What is air quality?

When addressing What is Air Quality, we are talking about improving (lowering) the concentrations of pollutants in the air.  

Gas Plant Emissions

Emissions from pipe leaks and the flare stacks can affect air quality.

In my experience, the common pollutants in most countries are:

  • carbon monoxide CO which leads to poisoning and suffocation and cannot be detected by smell
  • sulphur dioxide SO2 which can cause or aggravate disease
  • ozone O3 which irritates the lungs if inhaled
  • nitrogen oxides NOx which transform into more-harmful nitrogen dioxide NO2 and nitrates NO3
  • particulate matter, which includes larger PM10 (10 µm) and smaller PM2.5 particles, 
  • hydrogen sulphide H2S which leads to odours and toxic effects
  • ammonia NH3 which leads to odours and 
  • volatile organic compounds, VOCs, which cause headaches, nausea and even cancer

These may be contained in the air at any location and time.  The levels of these contaminants can be affected by emissions sources such as fires and industrial stacks, weather conditions and topography.  And these concentrations can rise rapidly in areas where airflow is blocked in any way.  We say ambient air quality when talking about the outdoor environment surrounding a specific place (such as a factory) and we care about these concentrations at ground level, away from emission-sources at this factory.

Air pollution (air quality) is monitored, measured and examined within regions called airsheds.  Airsheds are specific geographical zones where the air acts uniformly and the dispersion of emissions is quite consistent within each region.  This may also mean air movement can be consistently hindered by the same local geographic features, such as mountains or valleys. 

Alberta has nine airsheds recognized by the the province's Clean Air Strategic Alliance (CASA), British Columbia has 13 and Saskatchewan has six.  The land and monitoring activity in each airshed zone is administered by its local organization as authorized by the respective provincial government.

What is Air Quality Health Index (AQHI)

On a scale of one to 10 (usually), where one is considered low and 10 (or greater occasionally) is very high risk, air quality as monitored is summarized via the Canadian federal AQHI.  The AQHI allows people in the at-risk population (e.g., children, the elderly or those with a health condition such as asthma) and the general population to quickly assess the health risk of the air. 

This single number is determined based on three-hour average measurements of the concentrations of a combination of the common pollutants – ground level O3, particulate matter (specifically PM2.5, the smallest particles capable of deepest penetration into the lungs where they block respiration) and NO2.

These are all known to cause health problems.  This index does not consider sulphur compounds, carbon dioxide, pollen, heat or humidity, and some of these parameters are evaluated independently.

Objectives, Dispersion Modelling and Ambient Monitoring

Many jurisdictions, such as each western province, have Ambient Air Quality Objective values – concentrations outlined for offending substances which are generally not to be exceeded in the surrounding area.  What is air quality modelling?  This kind of dispersion modelling allows us to predict concentrations of these substances when and where monitoring data is not available, and modelling is far more efficient than monitoring. 

What is Air Quality monitoring need for then?  When necessary, continuous monitoring does provide up-to-date measurements of ambient concentrations for troublesome contaminants and is the best solution for specific problems.  If both types of data are available, they can be compared for consistency.

Fixed monitoring stations monitor the air continuously, non-continuously or passively at locations that are determined by population, by the presence of sites and their types of industrial emissions.  If a permanent continuous station is more expensive than what is needed for a given situation, mobile monitoring stations can take measurements to give a snapshot of the air quality at the location during a specific time period.

In my air quality group at Calvin Consulting, (CCGL Services) we specialize in dispersion modelling, determining locations and equipment to be used for ambient monitoring and analyzing the data obtained by the monitoring for making operational decisions.  Please contact me at 403 547 7557 or by email for more details.

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