Hazards of Silica Dusts in Construction, Demolition and Mining

Silica is a naturally-occurring substance found in most rocks, sand and clay; hence, also found in products such as bricks and concrete. In the workplace silica exposure is a great risk for workers who perform high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work and tunnelling. The serious health hazards resulting from silica exposure are demonstrated by the fatalities and disabling illnesses that have occurred and continue to occur in these types of occupation.

Respirable Crystalline Silica (RCS) has been classified as a human lung carcinogen but the effects of breathing crystalline silica dust can also cause silicosis, which can result in disabling or even fatal lung disease.

Silica dust is inhaled into the lungs and contact with lung tissue causes the formation of scar tissue, reducing the lungs’ ability to take in oxygen. Since silicosis affects lung function, it also makes the sufferer more susceptible to lung infections.

Silicosis is classified as either chronic/classic, accelerated or acute. Chronic and classic silicosis occurs after 15–20 years of low to moderate exposure to respirable crystalline silica. The symptoms of chronic silicosis may or may not be obvious; as such workers need to have a chest x-ray to determine if there is lung damage. As the disease advances the sufferer will experience shortness of breath upon exercising and have clinical signs of poor oxygen/carbon dioxide exchange. Latter stages of the disease present as fatigue, extreme shortness of breath, chest pain or respiratory failure. Accelerated silicosis can occur after five–ten years of high exposures and result in severe shortness of breath, weakness and weight loss.

Acute silicosis can occur after a few months or as long as two years following exposure to extremely high concentrations of respirable crystalline silica. Symptoms of acute silicosis include severe, disabling shortness of breath, weakness and weight loss, which often leads to death.

The routes of exposure to respirable crystalline silica occur in a vast number of different construction/demolition activities. The most severe exposures generally occur during abrasive blasting with sand to remove paint and rust from bridges, tanks, concrete structures and other surfaces. Other construction activities that may result in severe exposure include: Jack hammering, rock/well drilling, concrete mixing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing and tunnelling operations. Other exposures to silica dust occur in cement and brick manufacturing, asphalt pavement manufacturing, china and ceramic manufacturing and the tool and die, steel and foundry industries. Crystalline silica is used in manufacturing, household abrasives, adhesives, paints, soaps, and glass. A further route of highest exposure is often from repair and replacement of refractory brick furnace linings.

In Britain, RCS has a workplace exposure limit (WEL), which contains exposure below a set limit, preventing excessive exposure. The WEL for RCS is 0.1 mg/m3 expressed as an 8-hour time-weighted average (TWA). Exposure to RCS is also subject to the Control of Substances Hazardous to Health Regulations 2002 (COSHH). This should be achieved initially through following good occupational hygiene practice to achieve adequate control of exposure and for instigation of control measures in keeping exposure below the WEL.

 

The following should also be considered:

- Replacing crystalline silica with safer substitutes materials

- Providing engineering or administrative controls such as local exhaust ventilation (LEV)

- Using protective equipment or other protective measures (where appropriate control measures are unable to reduce the risk sufficiently)

- Wearing only a Type CE abrasive-blast supplied-air respirator for abrasive blasting.

- Wearing disposable or washable work clothes and showering if facilities are available.

- Vacuuming dust from your clothes or changing into clean clothing before leaving the work site.

- Participating in training, exposure monitoring, and health screening and surveillance programs.

 

As part of this control process it is often critical to identify the sources and levels of crystalline silica exposure through the use of live dust monitors, such as the TSI DustTrak, TSI AM510 SidePak and through the use of gravimetric methods using respirable filter heads and sampling pumps, such as the Sensydine Gilair Plus.

Shawcity offers a wide range of the latest dust monitoring technology from some of the world’s leading specialist manufacturers. If you are involved in any of the industries or workplaces detailed above and you would like to discuss your options for monitoring crystalline silica in indoor or outdoor spaces, please contact us for an individual consultation on your particular requirements on Tel: 01367 899553 or email: info@shawcity.co.uk.

 

 

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