 < 0.010 < 0.010 N/A N/A N/A N/A N/A N/A N/A


31RJ Lee Group


𝐦𝐠𝐦𝟑


*Based on an 8 hour shift

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 20 40 60 80 100

Re

spir

able

Du

st P

EL m

g/m

3





Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004



32RJ Lee Group


𝐦𝐠𝐦𝟑



0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 20 40 60 80 100

Re

spir

able

Du

st P

EL m

g/m

3





Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004



33RJ Lee Group


𝐦𝐠𝐦𝟑


Compare this

value to the

calculated PEL

PELA=

0.10 mg/m3

PELB =

0.19 mg/m3

PELC =

0.31 mg/m3

PELD =

0.45 mg/m3

PELE =

0.83 mg/m3


0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 20 40 60 80 100

Re

spir

able

Du

st P

EL m

g/m

3





Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004



34RJ Lee Group


𝐦𝐠𝐦𝟑


Samples A, B and C have

Airborne Dust Concentrations

OVER the calculated PEL


PELA=

0.10 mg/m3

PELB =

0.19 mg/m3

PELC =

0.31 mg/m3

PELD =

0.45 mg/m3

PELE =

0.83 mg/m3




Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


New Proposed OSHA Personal Exposure Limits (PEL)

35RJ Lee Group

New Proposed OSHA PEL for quartz:

0.05 mg/m3

or

50 µg/m3

New Proposed OSHA Action level for quartz:

0.025 mg/m3

or

25 µg/m3

Compare this

value to the new

proposed OSHA

PEL




Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


New Proposed OSHA Personal Exposure Limits (PEL)

36RJ Lee Group


0.05 mg/m3

or

50 µg/m3


0.025 mg/m3

or

25 µg/m3

Samples A, B, C and D

are now OVER the new

proposed PEL for quartz




Sample A 001 1200. 0.500 0.500 < 0.005 < 0.005 100.0 < 1.0 < 1.0 0.417 0.417 < 0.004 < 0.004

Sample B 002 1200. 0.500 0.250 < 0.005 < 0.005 50.0 < 1.0 < 1.0 0.417 0.208 < 0.004 < 0.004

Sample C 003 1200. 0.500 0.150 < 0.005 < 0.005 30.0 < 1.0 < 1.0 0.417 0.125 < 0.004 < 0.004

Sample D 004 1200. 0.500 0.100 < 0.005 < 0.005 20.0 < 1.0 < 1.0 0.417 0.083 < 0.004 < 0.004

Sample E 005 1200. 0.500 0.050 < 0.005 < 0.005 10.0 < 1.0 < 1.0 0.417 0.042 < 0.004 < 0.004


New Proposed OSHA Personal Exposure Limit (PEL)

37RJ Lee Group


0.05 mg/m3

or

50 µg/m3


0.025 mg/m3

or

25 µg/m3

Samples A, B, C and D

are now OVER the new

proposed PEL for quartz

Sample E is at the

proposed action level

Concerns Raised by Proposed OSHA PELs

• Regulatory compliance will be more difficult

• There will be increased costs associated with monitoring and correcting non-compliance

• Can crystalline silica can be reliably measured at these levels?

38RJ Lee Group

0.1 mg/m3 (100 µg/m3)0.05 mg/m3 (50 µg/m3)0.025 mg/m3 (25µg/m3)

0.08 mg/filter (80 µg/filter) 0.04 mg/filter (40 µg/filter)0.02 mg/filter (20 µg/filter)

Flow rate of 1.7 L/min for an 8 hour shift

‘Current’ PEL (assume 100% Quartz):New Proposed PEL:

New Proposed Action Limit:

OSHA PEL Blind Study – Overview

• Make sets of 10 samples of known quartz loadings

– Quartz

– Mixed matrix• 50% quartz + 50% kaolinite

• 50% quartz + 50% feldspar

– Blanks

• The concentrations correspond to the current PEL, proposed PEL and proposed action limit

– 0.08 mg/filter (80 µg/filter)



• Send samples to labs for NIOSH 7500 analyses (blind)

39RJ Lee Group

OSHA PEL Blind Study – Preparation

• PVC filters were pre-weighed

• Known quantities of quartz (and mixed minerals) are deposited onto PVC filters

• PVC filters were post-weighed

40RJ Lee Group


• Filters were loaded into cassettes

• Taped and labeled to look like sample cassettes

• Cassettes were tested to ensure correct preparation

41RJ Lee Group

OSHA PEL Blind Study – Preparation Problems

• Depositing respirable particles suspended in liquid media onto 5µm pore size PVC filters resulted in a poor recovery of materials

– Solution: Switched to using 0.8 µm pore size PVC filters

• Recoveries after deposition onto 0.8 µm filters were lower than expected due to partial dissolution of the filters

– Solution: Selected filters were analyzed by XRD to confirm recoveries

42RJ Lee Group

20 µg Loading 40 µg Loading

93% Recovery 96% Recovery


• Filters were loaded into cassettes

• Taped and labeled to look like sample cassettes

• Cassettes were tested to ensure correct preparation

• Sent to five AIHA accredited laboratories for NIOSH 7500 analysis

43RJ Lee Group

OSHA PEL Blind Study – Results

• 34% (36/105 filters) of the non-blank filters were reported to be below the detection limit

– Loadings were above each laboratory’s reported Limit of Detection (LOD)

– These results were excluded from the following statistical data

44RJ Lee Group


45RJ Lee Group

Reference

Level (µg)

Lab Result

Means (µg)

Number of

Data Points*

Lab Result

Standard Deviation0 28.85 2 32.74

20 13.36 7 5.21

40 22.93 12 11.22

80 46.91 12 18.31

Silica-only and blank filters having positive reported results

*non-detects excluded

Silica-only and mixed-matrix filters having positive reported result

*non-detects excluded

Reference

Level (µg)

Lab Result

Means (µg)

Number of

Data Points*

Lab Result

Standard Deviation20 13.33 20 5.21

40 25.04 37 11.22

80 46.91 12 18.31


• Inter- and intra-laboratory variability was high

• None of the laboratory means came within 30% of the reference values

– Accuracy was problematic even when non-detects were excluded

– Most labs could not reliably distinguish between the different reference levels

Why?

46RJ Lee Group

NIOSH 7500 Sample Preparation –Muffle Furnace vs. Plasma Asher

47RJ Lee Group

Standard

(µg)

Average

(µg)

19.4 17.3

48.6 52.3

96.1 101.4

19.4 14.8

48.6 43.1

96.1 100.1

19.4 15.0

48.6 41.4

96.1 83.2

19.4 14.8

48.6 37.9

96.1 74.9

19.4 3.5

48.6 23.5

96.1 77.4

100.8 ± 4.7%

89.8 ± 4.3%

83.0 ± 4.9%

49.0 ± 3.8%

77.4 ± 4.0 %5 Muffle Used Partial

3 Muffle Used Complete

4 Muffle Used None

1 Plasma n/a n/a

2 Muffle New Complete

Test Ashing

DeviceCrucible Scraping

Crystalline Silica

Average Recovery

Recommendation to OSHA

• Data from blind study presented to OSHA

– It is possible to analyze for crystalline silica at low levels (proposed PEL)

– Preparation methods in some laboratories is a concern and this should be addressed before PELs are changed.

48RJ Lee Group

A recommendation was made to OSHA that a larger blinded study be conducted for all laboratories

performing the NIOSH 7500 method before adopting new PELs that may not be measured reliably using

current technology and preparation methods

the niosh 7500 analytical method and osha pels … the niosh 7500_shannon arlauckas.pdfthe niosh...

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