OSHA’s Proposed Silica Standard and the Epidemiology and ... s/EEI Fall 09/OSHA... · the Epidemiology and Management ofthe Epidemiology and ... Dennis Ertel, Jr., CIH, CSP, REM

OSHA’s Proposed Silica Standard and the Epidemiology and Management ofthe Epidemiology and Management of

Silica Exposures

A Presentation to:

The Edison Electric Institute

H d S dl MDHoward Sandler, MDDennis Ertel, Jr., CIH, CSP, REM

Sandler Occupational Medicine Associates, Inc.pOctober 2009

Silica (SiO2)Silica (SiO2)

• Amorphous v. CrystallineAmorphous v. Crystalline• “Most Abundant Mineral on Earth”• CrystallineCrystalline

– “Free”• Quartz (Most Common)/Cristobalite, ( ) ,

Tridymite– “Combined Silicate”

• Asbestos, Talc, Kaolinite• Degree of Crystallinity and Health Risk

Sandler Occupational Medicine Associates © 2009

Molecular Structure of SilicaThe term “crystalline” is applied when the arrangement of atoms in the material is highly ordered in boththe material is highly ordered in both short and long range in three dimensions repeating pattern.

Crystalline silica (2-D)

Amorphous silica (2-D)


History of SilicosisHistory of Silicosis

“Silicosis is a socialSilicosis is a social disease with medical

t ”aspects”Irving J. Selikoff, MD


Silica (SiO2)

• Percent Free Silica• Percent Free Silica– Granite – 30%

Sl t 40%– Slate – 40%– Sandstone – 100%


Deposition in Respiratory TractDeposition in Respiratory Tract

P i l Si ( ) L tiParticle Size (μm)> 15 μm

LocationOuter Portion Nasal Passage

10-15 μmNasal Turbinates, Pharynx

Considered INHALED Major5-10 μm

Considered INHALED – Major Airways Trachea, Major Stem Bronchi

<5 μm Considered RESPIRABLE –Terminal Bronchioles, Alveoli


Silica Exposure Measurements and Applicability to Epidemiology

MethodsMethods

• Measure two aspectsMeasure two aspects– Weight of Dust

Presence of Crystalline Silica– Presence of Crystalline Silica– Original Limits Designed around these two

componentscomponents• Size Selective Sampling


LimitsLimits

• Current LimitsCurrent Limits– OSHA/MSHA PEL is calculated using a

formula:formula:• PEL for respirable free silica = __10___

% free silica + 2– NIOSH REL= 0.05 mg/m3 (or 50 µg/m3)– ACGIH TLV (quartz and cristobalite) = 0.025 CG (qua t a d c stoba te) 0 0 5

mg/m3


Limits (cont’d)Limits (cont d)

• Historical Limits (NIOSH 1974 CriteriaHistorical Limits (NIOSH 1974 Criteria Document)

Prior to 1940: 4 20 mppcf– Prior to 1940: 4 – 20 mppcf– Early Concept: Limit = K / %SiO2 mppcf


Size Selective SamplingSize Selective Sampling

• Collects a fraction of smaller particles –Collects a fraction of smaller particles more likely to reach deeper portions of the respiratory systemthe respiratory system

• Device in Sampling TrainR i bl S li D i• Respirable Sampling Devices –Cyclones

• Other Size Selective Devices


CIP 10 SamplerCIP 10 Sampler

From AIHCE 2009, PDC 305


AnalysisAnalysis

• Goal – to be able to correctly identify theGoal to be able to correctly identify the polymorph of crystalline silica, distinguish from non crystalline forms of silica and

if 0 1 h h ld (AIHAJquantify at a 0.1 percent threshold (AIHAJ 1999).I• Issues– Sample Handling

Resolution– Resolution– Matrix Effects and Spectral Overlap– Relatively Low Concentrationse at e y o Co ce t at o s


Analytical MethodsAnalytical Methods

• Gravimetric (measures mass)Gravimetric (measures mass)• Silica Identification

O ti l Mi (P t hi )– Optical Microscope (Petrographic)– Chemical or Colorimetric Methods (usually

measures silicon and can’t distinguish)measures silicon and can t distinguish)– Infrared – Several Methods

Detection Ranges: 10 1000 µg; LOD: 5 10• Detection Ranges: 10 – 1000 µg; LOD: 5 – 10 µg

– X-Ray Diffraction – Several MethodsX Ray Diffraction Several Methods• Detection Ranges: 20 – 2000 µg; LOD: 5 µg


Comments on the Methodology -19571957

• “The [optical microscopic] method is not suitable [ p p ]for very fine particles and estimation based on particles less than 10 microns in size is not good petrographic practice ”petrographic practice.

• “The X-Ray diffraction method of dust analysis has become of increasing importance … from g pthe point of view of speed, while it appears to yield results of as great accuracy as obtained by other methods ”other methods.

(1957 Industrial Toxicology)



• “Differentiation of free silica (SiO2) from silicates ( 2)cannot be accomplished satisfactorily by chemical means. However, … [with the right particle size and mass] may be satisfactorilyparticle size and mass] may be satisfactorily determined … by combining chemical & petro graphic techniques.”

• “Where all dust particles are less than 5 ug in diameter, the only successful means so far devised of determining the crystalline free silicadevised of determining the crystalline, free silica content is by X-Ray diffraction.”

(1958 Pattys)(



• “Three principal methods are currently used.”p p y• “The colorimetric procedure is the most

universally used. However, there are two serious d b k t thi t h i l th d ”drawbacks to this wet chemical method.”

• “The infrared procedure is a relatively new analytical method [with] the potential for theanalytical method … [with] the potential for the qualitative identification of the free silica polymorphs … [A] drawback is the dependence of analytical results on particle size ”of analytical results on particle size.”

(1974 NIOSH Criteria Document)



• “The X-Ray diffraction procedure … isThe X Ray diffraction procedure … is specific for the various forms of free silica … and requires less preparation [than the

h h d ] ”other methods].” • “None of the methods … are ideal for

l i f d t f f ili d llanalysis of dust for free silica under all conditions, but … the X-Ray diffraction method is recommended as the method ofmethod is recommended as the method of choice.”

(1974 NIOSH Criteria Document)



• “The Results of the collaborative testsThe Results of the collaborative tests indicate that both the XRD and IR methods tested meet the NIOSHmethods tested meet the NIOSH accuracy criterion over the range of filter loadings measured ”loadings measured.

(1995 NIOSH Comments on Analytical Methods)



• “For respirable dusts NIOSH AnalyticalFor respirable dusts, NIOSH Analytical Method 7500 is the simplest and generally most applicable method thegenerally most applicable method … the useful range of analysis is from 5 to 200 µg and matrix effects are not a problemµg and matrix effects are not a problem because of the nature of the thin film of the sample ”the sample.

(1999 AIHAJ)



• “XRD and IR are the most commonXRD and IR are the most common techniques used for crystalline silica analyses but the accuracy is pooranalyses … but the accuracy is poor … at … concentrations near the NIOSH REL of 50 µg/m3 ”REL of 50 µg/m .

(2002 NIOSH Hazard Review)


Implications To Current ExposuresImplications To Current Exposures

• As the trend moves to lower exposureAs the trend moves to lower exposure limits, fuller data sets may be required to evaluate exposure – i e more data toevaluate exposure i.e. more data to increase statistical power and reduce the potential for the effects of analyticalpotential for the effects of analytical error.


Implications To Current EExposures (cont’d)

• Use multiple measures to evaluateUse multiple measures to evaluate exposure.

Combining air samples with direct read– Combining air samples with direct read instruments

– Using different size selective methodsUsing different size selective methods• Ensure other QA/QC procedures are as

thorough as possiblethorough as possible.


Implications Towards E id i lEpidemiology

• Epidemiology will use exposure data whenEpidemiology will use exposure data when applicable or available for specific studies.

• The methods used in the collection andThe methods used in the collection and analysis will impact the precision, accuracy and reliability of the data and findings.and reliability of the data and findings.

• Even when the collection and analysis methodology are consistent they havemethodology are consistent, they have evolved in ways where resolution and accuracy may not be fully comparable.y y y p


Histology of Silicosisgy


Common PneumoconiosesAsbestosis Silicosis


Silicosis ProgressionSilicosis Progression

Massive Fibrosis


Early Silicosis Massive FibrosisConglomerate Nodulation

Health Effects of Respirable C lli SiliCrystalline Silica

• Pulmonary EffectsPulmonary Effects– Classic Silicosis

• Pneumoconiosis (Interstitial Fibrosis)• Pneumoconiosis (Interstitial Fibrosis)• Upper/Middle Lung Fields (Low to Moderate

Exposures for > 20 Yrs.)• Small Percentage of Cases < 10 Yrs. Of

Exposure



• Progressive Massive FibrosisProgressive Massive Fibrosis– PFT Impairment

• With Lesser X-Ray Findings No PFT• With Lesser X-Ray Findings, No PFT Impairment

• Accelerated SilicosisAccelerated Silicosis– High Exposure for 5-10 years

• Acute Silicosis• Acute Silicosis


Lung Cancer and Silica/Silicosisg

• Studies Report Mixed Findings• Studies Report Mixed Findings (Most Find Elevated Risk)

• Risk Ranges < 1 to > 5• Risk Ranges < 1 to > 5• Is Silicosis Necessary?

H h t l (2001) S d W k• Hughes, et al (2001), Sand Workers– OR 2 – 5– Good Control For Smoking Other Exposures– Good Control For Smoking, Other Exposures– Greater Risk For Silicosis, But Risk Still Present

For Silica


– > 14,249 Exposure Measurements (1974-1998)


• COPDCOPD– Asthma (No causation, aggravation)– Chronic BronchitisChronic Bronchitis– Emphysema (Predominant)

• PFT AbnormailitesPFT Abnormailites– Loss 3-4 ml per mg/m3 years– 6.5 ml over 4-5 years – NIOSH REL6.5 ml over 4 5 years NIOSH REL– Normal decline with age – 14 to 30 ml/year

• Hnizdo (2003) – COPD without Silicosis


Hnizdo (2003) COPD without Silicosis

Recent Silica/Silicosis/Lung C S diCancer Studies

• Erron et al 2009 – Meta Analysis – NoErron et al 2009 Meta Analysis No cancer without silicosis

• Lacasse et al 2009 Meta Analysis• Lacasse et al 2009 – Meta Analysis –Positive dose response above PELs or RELsRELs

• IARC classification change


Exposure Morbidity and MortalityExposure, Morbidity and Mortality• Silicosis Risk

– 1 – 95% of Workers at OSHA PEL over 40 – 45 Years Working Lifetimeg

– 1 – 7% at ½ NIOSH REL – 0.025 mg/m3

– 20% Increased Risk at 0.04 mg/m3 for 45 Years

– Current Prevalence Unknown300 D th P Y– 300 Deaths Per Year


“Proposed” OSHA Silica StandardProposed OSHA Silica Standard

• Early stages – Scientific peer-reviewEarly stages Scientific peer review• PEL undetermined

0 10 0 075 0 050 0 025 / ³– 0.10, 0.075, 0.050, 0.025 mg/m³• Health basis – classical silicosis, cancer,

ffother health effects


“Proposed” OSHA Silica Standard (cont’d)

• Programmatic requirementsProgrammatic requirements– Written program

Training– Training– Warning/labeling

Route of exposure– Route of exposure– Exposure monitoring

M di l it i d ill– Medical monitoring and surveillance– Record keeping– PPE


SOMA EpidemiologyM di l T dMedical Trends


Overall SOMA Silica Health Fi diFindings

• At levels of control to 0 025 to 0 05At levels of control to 0.025 to 0.05 mg/m³

No pulmonary restriction with exposure– No pulmonary restriction with exposure– No evidence of significant obstructive

findings with exposurefindings with exposure– Some low perfusion findings to small

percentage of exposed populationspercentage of exposed populations– No related auto-immune disease


Overall SOMA Silica Health Fi diFindings (cont’d)

– No evidence of x-ray or disease progressionNo evidence of x ray or disease progression– Where silicosis found, earlier uncontrolled

exposures likely causalp y– No required respiratory protection routine


SOMA Silica Health SurveillanceSOMA Silica Health Surveillance

• Keys to successKeys to success– Long term management commitment to

program excellenceprogram excellence– State of the art exposure testing and

modelingmodeling– Exposure and health trend database – Mandatory covers worker participantsMandatory covers worker participants– Periodic exposure health trending analysis


SOMA Silica Health Surveillance (cont’d)

– Comprehensive positive finding medicalComprehensive positive finding medical evaluation and notification

– Continual fitness for duty determinationy– Individual/group disease surveillance– Identification screening diseaseIdentification, screening, disease

management for main health care cost drivers (obesity, smoking, diabetes, etc.)


Thank You For Your InterestCelebrating 25 Years! Please visit our website atCelebrating 25 Years!...Please visit our website at

www.somaonline.com


Documents

OSHA’s Proposed Silica Standard and the Epidemiology and ... s/EEI Fall 09/OSHA... · the Epidemiology and Management ofthe Epidemiology and ... Dennis Ertel, Jr., CIH, CSP, REM