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Physical hazard II: Suspended particles

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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 726Qa7Pco&feature=pyv&ad= &kw=industrial%20sandblasting 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

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

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