SILICA SEMINAR Linda Apthorpe & Ian Firth www.aioh.org.au AIOH - - PDF document

1

SILICA SEMINAR

www.aioh.org.au

Linda Apthorpe & Ian Firth

AIOH Seminars

• AIOH runs technical seminars throughout the year
• Purpose:
• Encourage professional development for members and
• thers working in the industry
• Find out about latest industry trends in health and

safety

• Determine what you can do to achieve effective

positive behaviour change in your workplace

• Hear what others are doing by networking with peers

with similar interests

2

Presenters

• Ian Firth

IC Firth OHs Solutions PTY LTD

• Linda Apthorpe

3

2

Your Turn!

• Please introduce yourself and tell us why you are here!

4

Crystalline Silica

• Present in many workplaces
• Recent publicity -> engineered stone industry
• SafeWork Australia
• State Jurisdictions

5

Topics

• RCS Occurrence and Types
• RCS Health effects
• RCS Exposure Standards
• Exposure Risk and Disease Incidence
• Sampling & Analytical Methods
• Control
• The future for RCS

6

3

SILICA SEMINAR

www.aioh.org.au

RCS - Introduction

Session Outcomes

• Describe different forms of silicon dioxide
• Discriminate between types/phases of quartz
• List workplaces where crystalline silica can be found

8

RCS Occurrence and Types

9

4

Silica SiO2 Crystalline Amorphous

10

Silicon Dioxide – Quartz

• SiO2 – oxide of silicon
• Most abundant mineral on earth
• Commonly found: sand, rocks &

diatoms

• Hard abrasive mineral
• Also present in soils & clays

11

Quartz Properties

• Quartz is slightly soluble in body fluids and soluble in HCl
• It is insoluble in water, organic solvents, most mineral

acids.

• Molecular weight: 60.09
• Specific density: 2.65
• Melting point: 1,600 deg C
• Boiling point: 1,723 deg C

12

5

Used for…

13

Crystalline Types

• Quartz
• Cristobalite & Tridymite (high temperature)

Source: touch of modern

14

Crystalline Types

• Coesite & Stishovite (dense, meteorites)
• Free silica

Source: Britannica.com Source: individual.utoronto.ca

15

6

Phase Diagram

16

Other Types of Silica

• Microcrystalline silica (opal, flint, tripoli, silica flour,

chalcedony)

Source: via Google

17

Other Types of Silica

• Amorphous silica

18

7

Other Types of Silica

• Fumed Silica
• Lechatelierite, rare amorphous glass

Source: Wikimedia commons

19

Other Types of Silica

• Silica fume (microsilica)

Average diameter: 150 mm

20

Terminology

• Terms for the same thing?
• Respirable crystalline silica (RCS)
• Respirable crystalline quartz
• Respirable silica
• Respirable quartz
• Respirable alpha quartz
• Crystalline quartz
• Crystalline silica

21

8

Workplace Silica

22

Crystalline Silica SiO2 α-Quartz Cristobalite Tridymite

Quartz in Workplaces

• What types of workplaces would RCS be found?
• Mining, rock-drilling, sandblasting, construction, foundry

work, stonecutting, drilling, quarrying (hard rock & sand), building and general construction work, road work and road construction, cement products manufacturing, demolition operations, sweeping, masonry, tunnelling, ceramics & brick manufacture, demolition, abrasive blasting, agricultural earth works, asphalt production, abrasives, glass & paint manufacture...

23 24

9

25 26 27

10

28 29 30

11

31 32 33

12

% Quartz

Type ~% Quartz Granite 25-50 Shale 22 Natural quartzite 65-90 Natural sandstone 65-90 Engineered stone Up to 90 (+ cristobalite) Natural Sand 80-90 Manufactured Sand 0-90 Concrete (as sand/quartz) 20-25 Concrete 20-60 (as SiO2)

34

Exposure Sources

• Exposure to RCS is widespread across Australia

(mainly from mining & construction industries)

• Cristobalite & Tridymite
• formed in high temperatures
• Remember to consider possibility of presence of

cristobalite (& tridymite) in workplaces

35

Session Recap

• Different forms of silicon dioxide
• crystalline & amorphous
• Discrimination between types/phases of quartz
• quartz, cristobalite, tridymite
• Workplaces where crystalline silica can be found

36

13

References

• ACGIH Documentation of the Threshold Limit Values &

Biological Exposure Indices, 7th Edition

• Pattys Industrial Hygiene & Toxicology, 3rd (rev) edition
• ILO Encyclopaedia of Occupational Health & Safety, 3rd (rev)

edition

• IARC monographs (No 68-6)
• OSHA website (www.osha.gov)
• NIOSH website (www.cdc.gov/NIOSH)
• SafeWork Australia (www.safework.gov.au)

37

SILICA SEMINAR

www.aioh.org.au

RCS – Health Effects

Session Outcomes

• Describe the health effects of RCS
• Specify the elements of a health surveillance program
• Explain the factors that affect the disease potential of

RCS

39

14

Health Effects of RCS

• Silicosis
• Bronchogenic carcinoma
• COPD
• Pulmonary tuberculosis
• Industrial bronchitis
• Auto-immune diseases
• Renal disease

40

The Respiratory Tract

41

Gas Exchange Region of the Lung

42

15

Defence Mechanisms

The respiratory system has a number of ‘dust filters’ that must be passed before dust can reach a point in the lung where it can cause damage. Clearance of dust is by:

• Hairs in the nose
• Transport via the mucociliary ladder
• Removal by scavenger cells (macrophages) in the alveolar

region Health effects can eventuate when these mechanisms become

• verloaded.

43

Defence Mechanisms

44

Healthy cilia Damaged cilia

Defence Mechanisms

45

Macrophage Action in Alveolar Region

Julie A. Champion and Samir Mitragotri, Role of target geometry in phagocytosis, Proc Natl Acad Sci U S A. 2006 March 28; 103(13): 4930–4934.

16

Lung Function Testing - Spirometry Graphs

2 ways of looking at a Spirometry result

46

FLOW VOLUME VOLUME TIME

Shapes of Spirometry Curves

47 Volume Volume Volume

Restriction Obstruction Mixed

Abnormal Ventilatory Function Normal (?)

From: DP Johns, R Pierce. Pocket Book of Spirometry. Sydney: McGraw-Hill, 2003. Flow Flow Flow

Lung disease - Obstructive symptom (COPD)

Asthma, Bronchitis, Emphysema

• Increased resistance of airways
• Narrowing of the airways from brochospasm
• Swollen tissues
• Excessive mucous
• Increased thickness of airway wall (collagen)

due to remodelling

• Loss of elastic recoil (due to alveoli

collapse - emphysema)

48

17

Lung disease - Restrictive symptom

Diffuse Lung Diseases

• decreased respiratory muscle strength
• stiff lungs (increased elastic recoil –

fibrosis)

• shrunken and non-homogeneous lung without
• bstruction of larger airways
• total lung volume reduced (forced vital

capacity, FVC)

• the ratio of FEV1/FVC is normal (forced

exhaled volume in 1 second, FEV1)

49

Interpretation Algorithm

50

No Yes Yes No

Is FVC below lower limit of normal?

Normal

Spirometry

Restriction

Referral for confirmation & diagnosis

Obstruction

Severity: Use % predicted FEV1

Is FEV1/FVC less than 70%

51

18

Grinders disease

Silicosis among the grinders of razors, forks, knives, saws and

• ther edge tools

in Sheffield, England

THE ILLUSTRATED LONDON NEWS, January/March, 1866 52

Potter’s Rot - 1840

The "scourers", chiefly young women, necessarily inhale, the room being literally filled with dust, the fine particles of flint, which produce similar effects to what is provincially denominated, in the Sheffield trade, " the grinder's rot; " something might be done, perhaps, to lessen this evil, if judicious precautionary measures were adopted. I have suggested the use of a wet sponge, so adapted to the mouth and nostrils that the air of respiration must necessarily pass through it…... "

http://www.thepotteries.org/jobs/scourer.htm

53

Pneumonoultramicroscopicsilicovolcanoconiosis

• Name given to silicosis when caused by the specific

exposure to fine silica dust found in volcanoes

• Longest word in the English language (45 letters)

54

19

Notice chalked up in a foundry in Coventry (1934)

55

Silicosis

• Progressive fibrotic lung disease

(pneumoconiosis)

• Frequently not the primary cause of death
• Classification is made according to the

disease's severity, onset and rapidity of progression:

• chronic silicosis (includes simple and

complicated silicosis)

• accelerated silicosis
• acute silicosis

56

Silicosis

Symptoms:

• Shortness of

breath

• Cough
• Rapid breathing
• Loss of appetite
• Chest pain

57

Source: ATS Silica Awareness

20

Silicosis

Diagnosis using:

• Patient history
• Physical check up
• Lung function test
• Chest X-ray
• CT scan
• Autopsy

Silica Essentials Presentation, BOHS April 17th 2007, Colin Davy HSE, HM Specialist Inspector

58

ILO Categorisation of Silicosis

ILO Category Qualitative description

0/0 No small (up to 1 cm) silicotic opacities (nodules) are present 0/1 Probably no nodules, but some areas of radiograph are suspect (possible silicosis) 1/0 Small silicotic nodules are most likely present, but not certainly (probable silicosis) HSE – only a minor radiographic abnormality, not necessarily indicative of silicosis development, no functional impairment

59

ILO Categorisation of Silicosis

ILO Category Qualitative description

1/1 Small silicotic nodules are definitely present HSE – particularly high degree of inter-reader variability so difficult to determine where to place on exposure-response curve 1/2 Small silicotic nodules are definitely present; other areas of the radiograph may indicate more advanced lesions including large

• pacities (> 1 cm), pleural thickening.

2/1, 2/2, 2/3, 3/2, 3/3 More advanced stages of silicosis/increasing certainty of the presence of lung abnormalities HSE – 2/1+ is the most reliable basis for identifying true cases

• f silicosis, low reader variability, more specific but less

sensitive (than 1/0 or 1/1) indicator of silicosis

60

21

ILO classification for silicosis – lung scarring profusion (source: Daniel Powers M.D. Radiology)

61

ILO classification for silicosis – lung scarring profusion (source: Daniel Powers M.D. Radiology)

62

Silicosis

63

Healthy lung Silicosis

22

Mechanism of disease

• The critical factor in the onset of silica disease appears to be

cessation of clearance of silica particles and the onset of inflammation (Tran 2005)

• This inflammation culminates in the development of nodules

which characterise the diagnosis of silicosis (Rao et al. 2004)

• Latency period largely independent of cumulative dust

exposure (Hnizdo & Sluis-Cremer 1993)

• Risk of silicosis increases exponentially with cumulative dust

dose (Hnizdo & Sluis-Cremer 1993, Steenland and Brown 1995, Chen et al 2001, Churchyard et al

2004 2003, Hughes et al 1998) 64

Relative fibrogenicity risk

• It was thought that cristobalite was more fibrogenic than

quartz based on invitro studies

65

• However the UK HSE

was unable to find any evidence that quartz and cristobalite should be treated differently when assessing human exposure (Meldrum et al 2001)

http://globalinvestmentwatch.com/2009/03/31/sp arkle-finger-dead-stonecutter-china/

Lung cancer

• International Agency for Research on Cancer (IARC)

1997

• crystalline silica inhaled in the form of quartz or cristobalite

from occupational sources is considered carcinogenic to humans (Group 1)

• reassessed and confirmed in 2012
• ACGIH classifies quartz as an A2 (confirmed animal,

suspect human) carcinogen

• Safe Work Australia classifies quartz / RCS as cat. 1A

(known human) & STOT (repeated exposure) cat. 1

66

23

Lung cancer

• IARC working group noted that carcinogenicity was not

detected in all industrial circumstances studied

• Determination specifically relates to occupational exposure and

not environmental exposure

• Findings of relevance to lung cancer and RCS exposure arose

from five main industrial settings:

• ceramics, diatomaceous earth, ore mining (not coal

mining), quarries, and sand and gravel

• Strongest evidence supporting carcinogenicity of RCS in the

lung comes from pooled and meta-analyses of selected epidemiological studies

67

Lung cancer

• EU Scientific Committee for Occupational Exposure Limits

(SCOEL):

• There is sufficient information to conclude that the relative

lung cancer risk is increased in persons with silicosis (and, apparently, not in employees without silicosis exposed to silica dust in quarries and in the ceramic industry).

• This continues to be studied
• Others have concluded that the weight of evidence from
• ccupational epidemiology does not support a causal

association of lung cancer and RCS exposure (Gamble 2011)

68

Lung cancer

• Effect of several carcinogens can lead to additive or more

complicated reactions – e.g. silica exposure and smoking = increased cancer risk

• Exposure periods of at least ten years with a latent

period of several decades up to the appearance of the illness has been observed

• Mechanism is impaired particle clearance leading to

macrophage activation and persistent inflammation - inflammation-driven secondary genotoxicity (IARC 2012)

69

24

Lung cancer

70

Healthy lung Lung cancer

Lung cancer X-ray

http://article.wn.com/view/2009/02/08/Whither_lung_cancer/?section=SectionResults&template=cheetah- meta%2Fmeta-related-stories.txt 71

Chronic obstructive pulmonary disease (COPD)

• COPD describes chronic airflow limitation that is usually

irreversible

• Includes four interrelated disease processes
• chronic bronchitis
• emphysema
• peripheral airways disease
• Cigarette smoking is a major cause of COPD, but community

air pollution and occupational exposure to dust, particularly among smokers, also contribute

• Studies indicate exposure to gold mine dust is an important

cause of COPD, particularly in smokers

• Risk of COPD appears greater for gold miners than for coal

miners

72

25

Chronic obstructive pulmonary disease (COPD)

Destruction of alveolar walls in silica dust exposed subjects can lead to emphysema which is the main cause of COPD

73

Decrements in lung function

• Initial studies of granite workers (0.1 mg/m3 exposure)

indicated decrements in pulmonary function parameters (Therialt et

al 1974)

• Follow-up studies of the same workers failed to detect

pulmonary function loss when smoking history was included

(Graham et al 1994)

• Cigarette smoking is associated with approximately twice the

lung function loss attributable to silica dust exposure

• Significant decrements in pulmonary function do not occur

early in simple silicosis and radiological changes may be a better diagnostic tool

74

Pulmonary tuberculosis

• Silica particles can destroy or alter the metabolism of the

pulmonary macrophage, thereby reducing its capacity for anti- bacterial defence

• Occupational exposure to silica dust renders a subject

susceptible to developing pulmonary tuberculosis - 10–30 fold increased incidence

• The risk of developing pulmonary tuberculosis while exposed,

and also after exposure ends, depends on the cumulative amount of silica dust exposure

• Presence of silicosis in the lung further increases the risk of

developing pulmonary tuberculosis

• Rate of tuberculosis in workers exposed to silica is related to

the rate of tuberculosis in the general population (SORDSA, 1999).

76

26

Industrial bronchitis with airflow limitation

• Generally accepted that this condition can be caused by
• ccupational exposure to dust
• Can lead to COPD
• Individual susceptibility is important
• Smoking is a significant cause
• May be caused by larger particles than those responsible for

disease in the deep lung

77

Auto-immune diseases

• Scleroderma (an autoimmune disorder) - hardening or

sclerosis in the skin or other organs

• Evidence to date not sufficient to conclude that RCS is a

causative factor for systemic sclerosis - no exposure-response data available

• Rheumatoid arthritis - significantly higher among granite

workers than in general male population of the same age - possible aetiological or pathophysiological role of granite dust may be based on the effects of quartz on the immune system

78

Renal disease

• Increased risk of renal disease has been implicated with

elevated exposures to RCS

• A US study found a doubling of risk of non-malignant renal

disease but no increase in renal cancer

• While studies of cohorts exposed to RCS have found elevated

standard mortality ratios (SMRs) for renal disease, there was no clear evidence of a dose–response relationship

• Pathogenesis of renal effects in RCS exposed workers is not

clear - elevated risk is perhaps attributable to diagnostic and methodological issues

79

27

Health surveillance

• Pre-employment medicals
• Ongoing medicals
• Termination medicals
• Annual employee testing for

respirable dust and crystalline silica exposure.

80

Health surveillance

• Demographics, occupational and medical history
• Health advice - workers informed of the potential health

effects

• Standardised respiratory questionnaire
• Standardised respiratory function test including, for example,

FEV1, FVC and FEV1/FVC

• Chest X-ray, full size posterior-anterior view
• Records of personal exposure
• Physical examination if indicated by occupational or medical
• history. Emphasis on respiratory system
• ACOEM and AIOH recommend health surveillance where

exposure to RCS is > 0.05 mg/m3

81

Health surveillance

• If at any point, the worker is suspected of having silicosis during a

surveillance evaluation, remove from exposure and refer immediately for definitive diagnosis

• Frequency of health surveillance (ACOEM):
• Follow-up evaluation within 12 months: Evaluate need for repeat

chest X-ray at this time

• if exposure is < 0.05 mg/m3, assess need for frequency of future

follow-up evaluations

• if exposure is > 0.05 mg/m3 for less than 10 years, 3 years
• if exposure is > 0.05 mg/m3 for 10 or more years, 2 years
• SWA focus on questionnaire and lung function tests to reduce use of

X-rays - every 5-10 years in first 20 years of work unless exposures > WES. BUT need for low threshold for early radiological screening

82

28

Health surveillance

• The employee should be informed of the results of the health

surveillance

• The employer should be informed when abnormal findings are

detected so that control measures can be checked

• Termination health surveillance:
• date of termination
• reason for termination
• if ill-health give details
• date and cause of death if in service
• examination

83

Factors thought to affect the potential for RCS to cause disease

• Polymorphic type of crystalline silica
• Presence of other minerals
• Particle number, size and surface area
• Freshly fractured and “aged” surfaces

84

Factors thought to affect the potential for RCS to cause disease

• Polymorphic type of crystalline silica: cristobalite,

tridymite and quartz appear more reactive and more cytotoxic than coesite and shishovite

• There is however no evidence from human experience

for any differences in the toxic properties of cristobalite and quartz (HSE 2002)

85

29

Factors thought to affect the potential for RCS to cause disease

The presence of other minerals

• the toxic effects of quartz are reduced in the presence
• f aluminium containing clay materials
• the protective effect of aluminium containing materials

is not permanent, as the quartz dust may be “cleaned” in the lungs, and this eventually begins to express its pathogenic properties

• iron enhances quartz toxicity

86

Factors thought to affect the potential for RCS to cause disease

The particle number, size and surface area:

• regardless of type of dust, total surface area of the

dust retained in the lungs is an important determinant

• f toxicity
• surface area is related to particle size – smaller

particles of RCS would be expected to produce more lung damage than equal masses of larger respirable size fractions

87

Factors thought to affect the potential for RCS to cause disease

Freshly fractured and “aged” surfaces:

• cleavage leads to formation of reactive radical

species

• leads to an increase in cytotoxicity
• the activity of the free radicals decays with time -

‘aging’

• ccurs slowly in air

, but rapidly (within minutes) in water

• freshly fractured silica with iron contamination

results in enhanced generation of reactive radicals

88

30

Session recap

• Describe the health effects of RCS
• Specify the elements of a health surveillance

program

• Explain the factors that affect the disease potential
• f RCS

89

Source: ATS Silica Awareness

References

• AIOH (2018). Respirable Crystalline Silica and its Potential for Occupational Health Issues

– Position Paper - https://www.aioh.org.au/resources/publications1/epublications

• American College of Occupational and Environmental Medicine (ACOEM)

http://www.acoem.org/

• HSE (2002). Respirable Crystalline Silica - Phase 1: Variability in Fibrogenic Potency and

Exposure-Response Relationships for Silicosis. Hazard Assessment Document: Guidance note, environmental hygiene/EH75/4, Health and Safety Executive, UK. http://www.hse.gov.uk/pubns/books/eh75-4.htm

• IARC (2012). Monographs on the evaluation of carcinogenic risks to humans Vol 100C,

Silica Dust, Crystalline, in the form of Quartz or Cristobalite. https://monographs.iarc.fr/iarc-monographs-volume-100c-silica-dust-crystalline-in-the- form-of-quartz-or-cristobalite/

• NIOSH (2002). Hazard Review – Health Effects of Occupational Exposure to Respirable

Crystalline Silica. DHHS (NIOSH) Publication Number 2002-129. https://www.cdc.gov/niosh/docs/2002-129/default.html

• Parker, JW & R Gregory (2011). Silicosis. International Labor Organisation (ILO)

Encyclopaedia of Occupational Health and Safety. http://iloencyclopaedia.org/part-i- 47946/respiratory-system/21-10-respiratory-system/silicosis

• Safe Work Australia (2013). Crystalline silica health monitoring.

https://www.safeworkaustralia.gov.au/doc/crystalline-silica-health-monitoring

90

SILICA SEMINAR

www.aioh.org.au

RCS – Exposure Standards

31

Session Outcomes

• Explain respirable size fraction
• Describe relevant Exposure Standards
• Consider WES adjustments

Exposure Standards

• Snowy mountains scheme
• NSW silicosis hot spots in 1970
• Development of ES in Australia
• 1905 hard rock mining investigation - WA
• 1914 Royal Commission at Broken Hill
• Silicosis board of NSW
• 1920’s dust control regulations (NSW & WA)

Particles greater than 100 µm Particles less than 100 µm - inhalable Particles less than 10 µm – respirable dust & quartz

32

Lung Diagram

Inhalable dust:

• <100 µm
• Toxic particles

effect upper respiratory tract

Respirable dust:

• <10 µm
• Toxic particles effect

alveolar region

Penetration of Dust

96 Equivalent Aerodynamic Diameter Respirability Micrometres (µm) % 100 1 100 2 97 3 80 4 56 5 34 6 20 7 11 8 6 10 2 12 0.5 14 0.2 16 0.1 18

AS 2985-2009 (ISO/CEN/ACGIH)

Size Fractions

50% cut point

33

Exposure Standards

• WES values set by SafeWork Australia
• WES based on an 8-hour day
• For longer shifts the ES can be adjusted as:-
• Longer time to be exposed per day
• Shorter times for recovery (non exposed time)
• WES development history

Time Weighted Average

100

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 1 2 3 4 5 6 7 8

Respirable quartz mg/m3 One 8 hour day Short term sampling & excursions Average = 0.03 mg/m3

34

WES - HCIS

101

Crystalline Silica

α-Quartz 0.1 mg/m3 Cristobalite 0.1 mg/m3 Tridymite 0.1 mg/m3

102

WES - HCIS

103

Amorphous Silica

Diatomaceous earth 10 mg/m3 Fumed silica 2 mg/m3 Silica gel 10 mg/m3 Precipitated silica 10 mg/m3

Note:

• there is no WES value for silica fume

35

International RCS (α-quartz) ES Values

Country ES (mg/m3) Austria 0.15 Belgium 0.1 Canada 0.1 UK 0.1 Finland 0.05 France 0.1 Ireland 0.05 Netherlands 0.075 New Zealand 0.1 US (ACGIH-non regulatory) 0.025 US (OSHA & NIOSH) 0.05 Australia 0.1

Source: Gestis Database, ACGIH, Worksafe NZ, SafeWork Australia

RCS ES History

1983-84 OES (mg/m3) Quartz 0.2 Cristobalite 0.1 Tridymite 0.1

• 1983-84 NHMRC recommended ES

RCS ES History

1983-84 ES (mg/m3) 1988 ES (mg/m3) Quartz 0.2 0.1 Cristobalite 0.1 0.05 Tridymite 0.1 0.05

• 1988 Worksafe (NOHSC) recommended ES (following ACGIH)
• Between 1988-96 no formal ES existed
• Some mining & OHS authorities assumed their own ES
• 1996 Worksafe reinstated NHMRC quartz value of 0.2 mg/m3
• After further review, new ES of 0.1 mg/m3 in effect from 2005

36

ES Adjustment

• For shifts longer than 8 hours (e.g. 10 or 12 hours)
• Safe Work Australia guidelines
• Brief and Scala
• (OSHA & pharmacokinetic)
• WA mining industry guidelines
• AIOH – based on Quebec model
• Choose which method best suits the workplace and is

conservative

Industry Specific OES

• Pursue ALARA principle
• Action Levels to investigate/remediate
• Industry specific action levels at reduced fractions of ES
• Coal industry (e.g. crib to crib sampling times)

Session Recap

• Respirable fraction explanation
• Current & Historical OES information & descriptions
• WES adjustments

37

References

• Safe Work Australia HCIS website: hcis.safeworkaustralia.gov.au
• Exposure Standards – search facility
• Hazardous Chemicals – search facility
• ISO 7708:1995 – particle size fraction definitions
• AS 2985:2009 –sampling & gravimetric determination of

respirable dust

• AIOH Position Paper: RCS and its potential for occupational

health issues

SILICA SEMINAR

www.aioh.org.au

RCS – Exposure Risk & Disease Incidence

Session Outcomes

• Evaluate the risk of

disease

• Classify acceptable levels
• f risk
• Select an appropriate level
• f exposure

112

RC drilling

38

Exposure Risk and Disease Incidence

• The two most important diseases associated with RCS

are silicosis and lung cancer

• A lot of epidemiological work has been done on the risk
• f developing these two diseases
• There are varying views on the risk of health effects at

RCS exposure concentrations of 0.1 mg/m3 and below

(AIOH 2018)

113

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 114

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 115

39

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52 Hong Kong granite workers 1/1+ 6 15

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 116

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52 Hong Kong granite workers 1/1+ 6 15 US gold miners 1/1+ 8 53

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 117

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52 Hong Kong granite workers 1/1+ 6 15 US gold miners 1/1+ 8 53 Chinese tin miners 1/1+ 11 45

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 118

40

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52 Hong Kong granite workers 1/1+ 6 15 US gold miners 1/1+ 8 53 Chinese tin miners 1/1+ 11 45 Colorado hard rock miners 1/1+ 11 53

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 119

Risk of developing silicosis from 2 and 4 mg/m3.years* (HSE 2002)

Population ILO silicosis category % with silicosis

2 mg/m3.years

% with silicosis

4 mg/m3.years

Scottish coal miners 2/1+ 5 15 South African gold miners 1/1+ 5 52 Hong Kong granite workers 1/1+ 6 15 US gold miners 1/1+ 8 53 Chinese tin miners 1/1+ 11 45 Colorado hard rock miners 1/1+ 11 53

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 120

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 121

41

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 122

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2 UK heavy clay industry 1/0+ 0.9

• * 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years.

123

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2 UK heavy clay industry 1/0+ 0.9

• Diatomaceous earth

workers 1/0+ 1.1 – 3.7 4 - 12

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 124

42

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2 UK heavy clay industry 1/0+ 0.9

• Diatomaceous earth

workers 1/0+ 1.1 – 3.7 4 - 12 Iron foundry workers 1/0+ 2 10

* 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years. 125

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2 UK heavy clay industry 1/0+ 0.9

• Diatomaceous earth

workers 1/0+ 1.1 – 3.7 4 - 12 Iron foundry workers 1/0+ 2 10 Vermont granite workers 1/0+ 4

• * 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years.

126

Risk of developing silicosis from 2 and 4 mg/m3.years*

(HSE 2002)

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

UK pottery industry 1/0+ 2 Ontario hard rock miners 1/1+ 0.4 1.2 UK heavy clay industry 1/0+ 0.9

• Diatomaceous earth

workers 1/0+ 1.1 – 3.7 4 - 12 Iron foundry workers 1/0+ 2 10 Vermont granite workers 1/0+ 4

• * 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years.

127

43

Uncertainties in studies with higher risk estimate

(HSE 2002)

Population Selection Bias Follow

• up

Other minerals Freshly fractured Exposure assessment

Scottish coal miners South African gold miners Hong Kong granite workers US gold miners Chinese tin miners Colorado hard rock miners

128

X   X  Yes  ?

• 

? Yes  X  X   ? Yes  X ? X  X 

• Yes 

X 

• 

? Yes  X  X   ? Yes  X ?

Uncertainties in studies with lower risk estimate

(HSE 2002)

Population Selection Bias Follow- up Other minerals Freshly fractured Exposure assessment

UK pottery industry Ontario hard rock miners UK heavy clay industry Diatomaceous earth workers Iron foundry workers Vermont granite workers

129

• X

X  No  X  ?

• X  ?

Yes  X 

• X 

? No  X 

• X 

X  No  X ?

• X 

X  Yes  X 

• X 
• Yes 

X ?

Summary of study assessment

• Lower risk studies lack adequate follow-up and/or

involved co-exposure to aluminium-containing minerals and/or exposure to aged rather than freshly cut surfaces

• Higher risk studies have poor exposure data, sometimes

selection bias and poor diagnosis. Also, risk levels relate to workplace situations where exposure is to freshly cut surfaces of RCS and no exposure to aluminium

130

44

Strongest studies

Two study populations stand out from the pack as the benchmarks:

• Scottish coal miners – 0.5% risk with 15 year exposure to 0.04

mg/m3 (0.6 mg/m3.years)

• Vermont granite workers – 0.85% risk with 20-40 year

exposure to 0.06 mg/m3 (1.2-2.4 mg/m3.years)

131

Population ILO silicosis category % with silicosis 2 mg/m3.years % with silicosis 4 mg/m3.years

Scottish coal miners 2/1+ 5 15 Vermont granite workers 1/0+ 4

• * 2 & 4 mg/m3.years is 0.1 and 0.2 mg/m3 respectively for 20 years.

Risk of death from silicosis from 2 and 4 mg/m3.years*

Population % with exposure of 2.25 mg/m3.years % with exposure of 4.5 mg/m3.years

6 occupational cohorts (ACGIH) 0.6 1.2

132

Sandstone block cutting

• OSHA (2010) conducted a comprehensive review of

RCS health effects from a range of studies

• Lifetime silicosis risk estimates over 45 years

associated with exposure to RCS generated using high-energy processes

• Estimated most reliable risks to be 30 cases per 100

workers for exposure to 0.1 mg/m3 and 5.5 cases per 100 workers for exposure to 0.05 mg/m3.

Lung Cancer – Strongest studies (HSE 2003)

133

Population SMR* / SIR**

Granite workers (US) Shed workers 1.27* Quarry workers 1.0* (0 extra cases) Early hire workers >1.67* (8 extra cases) Granite workers (Finland) 1.7** (18 extra cases) Industrial sand workers 1.5* (28 extra cases based on national mortality rates) 1.39* (23 extra cases based on local mortality rates) 10 pooled occupational cohorts 2.8% (above background of 3-6%)

* Standardised mortality ratio is the observed number of cases divided by the number of expected cases ** Standardised incidence ratio is the number of new cases in the exposed population divided by the number

• f new cases in the control population

45

Lifetime risks of mortality from lung cancer from RCS (Goldsmith

2006)

RCS concentration (mg/m3) Predicted lung cancer deaths per 1000 workers a,b

0.001 0.3 0.005 1.5 0.010 2.9 0.020 5.9 0.030 8.8 0.040 12.0 0.050 15.0 0.060 18.0 0.070 20.0 0.080 23.0 0.090 26.0 0.100 29.0

• a. Assumes constant 45 years exposure between age 20 and 65 and thereafter accumulating annual risks to 85 years; and
• b. Excess risk estimates/1000 workers exposed (i.e. the excess lifetime risk for lung cancer at 0.1 mg/m3 silica is 29 deaths per

1000 workers)

134

Lung Cancer

• There is increased lung cancer risk with increasing cumulative

exposure and/or duration of exposure

• Relative risk for those in the highest exposure categories tend

to be twice that of those in the lowest categories

• Unlikely that the increased risk is due to other factors such as

smoking, asbestos or socio-economic differences

• Appear limited to those groups with the highest cumulative

exposures, suggesting the existence of a threshold

• Limited to early hire workers who commenced employment

before the introduction of adequate dust controls

135

Lung Cancer

• Heavy and prolonged occupational exposure to RCS can cause

an increased risk of lung cancer

• RCS is a relatively weak carcinogen
• It appears that lung cancer mortality in RCS-exposed workers

is restricted to those with silicosis

• The weight of evidence suggests that exposures to RCS,

insufficient to cause silicosis, would be unlikely to lead to an increased risk of lung cancer, although the evidence is not definitive

136

46

Lung Cancer

• A recommendation from the EU Scientific Committee for

Occupational Exposure Limits (SCOEL) was adopted in June

• 2003. The main conclusions were as follows:
• The main effect in humans of the inhalation of respirable

silica dust is silicosis. There is sufficient information to conclude that the relative lung cancer risk is increased in persons with silicosis (and, apparently, not in employees without silicosis exposed to silica dust in quarries and in the ceramic industry). Therefore preventing the onset of silicosis will also reduce the cancer risk. Since a clear threshold for silicosis development cannot be identified, any reduction of exposure will reduce the risk of silicosis.

137

Threshold effect

• Exposure-response model for RCS and risk of silicosis / lung cancer

using an inflammatory mode of action implied a "tipping point" threshold (Cox, 2011)

• Applied to epidemiological data - levels on order of 0.1 mg/m³ are

probably below the threshold for triggering lung diseases in humans

(Cox, 2011)

• Study indicated an RCS dust exposure (8-hour TWA) concentration

threshold greater than 0.1 mg/m3 and possibly as high as 0.25 mg/m3 (Morfeld et al, 2013)

138

What does it all mean??

139

• A threshold for silicosis

development has been determined but is not acknowledged by all

• The risk is not linearly

related to cumulative exposure – it rises more steeply as absolute exposure concentrations increase

• If we can control silicosis

we can control the other diseases

Sandstone block cutting

47

Acceptability of risk (Hester & Harrison 1998)

140

Acceptable risk Intolerable risk – it does not imply that the risk will be acceptable to everyone, i.e. that everyone would agree without reservation to take the risk or have it imposed on them

• ‘tolerable’ does not mean ‘acceptable’

– it refers instead to a willingness by society as a whole to live with a risk so as to secure certain benefits in the confidence that the risk is one that is worth taking and that it is being properly controlled

Acceptability of risk (Hester & Harrison 1998)

• HSE upper limits of tolerable risk – deaths per year (annual

risk):

• Workers – 1 in 1,000 person.years
• General public – 1 in 10,000 person.years
• Individual – 1 in 1,000,000 person.years
• HSE believes:
• that an individual risk of death of one in a million per

annum corresponds to a very low level of risk

• should be used as a guideline for the boundary between

broadly acceptable and tolerable regions

141

Acceptability of risk

• Lifetime risk (80 year life)
• Workers – 8,000 in 100,000
• General public – 800 in 100,000
• Individual – 8 in 100,000

142

48

Acceptability of risk (Hester & Harrison 1998)

• NOAEL – no observed adverse effect level
• If a NOAEL cannot be established, use a LOAEL
• USEPA NOAEL
• The highest exposure level at which there are no

statistically or biologically significant increases in the frequency or severity of an adverse effect between the exposed population and its appropriate control

• WHO NOAEL
• No detectable adverse alteration of morphology, functional

capacity, growth, development or lifespan of the target

143

Acceptability of risk (Hester & Harrison 1998)

Uncertainly factors used for setting WESs were far smaller than those used in other areas of standard setting, such as exposure to pesticides, food contamination residues, and environmental contaminants

144

Comparison of risk estimates (Tran et al. 2005)

ACGIH NOAEL for silicosis (implied) DFG NOAEL for silicosis DFG LOAEL for silicosis 0.025 mg/m3 0.007-0.1 mg/m3 0.02-0.25 mg/m3 ACGIH NOAEL for lung cancer 0.046 mg/m3 Risk estimates from Scottish coal miners study (Silicosis Category 2/1 or greater) Risk 1/1000 (Occ NOAEL) 0.01 mg/m3 Risk 2.7/1000 0.025 mg/m3 Risk 17/1000 0.1 mg/m3 De Klerk (silicosis risk) Risk <1/100 0.13 mg/m3 Human NOAEL estimated from animal studies 0.0011 mg/m3 ACGIH recommended TLV 0.025 mg/m3

145

49

Comparison of risk estimates (Tran et al. 2005)

146

• The average NOAEL based on extrapolation from the

animal studies is some 9 to 45 times lower than those based on epidemiological studies

• May be overly conservative due to the application of

conventional uncertainty factors recommended by the US EPA

Relative risk

147

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 8,800 High 1,500 Elevated Frequent airline passenger 730 Motor vehicle 600 Moderate Light drinker 150 Low Cycling 75 Very low Vaccination 22 Lightning 3 Extremely low Environmental asbestos exposure 1

Relative risk – HSE upper tolerable limits

148

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 8,800 Upper tolerable limit Workplace 8,000 High 1,500 Upper tolerable limit General public 800 Elevated Frequent airline passenger 730 Motor vehicle 600 Moderate Light drinker 150 Low Cycling 75 Very low Vaccination 22 Acceptable Individual 8 Extremely low Lightning Environmental asbestos exposure 3 1

50

Relative risk – lung cancer mortality

149

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 8,800 Upper tolerable limit Workplace 8,000 RCS: cancer mortality?? 2,900 High 1,500 Upper tolerable limit General public 800 Elevated Frequent airline passenger 730 Motor vehicle 600 Moderate Light drinker 150 RCS: cancer mortality?? 100 Low Cycling 75 Very low Vaccination 22 Acceptable Individual 8

Relative risk – silicosis mortality

150

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 (22%) 8,800 (9%) Upper tolerable limit Workplace 8,000 High 1,500 Upper tolerable limit General public 800 (0.8%) Elevated Frequent airline passenger 730 (0.7%) Motor vehicle 600 (0.6%) RCS: silicosis mortality 600 (0.6%) Moderate Light drinker 150 RCS: lung cancer mortality 100 Low Cycling 75 Very low Vaccination 22

Relative risk – silicosis morbidity

151

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 (22%) 8,800 (9%) Upper tolerable limit Workplace 8,000 High RCS: silicosis (Scottish study) 1,700 (1.7%) RCS: silicosis (de Klerk) 1,000 (1%) Upper tolerable limit General public 800 (0.8%) Elevated Frequent airline passenger 730 (0.7%) Motor vehicle 600 (0.6%) RCS: silicosis mortality 600 (0.6%) Moderate Light drinker 150 RCS: lung cancer mortality 100 Low Cycling 75 Very low Vaccination 22

51

Relative risk – acceptable level of exposure?

152

Risk Level Situation Lifetime risk per 100,000 Extra high Smoking (all causes) Smoking (lung cancer) 21,900 (22%) 8,800 (9%) Upper tolerable limit Workplace 8,000 High 0.1 mg/m3 1,700 (1.7%) RCS: silicosis (de Klerk) 1,000 (1%) Upper tolerable limit General public 800 (0.8%) Elevated Frequent airline passenger 730 (0.7%) Motor vehicle 600 (0.6%) RCS: silicosis mortality 600 (0.6%) 0.025 mg/m3 270 (0.27%) Moderate Light drinker 150 (0.15%) RCS: lung cancer mortality 100 (0.1%) 0.01 mg/m3 <100 (<0.1%)

Session Recap

• Evaluate the risk of

disease

• Classify acceptable levels
• f risk
• Select an appropriate

level of exposure

153

RC drilling

References

• AIOH (2018). Respirable Crystalline Silica and its Potential for Occupational Health Issues

– Position Paper - https://www.aioh.org.au/resources/publications1/epublications

• de Klerk, NH, GL Ambrosini & AW Musk (2002). A Review of the Australian Occupational

Exposure Standard for Crystalline Silica. The University of Western Australia, December 2002.

• DFG (2000). Silica, crystalline: quartz dust, cristobalite dust and tridymite dust (respirable

fraction). MAK Value Documentation, Deutsche Forschungsgemeinschaft (DFG) - https://onlinelibrary.wiley.com/doi/10.1002/3527600418.mb0sio2fste0014

• HSE (2002). Respirable Crystalline Silica - Phase 1: Variability in Fibrogenic Potency and

Exposure-Response Relationships for Silicosis. Hazard Assessment Document: Guidance note, environmental hygiene/EH75/4, Health and Safety Executive, UK. http://www.hse.gov.uk/pubns/books/eh75-4.htm

• HSE (2003). Respirable Crystalline Silica – Phase 2: Carcinogenicity. Hazard

Assessment Document EH75/5: Health and Safety Executive, UK. http://www.hse.gov.uk/pubns/books/eh75-5.htm

• OSHA (2010). Occupational Exposure to Respirable Crystalline Silica – Review of Health

Effects Literature and Preliminary Quantitative Risk Assessment. Occupational Safety and Health Administration, Docket OSHA-2010-0034. https://www.osha.gov/silica/Combined_Background.pdf

154

52

SILICA SEMINAR

www.aioh.org.au

RCS - Sampling & Analysis

Session Outcomes

• Select correct sampling equipment
• Choose suitable analytical technique
• Explain detection limits

Historical Sampler

• MRE-113A horizontal elutriator

53

Konimeter Owens Dust Jet Thermal Precipator Impinger

Respirable Dust & Quartz Sampling

• AS 2985:2009 Method for sampling and gravimetric

determination respirable dust

• Gravimetric analysis for respirable dust
• Personal and static (fixed location) samples
• Minimum sampling duration is 4 hours (or ½ shift)

159

Sampling

• Comparison of results with relevant WES values
• Representative and non biased
• Size selecting cyclone sampler used for sampling

160

54

Respirable Dust Samplers

• AS 2985:2009 lists requirements for size selecting

samplers

• Examples are:-
• BCIRA cyclone
• (SIMPEDS) Modified Higgins & Dewell cyclone
• Aluminium cyclone
• No SIMPEDS terminology!

162

Cyclone Diagram

‘Modified’ Higgins & Dewell cyclone

55

Breathing Zone Sample Filters

• Sample filters are generally 25 mm
• Pore size is 5 µm or less
• PVC GLA 5000 filters are normally used for RCS
• Filters are normally pre & post weighed to estimate

respirable dust concentrations via gravimetric analysis

Analysis of Sample Filters

• NATA accredited laboratory (ISO 17025)
• NATA accredited labs for RCS analysis
• Two techniques:-
• Infrared (FTIR) analysis
• X-Ray Diffraction (XRD) analysis
• Based on Australian NHMRC & US NIOSH methods

56

Remember!!

• Conduct quartz analysis only on valid filters from

respirable dust samplers

FTIR Analysis

• Infrared absorbance at specific wavelengths
• Absorbance or transmission of infrared
• Interferences
• Organic materials - ashed

FTIR Instrumentation

57

798 cm-1 779 cm-1 694 cm-1 796 cm-1

58

912 cm-1 Twin peaks at 795 & 750 cm-1 800 cm-1

X-Ray Diffraction (XRD)

• Expensive instrument
• Needs a radioactive source
• Can determine (singularly or together):-
• quartz
• cristobalite
• tridymite
• amorphous silica

59

Crystal Lattice & Bragg’s Law XRD Schematic

177

XRD Instrumentation

60

10 15 20 25 30 35 40 45 50 55 2Theta (°) 100 200 300 400 500 Intensity (cps)

Q100 Q101 Q112 Ag111 Ag200 Theta Degrees Intensity

FTIR vs XRD

• FTIR
• Quick
• Cheaper (usually)
• Comparable detection limits
• Can’t speciate between quartz & cristobalite when

both together

• Some interferences

180

FTIR vs XRD

• XRD
• Longer analysis time
• May be more expensive
• Comparable detection limits
• Can speciate between quartz & cristobalite phases

when both together

• Some interferences
• Can analyse amorphous forms

181

61

Detection Limits

• Detection limits can be variable
• Limit of Detection – lowest practicable detection limit
• Limit of Quantitation – lowest amount determined

quantitatively

• Ensure LOD & LOQ are suitable

Detection Limits - Practicality

• Direct on Filter – lower DL than ashed or re-deposited

methods

• Based on 500 L sample (4hr @ 2.2 L/min)
• FTIR: 0.02 mg/m3
• XRD: 0.02-0.04 mg/m3
• In real life, real workplace samples
• <0.05 mg/m3 is problematic
• Better to take near shift length samples (8-12 hr)

183

Materials for Analysis

• Sample filters from respirable (size-selecting) dust

samplers

• Bulk samples – e.g. road dust, ores, quarry material etc.
• Respirable quartz in the respirable fraction of a bulk

material

62

Session Recap

• Sampling techniques (historical & selecting current

sampling devices)

• Analytical techniques (FTIR & XRD) description
• Limit of Detection & Limit of Quantitation explanation

AIOH Resources

• AIOH Position Paper – RCS and Occupational Health

Issues

• AIOH – Technical papers
• Sampling Pumps
• Flow Measuring Equipment
• Size-selective Samplers for Respirable Dust Sampling

186

References

• AS 2985:2009 –sampling & gravimetric determination of

respirable dust

• NHMRC Method of quartz in respirable airborne dust by

infrared & XRD, 1984

• ISO 16258-1 (2015) Workplace air – Analysis of RCS by

X-Ray Diffraction, Part 1 Direct on filter method

• NATA website: www.nata.asn.au

63

SILICA SEMINAR

www.aioh.org.au

RCS – Exposure Control Impact of dust control - Vermont granite workers (Graham et al 1991, 2001)

Year hired % of miners with silicosis (cases) 1940-44 17.9 (5) 1945-49 7.5 (8) 1950-54 4.2 (4) 1955-59 3.8 (2) > 1959 1.5 (1)

189

Session Outcomes

• Use the hierarchy of control
• Apply engineering and administrative control
• Set up a respiratory protection program

190

64

Most Effective Least Effective

Personal Protective Equipment Administration/Training Engineering/Isolation Substitute Eliminate

Hard controls Soft controls

191

Hierarchy of Control Substitution

• Olivine and zircon in moulds and cores in foundries
• Glass beads, metallic shot, slag or grit for abrasive blasting
• Alumina for flint in pottery
• Pre-fabrication
• design buildings with pre-built recesses for plumbing, gas,

and electric wiring so there is less need to cut or drill masonry

192

Principles of dust control

• 1. Prevention of dust formation
• 2. Prevention of dust spread
• 3. Prevention of worker dust exposure

193

65

Prevention of dust formation

• Engineering
• Tools and equipment
• Wet processes
• Administrative
• Work processes
• Maintenance of

equipment

194

Personal Protective Equipment Administration/Training Engineering/Isolation Substitute Eliminate

Prevention of dust formation – tools and equipment

• Sharp cutting tools minimise the

generation of dust at source through less grinding

195

Prevention of dust formation – wet processes

• Dust is eliminated if powdered

material is suspended or dissolved in a liquid

• If materials are adequately

moistened by capillary action or by condensation, the point is reached where they will cease to generate dust.

• moulding sand
• sandstone

196

66

Prevention of dust formation – work processes & maintenance

• Control of dust levels along

travelling roads

• Change cutting method
• Reduce cutting speed
• Equipment maintenance

197

Prevention of dust spread

• Engineering control
• Design
• Segregation
• Extraction ventilation
• Water suppression
• Physical barriers
• Packaging systems
• Administrative control
• Work processes
• Housekeeping

198

Personal Protective Equipment Administration/Training Engineering/Isolation Substitute Eliminate

Prevention of dust spread - design

199

• Concentrate dusty processes in
• ne area
• Ensure contaminated air does

not spread to clean areas

• Wall and flooring surfaces and

furniture that is easy to keep clean

• Use solid floors (mostly!!)
• Minimise fall distances and

slope angles

• Ensure flooring is designed to

allow drainage

67

Prevention of dust spread - design

200

• Protect electrical systems

against moisture and dust

• Adequate correctly positioned

water and vacuum points

• Low maintenance equipment
• Closed circuit television systems
• Equip silos with pressure relief

devices, high level alarms and dust extraction systems

• Consider downstream

maintenance

Prevention of dust spread - segregation

201

• Where possible full enclosure

should be considered:

• grinding mills in vented

enclosures

• blasting cabinets - operator

controls from outside the enclosure

• enclosed transfer points,

crushers, conveyor systems, bucket elevators & screen houses

• pneumatic transport systems
• enclosed automatic bag

dumping stations

Prevention of dust spread - segregation

202

68

Prevention of dust spread - segregation

203

Three deck screen with dust control (Hanson Quarries)

Prevention of dust spread - segregation

204

• Pneumatic systems
• consider highly abrasive nature of RCS
• for horizontal transport angle pipes downward
• minimise directional changes (large radius bends)
• properly seal pipe connections
• Conveyor belts equipped with

cleaning devices

• Consider maintenance access

for enclosed systems

• Enclosure normally requires

some form of extraction ventilation

Prevention of dust spread – extraction ventilation

205

• Removes contaminants at the

source of emission

• Enclose the dust source as much

as possible

• Incorporates a hood/enclosure or
• ther inlet to collect dust,

ductwork, a cleaning device, a fan and a discharge duct

• Ensure a clean air supply to the

work area to replace extracted air

69

Prevention of dust spread – extraction ventilation

206

• Hood/enclosure or other inlet to collect dust
• away from doors, windows and HVAC

system outlets

• as close to emission point as possible
• deep enough to contain equipment and

materials

• opening as small as possible
• see-through panels and plastic strips
• do not store items inside the ventilated

area

• easy way to check it is working – small flag

Industrial Ventilation A Manual of Recommended Practice. 23rd Edition American Conference of Governmental Hygienists (ACGIH)

Prevention of dust spread – extraction ventilation duct design

207

• Short and simple
• Under negative pressure &

properly sealed

• Minimise flanges and inspection

holes

• Avoid long sections of flexible duct
• Design so dust cannot settle
• Ensure transport velocities are

appropriate

• Minimise internal wear – have few

bends

• Provide an appropriate number of

resealable test points

Prevention of dust spread – extraction ventilation

208

Dust extraction cleaning devices

• Drop out boxes
• Cyclones
• Wet scrubbers
• Bag filters/houses
• Electrostatic precipitators

Design considerations – the need for pre-separator/pre-cyclone – particulate & noise emission limits – maintenance requirements – need for inclination of more than 60° at the base – access to the flue and sample ports

70

Prevention of dust spread – extraction ventilation maintenance

209

• Test against performance standards
• Never modify the system
• Monitor filters/bags &/or monitor

emissions

• Maintain water levels/supply in wet

scrubbers

• Temporarily seal leaks with duct

sealing tape

• Repair/replace damaged/dented

sections of ductwork

• Take extra precautions regarding

protection of maintenance workers

Prevention of dust spread – portable extraction ventilation systems

• Often difficult to install a

ventilation system because of moving process and/or equipment

• flexible ducts may be the

solution

210

• portable extraction

systems may be used

Prevention of dust spread – portable extraction ventilation

211

Small equipment such as laboratory grinders and stone mason tools should have integrated exhaust ventilation

71

Prevention of dust spread – water suppression

• Once a dust cloud has been generated it is not easy to control

it by wet methods

• difficult to wet fine airborne particles, particularly quartz
• However water suppression remains one of the main dust

control techniques

• High-pressure water jets/sprays that produce fog or fine mist

spray are most effective

• water sprays specifications
• close to breakage point
• sufficient water volumes
• sufficient pressure
• appropriate jets/nozzles/venturis

212

Prevention of dust spread – water suppression

• Wetting agents/surfactants may be added to increase the

surface tension of the water and hence enhance its wetting ability

• Examples
• Wet cutting
• Wet scrubbers
• Road watering
• Sprays on traffic routes, conveyors & crushers
• Water curtains - particularly at conveyor transfer points and

chute draw points

• Stockpile/muckpile sprinklers/watering
• Wet cleaning – mopping, wet brushing, hosing

213

Prevention of dust spread – wet cutting processes

214

Dry cutting

Wet cutting

72

Prevention of dust spread – water suppression wetting agents

215

Sprays being used on a cone crusher and conveyor system transfer point (Hanson Quarries)

Prevention of dust spread – water suppression - Longwall mining

216

Stock pile water suppression

217

Water sprays to control dust off stock piles. (Hanson

Quarries)

73

Road watering with wetting agents

218

Haul road without DustBloc. (Hanson Quarries)

Road watering with wetting agents

219

Haul roads with DustBloc. (Hanson Quarries)

Prevention of dust spread – physical barriers

• Rubber curtains to prevent dust

release - conveyor transfer points and chute draw points

• Wind barriers/sails
• Stockpile discharge

socks/curtains or retractable vertical chutes

220

74

Prevention of dust spread – packaging

• Enclosed bulk transport systems
• keep the loading point under

negative pressure

• collect displaced air from tanker
• if not enclosed tarp load

221

Prevention of dust spread – packaging

• Bag systems
• Bulker bags reduce exposure during

packaging but may be difficult to handle for the customer

• Small bags have the greatest

potential for exposure during packaging

• use plastic liners
• seal the bag collar onto the filling

spout

• use vibration to prevent hang-ups and

to compact material

222

Prevention of dust spread – administrative control

223

• Ore passes not emptied

below the brow point and crusher chutes are kept full

• Apply good house-keeping

practices to prevent dust build-up and dust spread

• clean workplace on a

regular basis – daily if necessary

• deal with spills

immediately

75

Prevention of dust spread – administrative control

224

• Dry cleaning - vacuum

cleaning systems

• ensure system is not
• verloaded
• not generally suitable for

damp materials

• follow procedures when

emptying vacuum of dust

• do not use dry brush or

compressed air

• Define specific storage areas

for silica based products – if

• utdoors, site area to

minimise wind entrainment of dust

Prevention of worker exposure

• Engineering control
• Dilution ventilation
• Segregation
• Automation
• Administrative control
• Maintenance systems
• Training
• Supervision
• PPE

225

Personal Protective Equipment Administration/Training Engineering/Isolation Substitute Eliminate

Prevention of worker exposure – dilution ventilation

226

• Natural ventilation from windows and doors
• r fan forced ventilation
• Should ensure the removal of contaminated

air and make it up with clean or filtered replacement air

• Seldom a correct solution in working with a

dust problem

• May use ducting to help focus air supply on

specific areas

• Consider conditioning air to warm or cool it
• Ensure dilution ventilation does not interfere

with local extraction ventilation

76

Variations in dilution ventilation designs

Air curtains

• A type of jet that reduces the exchange
• f air across an opening.
• Commonly used to reduce the flow of

cold air into a heated building or vice- versa.

227

Industrial Ventilation A Manual of Recommended Practice. 20th Edition American Conference of Governmental Hygienists (ACGIH)

Variations in dilution ventilation designs

Overhead Air Supply Island System (OASIS)

• Uses a wide nozzle or plenum at

low velocity to provide a zone of fresh air around the worker.

• Usually operate on either fresh air

from outside the workplace or filtered air from inside the workplace.

228

Industrial Ventilation A Manual of Recommended

• Practice. 20th Edition American Conference of

Governmental Hygienists (ACGIH)

Prevention of worker exposure – dilution ventilation

• How forced or natural ventilation is applied to a workplace

requires forethought and planning to be effective

• Fresh air should always pass the operator, collect the

contaminant, then pass to the outlet. Should the general ventilation operate in any other way, the air may become contaminated before reaching the worker’s breathing zone

229

Industrial Ventilation A Manual of Recommended Practice. 20th Edition American Conference of Governmental Hygienists (ACGIH)

77

Prevention of worker exposure – segregation

• Segregation in enclosed and filtered control rooms and mobile

equipment cabins

• have own clean air supply
• sealed and physically separated from dusty areas
• ventilate using positive pressure systems
• provide sufficient widows to monitor the process from

within the control room

• filters must remove very fine particles

230

Prevention of worker exposure – segregation

231

Prevention of worker exposure – segregation

232 Precleaned, pressurised and filtered external/recirculated air mixed in the HVAC plenum & blown into cabin Cleaned & Filtered Air To Recirculation RESPA Unit From Cabin Standard HVAC Unit External air & debris enter primary RESPA Unit. Debris goes through two ejective precleaning cycles. Precleaned air then passes through Merv 16 / 17 filter sending CLEAN air into HVAC system Maintaining a pressurised cabin is essential for effective air filtration. A sensor can be installed to monitor cabin pressure (0.049 kpa). Air from cabin enters RESPA Recirculation Unit, where it passes through second MERV 16/ 17 filter to remove particles that enter the cabin via the door, or carried in via boots &

• perator clothing

RESPA- HVAC Pre-cleaner Pressuriser + Filtration Technology

78

Prevention of worker exposure – segregation

233

RESPA- HVAC Precleaner Pressuriser + Filtration Technology

Debris laden air enters the RESPA Unit Debris particles ejected back into the environment. Pre-cleaned air continues into the filter Fresh air continues into the evaporator

Prevention of worker exposure – segregation

234

Prevention of worker exposure – automation

• Remote monitoring of

crusher from camera within control room

• Automated longwall

mining

• Remote control mucking

235

79

Typical control strategies

Process Enclosure Extraction Wet process Drying/calcining minerals Loading/unloading bulk material Lab crushing/drying Cutting and polishing refractory Concrete cutting Core making and moulding in foundries Knock-out and shake-out in foundries

236

Typical control strategies

Process Enclosure Extraction Wet process Mobile equipment – excavation and haulage Rock drilling Furnace charging Crushing, grinding and screening Bagging Grinding, sawing and drilling ceramic products Mixing Firing ceramics

237

Prevention of worker exposure – administrative controls

• Restrict access to dust generating work areas to authorised personnel
• Position personnel so they are out of the dust or so they are working

upwind of dust emission

• Job rotation
• Perform regular visual checks – look for build-up of fine dust that may

indicate a control failure

• Maintenance
• follow supplier/installer maintenance guidance & keep records
• Training, Supervision

238

80

Administrative control systems - training

• Hazards of RCS
• Dust exposure prevention
• Checking controls are working and using them
• When and how to use respiratory protective equipment –

limitations

• What to so if something goes wrong e.g. spillage
• Dust monitoring programs – including results
• Health surveillance
• Refresh every 2 years

239

Dust control systems - supervisors

• Have a knowledge of health hazards
• Understand the potential problem areas of the process
• Understand the control measures - their use and maintenance
• Know the health surveillance requirements
• Check control measures are in place and are being used
• Report faults to supervisors and get them fixed
• Set an example by following procedures

240

Prevention of worker exposure – respiratory protection

241

Half face disposable respirator (P1 or P2) PAPR – Powered air purifying respirator (P2 or P3)

81

Prevention of worker exposure – RPE

• There are three classes of particulate respirator
• Class P1 - for use against mechanically generated

particulates e.g. asbestos and silica

• Class P2 - for use against mechanically or thermally

generated particulates e.g. zinc or lead fume

• Class P3 - for use with any particulate including highly toxic

particulates e.g. beryllium and some microbiological agents.

• Filtering efficiency
• P1 - not more than 20% penetration
• P2 - not more than 6% penetration
• P3 - not more than 0.05% penetration.

242

RPE management program

243

• Set up in accordance with AS1715
• Conduct regular inspections to ensure PPE is

being utilised consistently and correctly

• Signage indicating areas where PPE is

required

• Store in a clean and fully operational

condition, safe from damage, and easily accessible e.g. disposable RPE at building entrances

• Regular checking & maintenance – keep

records

• Repair or discard if damaged or defective

RPE management program

• Individual fit-testing for face seal and

to ensure comfort (qualitative or quantitative)

• Personal issue (facial features &

protection factor)

• Training in use and limitations
• Simple written procedures and policy
• e.g. clean shaven policy if negative

pressure face seal respirators used

• For more details see: https://www.3m.com.au

244

82

Clean Shaven

• RCS – much smaller than facial hair
• Respirator relies on good facial seal
• Clean shaven –> shave before coming to work!

Need for more than one control

• US engineered stone top bench manufacture – 30-min RCS

samples in mg/m3: (Cooper et al 2015)

• dry cutting: 44.6
• wet blade alone: 1.87–4.85
• wet blade + curtain: 0.92–3.41
• wet blade + LEV: <0.12–0.20.
• UK stone working sectors - 61% RCS exposures where

water suppression used > 0.1 mg/m3

(Baldwin et al 2019)

246

Session Recap

• Use the hierarchy of control
• Apply engineering and administrative control
• Set up a respiratory protection equipment

247

83

References

• NEPSi ‘Good Practice Guide’ - http://www.nepsi.eu/ - with

more than 50 different task sheets that include controls for RCS generation.

• NIOSH Safety and Health Topic page on ‘Silica’ -

https://www.cdc.gov/niosh/topics/silica/constructionControlMa in.html - examples of engineering controls, including use of LEV to capture dust at source and use of water sprays to suppress dust.

• OSHA ‘Controlling Silica Dust in Construction Fact Sheets’ page
• https://www.osha.gov/dsg/topics/silicacrystalline/construction.

html.

• UK HSE ‘Control of exposure to silica dust’ page -

http://www.hse.gov.uk/pubns/indg463.htm.

248

SILICA SEMINAR

www.aioh.org.au

RCS – Future Initiatives

Safe Work Australia report that workers in Australia are 8 times more likely to die from an occupational illness or disease than an accident at work. Statistics released by Safe Work Australia indicate that on average 250 people will die from injury at work, while over 2000 people will die from an occupational disease Safe Work Australia 2012

84

Web based information hub: www.breathefreelyaustalia.org.au

What is available on the BOHS site AIOH site currently covers: Construction, Welding, Engineered Stone and Mining

85

HI Standard Self-Assessment Tool + other web- based resources Breathe Freely Australia - helping you take control

.

Let’s get going by deciding to treat health like safety. Then begin to breathe freely.

Join us and be part of the solution www.breathefreelyaustralia.org.au