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Silica! Its NOT just dust, Its Silica! The Health Hazards of Silica in Construction Work.

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Presentation on theme: "Silica! Its NOT just dust, Its Silica! The Health Hazards of Silica in Construction Work."— Presentation transcript:

1 Silica! Its NOT just dust, Its Silica! The Health Hazards of Silica in Construction Work

2 What is Silica? Silica is Quartz Quartz (silica) is found naturally in almost all rock, sand, and soil. It is also found in concrete products and bricks. It is also found in sandblasting (abrasive blasting) grit and is called silica sand. 4

3 Silica Content of Minerals Limestone % Granite % Sandstone % Shale % Slate % Coal %

4 Silica Health Hazards Inhaled silica dust scars the lungs A lung disease called silicosis is caused by breathing of dust containing silica. The dust causes fibrosis or scar tissue formation in the lungs. This reduces the lungs ability to extract oxygen from the air. There is no cure. 5

5 Silica Health Hazards What are the symptoms of silicosis? Early stages go unnoticed. Continued exposure results in shortness of breath during exercise. Prolonged high exposure can lead to extreme shortness of breath, chest pain, respiratory failure, and death. 6

6 Silica Health Hazards Other Health Effects Susceptibility to other lung diseases and infections such as tuberculosis. Acute silicosis may develop after very short periods of high exposure. Chronic silicosis develops after many years of lower levels of exposure. 7

7 Types of Silicosis: Simple chronic silicosis -- results from long-term exposure (more than 20 years) to low amounts of silica dust. This disease may cause people to have trouble breathing. Accelerated silicosis -- occurs after exposure to larger amounts of silica over a shorter period of time ( years). Acute silicosis -- results from short-term exposure to very large amounts of silica. The lungs become very inflamed and can fill with fluid, causing severe shortness of breath and low blood oxygen levels.

8 Silica Exposure Limits Is there a safe limit for silica? PEL is determined by using equation PEL (respirable fraction) = 10 ÷ [% quartz + (% cristobalite × 2) + (% tridymite × 2) + 2] The safest amount of silica in the air is zero. Respirable dust is that fine dust that is inhaled deep into the lungs where it causes its damage The legal limit is called a permissible exposure limit or PEL. Rule-of–thumb: if dust containing silica is visible in the air, its almost always over the permissible limit. 8

9 Silica Exposure in Construction Silica is found in many construction jobs Rock drilling Concrete & masonry building construction Earthwork and rock crushing Masonry or concrete building demolition Road construction and repair Abrasive blasting (sand blasting) 9

10 Silica Exposure – Rock Drilling Rock drilling without water produces large amounts of dust. Your actual exposure will depend on the wind, where you stand and if you use water to control the dust. 11 Drilling without water Drilling with water

11 Silica Exposure in Construction Concrete Work Generates moderate to heavy amounts of dust Generates heavy amounts of dust Jack-hammering Power sanding 12

12 Silica Exposure –Concrete Highway work Drilling concrete pavement dry Generates moderate amounts of dust 13

13 Silica Exposure – concrete cutting without water Generates large amounts of dust 14

14 Silica Exposure – brick and cinder block cutting Generates moderate to heavy amounts of dust without water. 15 Without water With water

15 Silica Exposure - Tuckpointing Generates heavy amounts of dust without water 16

16 Silica Exposure – cutting concrete siding with power saws On some new construction, a lightweight concrete siding (hardiplank) is being used. Cutting this siding with a power saw without water or ventilation can result in silica overexposure. 17

17 When dust is controlled, exposures are lower. When dust is uncontrolled, exposures are high. Many exposures are for short time periods, but at very high concentrations. Short, high exposure can still exceed permissible limits and cause lung damage. The Risk of Silica Exposure 19

18 Silica dust exposure can be controlled by use of water or exhaust ventilation Using water to cut concrete and bricks Concrete sander with exhaust ventilation 20

19 Silica Exposure Control Avoid dry sweeping and use of compressed air on concrete Both these activities can stir up large amounts of dust. Use a vacuum with high efficiency filters when possible. 22

20 Controlling Silica Exposures

21 Silica and Use of Respirators Respirators must be used if silica dust cant be controlled with water or ventilation Air-purifying respirator with dust cartridge Supplied air respirator or either 24

22 Respirators must fit properly to prevent leaks around the edges. Fit-testing must be done before first wearing a respirator. Beards are not allowed when wearing a respirator. Respirators Must Fit Properly 28

23 Employees using respirators must be trained Training is required by DOSH for anyone who wears a respirator. If you dont know how to use a respirator properly, you may think your respirator is providing protection when it is not. 27

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