1. Physical hazard II: Suspended particles
Occupational Health EOH3202
Environmental & Occupational Health
Faculty of Medicine and Health Sciences
University Putra of Malaysia

2. Learning goals
Able to identify work tasks associated with high exposures to suspended particles
Able to characterise the physical and chemical properties of suspended particulates
Able to understand particle size distribution and its relationship with site deposition and mechanisms of particle deposition in the lung
Able to identify health outcomes related to exposure of particulates

3. Classification of hazards: Recap
Physical - noise, heat, vibration, ionizing radiation, pressure, poor lighting, electricity, mechanical injury, particulate emissions
Chemical
- solid, liquid, semisolid, gas
- heavy metal, solvents, etc.
Biological – Bacteria, virus, parasite
Psychosocial – stress, violence
Ergonomic problem – lifting heavy objects, repetitive movements, poor posture

4. Examples of tasks at risk for high exposures to suspended particulates
Sandblasting work
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Quarry operation
Asbestos-related work
Cotton processing workers
Laboratory workers – animal handlers
Welding work

5. Cotton processing workers
Typical setting of grinding the pieces of cotton and mixed garments in the recycling industry in Nepal
A duvet maker beating the recycled cotton to make mattress in Nepal

6. Physical hazard: suspended particles
Aerosol is the dispersion of solid or liquid in the gasesous medium
–Cigarette smoke
–Welding fume
–Sea mist
DUST
Solid aerosols generated by the handling, grinding, abrasion, or cutting of a bulk material, with individual particle diameter being 0.1 µm or above
Dust particle size is related to the amount of energy involved in creation; the higher the energy—the smaller the particle created; the lower the energy—the larger the particle created
Examples: Saw dust, coal dust
FUMES
Solid aerosols generated by the condensation of vapors or gases from combustion or other high temperature processes
Usually very small and spherical
Sources: Welding, foundry and smelting operations, hot cutting or burning operations

7. Aerosol cont. MISTS SMOKE
Liquid aerosols generated by condensation from a gaseous state or by the breaking up of a bulk liquid into a dispersed state
Droplet size related to energy input as in dusts and fibers
Examples: Metal working fluid from lathe, paint spray, liquid mixing operations
SMOKE
Solid aerosols resulting from the incomplete combustion of carbonaceous materials
Wide range of particle sizes
Size related to combustion efficiency
High efficiency = smaller particles, Low efficiency = larger particles
Examples: Wood smoke, diesel exhaust

8. Aerosol cont. FIBERS BIOAEROSOLS
A special (based on toxicological properties) kind of dust that is fibrous in nature (i.e., longer than it is wide)
Aspect ratio (L:W) defined as 3:1 or 5:1
Toxicity a function of composition, size, and number of fibers
Examples: Asbestos, fiberglass, refractory ceramic fibers
BIOAEROSOLS
Solid or liquid aerosols from biological sources
May be infectious, allergenic, and/or irritating
Wide range of particle sizes
–Virus (0.002–0.03 um)
–Tree pollen (10–100um)
Examples: Mold spores, animal allergens, anthrax

9. Physical and chemical properties of suspended particulates
Particles size
Shape and aspect ratio
Surface area and volume
Solubility
Composition
Reactivity
These properties also determine its toxicity

10. Particle size: Aerodynamic Equivalent Diameter
The Aerodynamic Equivalent Diameter (AED) of a particle is the diameter of a unit density sphere that would have the identical settling velocity as the particle
Measure of behavior of particle in air
Function of particle diameter, density, shape, and surface characteristics
Determines site of deposition in lung
Effects air sampling characteristics
Referenced to spherical drop of water with identical settling velocity

12. Physical and chemical properties cont.
Shape and aspect ratio
important when dealing with fiber: eg asbestos
Respirability function: depend on diameter and not the length
Surface area and volume
reactivity increase when size reduce because the relative surface area rapidly increase
Solubility
This influence the rate of absorption in the body
Water or liquid soluble: the effect is generally systemically – ammonia (very soluble)
While the insoluble the effect is at the point of contact or deposited – eg deposited at nasopharynx can cause nasopharyngeal cancer

13. Physical and chemical properties cont.
Composition
Chemical composition has direct bearing on resulting health effect due to differing properties or chemical interaction
Eg a particulate with 10 % of silica bears less health effect compared to a particulate with 90% silica
Reactivity
Under certain conditions, chemical in particulates could give rise to dangerous reaction or decomposition
Release of toxic, flammable or combustible gases with release of heat

14. Cumulative log-normal size distribution of particles

15. Particle size distribution
Inhalable fraction (<100 μm AED)
Fraction of dust which can be breathed into nose or mouth
Thoracic fraction (<25 μm AED)
Fraction of dust which can penetrate head airways and enter lung airways
Respirable fraction (<10 μm AED)
Fraction of dust which can penetrate beyond terminal bronchioles to gas exchange region
Fine fraction (<2.5 μm AED)
Fraction of dust which can penetrate the alveoli or cross membranes to enter the bloodstream
Ultrafine fraction (<0.1 μm AED)
Fraction of dust which are smaller than 0.1 µm

16. Regional Particle Deposition

17. Routes of entry Inhalation: very significant route
50 µm AED will be filtered at the nose
7 – 20 µm AED: deposited at the nasopharynx
5 – 7 µm AED: deposited at tracheo-bronchial air ways
0.5 – 5 µm AED: alveolar region

18. Pulmonary alveoli

19. Site of Particle Deposition

20. Mechanisms of Particle Deposition in the Lung
Inertial impactions
Function of particle velocity and mass, deposition by impaction is greatest in the bronchial region
Interception
Function of particle diameter and is most significant for fibers, which easily contact airway surfaces do to their length. Fibers have small aerodynamic diameters relative to their size, so they can often reach the smallest airways
Sedimentation (gravitational settling)
Function of particle velocity (residence time) and mass, sedimentation plays a greater role in the deposition of particles with larger aerodynamic diameters
Diffusion
Function of particle diameter, concentration, velocity (time), and distance. Diffusional deposition occurs mostly when the particles have just entered the nasopharynx, and is also most likely to occur in the smaller airways of the pulmonary(alveolar) region, where air flow is low

21. Mechanism of particle deposition in lung cont.

22. Particle deposition in lung
Particle size
Example
Site of injury
>10 micron
Dust from earth crust
Upper airways
2.5 – 6 micron
Fire smoke particles
Lower airways
< 2.5 micron
Metal fumes, asbestos powder
Lung parenchyma

23. Pneumoconiosis Pneumoconiosis causes inflammation of the lungs
silicosis, asbestosis and coal worker's pneumoconiosis
The lung tissue in normal people is very elastic
This allows it to expand and contract while breathing
In the common types of pneumoconiosis, fibrous tissue gets deposited in the lungs, the condition being called fibrosis
Fibrosis tends to stiffen the lung tissue and restrict its expansion

24. Suspended particles: Asbestos
Asbestos – mineral fiber - used for 2500 years and have been commercially used since mid-1850’s
Among of it uses – boilers, steam pipe, insulation for locomotive and ships, fire blankets and fabrics, brake pads, roof top, special purpose clothing etc.
Asbestos insulated ship being dismantled
Asbestos Mills 1900′s
Asbestos Insulated Locomotive

25. Asbestos Exists in two groups:
Serpentine group: chrysotile – white asbestos – thin, long and snake-like
Amphibole group: crocodolite, amosite, actinolie, remolite and anthopylite – a.k.a. blue asbestos – thin, long and needle shape
Left: chrysotile
Right: Crocidolite

26. Asbestos cont.
Historically, name was derived from Greek word – asbestos, meaning ‘inextinguishable’
Asbestos had low thermal conductivity or resistant to fire, acids and is pliable
Early 1920’s, large number of deaths were observed in mining towns
Asbestos miners were observed to die unnaturally young – one woman, worked with asbestos since 13 yrs old, died at 33 in first asbestosis case
Asbestos, Canada where chrysotile is mined - particularly Quebec, show that individuals who live in the mine areas have a greater incidence of developing an asbestos-related disease
Banned in EU, US and other western countries except Canada

27. National Asbestos Bans
Latest update: Malaysia’s ban expected by 2015 through a voluntary phase-out plan developed in 2009

28. Asbestos related lung disease: Asbestosis
Types of disease
Specific – example such as asbestosis, mesothelioma, pleural plaques
Non-specific – example such as lung cancer, diffuse pleural thickening, pleural effusion, rounded atelectasis
Asbestosis – fibrotic - non-malignant lung disease – development depends on amount and duration of exposure
Symptoms – cough and shortness of breath on exertion
Treatment does not reverse progression of disease
Occurrence of asbestosis is Dose-dependent

29. Asbestos related lung disease: Lung cancer and mesothelioma
Increased risk of lung cancer in asbestos exposed workers – up to 5x
Direct and linear relationship between RR of lung cancer and cumulative exposure to chrysotile and amphiboles – no safe dose
Lung cancer attributable to asbestos is under recognised
Mesothelioma – cancer of pleural and peritoneal – tissues that lines lungs, stomach
Exposure for years
No threshold dose for the occurrence
Symptoms – persistent coughing, fatigue, sob etc

30. Factories and Machineries (Asbestos Process) Regulations, 1986
Establishes a PEL of 1 fiber/ml of air over 8 hour period
Requires exhaust equipment (Local Exhaust Ventilation) to be provided in order to keep exposures below PEL
Requires equipment to be examined and tested at specified intervals by a competent person
Provide PPE in the prescribed area or where concentrations exceed PEL
Obligation on employees to use PPE
Cleaning and housekeeping
Personal monitoring at least at 3 monthly intervals to comply with regulations
Medical examination of employees at least every 2 years (lung function test) - Specify details of the test

31. Factories and Machineries (Asbestos Process) Regulations, 1986
Provide employees with training on the process, controls, PPE and medical surveillance
Medical records kept for 20 years
Remove employees from work area if there is indications of asbestos related diseases
Example of asbestos removal task A&feature=related

32. Silicosis When small silica dust particles inhaled
Embed deeply into alveolus and ducts in the lungs - lungs cannot clear out the dust by mucous or coughing
Bilateral pulmonary fibrosis caused by
inhalation and deposition of dust containing silicon dioxide (SiO2) in crystalline form – either quartz, cristobalite and tridymite
Sources of exposure:
quarries, foundries (mold made from sand), porcelain factories, cement factories, glass making, sandblasting

33. Silicosis cont. Simple, chronic, complicated silicosis
Signs: obstructive lung disease or fibrosis in advanced stage of disease
Symptoms few or none – dry cough, sputum production, symptoms of pulmonary insufficiency with advancing disease
Exposure between years
Accelerated silicosis
Simple nodular silicosis rapidly develops into massive fibrosis
Developed between 5-10 years of exposure
Acute silicosis
Rapidly developing breathlessness, coughing, asthenia, weight loss, progressive respiratory insufficiency
Developed between 1-3 years of exposure

34. FMA 1967 (Mineral Dust Regulations)
PEL of 0.1 mg/m3 quartz and 0.5 mg/m3 TWA for cristobalite and trydimite
Employers provide and employees required to use protective clothing, respiratory equipment and PPE
Report any defects in the equipment
Sand blasting is prohibited unless written approval from DOSH is obtained

35. Occupational asthma
Variable airflow limitation and airway hyper responsiveness
due to causes and conditions attributable to a particular occupational environment
not to a stimuli encountered outside the workplace
Present in 2 types
OA that begins after preceding asymptomatic period of work exposure (latency period) to causative agent (allergic sensitisation)
Irritant-induced asthma or RADS or Reactive Airways Dysfunction Syndrome (no latency)

36. Occupational Asthma
Risk factor for IgE mediated OA caused by High Molecular Weight agents – natural/plant sources and LMW chemicals
Prevalence of OA is higher in atopics –
Microbial enzymes - Protein allergens in rubber latex gloves, detergent workers
Epidermal/urinary proteins – animal handlers
Atopy? – hyper reactive – propensity to produce specific IgE to environmental allergens
30% of population is atopic
Prevalence : 2-5% of all occupational cases
Bakers – 7-9% - alpha amylase
Lab workers – 8-12%
Manufacturing workers – diisocyanates 1 to 10%

37. Mechanism of OA Exposure
IgE mediated sensitisation in skin and airway mucosa – antigens processing by dendritic cells and B cells present antigens to TH cells
Activated t cells produce cytokines and stimulate B cells to produce IgE antibodies
Following sensitisation, clinical manifestation occur on re- exposure
Mast cells release histamine an other mediators – early allergic response
Secreted cytokines stimulate influx of inflammatory cells in late phase response

38. Allergic asthma and irritant-induced asthma
Airway inflammation: infiltration of bronchiol mucosa with activated lymphocytes, neutrophils and mast cells
Irritant effects: airway injury by exposure to high levels of irritants
Disrupt intercellular tight junctions between bronchoepitheliel cells
Disruption of epithelial barrier
Penetration of chemical antigens into Submucosa where IgE produced

40. Byssinosis
Acute or chronic lung disease characterised by chest tightness and breathlessness caused by exposure to cotton, flax, hemp, jute and sisal
Decline in FEV1 within few hours exposure to cotton dust after 48 hours separation from cotton dust
How to measure?
6 hour or work shift decrease FEV1 is the objective measure of response to cotton dust

41. Prevention and control
Screening to eliminate highly susceptible potential workers from exposure
Workers informed of additive effects of cigarette smoking
Relocate workers who develop hyperreactivity of hypersusceptibility
Fair and adequate compensation for those with byssinosis related pulmonary impairment

42. Hyper sensitivity pneumonitis/ extrinsic allergic alveolitis
Allergic lung disease due to sensitisation and recurrent exposure to allergens usually in agriculture settings
Acute form presents as recurrent influenza like illness and chronic form as insidious exertional dyspnea

43. Agents causing hypersensitivity pneumonitis
Thermophyllic actinomycetes
Micropolyspora faeni – farmers lung from moldy compost
Thermoactinomuces vulgars – mushroom workers lung
Thermoactniomyces sacharii – bagassosis – sugar cane
Fungi
Aspergillus clavatus – malt worker lung – moldy lung
Penicillum casee – cheese worker lung – cheese mold
Hair dust – furriers lung from animal proteins
Altered humidified water – humidifier lung

44. Hypersensitivity pneumonitis cont.
Bacterial, fungi and serum protein antigens causing HP have small AED <5micron presenting as aeroallergens in lung
Reach terminal bronchioles and alveoli
Clinical response depends on particle size, antigen load and concentration of aerosol
Symptoms – fever, cough, dyspnea, malaise
Management – avoidance of contaminated areas

45. Thank You