The most common types of pollution found on a construction site are dust and diesel emissions.
Toronto City Council defines dust, for the purpose of the Dust By-law, as: “solid particles which may become or be airborne as a result of residential construction activities, including, but not limited to, trimming, blasting, drilling, crushing, grinding, sawing, screening, cutting, altering or moving of clay, mortar, stone, rock, stucco, concrete, tile and insulation.” [Ref]
There are various types of dust that can be produced on a construction site:
- Soil & gravel dust - soil and gravel materials that are excavated, hauled, tipped or stockpiled on the construction site can create dust that can be blown offsite by wind or erosions and/or tracked offsite from vehicle ‘drag out’ (e.g. dirty tires, open truck beds). Soils with a high clay/silt content are especially likely to create dust when dry because of their small particle sizes. Smaller particle sizes pose greater health risks because they are easier to inhale and can impact your respiratory system.
- Wood dust - wood-based construction materials can create dust when the materials are cut, drilled or sanded on-site. Certain types of wood and wood products pose health risks to workers but are unlikely to travel off-site.
- Silica dust - construction materials such as sandstone, mortar and concrete as well as certain abrasives used for sand blasting contain silica, which can be released in a form called respirable crystalline silica when the materials are mixed, cut, drilled, sanded or used for sandblasting. Silica health risks are described below.
- Non-silica mineral dust - construction materials containing limestone, dolomite, gypsum, or hard stone (e.g. marble) can create dust when the materials are crushed, cut, drilled or sanded on-site. Non-silica mineral dusts pose fewer health risks.
- Demolition dust - most materials that went into the construction of the building could be released as various types of dust during the demolition of the building, including the dusts listed above. If any asbestos-containing or urea formaldehyde insulation materials were used in the building, highly toxic fibres and dusts could be released if not properly managed. Asbestos health risks are described below.
Diesel emissions can be produced on a construction site when an engine combusts diesel fuel for energy, which results in the creation of diesel exhaust. Diesel exhaust emissions from construction sites can come from:
- Heavy duty vehicles such as dump trucks, cement mixer, transport trucks
- ‘Road-building’ machines such as an excavator, crane, bulldozer, loader, compactor, street sweeper
- Stationary engines such as a generator, pump, compressors, mobile cement mixer trailer
Diesel exhaust gas-based pollutants include carbon dioxide, sulphur and nitrogen compounds, carbon monoxide, and hydrocarbons. Diesel exhaust particulate matter pollutants can include carbon, polycyclic aromatic hydrocarbons, and metals. Diesel exhaust from ‘heavy duty’ truck engines is worse than ‘light duty’ cars, which is why heavy duty vehicles like those involved in construction activities can be a concern. The amount of pollution released from diesel exhaust can also vary due to other factors like the type of emission control system the vehicle has, what type of fuel and oil it uses, the speed the truck is traveling and the weight of its truckload.
The Ontario Government’s Drive Clean Program requires heavy duty diesel trucks to be emissions tested annually for the ‘smoke density’ of their exhaust. Trucks should have a low smoke opacity of 20% or less.
The health impacts of diesel exhaust are described below.
Environmental & Health Impacts of Construction
Different types of construction result in varying types of environmental & health risks. Part of the environmental and health concerns stem from the specific materials and emissions that are released into the air, but impacts can also increase relative to the scale, duration, and activities of the construction project. There are also greater health and environmental risks if more than one activity takes place at the same time on the site and/or if there are sensitive populations or natural environments in close proximity to the project site.
Silica dust impacts
Silica is a very common earth mineral that is found in soil, sand and rocks. There are different types of silica: crystalline, quartz and cristobalite silicas. Silica is found in ceramics, pottery, cement, abrasives and sandblasting materials. Silica dusts can be released into the air when materials or products that contain silica are disturbed by grinding, cutting, drilling, etc. CAREX Canada defines Silica as a known carcinogen (IARC 1) which can cause lung cancer from inhaling the dust and fibres. Other occupational disease risks include silicosis, pulmonary tuberculosis, asthma, chronic obstructive pulmonary disease, and rheumatoid arthritis.
By far, the construction sector is the largest group of workers exposed to silica dust in Canada and the largest workforce is in Ontario. In particular, labourers in the construction trades, drywallers and plasters as well as operators of heavy equipment face the greatest occupational health risks. There are occupational exposure limits for the inhalation of silica dusts but the Ontario limit is not as strict as the Canadian Labour Code, which leaves room for improvement.
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Demolition dust impacts
Asbestos is one of the greatest exposure concerns when it comes to demolition related dusts. While the construction materials that contained asbestos, (e.g. fireproofing, insulation, and piping), have been phased out due to their toxicity there is still a large legacy of asbestos-containing materials in our aging building stock. For this reason, when older buildings are renovated or demolished, an asbestos abatement plan is often needed to manage the respiratory health risks posed by airborne asbestos fibres and dust.
According to the Ministry of Labour’s Construction Health and Safety Action Plan, “exposures to agents that cause occupational disease are a significant issue for the construction sector. WSIB claims data show that the construction sector had an annual average of 41 fatal occupational disease claims approved between 2010 and 2014.xi Over this period, the top causes of fatal occupational disease claims were mesothelioma (51%), lung cancer (35%), and asbestosis (5%).” Mesothelioma, asbestosis and some types of lung cancer are all caused by exposure to asbestos fibres and dust.
There are occupational exposure limits for the inhalation of asbestos fibres and dust, but it is difficult to measure exposure on job sites.
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Diesel emission impacts
Diesel engine exhaust is a complex mix of gases and particulates that is defined by CAREX Canada as a known carcinogen (IARC 1). Most of the particulate matter released by diesel engines is very small in size, which makes it easy to breathe into your lungs and cause harm to your health including lung cancer.
Unfortunately, there are no occupational exposure limits for diesel in Canada yet. While ultra low sulphur diesel fuels now must be used on construction vehicles and non-road machines, there are other gases and particulates that can only be managed by retrofitting diesel engines or using newer models which have higher emission standards.
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This information has been compiled by TEA thanks to the financial support of The Ontario Trillium Foundation.