Physical hazard II: Suspended
particles
Occupational Health
EOH3202
Environmental & Occupational Health
Faculty of Medicine and Health Sciences
University Putra of Malaysia
Learning goals
1. Able to identify work tasks associated with high
exposures to suspended particles
2. Able to characterise the physical and chemical
properties of suspended particulates
3. Able to understand particle size distribution and its
relationship with site deposition and mechanisms of
particle deposition in the lung
4. Able to identify health outcomes related to exposure of
particulates
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
Examples of tasks at risk for high
exposures to suspended particulates
• Sandblasting work
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http://www.youtube.com/watch?v=-TjqtXB8BtY&feature=related
http://www.youtube.com/user/allweldsandblasting?v=g726Qa7Pco&feature=pyv&ad=6850597350&kw=industrial%20sandblasting
• Quarry operation
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http://www.youtube.com/watch?v=vAW_Vvu2nYI
• Asbestos-related work
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http://www.youtube.com/watch?v=RZm7u6z6tLI
• Cotton processing workers
• Laboratory workers – animal handlers
• Welding work
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
Physical hazard: suspended particles
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Aerosol is the dispersion of solid or liquid in the gasesous medium
–Cigarette smoke
–Welding fume
–Sea mist
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DUST
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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
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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
Aerosol cont.
 MISTS
 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
Aerosol cont.
 FIBERS
 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
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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
Physical and chemical properties of
suspended particulates
6 properties:
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Particles size
Shape and aspect ratio
Surface area and volume
Solubility
Composition
Reactivity
These properties also determine its toxicity
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
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
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
Cumulative log-normal size distribution of particles
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
Regional Particle Deposition
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
Pulmonary alveoli
Site of Particle Deposition
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
Mechanism of particle deposition in
lung cont.
http://www.mfg.mtu.edu/cyberman/environment/air/depos.html
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
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
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 Insulated Locomotive
Asbestos Mills 1900′s
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
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 1924 - 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
National Asbestos Bans
Latest update: Malaysia’s ban expected by 2015 through a voluntary
phase-out plan developed in 2009
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
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 15-50 years
▫ No threshold dose for the occurrence
▫ Symptoms – persistent coughing, fatigue, sob etc
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
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
http://www.youtube.com/watch?v=5f7medwuIM
A&feature=related
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
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 20-30 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
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
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)
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%
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 reexposure
▫ Mast cells release histamine an other mediators – early
allergic response
▫ Secreted cytokines stimulate influx of inflammatory cells in
late phase response
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
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
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
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
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
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
Thank You