Data integration on carbon monoxide: National Pollutant Release Inventory & the Canadian Space Agency

Carbon monoxide (CO) is a colourless, odourless and tasteless poisonous gas that cannot be detected by humans. In the atmosphere, carbon monoxide is produced directly from the incomplete combustion of fuels based on organic compounds (i.e., hydrocarbons), for example by burning wood, oil, gasoline, coal, natural gas and propane. Besides being produced by industrial and commercial facilities, CO emissions also originate from vehicles, forest fires and heating. Furthermore, CO is produced by chemical reactions in the atmosphere from natural sources, such as emissions from plants.

Since 2002, the Government of Canada has been tracking releases of CO from industrial and commercial facilities through the National Pollutant Release Inventory (NPRI). Canadian facilities must report to the NPRI their CO releases to air if the annual reporting threshold of 20 tonnes of releases is exceeded, as measured from ground-based instruments.

Since 1999, the Canadian Space Agency (CSA), in collaboration with the National Aeronautics and Space Administration (NASA), measures CO concentrations in the atmosphere for the entire Earth with a tropospheric pollution measuring instrument (MOPITT) developed by the University of Toronto.

This data integration of CO illustrates how NPRI data can be used with concentrations measured by the CSA and NASA to identify hot spots across Canada.

These spatial data are the result of a global collaboration which allows them to be shared openly. They support regional and global decisions by making available datasets, scientific analysis, and establishing evidence that provides a global perspective on pollution. These space-based data are used daily by various levels of government and the industry to obtain information related to topics such as:

• the effects of climate change
• rising sea-levels
• forest protection
• weather forecasting

Measuring carbon monoxide

CO is a pollutant of interest because of its significant health impacts. When breathed in, it enters the bloodstream rapidly and prevents red blood cells from carrying oxygen throughout the body. Individuals with cardiac or respiratory conditions, children and the elderly are most vulnerable to CO intoxications. At low levels, CO causes effects such as tiredness, nausea, shortness of breath and headaches. At moderate levels, symptoms include impaired motor functions such as muscle weakness and loss of function of body parts. At high levels, it can cause poor vision, dizziness, difficulty thinking and chest pains. At very high levels, it can cause convulsions, coma and death. Health Canada has established guidance for CO below which there are no effects on health.

CO also has significant impacts when released into the atmosphere. Increased CO levels in the atmosphere increase the lifetime and greenhouse gas potential of atmospheric methane. CO also contributes to the formation of ozone and eventually converts to CO₂, the most significant greenhouse gas. Because of these effects, emissions of CO have a significant radiative forcing, i.e., contribution to global warming, although CO itself is not a greenhouse gas.

Carbon monoxide is a favoured target gas for space-borne measurements because of its atmospheric lifetime (on the order of many weeks). It is a useful tracer for studies on pollution dispersion and atmospheric processes because areas with high amounts of CO indicate the presence of other pollutant gases of interest that are not measured, such as benzene.

Although CO does not have a direct effect on the Earth’s temperature, it plays a major role in the chemistry of the lower atmosphere (i.e., the troposphere) by affecting the atmosphere’s capacity to remove other pollutant gases. When CO combines and interacts with other gaseous pollutants in the presence of sunlight, it also contributes to the formation of ground-level ozone and urban smog. For this reason, CO is a pollutant that serves as an indicator of ambient air quality.

MOPITT: an international CO-measuring instrument

The MOPITT instrument is one of five devices, launched on December 18, 1999, aboard Terra, a NASA satellite orbiting 705 km above the Earth. A Canadian team built and operates the instrument, and a United-States team develops the algorithms for processing the raw data to create data products used by international researchers.

The MOPITT instrument, which is a satellite the size of a school bus, continuously scans the Earth’s atmosphere to collect measurements of CO concentrations around the world for the purpose of studying environmental pollution and long-term trends.

NASA's interactive maps allow us to see the global distribution of CO concentrations from total column amounts in parts per billion by volume (ppbv) since 2000. Measurements from the MOPITT instrument clearly demonstrate how pollution emissions from one continent can travel across oceans and impact air quality elsewhere in the world, millions of kilometres away. This global transport of pollution means that measured concentrations over a given geographical location may not be specifically attributable to Canadian emission sources.

Map of 4 years average CO concentrations in ppbv

Information on MOPITT instrument limitations

It is important to know the limits and considerations of any scientific instrument that measures trace gases in our atmosphere. When using MOPITT, it should be known that:

1. The instrument cannot see everywhere due to cloud cover and also can only measure one place at a time, so a global picture must be built up over multiple days.
2. Canada’s instrument measures the layers of CO in the atmosphere, not specifically the surface. Therefore, it is challenging to compare these data directly to surface-based measurements.
3. The resolution of each measurement unit is approximately 22km x 22km on the surface. This means that the instrument cannot measure areas of smaller size whereas surface-based instruments usually measure at a single point.

These issues are not unique to MOPITT; all space-based instruments have similar issues. In order to address these issues, the instrument science team has improved the resulting data products over the past two decades. Further refinements continue to be developed and implemented and as the latest understanding is applied to the entire dataset through 2000 to now.

Reporting of CO to the NPRI

The map below illustrates the amount of CO in tonnes reported to the NPRI by Canadian facilities in 2018. We can see that the largest releases are located in southern British Columbia, Alberta, Ontario and eastern Quebec.

As shown in the chart below, the distribution of CO releases reported to the NPRI in 2018 was 44% for Quebec, 25% for Alberta, 12% for British Columbia and 8% for Ontario.

However, Alberta had the highest number of reporting facilities (54%), followed by Saskatchewan (14%) and British Columbia (11%).

The graph below shows that the amounts of CO reported to the NPRI have been increasing since 2002. The number of reporting facilities was fairly stable until 2017, when it increased substantially. This may explain the increase in CO releases in that year. Six facilities were releasing 37% of the total CO in 2017.

In 2018, the aluminium industry alone accounted for 45% of total CO releases reported to the NPRI, followed by the conventional oil and gas extraction sector (19%) and the pulp and paper sector (10%).

Surface measurements of carbon monoxide by the MOPITT instrument

The MOPITT instrument takes daily measurements of CO. For the purpose of this data integration, monthly averages for the year were calculated to map concentrations across the country.

The map below illustrates the average total concentration of CO measured in 2018 by MOPITT for low-level pollution, i.e. at the surface^{Footnote 1} . The distribution by concentration and province shows that concentrations are higher in the southern and eastern parts of the country. Concentrations are lower in northwestern British Columbia, western Alberta and northern Canada. This may be attributed to the prevailing winds in the Northern Hemisphere which are deflected to the east or by persistent clouds in these regions.

Note that the highest concentrations in dark blue are mainly located near major Canadian cities, e.g. Toronto, Vancouver and Montreal. The highest average concentration measured for 2018 was 334 molecules/cm² for Lake St. Clair in Ontario, followed by Lake Erie (301), Waterloo (283), Lake Huron (279) and Hawkesbury (276).

In the map below, the quantities of releases reported to the NPRI in 2018 are overlaid on the concentration data measured by MOPITT. In general, we can see that the areas with the largest reported CO releases correspond to the highest measurements from the MOPITT instrument.

The province of Alberta has the largest amounts of CO and the largest number of facilities reporting to the NPRI. MOPITT measurements are also high in Alberta. However, in 2018 the Québec City-Windsor Corridor had the highest CO concentrations measured as well as the largest amounts of CO reported to the NPRI. This can be explained by the fact that this region is Canada’s most densely populated and industrialized area, with an active transportation sector for cars, trains, planes and boats.

According to calculations for the Canadian Environmental Sustainability Indicators (CESI), the amounts reported to the NPRI appear to account for only 15% of all CO emissions in Canada.

As shown in the CESI graph below, CO emissions appear to have been declining since 1990 and are largely produced by the transportation sector. This could explain why there are areas with high levels of CO despite few to no CO emissions reported to the NPRI.

MOPITT measurements in other layers of the troposphere

The diagram below demonstrates that the Earth’s atmosphere is divided into five layers:

• the troposphere
• the stratosphere
• the mesosphere
• the thermosphere
• the exosphere

The MOPITT instrument takes measurements in the first layer of the atmosphere (the troposphere) at various heights and pressure levels, which are measured in hectopascals (hPa). The instrument measures CO concentrations at pressure levels between 100 hPa and 900 hPa. The greater the atmospheric pressure, the closer the measurements are to the Earth’s surface.

These measurements cover about the first 15 kilometres of the Earth’s atmosphere. For comparison, Mount Everest is 8.849 kilometres high and airplanes fly at an altitude of 9.2 to 12.2 kilometres.

CO measurements are also affected by weather conditions, wind speed and direction. With increasing altitude in the upper troposphere, the measurements are more likely to include gases and aerosols that have travelled from elsewhere in the world.

The map below shows CO measurements taken in 2018 at 200 hPa, i.e. in the uppermost layer of the troposphere. Note that the general measurements (concentrations) are much lower because they are taken at higher altitudes; therefore, they are farther away from emission sources and are more uniform across Canada.

The second map below illustrates the concentrations measured at 600 hPa. The concentrations measured by the MOPITT instrument are higher, particularly in northern Québec, northern Ontario, northern Alberta and Newfoundland and Labrador.

The map below shows the concentrations measured at 900 hPa, i.e. near the surface. The highest concentrations measured were between 200 and 248 parts per billion by volume (ppbv). These measurements were mainly from Alberta, Saskatchewan and Québec, with very low concentrations measured in British Columbia and northern Canada. The low concentrations in British Columbia are related to the presence of the Rocky Mountains, not the absence of CO.

Government measures and pollution prevention

The Government of Canada, as well as provincial and territorial governments, provide extensive information on preventing CO poisoning and maintaining indoor air quality.

Although CO is not on the List of Toxic Substances, Schedule 1 of the Canadian Environmental Protection Act, the Act sets out CO limits for petroleum and refinery gases.

Under the Canada-United States Air Quality Agreement and the Clean Air Act, every five years the US Environmental Protection Agency reviews the data on which the National Ambient Air Quality Standards for six criteria air contaminants are based. The standards for CO, which may not be exceeded more than once a year, is 9 ppm over 8 hours and 35 ppm over 1 hour.

Other guidelines have been established by various organizations and government departments, such as the World Health Organization. Some provincial and territorial governments have issued atmospheric quality standards, such as Québec’s:

• Regulation respecting the quality of the atmosphere, which establishes atmospheric quality standards for CO at a maximum of 0–30 ppm, average over 1 hour, and 13 ppm, average over 8 hours
• Clean Air Regulation, which also establishes CO limit values for various industrial equipment.

In Ontario, the Ambient Air Quality Criteria for 1-hour average CO concentrations is set at 30 parts per million (ppm). CO is also included in the province’s Air Quality Health Index. Alberta provides an information bulletin on sources of CO in the workplace and its health effects to inform the public of the risks posed by CO and exposure limits.

More information on carbon monoxide

To do your own analysis of CO or any other substances tracked by the NRPI, you can download the NPRI datasets containing the pollutant quantities reported since 1994. Access to data from the Canadian Space Agency is also free.

Access to the most recent NASA datasets on CO can be found through NASA's Atmospheric Science Data Centre. For more information about the NASA’s Terra satellite and the MOPITT instrument, visit the Terra mission website.

You can also conduct searches to learn about pollutant releases in your community by entering your postal code in the NPRI online query site or by consulting the NPRI maps. Other overviews and data integrations are also available for many other NPRI substances and sectors.