National Pollutant Releases Inventory: total reduced sulphur

Every year since 1993, the Government of Canada, has collected data from Canadian facilities on pollutant releases to water, air and soil through the National Pollutant Release Inventory (NPRI). Facilities that meet the reporting thresholds or that carry out certain activities are required to report the quantities of each substance released. This overview explores the reported quantities of total reduced sulphur (TRS).

Although there are natural sources of TRS, such as marshes, bogs, lakes and coastal regions, TRS is most often the result of industrial processes. These processes must be monitored in order to ensure that concentrations remain below a safe threshold for health and the environment and that they decline each year. The map below shows TRS releases reported to the NPRI in 2019.

TRS releases reported to the NPRI in 2019

TRS releases reported to the NPRI in 2019
Long Description

This map show the location of facilities that have reported total reduced sulphur to the NPRI in 2019. Each purple dot represents a facility.

You can find the data used to create this map using our single year data tables.

From this overview on TRS, you will learn about:

Background

Total reduced sulphur (TRS) is a gaseous mixture of pollutants that contain sulphur (S) in its reduced state. There are many TRS compounds, but for the purposes of reporting to the NPRI, TRS refers to the following substances:

TRS was added to the NPRI substance list in 2007. In order to compare reports of TRS from facility to facility, the individual quantities reported for each pollutant (i.e., H2S, CS2, COS, C2H6S, CH4S, C2H6S2) are converted to a single unit (tonnes of H2S) using a mathematical formula and equivalency factors.

Three TRS compounds are tracked individually in the NPRI:

These compounds have more significant effects on human health. In the case of CS2, even very small releases must be declared to NPRI (< 1 tonne/year).

The map below shows the location of facilities that have reported individual TRS compounds to the NPRI in the past 10 years.

Individual TRS releases reported to the NPRI over the last 10 years

Map of facilities that have reported TRS compounds in the last 10 years.
Long Description

Map showing the total reduced sulphur releases reported to the NPRI over the last 10 years.

The following substances are represented on the map: hydrogen sulphide, carbonyl sulphide and carbon disulphide.

You can find the data used to create this map using our bulk data files for all years.

H2S was added to the NPRI substance list in 1999. In the figure below, we see that the trend in H2S releases declined from 2002 to 2011, with few facilities reporting large releases. In 2011, there was an increase in the trend as a function of the number of reporting facilities, followed by return to a downward trend.

Hydrogen Sulfide releases
Long Description
Releases of hydrogen sulfide between 1999 and 2019
Year Quantity (tonnes) Facilities
1999 5,618 158
2000 4,868 181
2001 5,733 187
2002 4,104 237
2003 3,845 221
2004 2,843 224
2005 2,373 251
2006 1,660 242
2007 2,175 239
2008 1,772 247
2009 1,382
246
2010 1,483 226
2011 2,171 296
2012 2,109 277
2013 1,908 249
2014
2,152 256
2015 1,868 248
2016 1,822 230
2017 1,519 216
2018 1,739 223
2019 1,654 225

COS was added to the NPRI substance list in 2003. The graph shows an upward trend in COS releases and reporting facilities until 2011. Since then, there has been a downward trend in releases and number of reporting facilities.

Carbonyl sulphide releases
Long Description
Releases of carbonyl sulphide between 2003 and 2019
Year Quantity (tonnes) Facilities
2003
2,089
17
2004 1,955
27
2005 2,552
32
2006 2,494
39
2007 3,143
45
2008 3,345
53
2009 4,768
45
2010 2,924
44
2011 5,246
73
2012 4,495
65
2013 4,559
57
2014 4,109
59
2015 3,286
60
2016 3,561
54
2017 3,563
52
2018
3,178
57
2019 2,724
49

CS2 was added to the NPRI substance list in 1996. Few facilities report individual CS2 releases. The graph below shows a declining trend in CS2 releases since 2009, despite an increase in the number of reporting facilities.

Carbon disulphide releases
Long Description
Releases of carbon disulphide between 1996 and 2019
Year Quantity (tonnes) Facilities
1997 997 7
1998 1,088 10
1999 1,616 14
2000 1,439 19
2001 1,301
15
2002 1,556
11
2003 1,770
18
2004 3,471
25
2005 2,882
25
2006 2,464
26
2007 2,686
27
2008 2,045
30
2009 3,602
23
2010 4,142
22
2011 1,887
37
2012 1,337
38
2013 1,157
31
2014
702
28
2015 485
28
2016 481
24
2017 386
22
2018 388
19
2019 298
17

Releases across Canada

In 2019, 278 Canadian facilities reported TRS releases to air. As shown in the map on the right with 2019 data, and in the figure below, the provinces of Quebec, Alberta, Manitoba and British Columbia reported the largest TRS releases to air. The figure below shows the reported releases in tonnes by province in 2019, along with the number of facilities.

TRS releases reported to the NPRI in 2019

Releases of TRS to air
Long Description

Map showing the total reduced sulphur releases reported to the NPRI in 2019.

You can find the data used to create this map using our single year data tables.

Distribution of TRS releases by province in 2019
Long Description
Distribution of TRS releases per province in 2019
Province Quantity (tonnes)
Facilities
British Colombia
799 30
Northwest Territories
3 3
Alberta 1,376
122
Saskatchewan 90 20
Manitoba 1,033 4
Ontario 568 52
Québec 1,569 39
Newfoundland 16 3
New Brunswick 114 4
Nova Scotia
65 1

Quebec accounted for 28% of total TRS releases reported to the NPRI, Alberta for 25%, Manitoba for 18% and British Columbia for 14%. There were no reported releases of TRS in Yukon, Northwest Territories or Prince Edward Island.

The map show that the largest TRS releases reported to the NPRI are generally outside large urban centres. In 2019, the following cities had the highest TRS releases:

Reporting sectors

The industrial sectors that have the largest TRS releases are petroleum refining, pulp and paper manufacturing, aluminium production, landfilling and wastewater treatment. The figure below shows the breakdown of TRS releases by sector in 2019. The pulp and paper, aluminium, and oil and gas sectors accounted for 86% of total TRS releases reported to the NPRI in 2019.

Distribution of TRS releases by industrial sector in 2019
Long Description
Distribution of TRS releases per key industrial sector in 2019
Key industrial sector
Quantity (tonnes)
Aluminum 1,290
Non-Metallic Minerals
20
Chemicals 37
Conventional Oil and Gas extraction
795
Iron and Steel
135
Mining and Quarrying 134
Non-Conventional Oil Extraction (including Oilsands and Heavy Oil)
326
Other 13
Petroleum and Coal
108
Pulp and Paper 2,762
Waste Treatment and Disposal
2
Water and Wastewater Systems
10

Recent trends

Both maps below illustrates the TRS releases reported between 2012 and 2016. We see that the largest releases and the majority of reporting facilities are in the province of Alberta.

Since 2009, there has been a downward trend in TRS releases, despite the increase in the number of reporting facilities.

TRS releases reported to the NPRI in 2012

TRS releases reported to the NPRI in 2012
Long Description

Map showing the total reduced sulphur releases reported to the NPRI in 2012.

You can find the data used to create this map using our bulk data files for all years.

TRS releases reported to the NPRI in 2016

Long Description

Map showing the total reduced sulphur releases reported to the NPRI in 2016.

You can find the data used to create this map using our bulk data files for all years.

In the figure below, we see an increase in TRS releases between 2007 and 2010, due to growth in the oil and gas sector. From 2010 to 2011, total TRS releases declined significantly following changes in the estimation methods and emission factors used by several oil and gas extraction facilities. Releases further declined in 2014 following the closure of a facility in British Columbia and a decrease in releases reported by another facility in the same province. Reported quantities have since remained relatively stable.

Total releases of TRS (tonnes) by year
Long Description
Total releases of TRS reported to the NPRI between 2007 and 2019
Year
Quantity (tonnes)
Facilities
2007 7,890 150
2008 9,090 193
2009 12,721 203
2010 12,550 195
2011 9,157 305
2012 7,924 297
2013
7,545 281
2014 6,979 277
2015 5,916 267
2016 6,122 290
2017 5,687 274
2018 5,754 278
2019 5,638 278

In 2014, a change was made to the NPRI reporting criteria, restricting the reporting requirement for TRS to air releases only. This change excludes releases to water and soil and transfers off site for purposes of recycling in order to avoid double counting of substances. For example, it used to be possible for the individual TRS compounds to be reported to the NPRI as total TRS and also as disposals, releases to water, underground injection disposals or transfers for recycling.

Human health effects

Of the various TRS compounds, hydrogen sulphide (H2S), carbonyl sulphide (COS) and carbon disulphide (CS2) are the most likely to cause human health effects because they are quickly absorbed into the body when inhaled. Exposure to TRS is associated with irritation of the mucous membranes (i.e., eyes, nose, throat, respiratory system). Long and repeated exposure to TRS can also cause long-term health effects, such as:

Sensitivity to these pollutants varies from person to person. According to a 2017 Health Canada report that found that current levels of H2S in ambient air did not pose a risk to the health of Canadians. However, H2S could pose significant health risks if levels were to increase, primarily for employees exposed to it in the workplace. For that reason, workers who are in close contact with TRS compounds must wear proper personal protective equipment (PPE), be aware of the risks posed by these substances and wear a gas monitor at all times.

Environmental effects

When released to the air, TRS can also have harmful environmental impacts. It contributes to the formation of acid rain, which has devastating effects on vegetation and stream health. Acid rain affects the growth of vegetation and is harmful to aquatic organisms. TRS can also contribute to physical damage, such as premature metal corrosion and paint discoloration.

All TRS compounds can be easily detected in ambient air even at very low concentrations because they have a distinct odour similar to rotten eggs or boiled cabbage. Even at concentrations as low as 1 to 5 ppb (parts per billion), TRS can produce an unpleasant odour. For example, carbon disulphide (CS2) can remain in the atmosphere for 11 days. The odour can travel long distances and can become a nuisance to neighbouring areas, depending on wind speed and weather conditions.

Industries located near residential areas must closely monitor their TRS emissions to avoid odour complaints from residents. Some cities and provinces have chosen to set ambient air quality criteria for TRS. For example, Hamilton, Ontario and Pictou, Nova Scotia have established odour targets and measure ambient air TRS concentrations to more effectively control industrial releases and limit nuisance odours in communities. See Clean Air Hamilton and Pictou TRS Hourly data for more information.

Persistent odours can increase stress in communities by preventing residents from enjoying outdoor activities or forcing them to close their windows. TRS releases to air can significantly reduce Canadians’ quality of life. See Indicator supporting the Federal Sustainable Development Strategy for more information.

Disposals and transfers for recycling

Between 2007 and 2013, 99% of disposals and transfers for recycling consisted of underground injection, either on-site (69%) or off-site (30%). On-site tailings management and transfers off-site for recycling for the reuse or refining of used oil accounted for less than 1%.

TRS compounds are generally recovered and incinerated on site with other odorous or toxic gases for disposal.

Distribution of disposals of TRS between 2017 and 2013
Long Description
Disposals and transfers of TRS between 2007 and 2013
Year Underground Injection on site (tonnes) Underground injection off site (tonnes)
Landfill off site (tonnes)
Tailings management on site (tonnes)
2007 28,627 2 4 1,303
2008 23,535 2 3 1,291
2009 17,004 2 0.15 1,080
2010 17,307 2 0.2 -
2011 85,094
40,342 3 2
2012 67,785 51,694 6
2
2013
57,937 38,544 2 1.83

Environmental management measures

Although the trend in TRS releases to air has declined since 2007, some facilities still report high TRS releases. For example, one Canadian facility released a total of 958 tonnes of TRS in 2019, which accounts for an annual average of 2.62 tonnes per day. The NPRI reporting threshold for TRS is 10 tonnes annually (H2S equivalent), which means that that particular facility exceeded that threshold after just four days.

In an effort to offset TRS releases, a number of  initiatives have been introduced by the provincial governments to encourage Canadian facilities to reduce or mitigate TRS concentrations in the air. For example, some facilities create buffer zones by planting trees, whereas others improve gas treatment through the capture of new sources of emissions or incineration of gases.

Although TRS is not regulated by the Government of Canada, some provincial environment ministries have chosen to use their own monitoring and regulatory mechanisms to set ambient air quality standards for TRS. For example:

Provincial governments can also impose additional operating conditions on facilities if they exceed the air quality standards.  For example:

Facilities reporting to the NPRI can also implement pollution prevention measures to reduce their TRS emissions.

For more information

As a result of the measures put in place by the Government of Canada, the provinces and industry, TRS releases to air are declining. However, it is imperative to continue to monitor annual reporting by facilities to detect any change in trends or processes to better protect the environment.

To do your own analysis of TRS or any other substance tracked by the NRPI, you can download the NPRI datasets containing the pollutant quantities reported since 1994. You can also consult NPRI maps. Additional substance overviews are also available on the NPRI website.

Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: