Cutting Through the Dust: Silica Monitoring in High-Risk Industries

© Gular – stock.adobe.com

By: Tim Turney, Contributor

Dust can be a deadly byproduct of working with materials that contain silica. Materials such as sand, soil, concrete, granite and quartz contain silica that can be released into the air when crushed, drilled, sanded or otherwise disturbed.

When the dust particles are small enough to be inhaled deep into the lungs, it is called respirable crystalline silica (RCS). It is estimated that as many as 2.3 million workers in the U.S. are exposed to RCS every year, and all are at risk of developing chronic lung conditions, such as silicosis, lung cancer and chronic obstructive pulmonary disease.1

Employees who are aware of the potential effects of silica dust are more likely to engage in safer working practices and highlight any risks to management. (photo courtesy Casella)

Some industries are naturally at a higher risk of exposing workers to RCS. Construction, mining, quarrying, demolition and any other industry that performs activities that disturb or process materials containing silica should be extra vigilant in controlling silica dust exposure.

As with any known workplace health risk, the most effective means of reducing worker exposure to RCS is a correctly implemented control scheme. Following this standard decision-making procedure allows employers to effectively control the risks associated with silica dust and reduces the likelihood of legal ramifications for not complying with regulatory standards. Measures include implementing a correctly executed air-monitoring program to quantify the level that employees are exposed to; and acting to minimize levels by implementing controls—and making sure the controls remain effective.

The Occupational Safety and Health Administration (OSHA) set a limit on the airborne concentration acceptable for employee exposure, as part of the Toxic and Hazardous Substances standards. This is known as the permissible exposure limit (PEL) and states that airborne concentration be under 50μg/m3 (micrograms per cubic meter of air), calculated as a time-weighted average (TWA).

OSHA recently reduced the PEL from 100μg/m3 to 50μg/m3 after research indicated that, over a 30-year period, the risk of developing silicosis falls from 25% to just 5%.2 Failure to comply with the prescribed limit may result in penalties, such as fines.

Monitoring

Regularly sampling dust in the workplace is essential to protect employees from lifelong and often incurable occupational diseases. (photo courtesy Casella)

The most accurate way to quantify the level of exposure on site is through a personal air sampling pump regime. Air monitoring can quantify exposure levels or, if controls are in place, check that they are effective and measure any residual risk. These pumps are essential in places where there is a significant risk of highly concentrated hazardous pollutants in the air, i.e., in a quarry, mine or construction site.

Employers must determine the amount of silica to which workers are exposed, if it is, or expected to be, at or above the action level of 25μg/m3, averaged over an 8-hour day. It is important that the pumps are used with the correct sampling head and, in the case of RCS, a cyclone and filter designed to collect the dust. It is also necessary to choose an intrinsically safe (IS) rated pump if monitoring is to take place in potentially flammable atmospheres.

Before use, pumps must be calibrated using a representative sample. They should also be checked at the end of the day to make sure flow has not deviated by more than 5%; if it has, there may be a leak or another malfunction.

The personal sampling unit should then be attached to an employee that conducts work in any area that may generate levels of dust above the action level. This unit should be fixed to the body in a position that will not stop employees from carrying out their jobs, as there is a risk it will be removed in the interest of comfort. The cyclone that draws the sample through the pump should be placed near the breathing zone of the wearer.

Once the sample is analyzed by a laboratory, the level of exposure can be calculated. If the results show that the exposure level is above the PEL of 50μg/m3, action must then be taken to improve control measures to ensure exposure is reduced to as low as practicably possible. This might take the form of changing the materials used; removing workers from the area that generates dust; or using a local exhaust ventilation (LEV) system.

Monitoring should be conducted in all areas that are at risk of exceeding the action level at regular intervals to ensure there has not been a deviation in exposure and to check that control measures have been successful and remain effective.

Advances in personal air sampling pumps have made it easier to measure exposure to a greater degree of accuracy by minimizing the deviation in flow rate. In high-risk industries, making sure samples are accurate can save employees’ lives.

Education

Air sampling is more than just selecting the right pump. The person conducting the sampling must have a thorough understanding of practice and procedure; how sampling pumps function; and use of the correct sampling head and filters. For smaller businesses, this might not be possible internally, in which case industry experts always recommend consultation with external professionals. This is especially important in high-risk industries.

Equally, employers must train and educate employees on the risks associated with dust and the importance of monitoring. Employees who are aware of the potential effects of silica dust are more likely to engage in safer working practices and highlight any risks to management. This will help employers keep people safe at work and mitigate the likelihood of non-compliance in the workplace, which can incur costly fines.

Conclusion

Regularly sampling dust in the workplace is essential for employers to protect employees from lifelong and often incurable occupational diseases. This is especially true in high-risk environments, where it is more likely for exposure levels to exceed OSHA’s permissible exposure limits. Ensuring that a competent and qualified person conducts the air sampling ensures that employers will adequately control the risks to remain compliant with industry standards. IHW

Tim Turney is Global Marketing Manager at industrial hygiene monitoring equipment manufacturer, Casella. For more information on air sampling monitoring by Casella, visit: https://www.casellasolutions.com/uk/en/Knowledge-Bank/KB-Dust/dust-
construction.html