for respirable crystalline silica operations - feb. 28 · risks for respirable crystalline silica...

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Risks for Respirable Crystalline Silica (Quartz) Exposures in Hydraulic

Fracturing Operations

Michael Breitenstein

Eric J. Esswein

John SnawderDISCLAIMERS: THE FINDINGS AND CONCLUSIONS IN THIS PRESENTATION HAVE NOT BEEN FORMALLY DISSEMINATED BY NIOSH AND SHOULD NOT BE CONSTRUED TO REPRESENT ANY AGENCY DETERMINATION OR POLICY. MENTION OF COMPANY NAMES AND/OR PRODUCTS DOES NOT CONSTITUTE ENDORSEMENT BY THE NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH.

• Mission: improve OS&H by partnering with industry, conduct innovative research, develop practical solutions

• Upstream Oil & Gas (O&G) Industry

• 3 types of companies

• Land‐based operations

• Domestic focus

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Source PA Fire Commission, Chesapeake Energy

Each phase of wellsite activity has different hazards…

ProductionCompletionsWell Construction

Site Selection& Preparation

2 5 3 3

Operator experts rated the hazards in each phase of wellsite activity on a 1‐5 index, where 5 is considered the most hazardous…

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www.cdc.gov/niosh/docs/2010‐130/pdfs/2010‐130.pdf

NIOSH O&G Field Effort ‐ Chemical Exposures

1. Field (IH) research2. Upstream Oil & Gas (O&G) Industry3. Hazard identification /

determination 4. Risk evaluation / determination 5. Risk communication6. Controls (if necessary)7. Evaluation

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Industrial Hygiene Sample Collection and Analysis

• Respirable Particulates‐NMAM 0600• Respirable Silica‐NMAM 7500• Diesel Particulate Matter as Elemental Carbon‐

NMAM 5040• BTEX‐ NMAM 1500, 1501• Total VOCs (qualitative)‐NMAM 2549• PAHs/PACs‐ NMAM 5506/5800• Petroleum ethers/Naphthas‐ NMAM 1550• Drilling Fluid Aerosol‐ NMAM 5524• Elements on Wipes‐ NMAM 9102

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Sampling Equipment

BGI GK 2.69 Cyclone

Use of this company name does not imply Endorsement by NIOSH

SKC AirChek XR5000

Use of Real‐Time/Direct Reading Instruments

• 4‐gas + PID (photoionization detector) monitors with data logging and telemetry (CO, H2S, SOx, CH4, NOx, LEL, O2 and VOCs)

• Respirable Silica (Haz‐Dust)• Respirable fine particulate (diesel particulate, Haz‐Dust DPM)

• Drager Chip Measurement System (CMS: Total hydrocarbon, benzene, aldehydes, etc.)

• Field portable gas chromatograph • Advanced personal monitors• Infra‐red hydrocarbon camera

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Silica (Quartz)

• Silicon (Si) an element • SiO2 (silicon dioxide= silica, quartz)• Respirable crystalline silica (fine dusts) • Exposures regulated by OSHA• Silicosis, COPD, lung cancer, other disease • Occupational hazard of antiquity• ≈200 workers deaths per year U.S. • Preventable disease

Occupational Exposure Criteria Respirable silica (quartz)

• ACGIH TLV : 0.025 mg/m3 TWA

• NIOSH REL: 0.05 mg/m3 TWA

• OSHA PEL: 10 mg/m3 Resp. dust containing

( % silica + 2) silica

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Sand Use

• Hundreds of thousands of pounds per stage

• Proppant • Various shapes and

sizes • Virtually 100% silica

• Highest exposures are periodic. Silica exposures were found to increase during periods of heavy pumping; i.e., during hydraulic fracturing operations and/or during sand transfer.

• Traffic and site dusts are contributors to exposure.

• Prevalent winds and location in relation to the source are major determinants of exposure.

Respirable Silica Exposure

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Real‐time Respirable Silica

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Respirable Silica Results by Location

Site > ACGIH TLV* > NIOSH REL* > OSHA PEL* Total #

samples

A 24 (92.3%) 19 (73.1%) 14 (53.9%) 26

B 16 (84.2%) 14 (73.7%) 12 (63.2%) 19

C 5 (62.5%) 5 (62.5%) 4 (50.0%) 8

D 19 (90.5%) 14 (66.7%) 9 (42.9%) 21

E 25 (92.6%) 23 (85.2%) 18 (66.7%) 27

F 4 (40%) 1 (10%) 0 10

Total 93 (83.8%) 76 (68.5%) 57 (51.4%) 111

* Number of samples/%

Relative Comparisons, Geometric Means (mg/m3 ) by Job Titles

0

0.1

0.2

0.3

0.4

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Comparisons, Geometric Means, 95% Confidence Intervals

Exposure Comparisons by Job Title

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T‐Belt Operator

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Sand Mover Operator

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Blender Operator

Hydration Unit Operator

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Water Tank Operator

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Sand Coordinator

7 Primary Points of Dust Generation

1. Release from top hatches, sand movers 2. Transfer belt under sand movers3. Site traffic 4. Sand dropping in blender hopper5. Release from T‐belt operations6. Release from “dragon’s tail” 7. Dust ejected from fill ports on sand

movers

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1. Eliminate

2. Substitute

3. Engineering Controls

4. Administrative Controls

5. Personal Protective Equipment

Industrial Hygiene Hierarchy of Controls

Control of Dust Generation

1. Prevention through Design (PtD)2. Remote operations 3. Substitution (ceramic vs. quartz) 4. Implement Engineering Controls 5. Passive enclosures

Stilling (staging) curtains, shrouding 6. Minimize distance that sand falls 7. End caps on fill nozzles 8. Use amended water for site dust control 9. Effective respiratory protection program

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mini‐baghouse retrofit assembly

Proposed Controls, Sand Movers

Mini Baghouse Retrofit Ass’y

Proof of concept evaluation, June 2012

Patent pending

Self cleaning

No additional power req’d.

Control at point of generation

Bolt‐on, low cost control

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enclosure, skirting

end caps on fill nozzles


Caps on fill nozzles

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Screw augur retrofit


Screw augur to replace belt

Communicate the Risk • Signage

• Hazard Communication

• Include in JSA’s

• Periodic training

• Effective respiratory program

• Medical monitoring

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Conclusions• Silica: occupational health hazard for completions crews • Greater focus of “H aspects” of O&G extraction needed • Silica exposures can exceed the MUC for respirators • Numerous sources of dust generation• Respirators: workers need to be clean shaven • Simple controls: Caps on fill nozzles, close thief hatches, worksite

dust control, staging curtains, enclosures, shrouding, correct respirator use

• More involved controls: Development + implementation of engineering controls, reconfiguration of sand movers

• Prevention through Design (PtD) for sand movers & well site itself

Contact: Michael Breitenstein, NIOSH, Division of Applied Research and Technology, Cincinnati, OH(513) 533‐8290 [email protected]

Eric Esswein, CIH, NIOSH, Western States Office, Denver, CO(303) 236‐5946 [email protected]

John Snawder, Ph.D., DABT, NIOSH, Division of Applied Research and Technology, Cincinnati, OH(513) 533‐8496 [email protected]

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Respirable Dust Exposures of Workers Dowel Drilling Concrete Pavement and Evaluation of

Control Measures

Alan EchtIndustrial Hygienist

2013 Indiana Safety and Health Conference and ExpoMarch 11, 2013

National Institute for Occupational Safety and Health

Division of Applied Research and Technology

Disclaimers

The findings and conclusions in this presentation have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Mention of any company or product does not constitute endorsement by the Centers for Disease Control and Prevention or the National Institute for Occupational Safety and Health.

Subhead for Section – Myriad Pro, 20pt

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BACKGROUND

Background

Silica (quartz) dust causes silicosis Exposure also associated with other diseases

• Lung cancer

• Autoimmune disease

Concrete contains quartz

Concrete is used in highway construction

Repair and demolition produce respirable dust

Highway construction workers at risk of illness from exposures

Exposures should be controlled to reduce risk

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Background

New Jersey Department of Health and Senior Services (DHSS) has received funding since 1988 from the National Institute for Occupational Safety and Health (NIOSH), under their Sentinel Event Notification System for Occupational Risks (SENSOR) Program, to conduct disease surveillance for silicosis

The DHSS SENSOR identified 11 cases of

silicosis in road and elevated highway construction

NJ DHSS developed a sampling strategy to be used at worksites of ten partner contractors

New Jersey Department of Health and Senior Services (2001). Occupational Health Surveillance Update. Trenton, NJ, February 2001

Background

11 sets of samples collected at 9 different worksites

Sites involved 7 of 10 partner contractors.

53 samples collected for 7 different tasks

jackhammering concrete clean-up

dowel drilling concrete milling

concrete sawing asphalt milling

asphalt clean-up

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Background

NJ DHSS dowel drilling results

Data and photo courtesy of Daniel Lefkowiitz, NJ DHSS

JobDuration(minutes)

RespirableDust

(mg/m3)

QuartzContent

(%)

Laborer 271 5.19 5.4

Laborer 273 1.40 6.7

Background

NIOSH Division of Respiratory Disease Studies (DRDS) also evaluated silica exposures from concrete in construction and demolition

Tasks evaluated Abrasive blasting of concrete

Dowel drilling

Concrete grinding

Concrete sawing

Pavement milling

Linch, Kenneth D (2002). Respirable Concrete Dust—Silicosis Hazard in the Construction Industry. Applied Occupational and Environmental Hygiene 17(3): 209–221.

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Background NIOSH DRDS dowel drilling results

Photos and data courtesy of Ken Linch,

JobNumber

ofSamples

Geometric Mean Respirable Dust

(mg/m3)

RangeRespirable

Dust(mg/m3)

RangeQuartz

Content(%)

Backhoe 8 1.1 0.49-2.0 ND-8.9

Driller 8 3.7 2.0-12 10-17

Background

Dowel drilling process Full depth pavement repair

• Saw cut perimeter of repair

• Break-out or lift old concrete

• Drill into perimeter of repair

Airport runway construction• Pour new slab

• Allow to cure

• Drill into edges of slab

Dowels transfer load between slabs

Photo courtesy E-Z Drill. Inc.

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Background

Dowel drills 1-5 pneumatic or hydraulic rock drills arranged in parallel

Frame aligns drills perpendicular to concrete surface

On-slab, on-grade, or boom mounted

Two manufacturers

Both sell optional dust controls

No documentation that they reduce exposures

Photos courtesy of E-Z Drill, Inc. (l) and Minnich Manufacturing(r)

Background

Dust controls for small pneumatic rock drills first reported in the 1920s Hay 1926

Kadco 1932

Drill-Vac 1937

Cooper, Susi, & Rempel 2012

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A LABORATORY STUDY OF DOWEL DRILL DUST CONTROLS

A laboratory study of dowel drill dust controls

Objective To determine the relative reduction in respirable dust emissions

achieved through the use of local exhaust ventilation dust control systems

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Process description Minnich A-5SCW E-Z Drill 210-3


Sampling strategy• Compared respirable dust emissions dust “control on” versus dust

“control off”

• Paired “control on” and “control off” trials

• Randomized “control on” and “control off” order in pairs

• A round consisted of a pair of “control on” and “control off” trials

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Sampling procedures Respirable dust samples collected during “control-on” and

“control-off” trials at three locations around the drills at breathing zone height

Samples collected and analyzed according to NIOSH Method 0600 - pre-weighed filters were desiccated and weighed after sampling.

Samples collected using Higgins-Dewell cyclones (Model 4L, BGI, Inc. Waltham, MA) at 2.2 liters/minute


Test procedure Position drilling machine

Position samplers

Start samplers – record start time

Close tent

Start drills by remote control

Record last drill stop time

Wait five minutes

Open tent

Stop samplers – record stop time

Purge tent

Position drilling machine

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Measured control parameters Measured exhaust air and bailing air (flow through the drill stem

and bit to flush the cuttings from the hole)

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Sample size calculations Used RSD from pilot study

One sided test (i.e., only concerned about the significance of the reduction)

Log-normal distribution, split-plot design

Designed to observe a 75% emissions reduction with a power of .80 and 95% confidence

At least 4 test rounds with samples in three positions were required


Statistical analysis Univariate procedure used to test lognormality of the data

Took natural logs (ln) of dust concentration. ln dust concentration was dependent variable

Calculated geometric mean (GM) dust concentration for each position and both conditions

Calculated GM reduction ratio (1 - GM “control on”/GM “control off”)

T-tests used to test hypothesis that “control on” ≠ “control off”

General Linear Model procedure was used to construct a model of the emissions reduction

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Results Minnich site

• n = 42 respirable dust samples collected in 7 rounds of sampling

o 7 samples in 3 locations “control-on” condition = 21 samples

o 7 samples in 3 locations “control-off” condition = 21 samples

E-Z Drill site• n = 48 respirable dust samples collected in 8 rounds of sampling

o 8 samples in 3 locations “control-on” condition = 24 samples

o 8 samples in 3 locations “control-off” condition = 24 samples

Total n = 90 samples, 45 in each control condition.


Number of Samples

Geometric Mean

(mg/m3)

GeometricStandard Deviation

Range(mg/m3) p-Value

E-Z Drill

Control OFF 24 54 1.3 30-82<0.0001

Control ON 24 3.0 1.5 1.9-6.0

Minnich

Control OFF 21 57 1.2 39-79<0.0001

Control ON 21 5.3 1.9 1.6-12

Overall

Control OFF 45 55 1.3 30-82<0.0001

Control ON 45 3.9 1.8 1.6-12

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Results Emissions without dust control 14 times higher

93% reduction in emissions

Location of sample not significant (p = 0.3488)

Controls significantly reduced dust (p<0.0001)

A FIELD STUDY OF DOWEL DRILLING DUST CONTROLS

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A field study of dowel drilling dust controls

Objective Ascertain the effectiveness of the controls on job sites by

comparing exposures associated with the use of the controls to exposures without controls


Site Descriptions Site 1 – Full-depth concrete pavement replacement with two 3-

drill boom-mounted dowel drills without dust collection systems

Site 2 – Full-depth concrete pavement replacement with two 3-drill boom-mounted dowel drills without dust collection systems

Site 3 – Concrete runway construction with two 4-drill slab-rider dowel drills without dust collection systems

Site 4 – Concrete runway construction with two 5-drill slab rider dowel drills with dust collection systems

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Sample size calculations Based on desire to determine at least a 75% reduction in

exposures power of .80 and 95% significance

Used data from sites 1 and 2, with GSD of 1.94

Lyles, R.H., & Kupper, L.L. (1996). On Strategies for Comparing Occupational Exposure Data to Limits. American Industrial Hygiene Association Journal, 6-15.

Alpha Power n GSD RSD STDln

Limit/Exposure % Change

0.05 0.8 15 1.81 0.65 0.59 2.0 50

0.05 0.8 10 1.81 0.65 0.59 2.5 60

0.05 0.8 6 1.81 0.65 0.59 4.0 75

0.05 0.8 18 1.96 0.75 0.67 2.0 50

0.05 0.8 12 1.96 0.75 0.67 2.5 60

0.05 0.8 7 1.96 0.75 0.67 4.0 75


Sampling strategy Tasked-based sampling

Partial period-consecutive samples

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Sampling procedures Air sampling sites 3 and 4

• Higgins-Dewell (model 4L, BGI, Inc., Waltham, MA) cylone and pre-weighed PVC filter clipped in breathing zone and sampling pump (model 224, SKC, Inc., Eighty Four, PA) calibrated to 2.2 L/min worn at belt on worker’s waist


Sampling procedures Weather monitoring

• Wind speed and direction data collected at sites 3 and 4 using tripod-mounted data-logging wind meters

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Sampling procedures Measurement of dust control flow rate – site 4

Measured air flow at dust collectors of both drills using in-line mass flow meter (model 730-N5-1, Sierra Instruments, Inc., Monterey, CA)


Data analyses Time weighted average (TWA) exposure data were transformed

to their natural logs (ln) and analyses were performed using lnTWA as the dependent variable

Descriptive statistics were calculated

T-tests used to assess exposure differences with and without dust controls

T-tests used to assess exposure differences between backhoe operators and drillers at sites 1 and 2

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Data analyses General linear model used to assess the impact of other

variables on ln exposure

Mixed model analysis used to assess effect of control, adjusting for job and controlling for unequal exposure measurement between workers

Nonparametric analyses conducted on the effect of controls due to very small sample size


ResultsPersonal Respirable Dust Exposures by Site and Job

Site Job nGM

(mg/m3)GSD

Range(mg/m3) p-Value

1 Backhoe 4 0.85 1.6 0.49-1.6

1 Driller 4 3.2 1.5 1.7-6.0

2 Backhoe 4 1.5 1.3 1.1-2.0

2 Driller 4 3.0 2.3 2.0-12

3 Driller 6 3.3 4.0 0.45-21

4 Driller 3 3.0 1.9 1.7-6.0

Total 25 2.4 2.5 0.45-21

Comparing Exposures Across Sites 1 and 2

Backhoe 8 1.1 1.6 0.49-2.00.0006

Driller 8 3.7 1.8 2.0-12

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ResultsDust Control was not Significantly Different from No Control

Parametric Statistics

Dust ControlMeasures

nGM

(mg/m3)GSD

Range(mg/m3)

ProbabilityStatistic

Student’s T-test

Off 14 3.48 2.60 0.45-210.795

On 3 2.98 1.90 1.7-6.0

General Linear ModelAnalysis of Variance

R2 Estimate F Value0.795

0.0046 0.154 0.007

Mixed Model ProcedureAIC Estimate F Value

0.46244.7 0.648 0.60


ResultsDust Control was not Significantly Different from No Control

Non-Parametric Statistics

Wilcoxon Rank Sums

ControlNumber

ofSamples

Mean Score

0.757Off 14 8.0

On 3 9.2

Median Scores

ControlNumber

of Samples

MeanScore

0.611Off 14 0.33

On 3 0.50

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Results Simple linear regression using the General Linear Model

y=3.27-0.3x+e

Where:

y is the dependent variable, ln TWA exposure

3.27 is the intercept

-0.3 is the coefficient

x is the wind speed (mph)

e is the error


Results Air flow measurements

• Worker c’s drill – 90 m3/hr

• Worker d’s drill – 96 m3/hr

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Discussion and Conclusions GM respirable dust exposures with the dust control were not

significantly different from exposures without the control

Wind speed (which approached significance) had more effect on exposure reduction than the control

Performance could be due to design (low transport velocity, extensive use of flexible duct), maintenance practices, or work practices. More sites needed to find out.

EVALUATION OF A HIGH-VOLUME SAMPLER FOR SHORT-TERM TASKS

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Evaluation of a high-volume sampler for short-term tasks

Objective To design, fabricate, and test a new cyclone sampler


Background 19% of the samples collected during the laboratory evaluation

were less than the limit of detection (LOD), 24% were between the LOD and the limit of quantitation (the mass of analyte equal to 10 times the standard error of the calibration graph divided by the slope)

Minimum detectable concentration (MDC) = LOD/Sample Volume

Sample volume = time x flow rate

Increasing flow rate can reduce the MDC

Cyclone samplers use centrifugal force to separate particles by size

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Background Cyclone samplers evaluated against respirable dust convention

Particle Aerodynamic Diameter (µm) Respirable Particulate Matter

Fraction Collected (%)

0 100

1 97

2 91

3 74

Particle Aerodynamic Diameter (µm) Respirable Particulate Matter

Fraction Collected (%)

0 100

1 97

2 91

3 74

4 50

5 30

6 17

7 9

8 5

10 1


Background Kenny and Gussman (1997) described a scalable cyclone

design

The UK Health and Safety Laboratory (HSL) has extensive experience evaluating respirable dust samplers

Contracted with Gussman’s company and the HSL to design, fabricate, and evaluate a new

cyclone sampler

Photo and drawing courtesy of BGI, Inc.

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Methods Measured aerosol penetration through the sampler

Measured the challenge aerosol

Compared the two to characterize the sampler


Methods Measured aerosol penetration through the sampler

• Generated polydisperse aerosol of glass beads in sampling chamber

• Connected sampling tube to cyclone

near inlet

• Particle size distribution measured with

aerosol particle sizer (APS)

Photo courtesy Andrew Thorpe, Health and Safety Laboratory

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Methods Measured the challenge aerosol

• Prepared an identical set of tubing without the cyclone attached

• Collected a series of 1-minute samples

• Alternated between cyclone and reference

samples with 1-minute break to clear tubing

Photo courtesy Andrew Thorpe, Health and Safety Laboratory


Data Analyses Particle concentrations measured with and without cyclone

(reference aerosol) were averaged at each particle size

Cyclone:Reference ratio is measure of penetration

Normalized the penetration to 1 at 1 micrometer to compensate for APS characteristics for particles less than 1 micrometer

Used bias map technique to assess the difference between the sampler and the respirable dust convention

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Results Measured D50 values

FlowRate

(L/min)

D50

Test 1 Test 2 Test 3 Mean SDCOV (%)

7 4.90 4.90 4.88 4.89 0.012 0.24

8 4.37 4.28 4.38 4.34 0.055 1.27

8.5 4.18 4.05 4.05 4.09 0.075 1.83

9 3.99 3.87 3.88 3.91 0.067 1.70

9.5 3.70 3.67 3.65 3.67 0.025 0.69

10 3.52 3.45 3.43 3.47 0.047 1.36


Results Measured D50 values versus flow rate

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Results Bias Maps

At 8.5 L/min, sampler was

within 2% of target

85% of bias was within +/-10%

of target value


Results Bias Maps


within 2% of target


of target value

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Results Bias Maps


within 2% of target


of target value


Discussion and conclusions Cyclone agrees with sampling convention at 3 flow rates

Simpler, cheaper, better, and made in USA (and tested in the UK) versus French and German high-flow personal samplers

Drawings from Arelco and Gesellschaft für Schadstoffmessung und Auftragsanalytik) Messgerätebau GmbH,

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Discussion and Conclusions New cyclone will be able to detect and quantify respirable

particles, such as quartz, in a much shorter time

Suitable for short term tasks or breaking down larger tasks into components for exposure evaluation

Subject to overloading in dusty environment

For more information please contact Centers for Disease Control and Prevention1600 Clifton Road NE, Atlanta, GA 30333Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348E-mail: [email protected] Web: www.cdc.gov

Alan EchtEngineering and Physical Hazards BranchDivision of Applied Research and TechnologyNational Institute for Occupational Safety and Health4676 Columbia Parkway, R-5Cincinnati, Ohio [email protected](513) 841-4111 phone(513) 841-4506 fax


Division of Applied Research and Technology

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Engineering Controls to Prevent Silica Exposure during Asphalt Pavement Milling

Duane Hammond, M.S., P.E.

2013 Indiana Safety and Health Conference and ExpoMarch 11, 2013


Division of Applied Research and Technology – Engineering and Physical Hazards

Disclaimer: “The findings and conclusions in this presentation are

those of the author(s) and do not necessarily represent the views of

the National Institute for Occupational Safety and Health.”

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Presentation Outline

Silica hazard

Cold milling in highway construction and repair

Background – Forming the Partnership

2003-2006 individual milling studies Evaluated water-spray controls

Millfest studies 2008 Marquette, Michigan airport (four manufacturers)

2010 Shawano, Wisconsin (five manufacturers)

2011 tracer gas studies of ventilation controls

2012 field testing of ventilation controls

What is silica?

Silicon dioxide (SiO2) Occurs in crystalline or non-crystalline form

Forms of crystalline silica alpha quartz (most common)

beta quartz

tridymite

cristobalite

keatite

coesite

stishovite

moganite

Ampian SG, Virta RL [1992]. Crystalline silica overview: Occurrence and analysis. Washington, DC: U.S. Department of the Interior, Bureau of Mines, Information Circular IC 9317.

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How are workers exposed?

Silica is commonly found in rocks, sand, and construction materials.

Silica dust is generated by rock drilling, concrete sanding or cutting, tuck pointing, concrete sawing, concrete grinding, and abrasive blasting.

Lung disease called silicosis develops by breathing respirable crystalline silica particles.

Asphalt milling

rotating cutter drum to grind and remove the pavement to be recycled

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Silica exposure during asphalt milling

Road milling has been shown to result in overexposures to respirable crystalline silica Linch KD [2002]. Respirable concrete dust – silicosis hazard in the construction industry. Appl OccupEnviron Hyg 17(3):209–221.

Rappaport SM, Goldberg M, Susi P, Herrick RF [2003]. Excessive exposure to silica in the U.S. construction industry. Ann Occup Hyg 47(2):111–122.

Valiante DJ, Schill DP, Rosenman KD, Socie E [2004]. Highway repair: a new silicosis threat. Am J Public Health 94(5):876–880.

Asphalt Partnership

Originated in 1994 with the asphalt fume study

Seven engineering studies were conducted between 1994 and 1997.

The 1990’s research resulted in the publication of engineering control guidelines: ENGINEERING CONTROL GUIDELINES

FOR HOT MIX ASPHALT PAVERS (1997)http://www.cdc.gov/niosh/asphalt.html

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Engineering Controls were put on all new highway class pavers

* The asphalt fumes studies were led by NIOSH researchers Kenneth R. Mead, Ph.D., P.E. and R. Leroy Mickelson, M.S., P.E.

Formation of Silica/Milling Machines Partnership

April 5, 2002 NIOSH meeting to propose silica partnership Association of Equipment Manufacturers (AEM) Compaction and Paving Machinery Technical Committee

July 23, 2002 NIOSH phone call to propose partnership National Asphalt Pavement Association (NAPA) The Asphalt Institute Harvard

January 15, 2003 NAPA meeting The silica/milling machines partnership was formed Shared many of the members as the asphalt fumes partnership

Milling studies began later in 2003 in Wisconsin.

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SILICA/MILLING MACHINE PARTNERSHIP MEMBERS

National Asphalt Pavement Association (NAPA)

Wirtgen Caterpillar Terex Roadtec Volvo Payne and Dolan Midwest Paving/Delta Paving Northeast Asphalt E&B Paving Inc. L&L Astec Industries Sakai America, Inc. Bomag Colas Inc Midwest Asphalt Corporation NIOSH

OSHA Association of Equipment

Manufacturers (AEM) International Union of Operating

Engineers (IUOE) Federal Highway Administration (FHWA) Dynapac Delta Companies, Inc. Barrett Paving Materials, Inc. Tilcon Connecticut Inc. Laborers' Health Safety Fund of North

America (LHSFNA) Asphalt Recycling & Reclaiming

Association (ARRA) Upper Plains Contracting Inc. (UPCI) Asphalt Paving Association of California

(APACA) Laborers’ International Union of North

America (LIUNA)

Initial project goals

Determine if existing water-spray systems used to cool cutting teeth could also control respirablecrystalline silica exposures.

Improve dust controls by modifying water-spray flow, nozzle pressure and nozzle location.

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Area sampling methods

Continuous-monitoring, data-logging optical particle counters (pDR instruments) were mounted at fixed locations on each machine.

Two battery-operated sampling pumps, each connected through flexible tubing to a sampling head consisting of a standard 10-mm, nylon, respirable size-selective cyclone followed by a pre-weighed, 37-mm diameter, 5-micron (μm) pore-size polyvinyl chloride filter.

Area dust sampling setupArea dust sampling setup

pDR Instantaneous dust monitor (one sample every 10 sec)

pDR Instantaneous dust monitor (one sample every 10 sec)

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Conveyor TopConveyor Top ConveyorConveyor

Cutting Drum BackCutting Drum Back

OperatorOperator

Cutting Drum Front

Cutting Drum Front

Ten Respirable Dust Sampling LocationsTen Respirable Dust Sampling Locations

Four of Ten Dust Sampling LocationsFour of Ten Dust Sampling Locations

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2003 Pilot Study

Two day study on US Route 12 in Wisconsin

Evaluated higher flow water-spray nozzles

Measured respirable dust and respirable quartz exposures in personal and area samples

Reductions were not statistically significant

2004 Silica/Milling Machines Partnership Study

Asphalt Milling of US Route 22 and SR 64 in Wisconsin Increasing the water flow

Cutter drum spray bars from 5 gallons per minute (gpm) to 9 gpm

2 gpm to 3 gpm at the conveyor sprays Resulted in an overall reduction in respirable dust

emissions of about 50%, and nearly as great a reduction in respirable quartz emissions.

Results varied by location with the greatest reduction occurring at the conveyor sampling location.

Six trials are not sufficient to make good predictions

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2006a Silica/Milling Machines Partnership Studies

U.S. Highway 2 resurfacing project Minnesota, June 20-22, 2006 Increased the water-flow rates to the spray nozzles

at the cutter drum from 16 gpm to 18.5 gpm. Resulted in no clear reduction in respirable dust

concentrations at area air monitoring locations around the machine.

Factors affecting the studySmall difference in the water flow rates Interruption in the flow of trucks removing the

milled asphaltSubstantial down time in the actual milling

2006b Silica/Milling Machines Partnership Studies

South Dakota Highway 79 South Dakota, August 15-17, 2006 Increasing the total water flow to the water-spray

nozzles from 12.5 gpm to 18.8 gpm . 41% average reduction based on the results of the

time-integrated air sampling method 53% mean reduction based on the real-time data-

logging instrumentation Both of these reductions were statistically

significant at the 95% confidence level (or the p < 5% level).

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2006c Silica/Milling Machines Partnership Studies

New York State Thruway (Interstate Highway 90) resurfacing project Hamburg, New York, September 25-26, 2006

Increased the total water flow to the water spray nozzles from about 12.5 gpm to about 20 gpm

Did not result in overall reductions in respirable dust and quartz concentrations at area air-monitoring locations around the machine.

Summary of PBZ Air-Sampling Results(pre-2008)

PBZ Air Sampling:Summary of Results (mg/m3)

Mfr. AWisconsin 2004

Mfr. BMinnesota 2006

Mfr. CSouth Dakota 2006

Mfr. DNew York state2006

Maximum / GM concentrations:Respirable dust, high H2O flow, operator

1.60.90

0.250.15

0.440.11

2.31.14

Maximum / GM concentrations:Respirable dust, high H2O flow, ground man

0.570.36

1.060.87

0.300.14

0.890.79

Maximum / GM concentrations: Respirable crystalline silica, high H2O flow, operator

(0.07)0.053

NDND

NDND

0.370.18

Maximum / GM concentrations: Respirable crystalline silica, high H2O flow, ground man

(0.04)0.022

(0.058)0.048

NDND

0.160.14

# Exceedances of 0.05 mg/m3 silica / # samples: High H2O flow, Low H2O flow

3/64/6

2/61/6

0/120/10

6/62/4

# Exceedances of PEL / # samples:High H2O flow, Low H2O flow

0/62/6

0/60/6

0/120/10

6/61/4

12

2008 Silica/Milling Machines Partnership Studies – Mill Fest I & II

Abandoned airport runway in Marquette, MI during June and August of 2008

Four manufacturers, each with multiple water spray configurations and one with a ventilation control

Water spray controls indicated reductions in respirable dust emissions of approximately 43%

Ventilation controls indicated reductions in respirable dust emissions of approximately 65%

2010 Silica/Milling Machines Partnership Study –Mill Fest III

Wisconsin State Hwy 47 south of Bonduel, WI Five manufacturers, each with multiple water spray

configurations and one with a ventilation control Water spray configurations that indicated reductions in 2008,

did not show similar reductions in 2010 when more trials were completed

Wet drum water spray controls tested in 2010 indicated reductions in respirable dust emissions of approximately 32% but were not statistically significant due to high variability

Ventilation controls indicated reductions in respirable dust emissions of 81%

13

2012 Silica/Milling Machines Partnership testing

Laboratory/Factory tracer gas testing Manufacturer A (Racine, WI) August 2-3, 2011

Manufacturer D (Oklahoma City, OK) August 16-17, 2011

Manufacturer B (Chattanooga, TN) April 17, 2012

Manufacturer C (Minnesota) August 23, 2012

Field testing Manufacturer A - vacuum cutting system (VCS)

• June 26 – August 1, 2012 (11 days spread over four sites)

Manufacturer E – prototype wet drum• August 17-18, 2012 (2 days of testing including 19 trials)

Manufacturer B local exhaust ventilation (LEV)• September 18 – October 13, 2012 (10 days spread over seven sites)

Tracer gas testing at each manufacturer’s facility

14

Tracer gas set-upWood blocks and cardboard allowed space for test equipment under edge protection plates

Wood blocks and cardboard allowed space for test equipment

Oil boom under front gradation control beam

Set-up continued

Rear scraper blade was flush to the ground

15

Tracer gas methods

Smoke Release Chauvet Category 2 Hurricane” fog machine

Tracer Gas (TG) Sulfur Hexafluoride (SF6)

Measured in the duct downstream of the fan

CSF6 = mean concentration TG released under the drum

CSF6 = mean concentration when TG released in duct

Smoke test

Provides visual check of large leaks

Released under the cutting drum 8 foot long, 2 inch diameter PVC pipe

16, ¼ inch holes drilled along the length

16

Tracer gas test

Cylinder of pure SF6 with CGA-590 pressure regulator

Omega mass flow controller

¼ in diameter Teflon tubing with Swagelok connections

Quick-release connection for switching between 100% capture release point and the cutting drum release point.

100% capture injection location

Tracer gas distribution pipe inserted here

Tracer gas sampling

¼ in dia copper probe located in the duct downstream of the fan.

Two gas meters were used to pull samples simultaneously from the air stream. Miran SapphIRe infrared spectrometer

Brüel & Kjær multigas monitor

17

Manufacturer A laboratory tracer gas capture efficiency results from 2011

Trial Capture Efficiency (B&K)

Capture Efficiency (Miran SapphIRe)

1 91.6% 92.3%

2 93.2% 94.0%

3 93.4% 93.6%

4 93.0% 94.2%

5 92.4% 93.3%

Average 92.7% 93.5%

Lower 95% confidence

limit

92.0% 92.7%

Manufacturer D laboratory tracer gas capture efficiency results from 2011

Trial Capture Efficiency (B&K) Capture Efficiency (Miran SapphIRe)

1 (900 acfm) 99.5% 100%

2 (900 acfm) 99.3% 99.6%

3 (900 acfm) 99.8% 100%

4 (900 acfm) 100% 100%

Average 99.7% 99.9%

Lower 95% confidence limit

99.3% 99.7%

Trial Capture Efficiency (B&K)


1 (1300 acfm) 100% 100%

2 (1300 acfm) 100% 100%

1 (600 acfm) 97.1% 98.2%

2 (600 acfm) 97.0% 97.4%

1 (900 acfm)* 99.2% 100%

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Manufacturer B laboratory tracer gas capture efficiency results

Trial Capture Efficiency (Photoacoustic

monitor)


1 99% 100%

2 99% 99%

3 98% 99%

4 96% 95%

5 100% 100%

Average 98% 99%


limit

97% 97%

Manufacturer C laboratory tracer gas capture efficiency results

Fan Speed (RPM) Trial 1 Trial 2 Trial 3 Mean


limit

3,500 100.0% 97.0% 97.4% 98.1% 95.7%

3,000 99.4% 99.4% 93.8% 97.5% 95.1%

2,500 95.6% 93.3% 95.3% 94.7% 92.3%

2,000 87.5% 91.3% 87.0% 88.6% 86.2%

19

LEV control field studies

Field Testing Goals

The aim is to determine whether the exposures are below the NIOSH REL of 0.05 mg/m3 and the ACGIH TLV of 0.025 mg/m3, which can be demonstrated if the upper confidence limits for each occupation’s arithmetic mean is less than the REL and TLV.

20

Personal breathing zone (PBZ) sampling methods

Full-shift time weighted average personal breathing zone sampling was conducted for respirable crystalline silica.

Respirable dust cyclones (model GK2.69, BGI Inc., Waltham, MA) at a flow rate of 4.2 liters/minute (L/min) were attached to the breathing zone of the operator and ground man.

Crystalline silica analysis of filter samples was performed using X-ray diffraction in accordance with NIOSH Method 7500.

Manufacturer A vacuum cutting system (VCS) summary results

11 days of sampling over four sites

Operator and ground man PBZ

22 PBZ samples

Ranged from 0.003 mg/m3 to 0.013 mg/m3

Silica content ranged from 7% to 23%

21

Manufacturer A vacuum cutting system (VCS) statistical results

Occupation Arithmetic mean (AM),

mg/m3

Relative Standard

Deviation (RSD) between sites

Relative Standard

Deviation (RSD), within sites

Simultaneous Upper 95% Confidence Limits (AM) for both Occupations, mg/m3

Operator 0.0071 22% 47% 0.011

Ground man 0.0066 11% 38% 0.0093

Data treated as lognormally distributed

Data treated as normally distributed

Occupation Arithmetic mean

(AM), mg/m3

Geometric mean (GM),

mg/m3

Geometric standard deviation

(GSD), between sites,

mg/m3

Geometric standard deviation

(GSD), within sites, mg/m3

Simultaneous Upper 95% Confidence Limits**(AM)

for both Occupations,mg/m3

Operator 0.0075 0.0061 1.37 1.76 0.019Ground

man0.0068 0.0061 1.13 1.59 0.013

Manufacturer E - wet drum % reduction results

19 short-term trials were conducted to compare reductions in respirable dust concentrations between the wet drum and baseline water configurations.

Ratio = Wet drum/baseline

Ratios with upper 95% confidence intervals greater than 1 were not statistically significant.

Lower 6 Operator Conveyor Top

Estimated Ratio (GM) 0.63 0.73 1.15

(lower conf limit, upper conf limit) (0.39,1.01) (0.46,1.18) (0.72,1.86)

Geometric mean ratios and 95% confidence limits

22

Manufacturer E - wet drum personal breathing zone results

Personal breathing zone samples were also collected during the two days of sampling for the operator and the ground man.

Operator 0.085 mg/m3 on day 1

0.028 mg/m3 on day 2

Ground man 0.040 mg/m3 on day 1

0.043 mg/m3 on day 2

Bulk samples contained 14% quartz, 0.51% cristobalite

Manufacturer B - local exhaust ventilation (LEV) summary results

10 days of sampling over seven sites

Operator and ground man PBZ

20 PBZ samples

Ranged from 0.002 mg/m3 to 0.013 mg/m3

(except for 1 day at 0.024 mg/m3 with partly clogged LEV)

Silica content ranged from 5% to 12%

23

Manufacturer B - local exhaust ventilation (LEV) statistical results

OccupationArithmetic mean (AM),

mg/m3, from models

Relative standard deviation (RSD),

between sites

Relative standard deviation (RSD), within

sites

Simultaneous Upper 95% Confidence

Limits(AM) for both Occupations , mg/m3

Ground man 0.011 61% 26% 0.018

Operator 0.0049 52% 35% 0.0083

Occupation

Arithmetic mean (AM),

mg/m3, from model

Geometric mean (GM),

mg/m3

Geometric standard deviation (GSD),

between sites, mg/m3

Geometric standard deviation (GSD), within

sites, mg/m3

Simultaneous Upper 95% Confidence Limits (AM) for both Occupations ,

mg/m3

Ground man 0.011 0.00871.76 1.39

0.0246

Operator 0.0053 0.0043 0.012

Data treated as normally distributed

Data treated as lognormally distributed

Summary

The LEV systems of manufacturer’s A and B have the potential to significantly reduce worker exposure to respirable crystalline silica during pavement milling operations.

NIOSH researchers recommend that manufacturers of half-lane and larger cold milling machines should implement dust controls that include local exhaust ventilation as a control for silica exposures.

24

NIOSH Team

NIOSH Cincinnati Duane Hammond, M.S., P.E.

Leo Blade, M.S., C.I.H.

Stanley Shulman, Ph.D.

Alan Echt, M.S., C.I.H.

Liming Lo, Ph.D.

Mike Gressel, Ph.D., C.S.P.

Kenneth R. Mead, Ph.D., P.E.

Nick Trifonoff

NIOSH Pittsburgh Andrew Cecala

Jay Colinet

Jeanne Zimmer

Gregory Chekan, B.S., MinE

Gerald Joy, C.I.H., C.S.P.

Duane Hammond, M.S., P.E.National Institute for Occupational Safety and Health4676 Columbia Pkwy MS R-5Cincinnati, OH 45226(513) 841-4286

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