Air quality: frequently asked questions

Air pollution

What is air pollution?

There are many different types of air pollutants from a wide range of sources. The pollutants of greatest importance to health are the gases and particles that have been found to contribute to cardiovascular and respiratory disease. These pollutants are often lumped together under the term smog.      

Air pollution and health

How does air pollution affect my health and the health of my family?

Depending on the length of time you are exposed, your health status, your genetic background and the concentration of pollutants, air pollution can have a negative effect on your heart and lungs.  It can:

  • Make it harder to breathe
  • Irritate your lungs and airways
  • Worsen chronic diseases such as heart disease, chronic bronchitis, emphysema and asthma

Each individual reacts differently to air pollution.  Children, the elderly and those with diabetes, heart or lung disease are most sensitive to the adverse health effects of air pollution.

Negative health effects increase as air pollution worsens.  Studies have shown that even modest increases in air pollution can cause small but measurable increases in emergency room visits, hospital admissions and death.  Small increases in air pollution over a short period of time can increase symptoms of pre-existing illness among those at risk.

How do I know if I am at risk?

People with diabetes, lung disease (such as chronic bronchitis, asthma, emphysema, lung cancer) or heart disease (such as angina, a history of heart attacks, congestive heart failure, arrhythmia or irregular heartbeat) are more sensitive to air pollution

 Seniors are at higher risk because of weakening of the heart, lungs and immune system and increased likelihood of health problems such as heart and lung disease.

Children are also more vulnerable to air pollution: they have less-developed respiratory and defense systems.  Because of their size, they inhale more air per kilogram of body weight than adults.  Children also spend more time outdoors being physically active, which can increase their exposure to air pollution.

 People participating in sports or strenuous work outdoors breathe more deeply and rapidly, allowing more air pollution to enter their lungs.  They may experience symptoms like eye, nose or throat irritation, cough or difficulty breathing when air pollution levels are high.

What can I do to protect my health and the health of my family? How can I find out about the health risks posed by air pollution in my community?

You can better protect yourself and those in your care by understanding how air pollution affects your health, and by checking the Air Quality Health Index on a regular basis to find out what the health risks from air pollution are in your community. 

To check the Air Quality Health Index reading for your community and learn more about how air pollution can affect your health, visit or select the location of interest on the map of Canada..

We can protect our health from the negative health effects of air pollution by appropriately changing our behaviour to reduce our exposure to air pollutants when air quality deteriorates. 

Canadians can assess whether they are at greater risk based on their age, health status and level of outdoor physical activity, and whether or not they are experiencing symptoms.

When the Air Quality Health Index reading rises, they can  decide whether they need to:

  • Reduce or reschedule outdoor physical activities
  • Monitor possible symptoms, such as difficulty breathing, coughing or irritated eyes
  • Follow a doctor’s advice to manage existing conditions such as heart or lung disease

They can also use the index as a reminder of the need to take action to reduce air pollution.

Should air pollution prevent me from exercising?

Exercise plays an important role in long-term health. People who are physically active live longer, healthier lives. It is suggested that children (aged 5 to 18) do 60 minutes a day of vigorous activity and adults do 150 minutes a week. The air quality in Canada is generally good, and should not impact outdoors activities. When the AQHI is higher, some may develop symptoms such as coughing and shortness of breath due to a decrease in air quality. It is recommended to reduce outdoor strenuous activity or to reschedule, when you or your child experience symptoms.

About the Air Quality Health Index

What is the Air Quality Health Index (AQHI)?

The Air Quality Health Index is a scale designed to help you understand what the quality of the air around you means to your health.  It is a tool developed by health and environmental professionals to communicate the health risk posed by air pollution.

It is designed to help you make decisions to protect your health and the environment by:

  • Limiting short-term exposure to air pollution
  • Adjusting your activity during episodes of increased air pollution and encouraging physical activity on  days when the index is lower
  • Reducing your personal contribution to air pollution

The index provides specific advice for people who are especially vulnerable to the effects of air pollution as well as the general public.

What can the AQHI tell me about the health risks I may experience due to the current local air quality? What are its limitations in this regard?

The Air Quality Health Index provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality.  Occasionally, when the amount of air pollution is abnormally-high, the number may exceed 10.

The higher the number, the greater the health risk and our need to take precautions. 

The index describes the level of health risk associated with this number as ‘low’, ‘moderate’, ‘high’ or ‘very high’, and suggests steps we can take to reduce our exposure.

It also forecasts local air quality for today and tomorrow and provides associated health advice. .

The index does not measure the effects of odour, pollen, dust, heat or humidity on your health.

You can refer to the Air Quality Health Index to check the quality of outdoor air in your community before heading off to work or play.  And you can use the forecasts to plan your activities, whether over the next hour or the next day.

Seniors, parents of children with asthma, and people suffering from diabetes, heart or lung disease, can use the index to assess the immediate risk air pollution poses to your health and take steps to lessen that risk.

Even if you’re relatively healthy, fit and active, you can consult the index to decide when and how much to exercise or work outdoors. 


How is the Air Quality Health Index presented?

The Air Quality Health Index is a scale that lists a number from 1 to 10+ to indicate the level of health risk associated with air quality. 

Scientists created the index by estimating the daily change in mortality risk for ten cities from 1998-2000 and plotting it on a 10 point scale.

The higher the number, the greater the risk and the need to take precautions. 

What is the scale for the Air Quality Health Index?

The Air Quality Health Index is measured on a scale ranging from 1 to 10+:

  • 1-3 = ‘Low’ health risk
  • 4-6 = ‘Moderate’ health risk
  • 7-10 = ‘High’ health risk
  • Above 10 = ‘Very high’ health risk
How is the AQHI calculated?

Additional information for new communities in New Brunswick (where current conditions are estimated).

The AQHI is designed as a guide to the relative risk presented by common air pollutants which are known to harm human health.  Three specific pollutants have been chosen as indicators of the overall mixture:

  1. Ground-level Ozone (O3),  is formed by photo-chemical reactions in the atmosphere.  It can be a major component of smog during the summer, especially during hot sunny weather, but is generally low in the wintertime. Ozone can be transported long distances within a polluted air mass and can be responsible for large regional air pollution episodes.
  2. Fine Particulate Matter (PM2.5), is a mixture of tiny airborne particles that can be inhaled deep into the lungs .  These particles can either be emitted directly by vehicles, industrial facilities or natural sources like forest fires, or formed indirectly as a result of chemical reactions among other pollutants. Particulate matter can reflect both local air pollution sources or widespread air pollution episodes.
  3. Nitrogen Dioxide (NO2), is released by motor vehicle emissions and power plants that rely on fossil fuels. It contributes to the formation of the other two pollutants.  Nitrogen dioxide is often elevated in the vicinity of high traffic roadways and other local sources.

All three can have serious, combined effects on human health--from illness to hospitalization to premature death--even as a result of short-term exposure.  Significantly, all of these pollutants appear to threaten human health, even at low levels of exposure, especially among those with pre-existing health problems. 

In the development of the Air Quality Health Index, a formula that combined these three pollutants was found to be the best indicators of the health risk of the combined impact of the mix of pollutants in the air.

Additional information for new communities in New Brunswick (where current conditions are estimated)

In March 2014, the Air Quality Health Index (AQHI) was expanded to three additional communities in New Brunswick: Edmundston, Campbellton and Miramichi. This new service will bring the benefits of the AQHI to more people in the province.

For the three new communities, the current conditions are estimated, using AQHI values from other communities.  Air quality research carried out in these new communities has demonstrated that this is a viable approach for bringing the AQHI to communities that do not have local air quality monitoring.  The calculation of these estimated values will continue to be monitored and improved as development continues on more advance procedures for incorporating nearby monitoring sites.  For Campbellton and Miramichi, the AQHI conditions are based on measurements from the air quality monitoring station in Bathurst.  For Edmundston, the monitoring station in Fredericton is used. 

Why aren’t sulphur dioxide and carbon monoxide captured in the Air Quality Health Index?

Sulphur dioxide and carbon monoxide were dropped from the AQHI, because they were not associated with additional health risk once the effects of ozone, nitrogen dioxide and particulate matter were taken into account.

What’s the difference between the air quality index I am used to and the Air Quality Health Index? Won’t people get the existing air quality index and the Air Quality Health Index mixed up?

The Air Quality Health Index is an entirely new approach to communicating about air quality that differs from more familiar air quality indices which all follow an approach developed in the 1970s.

All previous air quality indices have reported air quality in term of air quality objectives for different pollutants and address each pollutant separately. The Air Quality Health Index presents the immediate health risk of the combined effects of air pollution (smog) mixture.

The air quality objectives or standards that old air quality index uses in its calculations are based on a variety of factors including effects on human health, vegetation, and consideration of the technical and economic achievability of the objectives as air quality management goals.  The Air Quality Health Index is a personal health protection tool for individual Canadians, especially those most at risk: children, seniors, and people with diabetes, heart and lung disease. It does not attempt to consider any issues other than the day to day health impact of air pollution.

The old index is usually presented in a way that implies a safe level of air pollution below a specified threshold.  The Air Quality Health Index reflects scientific evidence that negative health effects can occur even at low levels of exposure. 

The old air quality index is not the same across the country as provincial and municipal governments have adopted different air quality standards as a basis for the index in their jurisdiction.  The Air Quality Health Index has been developed through a national process and is designed to apply across the country.

The old air quality index usually has values in the range of 10 -60, with poor air quality designated as values above 50. The Air Quality Health Index is on a 1-10 scale and three categories “low, moderate and high risk” within this range. For this reason confusion is unlikely. 

What difference will the Air Quality Health Index make in the lives of Canadians?

It will help Canadians better understand how to protect their health from the adverse effects of air pollution on a daily, or even hourly, basis, just like the UV Index helps Canadians protect themselves from the harmful effects of too much sun.

This means that senior citizens, parents of children with asthma, and people suffering from diabetes, heart or lung disease now have an effective tool to help them assess the health risks posed by the levels of air pollution where they live, and to take action to protect their health and the health of those under their care.

This also means that average Canadians can check the quality of outdoor air before heading off to work or play, whether over the next hour or the next day.

What does the Air Quality Health Index look like?

The health-based index is much easier to understand because it:

  • Illustrates the level of risk with a number and colour scale from 1 to 10+
  • Labels health risk levels as “low”, “moderate”, “high” or “very high”
  • Forecasts local air quality for today and tomorrow
  • Suggests actions we can take to reduce our health risks
  • Indicates how we can reduce air pollution
  • Encourages physical activity as appropriate based on personal susceptibility and index reading
Why isn't the AQHI forecast in my region?

Health Canada and Environment Canada are supporting provinces, municipalities and non-government organizations as they begin to implement and communicate the AQHI. Provinces are responsible for the majority of air quality monitoring in Canada and their agreement and participation is essential to the implementation of the index.

By staggering implementation, it will allow the index to be implemented in a way that is most beneficial to the province. This will include the development of communication tools and educating and informing the public about the tool and how to use it.

Evaluations of these initial projects will be done to ensure that the Air Quality Health Index is being implemented and used in an effective and efficient way.

The AQHI was developed based on the best available data set of national air pollution measurements. However, air quality data is not readily available in all areas of Canada: for example, the technical capacity to monitor air pollution is limited in rural areas.

What’s the federal role in implementing the Air Quality Health Index? What’s the provincial/municipal role?

Health Canada and Environment Canada have led the development of the Air Quality Health Index and continue to collaborate with government, health and environmental NGO partners on development of the Air Quality Health Index.

Health Canada made sure that the latest cutting-edge epidemiological research informed the creation of the AQHI. Department officials are also providing the health information necessary to help Canadians better understand how to protect their health from the negative effects of air pollution.

Environment Canada is overseeing the technical development of the index and updating its capacity to provide Air Quality Health Index forecasts.

What’s the difference between the American Index and the Canadian Air Quality Health Index? Why aren’t they the same? Won’t this be confusing for people who live close to the border and hear both versions being used?

The American index is standards-based and emphasizes the impact of a single pollutant, much in the same way as provincial  air quality indices have done up until now, The different jurisdictions have  different standards and in addition the US uses different scales and categories. 

Unlike the American index, the Air Quality Health Index looks at the combined effects of air pollutants on health, rather than emphasizing the impact of one pollutant over others.

Like the older Canadian AQIs the US AQI has a broad range, with the category “unhealthy for sensitive groups beginning at a value of 101.  This is unlikely to be confused with the AQHI’s 1-10+ scale.

The United States Environmental Protection Agency and Canadian partners will work together to reduce confusion.

What are the real impacts of air pollution on human health? How many doctor/hospital visits and deaths can be directly attributed to air pollution?

Air pollution exacerbates health conditions in people who already suffer from chronic conditions such as heart and lung disease, or makes those who are vulnerable to its effects--such as children and the elderly--more susceptible to illness. 

Air pollution may also contribute to the development of new cases of heart and lung disease.

In Canada, thousands of hospital visits and millions of days with restricted activity can be attributed to current levels of air pollution. As well, over 14,000 premature deaths each year are linked to air pollution 1 .

1  Health impacts of air pollution in Canada

Does the Air Quality Health Index measure, manage and report on air quality over time? Can it be used as a tool for assessing accountability and progress relevant to clean air legislation and regulation?

No.  The Air Quality Health Index has been designed as a tool to help individual Canadians make choices that will protect their personal health and reduce their exposure to air pollution.

AQI vs. AQHI: What is the Difference?

While air quality has been reported for many years, this new Air Quality Health Index (AQHI) has been created with a different goal - to report on the health risk posed by a specific level of air quality. 

What is reported?

The Air Quality Index (AQI) reports current air quality based on a specific level of an individual air pollutant.  Two-day air quality forecasts are also provided. The Air Quality Health Index (AQHI) reports on the health risk posed by a mixture of pollutants including ground-level ozone, particulate matter and nitrogen dioxide.

How are they measured?

The Air Quality Index (AQI) communicates the air quality of the single worst pollutant.  The index rating for the new Air Quality Health Index (AQHI) is the sum of the health risks from each of the pollutants in the index.

Why is this more useful to most of us?

The Air Quality Health Index (AQHI) reflects current knowledge of the health effects associated with air pollution. The traditional Air Quality Index (AQI) is based on air quality standards and takes into consideration both environmental and human health concerns.

Which is better?

While both the traditional Air Quality Index (AQI) and the new Air Quality Health Index (AQHI) have their respective strengths, this new index has been designed to tell you more about your health risk from air pollution on any given day. 

Why does AQHI show improved or degraded air quality in my community compared to the old AQI?

The two indices were developed with different objectives in mind and for that reason, should not be compared, however it is inevitable that there will be comparisons. The new Air Quality Health Index (AQHI) captures the health risk from air pollution. The traditional Air Quality Index (AQI) provides us with information on the quality of the air compared to Canadian air quality standards and/or criteria for pollutants. For this reason, there is bound to be a difference in the perceived air quality in your community.

The community AQHI value and the individual station observation

What is the difference between the community AQHI value and the individual station observation?

The Air Quality Health Index (AQHI) is based on measurements of air quality from monitoring stations across Canada. For most communities, the AQHI value is produced by averaging information from the air monitoring stations in the local area. This average community value is provided for the locations on the provincial map. AQHI values from the individual air monitoring stations are provided in the accompanying list.

I can see the different levels of air pollution in different areas of the my community, and noticed that the AQHI number is an average of the locations. Wouldn’t broadcasting the highest reported levels protect my health better than averaging the levels?

Air pollution concentrations change over time (on an hourly and daily basis) and space (e.g. areas close to high traffic or an industrial source). Generally, people move around their communities in the course of normal daily activities and may be exposed to air pollutants in different areas of their community.

The information used to provide current and forecasted AQHI conditions is collected from monitors spread across communities, to give the average levels of air pollution in a given city. This information provides the most accurate measure for the mixture of air a person would be exposed to in their day to day travels throughout their community.

What if I don't live very close to any of the air quality stations? How well does the AQHI represent the air I am breathing?

The Air Quality Health Index is designed to measure the relative health risk of the air pollution mixture at a community level and monitoring stations have been carefully selected to be representative of the surrounding community.

Air pollution levels can vary significantly throughout a community depending on weather and how close you are to air pollution sources.  Areas close to traffic and some industries tend to have higher AQHI values. Areas downwind from these sources may also have higher pollution concentrations.

The AQHI provides a good measure of the overall relative health risk within a community and a good indication of the quality of the air in your area, even if you travel throughout your community during the day.

While it is important to pay attention to the AQHI as a guideline, you should always pay attention to your own symptoms and be aware of when you, or those in your care, need to take it easy. You can also reduce your exposure to air pollutants by changing when and where you are active outdoors by rescheduling outdoor exercise during times of high traffic volume or changing where you exercise to ensure that you avoid areas of high traffic.

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