Respirable Crystalline Silica Guidance

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Silica Dust

Respirable Crystalline Silica has come under the focus of Worksafe NZ as part of their Clean Air Programme. Respirable crystalline silica is a known carcinogen and a health risk to those primarily working in the construction and manufacturing industries.  The Workplace Exposure Standard (8th edition) for crystalline silica has been halved to 0.1mg.m-3 in recognition of its hazard.

Crystalline silica is a form of silica (silicon and oxygen) and is one of the most common minerals in the earth’s crust. Its abundance means it is found in a variety of construction materials such as concrete, stone, blockwork, brick, sand and clay. However, not all silica materials are crystalline silica.  You must determine whether crystalline silica is present by consulting the safety data sheet in the first instance. 

Cutting, grinding, abrading, sanding, hammering or blasting materials containing crystalline silica will cause this material to become airborne and small enough to be breathed deep into the lower lungs.

Crystalline silica is very stable and the body’s immune system is unable to remove or break the silica down. Chronic long term exposure, which is the most common form of exposure can lead to lung cancer, cardio pulmonary obstructive disease (COPD) and silicosis, a form of scarring of the lungs. Silicosis is a condition where the lungs are not able to effectively exchange oxygen and carbon dioxide leading to extreme tiredness, exhaustion and secondary complications such as pneumonia. Along with silicosis, exposure to respirable silica can also lead to lung cancer.

The Health and Safety at Work Act 2015 states a hierarchy of controls; elimination and minimisation.  If a hazard cannot be eliminated then it should be minimised using engineering controls, administrative controls, and/or personal protective equipment. 

Replacing products that contain crystalline silica for products without crystalline silica is the most effective way of avoiding exposure. Engineering controls to lower exposure would include the use of widely available dust suppression equipment such as water suppression systems and dust vacuums for power tools. Cleaning of waste should be performed using high efficiency particulate air (HEPA or H-Class) vacuum units instead of sweeping which more readily increases crystalline silica air concentrations.

Respiratory protective equipment (RPE) is the least favoured method of lowering exposure. Fit tested half face or powered air purifying respirators (PAPR) with P2 or P3 filters can be used to minimise worker exposure.  The level of RPE required depends on the amount of crystalline silica (and other dusts / contaminants) present in the operators breathing zone.

Air monitoring for crystalline silica exposure should be performed if there is any concern regarding personal exposure in the workplace.  The monitoring should include assessing other airborne hazards and observing operational procedures.  Results must be compared to the Workplace Exposure Standards to assess exposure risk. 

The following link will take you to the Worksafe website for the latest fact sheet regarding crystalline silica.

http://www.worksafe.govt.nz/worksafe/information-guidance/all-guidance-items/silica-dust-in-construction-fact-sheet