A Primer on Air Quality in British Columbia

We all share the air

Air quality is of growing concern in communities across BC because it can affect our health, the environment, and the economy. Poor air quality is the result of many factors, both natural and human caused. Choices we make every day, like driving our cars or burning wood to heat our homes, can significantly impact our local air quality. By understanding the basics of air quality, we can take actions that improve the quality of air in our communities. This primer is intended to help you better understand the terms used when discussing air quality, what factors affect air quality in our communities, and the management tools available to maintain and improve air quality in the future. Inside you’ll find:

• A glossary of common terms used when discussing air quality issues.
• A description of the factors that affect air quality, including how air behaves, and how weather patterns and local topography combine to impact local air quality. These concepts will help you understand why sometimes pollutants get trapped and accumulate locally, while at other times they disperse into the atmosphere.
• A description of some of the main pollutants of concern in BC and some of their health and environmental impacts.
• An overview of the management tools that are being used in BC to evaluate current air quality, predict future trends and help us develop plans to protect and enhance air quality in the future.

Remember, we all share the air. Everybody can help keep it clean!

Glossary of Air Quality Terms

The following definitions explain some common terms used when discussing air quality and air quality management issues in BC.

What is an airshed?

Topography (hills and valleys) and weather conditions can interact to prevent the mixing and exchange of air from inside and outside a given area. This area is called an “airshed.” A good example of an airshed is a valley where the surrounding mountains act as a physical barrier to air moving out of the valley when the air is still. An ocean coast can also define a boundary of an airshed where sea breezes can prevent air from moving out of coastal valleys. Because weather and wind conditions change from day to day, the boundary of an airshed isn’t constant; it can change with the weather. (For more information about airsheds and how they relate to air quality, see the section “Factors Affecting Air Quality”.)

Air Pollutants are any gas, liquid or solid substances that are present in the atmosphere in high enough concentrations to be considered harmful to the environment or human health. Common examples of pollutants include: dust, wood smoke, nitrogen dioxide, ground-level ozone, and particulate matter. (Refer to the “Main Pollutants” section for more details.)

Greenhouse gases (GHGs) are gases that contribute to global climate change. The major GHGs are carbon dioxide (CO2), methane (CH4) and nitrous oxides (N2O).

Air Emissions are any kind of substance released into the air from natural or human sources.An emission inventory provides information on the amount of emissions coming from various sources in a given area within a given period of time (usually a year).

Sources of air pollution are normally described by the activity that caused the emission. Sources can be natural or human generated. Natural sources include wind-blown dust, volcanoes, and forest fires. Human sources include the burning of fossil fuels (oil, gas and coal), stirring up dust (while driving or during construction), and burning of wood or leaves.

A point source is a single, stationary source of pollution that can be well defined. A smokestack is an example of a point source; it is easy to measure and define the source of the pollutants. It is also easy to regulate using an emission permit process.

A non-point source is a combination of a variety of pollution sources that are difficult or too small to measure on an individual basis. There are far too many cars, fireplaces, and lawnmowers to track exactly how much each one is emitting by itself, but they can all add up to a significant amount of total emissions. Therefore, for the purpose of developing an emission inventory, these sources are combined into categories called “non-point” sources.

Ambient air quality refers to the air in our immediate surroundings. Ambient air quality describes the level of air pollutants in a particular region. Poor ambient air quality means pollutant levels are high enough to cause concerns. Ambient air quality is measured near ground level, away from direct sources of pollution.

Concentration is the amount of a pollutant in the air at a given location, expressed as the weight of volume of pollutant per volume of air, such as parts per billion (ppb) or micrograms per cubic metre of air (µg/m3).

One ppb is about the same as one drop of water in an Olympic-sized swimming pool.

One µg/m3 is similar to a grain of sand suspended in a small apartment.

Exposure is a combination of the level of a pollutant and the amount of time that a person spends in the presence of a pollutant. Exposure determines the level of risk associated with different levels of pollutants.

Dosage is the amount of a pollutant that a person inhales.

Factors that Affect Air Quality

Poor air quality can result from a combination of factors. Regional air quality is affected by how air behaves as a result of the interaction of topography and weather, and by the emission sources themselves.

How Air Behaves

Let’s consider an analogy using water to help explain how air and air emissions behave. Imagine pouring red dye into the ocean. You’ll see a red pool of water for a few seconds, but it quickly disappears as the waves mix the dye into the huge mass of water. It is a combination of the amount of water, and the vigorous mixing that makes the dye disappear.

Now imagine pouring that same amount of red dye into a bathtub. The bathwater will turn very red because there is far less water than in the ocean, and there is no mixing with a source of clean water to dilute the dye.

Just as red dye disappears in the ocean, air pollutants mix and disperse quickly in a large airshed because the air flow is not limited by topography but can travel and mix over great distances. This results in good air quality in the airshed.

Sometimes, however, topography and weather combine to prevent pollutants from mixing and dispersing. In this case the pollutants become trapped within the area, like the red dye in the bathtub that continually builds up with nowhere to go. This results in poor air quality in the airshed.

Weather, Wind and Geography

Once pollutants are emitted into the air, the weather largely determines how well they disperse. Turbulence mixes pollutants into the surrounding air. For example, during a hot summer day, the air near the surface can be much warmer than the air above. Sometimes large volumes of this warm air will rise to great heights. This results in vigorous mixing. Wind speed also contributes to how quickly pollutants are carried away from their original source. However, strong winds can also result in high pollutant levels from wind-blown dust.

Sometimes the condition of the atmosphere is very still (stable) and there is very little mixing. This occurs when the air near the surface of the earth is cooler than the air above (a temperature inversion). This cooler air is heavier and will not want to move up to mix with the warmer air above. Any pollutants released near the surface will get trapped and build up in the cooler layer of air near the surface. Inversions are very common in BC and often form during calm clear nights with light winds. They can even persist throughout the day during the winter.

Emission Sources

Pollutants are released into the air from natural and human sources, from point and non-point sources. The number and size of emission sources in each area, along with weather conditions and topography, will determine the level of pollutants in the air within an airshed.

Do pollutants change form once they get into the air?

Many pollutants undergo chemical reactions when they encounter other pollutants in the air. The products of these chemical reactions are called secondary pollutants, as opposed to primary pollutants that are emitted directly into the atmosphere. Ground-level ozone is an example of a secondary pollutant that forms when nitrogen dioxide (NO2) and volatile organic compounds (VOCs) mix in the presence of sunlight.

How much is too much?

Pollutants can become dangerous to our health in two ways: through extended exposure or through high doses. Therefore, to understand the health impacts of the air you breathe, you need to know how long the pollutants are present, and in what concentration.

Main Pollutants

What are the main pollutants? The two air pollutants of greatest concern in British Columbia are Particulate Matter (PM) and Ozone (O3), because they are widespread and can have serious impacts on our health and environment. There are also several other pollutants to be concerned about.

Tools to Manage Air Quality

The various tools to manage air quality fall into three categories: Regulation, Evaluation, and Planning.

Regulatory Tools – Set Limits on Acceptable Levels of Air Emissions

Air Quality Objectives

Air quality objectives are benchmarks set by the government for the purpose of protecting human health, protecting vegetation, and maintaining good visible air quality.

Standards for Ambient Air Quality

The federal and provincial governments set standards for ambient air quality to protect human health and the environment. Standards are usually expressed in terms of allowable concentrations.

Waste Discharge Permits

A waste discharge permit authorizes the operation of a specific emission source (e.g. an industrial plant) and sets various conditions of operation (e.g. allowable levels of air emissions, types of emission controls required). A permit is issued only after consideration of potential impacts of the proposed source on human health and the environment. Permits are legally enforceable, and operators can be charged if they fail to comply.

Air Quality Regulations

Federal and provincial governments develop regulations that set conditions on how certain classes of activities (e.g. a type of industry or business) may be undertaken. In addition, local governments can pass by-laws to control emissions from activities such as backyard burning.

Environmental Assessment Process

Depending on specific criteria under federal or provincial legislation, proposed projects may need to undergo a formal environmental assessment (EA). The EA process identifies and assesses the potential impacts of a proposed project and develops measures to eliminate, minimize or manage those impacts. The EA takes into account facilities at the proposal’s main site and may also consider off-site facilities or related activities.

Evaluation Tools – Measure Current State and Predict Future Impacts

Emission Inventories

To maintain and improve our air quality, it is important to understand where air emissions are coming from, and in what quantities. An emission inventory identifies the major emission sources and is used to develop action plans to address regional air quality. Periodic updates of air emission inventories can be used to measure the progress of these action plans.

Air Quality Monitoring

To determine if objectives are being met, air quality is measured at several monitoring sites across BC. Measuring concentrations of pollutants in the air helps to identify areas where action is needed and standards are not being met. Monitoring helps assess if the actions we have already taken are making a difference. The measurements from monitoring stations are used to calculate an Air Quality Index (AQI) every hour for several locations in BC. When the AQI reaches certain levels, community air quality alerts may be issued.

Dispersion Modelling

An air dispersion model uses a series of mathematical equations to simulate the behaviour of pollutants in the air. By combining information about air quality, weather and the source of the pollutant, these models can predict concentrations in the air of a pollutant from that source, and so can be used to estimate the environmental and health impacts of the emission source. Governments use dispersion models to make regulatory decisions, to control existing sources, or to assess new industrial development proposals.

Planning Tools – Identify Actions to Maintain and Improve Air Quality

Rather than considering one source and its potential impacts in isolation, airshed management plans (AMPs) are being developed to address how emissions from several diverse sources may collectively affect air quality in a given airshed. AMPs are being developed for many airsheds in BC, helping communities focus on issues that are most important to them.

Other community planning processes that affect air quality include Community Energy Planning, and land-use and transportation planning.

Government Sources for Additional Air Quality Information

Local Government

For information about air quality initiatives and programs in your community, contact your local or regional district government listed in the blue pages of your local phone book.

Provincial Government

Air Quality Programs

For information on provincial government air quality initiatives and programs visit the BC Air Quality web site http://www.bcairquality.ca, the BC Ministry of Environment web site http://www.gov.bc.ca/env/ or contact one of the following BC Ministry of Environment regional offices directly, or toll-free through Enquiry BC 1-800-663-7867:

Vancouver Island Region, Nanaimo 250-751-3100
Cariboo Region Williams Lake 250-398-4530
Lower Mainland Region, Surrey 604-582-5200
Skeena Region, Smithers 250-847-7260
Thompson Region, Kamloops 250-371-6200
Omineca Region, Prince George 250-565-6135
Kootenay Region, Nelson 250-354-6333
Okanagan Region, Penticton 250-490-8200
Peace Region, Fort St John 250-787-3411
Ministry of Environment, Water, Air and Climate Change Branch, Victoria, 250-387-9933
Ministry of Healthy Living and Sport, Health Protection Branch, Victoria 250-952-1469.

Environmental Assessment Process

For information on BC’s Environmental Assessment Process, visit the Environmental Assessment Office website at www.eao.gov.bc.ca or by email at eaoinfo@gems5.gov.bc.ca

To contact the Project Information Centre by phone call 356-7441 (in Victoria) or toll-free through Enquiry BC at 1-800-663-7867.

Federal Government

For information on federal government initiatives in British Columbia, the Georgia Basin and the weather office services, visit the following web sites:

Georgia Basin/ Puget Sound International Airshed Strategy and Inventory of Air Quality Practices: http://www.pyr.ec.gc.ca/airshed/index_e.shtm

Environment Canada’s Pacific and Yukon- Clean Air information: http://www.pyr.ec.gc.ca/EN/Air/index.shtml

Georgia Basin Ecosystem Initiative “Sharing the Air” Fact Sheet: http://www.pyr.ec.gc.ca/georgiabasin/reports/
5_year_perspective/supplement_4_e.htm

Environment Canada’s Weather Office-Air Quality and Weather Information: http://www.weatheroffice.pyr.ec.gc.ca/wxhealth/airquality/default_e.htm