User:AQHI/Air Quality Health Index

Description
The Air Quality Health Index (AQHI) is a risk communication tool intended to allow people to make more informed choices to protect themselves and those in their care from short-term health impacts of air pollution (JAWMA)

The Air Quality Health Index or "AQHI" is a scale designed to help you understand what the air quality around you means to your health.

It is a health protection tool that is designed to help you make decisions to protect your health by limiting short-term exposure to air pollution and adjusting your activity levels during increased levels of air pollution. It also provides advice on how you can improve the quality of the air you breathe.

This index pays particular attention to people who are sensitive to air pollution and provides them with advice on how to protect their health during air quality levels associated with low, moderate, high and very high health risks.

The AQHI communicates four primary things;

A number from 1 and 10+ indicating the quality of the air. The higher the number, the greater the health risk associated with the air quality. When the amount of air pollution is very high, the number will be reported as 10+. A category that describes the level of health risk associated with the index reading (e.g. Low, Moderate, High, or Very High Health Risk). Health messages customized to each category for both the general population and the ‘at risk’ population. Current hourly AQHI readings and maximum forecasted values for today, tonight and tomorrow. The AQHI is designed to give you this information in one place along with some suggestions on how you might adjust your activity levels depending on your individual health risk from air pollution. Follow this guide on how to use the AQHI or learn about the history of the AQHI.

How is the AQHI calculated? The AQHI is calculated based on the relative risks of a combination of common air pollutants which are known to harm human health. These pollutants include:


 * Ozone (O3) at ground level,
 * Particulate Matter (PM2.5/PM10) and
 * Nitrogen Dioxide (NO2).

What is the scale for the AQHI? The AQHI is measured on a scale ranging from 1-10+. The AQHI index values are also grouped into health risk categories as shown below. These categories help you to easily and quickly identify your level of risk.


 * 1-3 Low health risk
 * 4-6 Moderate health risk
 * 7-10 High health risk
 * 10 + Very high health risk

History
Since 2001, Environment Canada and Health Canada, in cooperation with provincial, municipal and non-governmental partners, have been developing the AQHI through a multi-stakeholder committee process involving the provinces, municipalities and members from the health and environmental non-government organization community. Environment Canada's Meteorological Service of Canada (MSC) and the Air Health Effects Division of Health Canada provide secretariat support to the committee and technical and financial support of priorities identified jointly by stakeholders.

A Committee of national air quality stakeholders oversees the AQHI process. In 2002, the committee approved the development of a multi-pollutant, health risk based index - later named "the Air Quality Health Index". The Deputy Ministers' Committee of the Canadian Council of Ministers of the Environment expressed support for continuing the process as a federally led multi-stakeholder activity.

To create a truly multi-pollutant index, the AQHI has been designed to make use of a formula that represents the combined effects of the air pollution mixture rather than using the concentration of a single pollutant as an indicator of air quality. Previous air quality indices represent the concentration of only one pollutant at a time, potentially underestimating the combined impacts of the several pollutants known to affect health.

The AQHI is derived directly from the health risk relationships between air pollution concentrations and health endpoints. A large dataset of Canadian air pollution data and health endpoints was analyzed and used to construct risk estimates that characterize the health risk created by the air pollution mixture.

Formulating the Air Quality Health Index
To develop a multi-pollutant index, five common air pollutants were initially examined:
 * ozone (O3)
 * fine and course particulate matter (PM2.5 and PM10)
 * nitrogen dioxide (NO2)
 * sulphur dioxide (SO2)
 * carbon monoxide (CO)

These pollutants have historically been associated with ambient air quality criteria, targets, standards or objectives in Canada and elsewhere. There is an extensive historical database of concentrations of these pollutants both in this country and in many others. These pollutants have been studied separately and in combination to identify their impacts on human health. They can all be monitored continuously in the atmosphere and all have the potential to contribute to the short term health impacts of the air pollution mixture commonly described as smog.

Adverse health effects associated with air pollution have been identified using a variety of research approaches. Time-series studies, in which the day-to-day variability in average exposure levels in a community is related to the day-to-day variability in the rate of an event such as death or admission to hospital, are most relevant from the perspective of quantifying population-level health effects of short-term exposures to the ambient mix of air pollutants. Numerous methodological issues arise in accurately characterizing the impacts of air pollution in these studies. The methodology has to take into account seasonal cycles in exposures and health outcomes, and factors such as weather and influenza epidemics, which operate on the same time scale as air pollution. If not properly accounted for, some of the effect of these other factors on health might erroneously be attributed to air pollution, or vice-versa.

While time series studies that can be used to formulate the index are limited to a relatively small set of health endpoints that are consistently available for an extended period of time, other research has shown that a range of effects, such as emergency room visits, asthma attacks and days missed from work and school is consistent with these studies. In addition, clinical and toxicological research has developed plausible mechanisms that are also consistent with epidemiological research.

It should also be acknowledged that some aspects of air pollution cannot be incorporated into a scientifically derived multi-pollutant risk based index. For example, odorous pollutants such as reduced sulphur compounds are problems in some Canadian communities. They can have direct and indirect health impacts but these cannot be directly incorporated into the time series based risk estimates that are used for other pollutants. This creates a potential problem because the air could smell bad, but the index would not “respond” to the odour. Supplemental information and air quality reporting systems may be needed in some communities in addition to the Index.

Construction of the health risk-based AQI using time-series data began in 2002 with the application of results from a multi-city Canadian time-series study of air pollution and mortality. Problems were subsequently identified, however, with the particular statistical approach (Generalized Additive Models or GAM) employed in this and other time-series studies. A re-analysis of these data using robust statistical approaches was completed in 2003. Additional analyses pertaining to the application of these data to the numerical AQHI formulation were completed in 2004 and refinements of the index formula have continued to be introduced up to the summer of 2006.

Building on these analyses, the recommended index formulation is based on the observed relationship of NO2, O3 and PM2.5 with mortality from an analysis of multiple Canadian cities. These pollutants were associated with the strongest and most consistent effects. Linear, no-threshold concentration response relationships were employed. The index is expressed on a 0–10+ scale. Values more than 10 reflect air pollution-related mortality risks exceeding the maximum observed during the reference period during which the scale was calibrated. It is recommended that the index be reported based on rolling 3-hour average pollutant concentrations, which were considered responsive to short-term peaks but stable relative to very short peaks.

The final formulation is calculated as follows:

AQHI = 10/10.4*(100*(e(0.000871*NO2)-1 + e(0.000537*O3)-1 + e(0.000487*PM2.5)-1))

(All pollutants are input as 3-hour averages, and all numeric values have been rounded to three significant figures.)

Monitoring for the AQHI
The capacity of air quality monitoring networks to provide near real-time, continuous data for the pollutants included in the AQHI formulation is a crucial factor in its success.

The National Air Pollution Surveillance Network (NAPS) was established in 1969 as a joint program of the federal and provincial governments to monitor and assess the quality of the ambient air in Canadian urban centres. NAPS data from provincial and municipal air quality networks, for major urban sites across Canada were used to develop the AQHI risk formulation and is currently being used to issue the AQHI.

Communicating the AQHI
The AQHI communicates 4 elements:
 * A number from 1 to 10 indicating the current quality of ambient air within the community. The higher the number, the greater the health risk associated with the air. Occasionally, when the air pollution related health risk exceeds the maximum observed during the reference period for which the scale was calibrated, the number will be reported as 10+.
 * A category that describes the health risk as "low", "moderate", "high" or "very high"
 * Health messages customized to each health risk category for both the general population and the "at risk" population.
 * Maximum forecasted AQHI values for today, tonight and tomorrow.

People with heart or breathing problems are at greater risk. Follow your doctor's usual advice about exercising and managing your condition