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Health Hazards of Silica

Learn about the health hazards of silica exposure in the workplace, identify crystalline silica risks, assess potential dangers, and discover protective measures to safeguard your health and well-being.

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Health Hazards of Silica

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  1. Health Hazards of Silica Occupational Health Department Equal Code SSR024

  2. Identify the Hazard • What is Silica? SiO2 • Group of minerals that contain silicon and oxygen. • Free silica exists in two main forms; amorphous or CRYSTALLINE • Crystalline silica is one of most common minerals found on the surface of the earth.

  3. Identify the Hazard • CRYSTALLINE SILICA • Silica quartz is the most common constituent in sand. • Sand is the principal component of most glass andsubstances such as concrete, foundry castings, etc. • Used in sandblasting QUARTZ CRISTOBOLITE TRIDYMITE

  4. Identify the Hazard • Chemical and Physical Properties of • Crystalline Silica, Quartz • Colourless, odourless, noncombustible solid • Melting point 1650 (±75)°C • Boiling point 2230 °C • Solubility in water 0.012 g in 100mL • Molecular Weight 60.09 • Solubility Insoluble

  5. Identify the HazardWhere it exists at work? • Silica is a component of most rock and ore, therefore mining operations are at risk of exposure. • Products containing silica are widely used in the industry. • Crushing, drilling, hauling, chipping, etc. silica containing material are activities that cause silica to become airborne.

  6. Identify the Hazard • Silica can be present in the process stream. • Example: Hardrock Mining

  7. Identify the Hazard • Designated Substance • Silica is identified as a Designated Substance in Ontario (Regulation 490/09). • The Occupational Health and Safety Act defines a Designated Substance as: • …”a biological, chemical or physical agent or combination thereof …to which the exposure of a worker is prohibited, regulated, restricted, limited or controlled.”

  8. Assess the Risk • How can silica enter my body • & • How can it affect my health?

  9. Assess the Risk • Route of Exposure: • Hazardous when inhaled and deposited in the lung tissue. • Health Effects: • Lung disease (silicosis) • Connective tissue disorders (i.e. scleroderma) • Lung cancer • ACGIH: A2 (Suspected Human Carcinogen) • IARC: Group 1 (Carcinogenic to humans) Is all dust containing free crystalline silica potentially harmful? No, dependent upon several properties…

  10. Assess the Risk • Factors That Influence Development of Disease Airborne concentration % of silica in the dust Form of silica Size of particles inhaled Duration of exposure Resistance of the individual Presence or absence of complicating process such as infection

  11. Assess the Risk • Ontario’s Occupational Exposure Limit (OEL) • Time-Weighted Average (TWA) concentration for a normal 8-hour workday and 40-hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effects. • TWA for Silica = 0.1 mg/m3 for 8 hr workshift • = 0.067 mg/m3 for 12-hr workshift

  12. Assess the Risks • Air Monitoring: • Silica from respirable component of dust sampled. • Particle size less then 10 microns. • The sampling train consists of a 25 mm Silver membrane filter, a 10 mm cyclone and a pump.

  13. AREA SAMPLING: Placing the sampling equipment in a representative fixed position in the work area. Useful as an index of general contamination. Can be used to determine whether to post as a “Respirator Protection Required” area. Assess The Risk:Air Sampling

  14. *Results determine worker exposure (for comparison to OELs) Assess the RisksAir Sampling • Personal Monitoring is conducted: In the worker’s breathing zone. Doing his/her normal work activities. Over an entire work shift.

  15. Controls • Types of Controls Engineering Controls Administrative Controls Work and Hygiene Practices PPE

  16. ControlsEngineering Controls • Includes: Substitution Ventilation Enclosure/isolation • The above controls can be implemented: At the source Along the path At the worker

  17. ControlsAdministrative Controls • Includes: Training on hazards recognition, safe work & hygiene practices Maintaining adequate hygiene facilities (hand washing and showering) Transferring high risk workers out of work area Occupational Health & Medicine Programs Written documentation of safe work procedures (site specific)

  18. ControlsWork and Hygiene Practices • Some of the things you can do to protect your health: Follow adequate controls (ie. wearing PPE, vacuum vs. dry sweep) Keep your work area clean – daily housekeeping Eat & drink only in designated areas • REPORT any symptoms or illnesses right away (even if you think they are minor)

  19. ControlsPPE: Respirators • The type of respirator is based on the silica concentration. • Respirator fit testing can be done at Vale’s First Aid facilities. • Refer to the Divisional Respirator Protection Program.

  20. ControlsPPE: Respirator Selection • Where airborne concentrations are: • < = to 1.0 mg/m3 • Half-face air-purifying respirator equipped with a high efficiency filter. • Assigned Protection Factor (APF) of 10 (NIOSH) • < = to 2.5 mg/m3 • Powered air-purifying respirator (PAPR) equipped with high efficiency filter. • APF of 25 (NIOSH)

  21. *Never remove respirator in the contaminated area.* ControlsPPE: Respirator Selection • The respirator must: • Have the proper cartridge or filter to protect against the contaminant. • Must provide adequate protection, depending on exposure limit and concentration.

  22. Positive Negative ControlsPPE: Respirator Seal ChecksDo a seal check each time you put on your respirator

  23. Please Ensure these Practices (Controls)are Protecting YOU by….. • Participatingin air monitoring program (wearing a pump)! • tells us about YOUR lung exposure to dusts that shift • Participating in medical surveillance program(attending medicals)! • THEY ARE COMPLIMENTARY!!

  24. ControlMedical Surveillance • Persons on the control program are enrolled in the Medical SurveillanceSilica Control Program: Medical examination/History Clinical tests Health education Record keeping

  25. ControlMedical Surveillance: Pre-placement Medical Periodic Medical (carried out at least every two years on a voluntary basis) Where a respiratory is required, physician should also assess whether the worker is fit to use.

  26. ControlMedical Surveillance: Clinical Tests Chest X-Rays Pulmonary Function Tests

  27. Take home message • Emphasis is on what you can do; how you go out in the plant and recognize and understand a hazard and assess the level of risk. • Planning for controls is done ahead of time. If no control is in place or you think the hazard still exists, talk to your supervisor • Following established controls and continually monitoring and assess controls; if no control is in place or you think the hazard still exists, talk to your supervisor

  28. Document Control

  29. Thank you!

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