Clean Air Partnership

About the AQHI

Back to Top

WHAT IS THE AIR QUALITY HEALTH INDEX? 

The Air Quality Health Index (AQHI) is a scale that measures the health risk associated with local air pollution levels. Since 2001, Environment Canada and Health Canada have led the development of a national, health risk based air quality index known as the Air Quality Health Index (AQHI). The AQHI was developed through a multi-stakeholder committee process involving the provinces, municipalities and members from the health and environmental non-government organization community.
 
The AQHI helps individuals make decisions to protect their health by providing information on the level of risk associated with pollution levels. Depending on their risk level, residents may wish to reduce short term exposure to air pollution, adjust their activity levels during increased periods of air pollution, as well as reduce their personal contributions to air pollution by reducing energy consumption and vehicle use.

Back to Top 

WHAT DOES THE AIR QUALITY HEALTH INDEX TELL THE PUBLIC? 

The AQHI is a communications tool that enables individuals to protect their health, and that of people in their care. The AQHI indicates the level of health risk associated with local air quality on an easy-to-read, colour-coded scale ranging from 1 to 10+. The higher the number, the greater the health risk and hence the greater the need to take precautions.
 
One important feature of the AQHI is its ability to enable individuals to assess their own health risk based on symptoms they experience, even if they have no known health problems. Once individuals learn what AQHI values triggers symptoms in them, they can use the AQHI forecasts to plan their outdoor activities.
 
The AQHI provides different messages to those who are more sensitive to air pollution than to the general population. The index enables everyone to take the appropriate actions to protect their health. Individuals can check the AQHI on a regular basis to find out how they can best be protected from air pollution.

Back to Top 
 
WHAT IS THE DIFFERENCE BETWEEN THE AIR QUALITY HEALTH INDEX (AQHI) AND THE AIR QUALITY INDEX (AQI)?  

The public needs an accurate warning system to know when air pollution levels are predicted to pose a greater health risk so that individuals can take action to minimize exposure.
The provincial Air Quality Index (AQI) reflects air quality relative to provincial standards, but does not provide information about health risks. It reports on the air pollutant with the highest concentration, but does not take into consideration the combined effects of a variety of pollutants.
 
In addition, the Air Quality Index was mainly developed to serve as a policy strategy for monitoring and reporting on air pollution levels in order to set and ensure provincial and federal air quality standards, while the AQHI was developed to help individuals assess and respond to potential air pollution impacts from their personal health perspective.
 
We know that public health is harmed at pollution levels below existing air standards. The Air Quality Health Index (AQHI) provides a tool that enables people to better understand the connection between air pollution levels and its impact on human health and allows people to better protect themselves, and people in their care from the harmful effects of air pollution.
 
The AQHI provides GTA residents with information about:

  • Health risk and messages  from current air pollution levels, based on a number from 1 to 10 for vulnerable and general population groups
  • Forecasts of health risk from air pollution
  • Level of health risk – low, moderate, high or very high
  • Who is at greatest risk from air pollution
  • Actions individuals can take to minimize their health risks
  • Information on how to reduce air pollution     

Back to Top 

WHICH INDEX SHOULD I CHECK FOR INFORMATION ON THE PUBLIC HEALTH IMPACTS OF AIR POLLUTION LEVELS? 

The AQHI was developed to better gauge the public health impacts of air pollution levels. For that reason, it is best to check the AQHI readings on a daily basis, especially during the more common April – November higher air pollution period.

Back to Top

HOW DO I KNOW IF I AM AN “AT-RISK” POPULATION OR PART OF THE “GENERAL” POPULATION? 

The AQHI reading distinguishes between at-risk and general populations to provide them with different health messages.
 
The at-risk group includes children, seniors, and people of all ages with pre-existing heart and breathing problems. Among sensitive individuals, behaviour changes with respect to outdoor exercise or reducing exertion can reduce their exposure to air pollution.
 
Among the general population, taking similar steps to reduce exposure may at times be warranted.

Potential “at-risk” populations include: 

People with Respiratory and/or Cardiovascular Conditions
Exposure to air pollution can cause symptoms ranging from irritated eyes and throat, to coughing, wheezing, chest tightness and difficulty breathing. People with pre-existing lung or heart conditions or vulnerabilities may experience increased frequency and severity of symptoms.
 
People who have existing respiratory or cardiovascular illness should follow their doctor’s usual advice on management of their condition.
 
Children
Not only do children have less developed respiratory systems, but they inhale more air per kilogram of body weight compared to adults. Children also tend to have more exposure to air pollution because they spend more time outdoors being physically active.
 
The Elderly
Seniors may also be at increased risk from air pollution, not simply because of their age, but because seniors are more likely than other adults to have health problems such as heart and lung disease.
 
General Population
Even healthy people may have difficulty breathing when air pollution levels are high especially those who work or exercise outdoors.

Back to Top 
 
WHAT AIR POLLUTANTS DOES THE AQHI EVALUATE TO DETERMINE HEALTH RISK? 
 
The AQHI is based on the relative risks of a combination of common air pollutants that are known to harm human health.
 
These pollutants include:

  • Ozone at ground level – Ground-level ozone is both colourless and odourless. Ozone is formed by chemical reactions in the atmosphere and is a major component of smog during hot, sunny weather.  
  • Nitrogen dioxide (NO2) – Nitrogen dioxide is a reddish gas with a sharp, pungent smell. It is created during the combustion of fossil fuels, such as gasoline and coal. Nitrogen dioxide is one of the primary chemical precursors of ground-level ozone.  
  • Particulate matter (PM2.5/PM10) – Particulate matter refers to tiny airborne particles that are emitted by vehicles and industrial facilities, generated from natural sources such as forest fires, or formed indirectly as a result of chemical reactions among other pollutants. The burning of fuels, such as gasoline, oil, diesel and wood, produce most of the PM2.5 pollution found in outdoor air, and much of the PM10.

Back to Top 

WHAT ARE THE HEALTH SIGNS TO WATCH OUT FOR? 

While it is important to recognize that all levels of air pollution affect our health both on a short term and longer term basis, in general the higher the AQHI number the greater the risk for short term and longer term health effects.
 
It is also important to recognize that people react very differently to air pollution. Some people may notice initial effects such as burning eyes, sore throat and chest tightness with exposure to medium or higher levels of air pollution. While others may experiences impaired respiratory and/or cardiovascular functions, and others may not notice any effects.
 
It is important for each person to determine their level of vulnerability to the health effects of air pollution by monitoring for symptoms as pollutant levels change.Symptoms to monitor for:

  • Itchy and/or burning eyes
  • Sore or mucousy throat, coughing or wheezing
  • Reduced capacity for deeper breathing or other indicators of reduced respiratory ability
  • Reduced energy levels or dizziness when physically exerting oneself
  • Difficulty breathing, chest tightness, or angina symptoms  

Because exercise requires faster, deeper breathing, it may make the symptoms worse. People who have heart disease, such as angina (chest pain), or lung disease, such as asthma or emphysema, may be very sensitive to air pollution exposure, and may notice symptoms when others do not.

Children because their air passages are smaller than adults and because they breathe more often than adults are also more susceptible to the possible health impacts of air pollution and may notice symptoms when adults do not. Because children may not be aware to monitor for air pollution symptoms adults taking care of children should communicate to children the symptoms to watch out for and/or monitor children within their care.

Air pollution can affect both the respiratory and cardiac systems. The health effects of air pollution can be seen as a pyramid, with the mildest and most common effects at the bottom of the pyramid, and the least common but more severe at the top of the pyramid. The pyramid demonstrates that as severity decreases the number of people affected increases.
 

Figure 2: Pyramid of Health Effects of Air Pollution 
 


Health Endpoints Associated with Increased Air Pollutants Levels

Mortality: All non-accidental mortality causes
Hospital Admissions: Cardiovascular and Respiratory Hospital Admissions
Emergency Room Visits: Visit to an emergency department
Asthma Symptom Days: Exacerbation of asthma symptoms in individuals with diagnosed asthma
Restricted Activity Days: Days spent in bed, missed from work, and days when activities are partially restricted due to illness
Acute Respiratory Symptoms: Respiratory-related symptoms such as chest discomfort, coughing and wheezing

Back to Top 

HOW DO I FIND MY AQHI NUMBER?

The AQHI provides a number from 1 – 10+ to indicate the level of health risk associated with local air quality. The higher the number, the greater your need to be aware of the impact of air quality on your health.

The index describes the level of health risk associated with this number as a “low”; “moderate”; “high”; or “very high” and suggests steps we can take to reduce our exposure. At a moderate level some individuals may notice a need to take precautions. When air quality is rated high or very high most people will need to take precautions.

While it is important to recognize that all levels of air pollution have a health impact, in general the higher the AQHI number the greater the risk of health impacts from air pollution. Finding your AQHI number requires monitoring the AQHI levels and correlating when you experience symptoms with the AQHI number.

In most cases both members of the general public and more vulnerable populations are safe to exert themselves outdoors at low risk AQHI levels between 1 -3.

When AQHI levels reach moderate risk levels (between 4 -6) this is where greater care monitoring symptoms is required especially for more vulnerable populations. 

When AQHI levels are high risk (from 7 – 10) it is best for general populations and especially for vulnerable populations to watch for symptoms and take precautionary actions to ensure they minimize their exposure to air pollution.

Back to Top 

HOW OFTEN SHOULD I CHECK THE AIR QUALITY HEALTH INDEX?

In the Greater Toronto Area the period of higher AQHI days are most often between May – October, however depending on weather conditions moderate and even high days do occur between the November – April time period. Ideally it is best to check the Air Quality Health Index every day, especially during seasons of higher air pollution. The AQHI is updated hourly and a forecast is also provided for the next 2 days.

Back to Top 

HOW DO I USE THE AQHI TO PLAN MY ACTIVITIES?

By regularly checking the Air Quality Health Index, you can determine when to take precautions. Follow the recommendations for each level of the Air Quality Health Index.

Index Reading 1 to 3

  • People with breathing or heart problems should always pay attention to symptoms, even at low index levels.
  • Riding your bike, walking or rollerblading to work is healthy for you and keeps the air clean. 
  • Best time to exercise outdoors.  

Index Reading 4 to 6

  • Even moderate levels of air pollution can have a negative effect on the health of people, especially vulnerable people such those with cardio-respiratory problems.
  • People with heart or breathing problems should monitor symptoms as the index reading increases.
  • You can reduce your risk from air pollution by lessening the intensity of your exercise, for example, walking instead of jogging, as well as taking more breaks.
  • Try to minimize traffic related pollution by planning routine physical activity, such as running or jogging, away from high traffic areas.
  • If you are spending more time indoors, look for an air conditioned, smoke-free environment.  

Index Reading 7 to 10

  • Even healthy people may have more difficulty breathing on days when the index is high.
  • Air pollution affects everyone’s health in different ways, ranging from minor symptoms, such as throat irritation, to worsening of breathing and heart problems. Negative health effects will increase as air pollution increases.
  • You can reduce your risk from air pollution by lessening the intensity of your exercise, for example walking instead of jogging, as well as taking more breaks.
  • Try to minimize traffic related pollution by planning routine physical activity, such as running or jogging, away from high traffic areas.
  • People participating in sports or strenuous work outdoors breathe deeply and rapidly, allowing more air pollution to enter their lungs.  They may have difficulty breathing when air pollution levels are high, and should take more breaks.
  • If you are spending more time indoors, look for an air conditioned, smoke-free environment.  

Index Reading Above 10

  • Even healthy people may have more difficulty breathing on days when the index is very high. Most people should try to minimize outdoor physical exercise at this high AQHI level.
  • People participating in sports or strenuous work outdoors breathe deeply and rapidly, allowing more air pollution to enter their lungs. They may have difficulty breathing when air pollution levels are high, and should take more breaks. They should exercise extra caution when AQHI levels are high.
  • If you are spending more time indoors, look for an air conditioned, smoke-free environment.

Back to Top 

AQHI GENERAL GUIDELINES

Limit the amount of time you spend in highly polluted areas like busy streets and industrial zones, especially when you exercise.

When you exercise hard, you breathe faster and more deeply. This causes your body to be exposed to more pollutants. The harder or longer your activity, the more pollutants you body is exposed to. That’s why you should avoid intense or prolonged activity in a polluted area.

Exercise when pollution levels are lower.

In general air pollution levels are lower in the early morning and later evening and highest during mid day and into early evening (this is a generalization and it is always best to check the AQHI readings). In general, busy streets are usually more polluted during rush hour due to high traffic flows. Some residential neighborhoods are more polluted on winter evenings due to the high number of woodstoves.

By avoiding exercise in these places at these times, you limit your exposure.

But still stay active. 

Physical activity improves your health. Simply determine the Air Quality Health Index rating you feel comfortable at and learn to identify other factors that can trigger your symptoms. More often than not it is best for your physical and mental health to get out and exercise.

Remember to bring medication with you when you are on the move in case you need it.

Generally, taking the right medication can help prevent symptoms. Follow your doctor’s advice in order to carefully manage any preexisting cardiac or respiratory conditions.

Remember that indoor air can also affect your health.

Some outdoor air pollutants can enter the home. You can limit this problem by using a central air conditioning unit, heat pump, or geothermal system. Tobacco and cooking smoke, mold, volatile organic compounds emitted by cleaning products, and new furniture are also air pollutants. Make sure there is suitable ventilation and limit these pollution sources as much as possible.   

Back to Top