CASA - FAQs for Website

Real-time monitoring means that pollutants are measured on a continuous basis – that is, 24 hours a day, 7 days a week. Concentrations of pollutants can be checked at any given time.

Concentrations are averaged over a time period of interest, for example, every hour, and reported as a “1-hour concentration”. 

The CASA website shows real-time monitoring data from seven stations in the Sarnia area.  A list of the pollutants monitored on a real-time basis at each station is shown here.

The term “near real-time” data may also be used, as this describes the time it takes to collect monitoring data, take an average, and report the data on the CASA website.

Ontario’s Ambient Air Quality Criteria (AAQC) are benchmarks used to assess general air quality resulting from all sources of a contaminant to air, independent of location or source of a contaminant.

They are based on:

• effects on human health, vegetation, soiling, or visibility;
• odour detection; and
• approaches taken by other jurisdictions.

They are set at concentrations that are protective against adverse effects and are periodically updated based on new science. AAQC are also used to set regulatory air standards under O.Reg. 419/05, the local air quality regulation.

The AAQC for the pollutants monitored throughout the CASA network are listed in the Airborne Pollutants section.

Hourly pollutant concentrations shown on the website are colour-coded and classified as Good, Moderate, Poor, and Very Poor to help you understand how the concentrations compare to the Ministry of the Environment, Conservation and Parks (MECP) criteria.

Good: Pollutant concentrations are below all 1-hour reference values.

Moderate: One or more pollutant concentrations are either above or approaching the 1-hour reference values.

Poor: One or more pollutant concentrations are above the 1-hour reference values.

Very Poor: One or more pollutant concentrations are at elevated levels above the 1-hour reference values.

1-hour AAQC are available for Nitrogen dioxide (NO₂), Ozone (O₃), and Sulphur Dioxide (SO₂). Due to the updated, more protective AAQC for SO₂, unlike the other pollutants, the 1-hour AAQC for SO₂ is used as the threshold between “Good” and “Moderate”. For other pollutants, the 1-hr reference value is used as the threshold between “Moderate” and “Poor”. 1-hour AAQC are not available for Total Reduce Sulphur (TRS) and Fine Particulate Matter (PM_2.5). For these pollutants, the “comparable reference value” is based on the lowest concentration that would fall under the “Poor” category in Ontario’s modified Air Quality Index.

1-hour AAQC are also not available for volatile organic compounds (benzene, 1,3-butadiene, and ethylene). These pollutants have 24-hour and/or annual AAQC. The “comparable reference value” for these pollutants is 10 times the AAQC 1-hour equivalent, calculated using a conversion formula outlined in O. Reg. 419/05.

A detailed description and breakdown of the classification system is provided in the responses below.

The colour and classification that you see for each station on the map is driven by the pollutant with the highest concentration relative to its respective benchmark.  For example, if a station is classified as “Good” (green), then all pollutants monitored at that station fall within the “Good” concentration range.

If a station is classified as “Moderate”, then one or more pollutants fall within the “Moderate” concentration range.

If you click on a station to bring up the pollutant concentration table, you can see how each of the pollutants monitored at that station are classified.   

A detailed description and breakdown of the classification system is provided in the response below.

This classification system was established by Ministry of the Environment, Conservation and Parks (MECP) scientists to help you gain a general understanding of how hourly air contaminant concentrations compare to MECP criteria.  

The classification system is primarily based on the MECP’s Ambient Air Quality Criteria (AAQC). For pollutants that do not have 1-hour AAQC, comparable reference values have been derived.

A detailed breakdown of the concentrations associated with the Good, Moderate, Poor, and Very Poor categories for each pollutant is provided below. 

Common Air Pollutants

The classification for the common air pollutants (NO₂, O₃, PM_2.5, SO₂, and TRS) is based on Ontario’s Air Quality Health Index category divisions and the former Air Quality Index category names.

¹The PM_2.5 classification is based on the 3-hour running average (the average concentration over the previous 3 hours).

Notes

Total Reduced Sulphur (TRS) compounds at very low concentrations have an unpleasant, pungent odour and are not typically considered a health hazard. The categories for TRS do not consider the potential for impacts due to odour. It is possible for TRS concentrations to be above the odour threshold, but fall within the Good classification.  

Volatile Organic Compounds

Some CASA stations monitor volatile organic compounds (VOC) on an hourly basis, including benzene, 1,3-butadiene, and ethylene. 1-hour AAQC do not exist for these compounds, so comparable reference values have been derived.

The classification system is based on a conversion of the 24-hour AAQC for these compounds to a 1-hour equivalent value, using a formula described in Ontario Regulation 419/05. The divisions between the categories Good, Moderate, Poor, and Very Poor are set at 1, 10, and 100 times the 1-hour equivalent AAQC. 

Notes

The AAQC for 1,3-butadiene and benzene were derived from cancer risk levels based on continuous lifetime exposure. The AAQCs can be converted to 1-hour equivalent values for informational purposes, and as an indicator of whether the longer term AAQC may be exceeded. An exceedance of the AAQC 1-hour equivalent does not mean that cancer risks will increase unless the frequency of the exceedance and the magnitude above the AAQC is experienced over a long term.

The AAQC for ethylene is based on vegetation effects. An exceedance of the AAQC 1-hour equivalent does not mean that effects will occur unless the frequency of exceedance and the magnitude above the AAQC is experienced over several (2-3) days.

Ontario’s Air Quality Health Index (AQHI) was developed in partnership with Health Canada and Environment and Climate Change Canada, and provides the public with information on health risks based on the concentrations of common air pollutants.

The CASA network includes monitoring data from Sarnia's AQHI station (located on Christina Street) as well as six other ministry and industrial stations in the Sarnia area. Several of the CASA stations monitor pollutants in addition to those factored in to the AQHI calculation; for example, benzene and 1,3-butadiene.  

The classification system for the CASA website is intended to help you understand what the concentrations of air pollutants are, and how they compare to MECP criteria.

The classification for the common air pollutants (NO₂, O₃, PM_2.5, SO₂, TRS) as Good, Moderate, Poor, and Very Poor on the CASA website generally line up with the AQHI as outlined below:

It is important to note that AQHI values and forecasts are not presented on the CASA website. Visit the Air Quality Ontario website for information on the current and forecasted AQHI values.

Yes. If Ontario develops updated Ambient Air Quality Criteria for any of the pollutants monitored in the CASA network, the concentration breakpoints will be updated accordingly.

The air monitoring data presented on the CASA website is meant for educational and informative purposes, and is not intended to provide information on health risks.

Check the current Air Quality Health Index for Sarnia for information on health risks, steps you can take to reduce your exposure, and air quality forecasts.

Ontario’s Air Quality Health Index is based on concentrations of common air pollutants (PM_2.5, O₃, NO₂, SO₂, and TRS). These pollutants are known to have short-term health effects. 

The CASA network monitors additional pollutants that are not factored in to Ontario’s AQHI, including benzene and 1,3-butadiene. Health effects from these pollutants are generally associated with exposure over a long time. Learn more about other monitored pollutants and their health risks here, including benzene and 1,3-butadiene.

The air monitoring data presented on the CASA website is meant for educational and informative purposes, and is not intended to provide emergency response information.

For information on emergency planning in the Sarnia, Aamjiwnaang, St. Clair, and Lambton area, and to subscribe to the Sarnia-Lambton Alerts emergency notification system, please visit the Bluewater Association for Safety, Environment, and Sustainability (BASES) website at lambtonbases.ca or call 519-383-1222.

For information about the Aamjiwnaang Emergency Notification System, and additional emergency planning resources, please visit the Aamjiwnaang First Nation website: http://www.aamjiwnaang.ca/emergency-response-and-planning-3/

The real-time monitoring data on the CASA website is updated on an hourly basis. Updates typically take place around 15 minutes after the hour.

The “Collection Time” shown above the map tells you when the monitoring data was collected. 

No. The hourly air quality data on the CASA website is real-time, so it is automatically received from stations throughout the network, and has not undergone complete quality control and quality assurance procedures. Data may contain errors and are subject to change. The real-time air quality data on the CASA website are considered "unverified data" and should not be used in published documents.

Data integrity and validity may be affected by instrument malfunctions, telemetry connectivity, QA/QC requirements, instrument calibration times or power outages.

Real-time air quality data on the CASA website is meant for public awareness, and not for emergency response purposes. This website does not replace or supplement the existing emergency notification and response protocols, including Sarnia-Lambton Alerts.

Gaps in the data occur if the monitoring data is not available for a certain time period. Data may be unavailable for a variety of reasons, such as monitoring instrument malfunctions, issues with the network connection, power outages at the monitoring station, or regularly scheduled instrument calibration times.

From the View Meteorological Data panel on the left side of the page, select Wind Direction from the menu:

Arrows are now displayed on the map. The arrows show the direction that the wind is blowing.

The table at the left lists the wind direction (in degrees), and the cardinal direction (south, southwest, and so on). 

If the station names are covering up the wind arrows, you can uncheck the “Show Station Labels” box to hide the station names.

All wind directions are given based on the direction that the wind blows from. For example, a west wind means that the wind is blowing from the west.

The arrows on the map point to the direction that the wind is travelling.

For example, see the wind directions on the map below. Winds are coming from the southwest, and travelling to the northeast.

The size of the arrows depends on the wind speed. The bigger the arrow, the greater the wind speed.

The circles on the map show the location of the air monitoring stations, and the arrows represent the wind speed and wind direction. The wind arrows do not represent boundaries for the air pollutant concentrations measured at each station.

Some air pollutants, such as ozone, are regional in nature. This means that the pollutant concentrations measured at a station are likely to represent concentrations over a broad area.

Other pollutants, such as sulphur dioxide and benzene, are local in nature. Concentrations of these pollutants can vary greatly from one location to another.

The air monitoring stations in the CASA network are designed to represent the ambient air pollutant concentrations in the Sarnia area.   The air quality in your specific location may vary from the concentrations measured at the CASA stations, depending on a number of factors, such as:

• The characteristics of the pollutants measured, and whether they are regional or local in nature;
• The wind speed (higher winds tend to quickly disperse and dilute pollutants);
• The wind direction;
• Your proximity to other local pollutant sources, such as roadways and fuel refilling stations, for example.

Hourly air monitoring data going back to January 1, 2017 is available on CASA.

Non-continuous (laboratory) data goes back to 2014 for some pollutants and stations. See the Non-Continuous Reporting section for available laboratory results.

See the Technical Reports page for links to some CASA member organizations reports, which may include additional historical data.

The CASA website contains hourly air monitoring data going back to January 1, 2017.

To check hourly monitoring data for one hour at a time, change the Collection Date and Collection Time on the Network Map page to the date and time that you are interested in. For example, selecting September 20, 2017, from 2:00 – 3:00 pm will display the pollutant concentrations for that hour on the map and tables.  

To check hourly monitoring data for one week or one month at a time, go to the Reporting Tab, and click “Reporting Parameter Configuration”:

Select the time period (daily, weekly, or monthly), and the start date from the drop-down box.  Then select the pollutant(s) and station(s) you are interested in.

For example, to see all the SO₂ data from every station for the week of October 1, 2017, choose Reporting Period (Weekly), Start Date (Oct. 01, 2017), and check all the boxes under the SO₂ column (and click OK):

A graph is generated showing you the hourly pollutant concentrations from the station(s) and time period you are interested in.

To view this data in a table, select the Report tab. Click on the Save button to download the data into Word, Excel, or PDF format.

Several of the CASA stations take samples over a 24-hour period every 6 or 12 days, which are sent to a laboratory and analyzed for a wide range of pollutants, including particulate, metals, polycyclic aromatic hydrocarbons, and volatile organic compounds (VOCs).

VOCs (including benzene) are also measured on an hourly basis at temporary monitoring stations within the CASA network.

In addition, benzene or 1,3-butadiene are measured over a 2-week period at property line monitoring sites, operated by industry.

These results are posted on the CASA website under Reporting -> More Monitoring Data.

The Michigan Department of Environmental Quality operates the MIair website. You can visit this website to view real-time data collected at the Port Huron air monitoring station.

CASA will continue to work towards improving the monitoring network and sharing information about ambient air quality with the public, and may consider expanding the website in the future to include monitoring data from Michigan stations.