Reducing silica dust risk by adopting right workplace safety measures

Crystalline silica is a basic component of soil, sand, granite, and many other minerals. Quartz is the most common form of crystalline silica. Cristobalite and tridymite are two other forms of crystalline silica. All three forms may become respirable size particles when workers chip, cut, drill, or grind objects that contain crystalline silica. Some common silica-containing materials include: concrete, concrete block, cement, and mortar; masonry, tiles, brick, and refractory brick; granite, sand, fill dirt, and top soil; asphalt-containing rock or stone; and abrasive used for blasting.

 

Silica is so common that any workplace activity that creates dust can expose workers to airborne silica.

 

Danger of silica exposure 

Silica exposure remains a serious threat to workers, especially in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work and tunneling. The seriousness of the health hazards associated with silica exposure is demonstrated by the fatalities and disabling illnesses that continue to occur in sandblasters and rock drillers. Crystalline silica has been classified as a human lung carcinogen. 

 

Additionally, breathing crystalline silica dust can cause Silicosis, which in severe cases can be disabling, or even fatal. The respirable silica dust enters the lungs and causes the formation of scar tissue, thus reducing the lungs’ ability to take in oxygen. There is no cure for silicosis. Since silicosis affects lung function, it makes one more susceptible to lung infections like tuberculosis. In addition, smoking causes lung damage and adds to the damage caused by breathing silica dust.

 

Initially, workers with silicosis may have no symptoms. However, as the disease progresses a worker may experience: shortness of breath, severe cough and weakness. These symptoms can worsen over time and lead to death.

 

Exposure occurs during many different construction 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, tunneling operations. The most severe exposures to crystalline silica result from abrasive blasting, which is done to clean and smooth irregularities from moulds, jewelry, and foundry castings, finish tombstones, etch or frost glass, or remove paint, oils, rust, or dirt form objects needing to be repainted or treated. 

 

ALSO READ: Safety rating for chemical plants: A step in right direction

 

Reducing silica exposure 

Employers must make a commitment to prevent silicosis at their worksites and comply with Occupational Safety and Health Administration (OSHA) and other regulations on respirable crystalline silica. If employees are overexposed, companies can reduce exposure levels through the use of engineering controls. While these controls are being installed, or if they are being repaired, provide appropriate respiratory protection.

 

Companies need to perform air monitoring of worksites as needed, and when required by law, and take corrective action when silica levels are excessive. Monitoring provides a basis for:

 

By installing and maintaining engineering controls, companies can eliminate or reduce the amount of silica in the air and the build-up of dust on equipment and surfaces. Examples of controls include: exhaust ventilation and dust collection systems, water sprays, wet drilling, enclosed cabs, and drill platform skirts. Companies need to practice preventive maintenance because the extreme abrasiveness of the silica dust can damage the systems that has been installed.

 

Employers should train workers about health effects, engineering controls and work practices that reduce dust, the importance of maintenance and good housekeeping, as well as on the proper type and fitting of respirators. Employers should make sure that workers know what operations and materials present a silica hazard.

 

Companies must establish a written respiratory protection program. Outfits of employees should be appropriately selected and properly fitted with approved respirators when engineering controls alone are insufficient to keep exposures within safe levels. Employees must be trained to use respirators, which should be kept clean and properly maintained.

 

ALSO READ: Robust HSE strategy, the safety key to success

 

Workers’ role

Workers should use engineering controls installed by the employer to reduce silica dust levels, and make sure they are properly maintained. Tell the employer when they aren't working properly. It is important to minimise dust by following good work practices, such as removing dust with a water hose or vacuum with a high-efficiency particulate filter rather than blowing it clean with compressed air, or by wet sweeping instead of dry sweeping.

 

One of the ways to bring down silica exposure is by substituting less hazardous materials than crystalline silica for abrasive blasting. Wear, maintain, and correctly use approved particulate respirators when engineering controls alone are not adequate to reduce exposures below permissible levels. Beards and mustaches interfere with the respirator seal to the face, making most respirators ineffective.

 

If sandblast is required, use type CE positive pressure abrasive blasting respirators. Workers should participate in air monitoring, medical surveillance, and training programs offered by the employer or when required by law.

 

Remember: If it’s silica, it’s not just dust.

________________________________________________________________________________________________
The author is the Lab Head at 3M’s R&D Centre in Gurgaon