Update on Risks and Control of Mould, Lead and Silica
on Construction Projects

Part 6

Ministry Of Labour Guideline: Silica On Construction Projects, 2004

Silica is the most common mineral in the earth’s crust and is a major component of sand, rock and mineral ores. Silica exists in many forms, of which crystalline silica is of most concern.

Inhalation of excessive concentrations of airborne fine silica dust (respirable dust, with aerodynamic diameter of less than about 5 micrometres) can lead to development of silicosis and/or lung cancer. Crystalline silica containing materials are present on construction sites in many forms. Some disturbances of any of the following common silica materials may result in harmful exposures.

• Abrasives used for blasting.
• Brick or refractory brick.
• Concrete, concrete block, cement, mortar.
• Granite, sandstone, quartzite, slate.
• Gunnite.
• Mineral deposits.
• Rock and stone.
• Sand, fill dirt, top soil.
• Asphalt containing rock or stone.

The Ontario Ministry of Labour issued a guideline for disturbance of silica materials on construction projects in September of 2004. In this Guideline, silica-disturbing construction operations are classified into Type 1, Type 2 or Type 3, depending on the anticipated exposure level of the operation.

• Drilling of holes in concrete or rock that is not part of a tunneling operation or road construction.
• Milling of asphalt from concrete highway pavement.
• Charging mixers and hoppers with silica sand or silica flour (consisting of at least 95% silica).
• Any other operation at a project that requires the handling of silica-containing material in a way that may result in a worker being exposed to airborne silica.
• Entry into a dry mortar removal or abrasive blasting area while airborne dist is visible, for less than 15 minutes, for purposes of inspection and/or sampling.
• Working within 25 metres of an area where compressed air is being used to remove silica-containing dust outdoors.

• Removal of silica-containing refractory materials with a jackhammer.
• The drilling of holes in concrete or rock that is part of a tunneling or road construction.
• Use of a power tool to cut, grind, or polish concrete, masonry, terrazzo or refractory materials.
• Use of a power tool to remove silica containing materials.
• Tunneling.
• Tuck point and surface grinding.
• Dry mortar removal with an electric or pneumatic cutting device.
• Dry method dust cleanup from abrasive blasting operations.
• Use of compressed air outdoors for removing silica dust.
• Entry into area where abrasive blasting is being carried out for more than 15 minutes
  

• Abrasive blasting with an abrasive that contains > 1% silica.
• Abrasive blasting of a material that contains > 1% silica.
• The following general precautions will apply to all Levels of Silica Work.
• Provide appropriate training.
• A medical surveillance program is highly recommended.
• Warning signs should be posted.
• Clean-up after each operation is encouraged to prevent dust containing silica from spreading.
• Compressed air should not be used for removing dust from clothing.
• Workers should have access to washing facilities.
• Silica dust on personal protective clothing and equipment should be removed by damp wiping or HEPA vacuuming.
• Contaminated personal protective clothing and equipment should be handled with care to prevent generation of airborne dust.
• Washing facilities and laundering processes must be suitable for handling silica contaminated clothing.

Type 1 Silica Work Practices

• Provide N95 or better respirator. Respirators should also be provided when entering a dry mortar removal area with visible airborne dust for less than 15 minutes, for the purposes of inspection or testing, or if work is being performed within 25 metres of an outdoor area where silica-containing dust is being removed with compressed air.

Type 2 Silica Work Practices

• Respirators with a minimum protection factor of 50 are required (e.g., full-facepiece air purifying respirator with P100 filters).
• Minimize the generation of airborne dust by thorough wetting of the area prior to and during drilling or cutting and during loading, scraping and moving of rock.
• Other workers entering a Type 2 operation should remain at least 10 metres away. Ropes or barriers should be set up to prevent unauthorized entry. If this is not possible, enclose the work area.

Type 3 Silica Work Practices

• The abrasive blasting operator shall wear a Type CE abrasive blast respirator operated in pressure demand or positive pressure mode with tight-fitting mask or full-facepiece. Ensure breathing air meets CSA Standard Z180.1-00 and where an oil-lubricated compressor is used, provide a continuous carbon monoxide monitor/alarm.
• While abrasive blasting is in progress or airborne dust is visible, workers entering the work area for less than 15 minutes should wear a minimum of an N95 half-facepiece respirator. Any entry for more than 15 minutes, or workers engaged in cleaning dust from abrasive blasting operations, will require a respirator with a NIOSH assigned protection factor of 50 or greater.
• Where abrasive blasting is being conducted, barriers, partial enclosures or full enclosures should be used.
• If blasting is being conducted indoors and persons other than those doing the blasting may be exposed to airborne dust, the area shall be enclosed to prevent the spread of dust. At completion the enclosure should be cleaned with HEPA vacuuming, wet sweeping or wet shoveling.
• If blasting is being conducted outdoors and persons other than those doing the blasting may be exposed to airborne dust, the work are should be identified with ropes or barriers at least 25 metres from the operation. If this is not possible, provide an enclosure to confine the dust.

PEN # 19 "Update on Risks and Control of Mould,
Lead and Silica on Construction Projects"

continues with

PEN #19 "Update on Risks and Control of Mould, Lead and Silica on Construction Projects"

Bruce Stewart CIH, ROH
Senior Vice President
Pinchin Environmental Ltd.

Presented at Construction Superconference
Toronto, November 29, 2004

©Pinchin Environmental Newsletter 2007 - Disclaimer