Canada’s Air Pollutant Emissions Inventory Report 2025: chapter 2.3
2.3 Nitrogen Oxides
Approximately 1.2 Mt of nitrogen oxides (NOx) were released in Canada in 2023 (Table 2–5). Transportation and Mobile Equipment was the largest contributor, accounting for 38% (467 kt) of total NOx emissions. Within this source category, Off-Road Diesel Vehicles and Equipment, Heavy-Duty Diesel Vehicles, Domestic Marine Navigation, Fishing and Military and Rail Transportation sectors were the largest emitters, collectively contributing 32% (388 kt) of total NOx emissions. The Oil and Gas Industry accounted for 37% (452 kt) of total NOx emissions in 2023, with the Upstream Oil and Gas Industry sector accounting for nearly all of the Oil and Gas Industry total (96% or 432 kt). Electric Power Generation (Utilities) contributed 7.3% (90 kt) of total NOx emissions, with coal-fired generation contributing 3.8% (46 kt) of the national total. The remaining 18% of NOx emissions were distributed across multiple sources.
In 2023, national NOx emissions were 45% (1.0 Mt) below 1990 levels and 46% (1.0 Mt) below 2005 levels (Figure 2–3). Significant drivers of this trend were the decrease in emissions from Heavy-Duty Diesel Vehicles as well as Light-Duty Gasoline Trucks and Vehicles. Despite a 168% increase in total VKT from Heavy-Duty Diesel Vehicles and a 28% increase in the total fuel consumption of Light-Duty Gasoline Trucks and Vehicles, improved fuel economy and implemented regulations have effectively lowered NOx and hydrocarbon emissions from engines.Footnote 6
Within Electric Power Generation (Utilities), coal-electric power generation contributed to the downward trend across the time series, with a gradual decrease in emissions from 1998 to 2023. This decrease can be attributed to coal-fired power plants that have closed down and been replaced by lower-emission sources such as natural gas power plants.
The Oil and Gas Industry experienced an increase of 31% (108 kt) in emissions since 1990. This increase is attributed to expansion and growth in the industry. Between 2019 and 2021, most major contributors to NOx emissions experienced decreases. Notably, the Upstream Oil and Gas Industry saw a significant decrease between 2019 and 2020, a slight decrease between 2020 and 2021 and a minor increase between 2021 and 2023, resulting in an overall decrease of 17 kt (3.6%) over this five-year period. This can be attributed primarily to a 5.1% reduction in reported fuel gas consumption from 2019 to 2023.
The most significant changes in NOx emissions from 1990 to 2023 include:
- Transportation and Mobile Equipment: decrease of 63% (795 kt), with:
- Light-Duty Gasoline Trucks and Vehicles: decrease of 89% (264 kt)
- Heavy-Duty Diesel Vehicles: decrease of 65% (217 kt)
- Off-Road Diesel Vehicles and Equipment: decrease of 57% (173 kt)
- Electric Power Generation (Utilities): decrease of 65% (167 kt), with:
- Coal: decrease of 77% (160 kt)
- Oil and Gas Industry: increase of 31% (108 kt), with:
- Upstream Oil and Gas Industry: increase of 40% (123 kt)
The most significant changes in NOx emissions from 2005 to 2023 include:
- Transportation and Mobile Equipment: decrease of 63% (784 kt), with:
- Heavy-Duty Diesel Vehicles: decrease of 70% (280 kt)
- Light-Duty Gasoline Trucks and Vehicles: decrease of 88% (243 kt)
- Off-Road Diesel Vehicles and Equipment: decrease of 54% (156 kt)
- Electric Power Generation (Utilities): decrease of 64% (164 kt), with:
- Coal: decrease of 75% (140 kt)
Figure 2–3: Trends in Canadian NOx Emissions (1990 to 2023)

Long description for Figure 2-3
Figure 2–3: Trends in Canadian Nitrogen Oxides Emissions for 1990 to 2023.
Figure 2–3 is a stacked area graph displaying the seven major contributors to national nitrogen oxides trends. They are the following: Domestic Marine Navigation, Fishing and Military, Rail Transportation, Light-Duty Gasoline Trucks and Vehicles, Coal (Electric Power Generation), Heavy-Duty Diesel Vehicles, Off-Road Diesel Vehicles and Equipment, Other, and Upstream Oil and Gas Industry. The figure shows that Other and Upstream Oil and Gas Industry have the biggest shares in the total national nitrogen oxides emissions in 2023. The following table displays the contributions (kt) for the years 1990 to 2023.
Sector | 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Upstream Oil and Gas Industry | 308 | 303 | 322 | 346 | 377 | 396 | 409 | 453 | 468 | 484 | 427 | 419 | 419 | 461 | 392 | 397 | 401 | 424 | 435 | 431 | 425 | 439 | 431 | 436 | 446 | 447 | 439 | 447 | 453 | 452 | 427 | 422 | 427 | 432 |
Other | 724 | 703 | 703 | 700 | 714 | 714 | 718 | 727 | 715 | 720 | 740 | 711 | 738 | 700 | 679 | 636 | 558 | 548 | 512 | 474 | 500 | 488 | 454 | 441 | 435 | 422 | 408 | 417 | 416 | 412 | 382 | 386 | 390 | 397 |
Off-Road Diesel Vehicles and Equipment | 305 | 276 | 265 | 279 | 294 | 298 | 306 | 322 | 312 | 316 | 333 | 311 | 293 | 296 | 291 | 288 | 266 | 246 | 233 | 200 | 221 | 226 | 211 | 206 | 191 | 201 | 188 | 202 | 197 | 185 | 156 | 151 | 142 | 132 |
Heavy-Duty Diesel Vehicles | 336 | 312 | 315 | 330 | 365 | 396 | 407 | 430 | 426 | 431 | 414 | 379 | 375 | 397 | 395 | 399 | 382 | 387 | 382 | 367 | 359 | 320 | 287 | 271 | 253 | 213 | 177 | 165 | 160 | 145 | 124 | 127 | 123 | 119 |
Coal (Electric Power Generation) | 206 | 205 | 211 | 192 | 188 | 198 | 208 | 222 | 235 | 227 | 225 | 220 | 215 | 209 | 194 | 186 | 173 | 181 | 169 | 151 | 153 | 132 | 126 | 124 | 129 | 115 | 117 | 110 | 92 | 88 | 66 | 62 | 52 | 46 |
Light-Duty Gasoline Trucks and Vehicles | 296 | 316 | 356 | 409 | 467 | 477 | 502 | 508 | 517 | 497 | 484 | 456 | 423 | 365 | 326 | 275 | 244 | 226 | 197 | 175 | 155 | 110 | 97 | 88 | 77 | 69 | 62 | 53 | 49 | 44 | 33 | 32 | 31 | 32 |
Rail Transportation | 147 | 149 | 145 | 144 | 153 | 149 | 146 | 148 | 143 | 139 | 140 | 139 | 137 | 123 | 122 | 126 | 125 | 120 | 114 | 96 | 102 | 101 | 100 | 95 | 94 | 87 | 79 | 79 | 79 | 79 | 71 | 67 | 66 | 68 |
Domestic Marine Navigation, Fishing and Military | 60 | 61 | 62 | 63 | 63 | 64 | 66 | 67 | 68 | 69 | 70 | 72 | 73 | 75 | 76 | 78 | 77 | 76 | 75 | 74 | 72 | 71 | 69 | 68 | 67 | 65 | 65 | 68 | 71 | 71 | 62 | 62 | 67 | 70 |
Table 2–5: National Summary of Annual NOx Emissions (tonnes)
Source | 1990 | 2000 | 2005 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 |
---|---|---|---|---|---|---|---|---|---|
Ore And Mineral Industries | 100,000 | 99,000 | 110,000 | 82,000 | 80,000 | 77,000 | 82,000 | 79,000 | 85,000 |
Oil And Gas Industry | 340,000 | 460,000 | 430,000 | 470,000 | 470,000 | 440,000 | 440,000 | 440,000 | 450,000 |
Downstream Oil and Gas Industry (Oil And Gas Industry) | 35,000 | 30,000 | 31,000 | 17,000 | 16,000 | 17,000 | 17,000 | 17,000 | 20,000 |
Upstream Oil and Gas Industry (Oil And Gas Industry) | 310,000 | 430,000 | 400,000 | 450,000 | 450,000 | 430,000 | 420,000 | 430,000 | 430,000 |
Electric Power Generation (Utilities) | 260,000 | 330,000 | 250,000 | 130,000 | 120,000 | 100,000 | 100,000 | 94,000 | 90,000 |
Coal (Electric Power Generation (Utilities)) | 210,000 | 230,000 | 190,000 | 92,000 | 88,000 | 66,000 | 62,000 | 52,000 | 46,000 |
Diesel (Electric Power Generation (Utilities)) | 3,200 | 8,500 | 8,500 | 9,800 | 9,900 | 9,800 | 8,400 | 9,800 | 11,000 |
Landfill Gas (Electric Power Generation (Utilities)) | 45 | 400 | 300 | 150 | 140 | 130 | 100 | 100 | 130 |
Natural Gas (Electric Power Generation (Utilities)) | 20,000 | 65,000 | 38,000 | 18,000 | 18,000 | 18,000 | 23,000 | 25,000 | 25,000 |
Other (Electric Power Generation) (Electric Power Generation (Utilities)) | 27,000 | 27,000 | 21,000 | 8,900 | 8,800 | 8,100 | 7,000 | 7,300 | 7,200 |
Manufacturing | 190,000 | 180,000 | 140,000 | 72,000 | 70,000 | 66,000 | 70,000 | 70,000 | 70,000 |
Transportation and Mobile Equipment | 1,300,000 | 1,600,000 | 1,300,000 | 610,000 | 580,000 | 490,000 | 480,000 | 480,000 | 470,000 |
Air Transportation (LTO) (Transportation and Mobile Equipment) | 5,100 | 5,900 | 5,900 | 7,500 | 7,500 | 3,800 | 4,100 | 6,400 | 7,100 |
Domestic Marine Navigation, Fishing and Military (Transportation and Mobile Equipment) | 60,000 | 70,000 | 78,000 | 71,000 | 71,000 | 62,000 | 62,000 | 67,000 | 70,000 |
Heavy-Duty Diesel Vehicles (Transportation and Mobile Equipment) | 340,000 | 410,000 | 400,000 | 160,000 | 150,000 | 120,000 | 130,000 | 120,000 | 120,000 |
Heavy-Duty Gasoline Vehicles (Transportation and Mobile Equipment) | 37,000 | 35,000 | 25,000 | 9,200 | 7,700 | 5,700 | 5,200 | 4,600 | 4,800 |
Heavy-Duty LPG/NG Vehicles (Transportation and Mobile Equipment) | 6,700 | 340 | 140 | 86 | 97 | 87 | 90 | 100 | 95 |
Light-Duty Diesel Trucks (Transportation and Mobile Equipment) | 4,000 | 7,900 | 5,800 | 720 | 670 | 590 | 660 | 680 | 650 |
Light-Duty Diesel Vehicles (Transportation and Mobile Equipment) | 1,900 | 2,300 | 1,700 | 230 | 220 | 180 | 190 | 200 | 180 |
Light-Duty Gasoline Trucks (Transportation and Mobile Equipment) | 110,000 | 230,000 | 150,000 | 31,000 | 29,000 | 22,000 | 21,000 | 21,000 | 22,000 |
Light-Duty Gasoline Vehicles (Transportation and Mobile Equipment) | 190,000 | 250,000 | 120,000 | 17,000 | 16,000 | 11,000 | 11,000 | 11,000 | 10,000 |
Light-Duty LPG/NG Trucks (Transportation and Mobile Equipment) | 290 | 50 | 25 | 6.3 | 5.3 | 3.1 | 3.7 | 3.5 | 3.7 |
Light-Duty LPG/NG Vehicles (Transportation and Mobile Equipment) | 0.95 | 0.69 | 0.20 | 0.073 | 0.072 | 0.12 | 0.23 | 0.20 | 0.23 |
Motorcycles (Transportation and Mobile Equipment) | 660 | 970 | 980 | 1,700 | 1,700 | 1,400 | 1,500 | 1,400 | 1,500 |
Off-Road Diesel Vehicles and Equipment (Transportation and Mobile Equipment) | 310,000 | 330,000 | 290,000 | 200,000 | 190,000 | 160,000 | 150,000 | 140,000 | 130,000 |
Off-Road Gasoline/LPG/NG Vehicles and Equipment (Transportation and Mobile Equipment) | 62,000 | 62,000 | 46,000 | 36,000 | 36,000 | 33,000 | 33,000 | 32,000 | 33,000 |
Rail Transportation (Transportation and Mobile Equipment) | 150,000 | 140,000 | 130,000 | 79,000 | 79,000 | 71,000 | 67,000 | 66,000 | 68,000 |
Tire Wear and Brake Lining (Transportation and Mobile Equipment) | NA | NA | NA | NA | NA | NA | NA | NA | NA |
Agriculture | 2,100 | 2,200 | 2,100 | 2,800 | 2,900 | 2,600 | 2,700 | 2,900 | 2,800 |
Commercial/Residential/Institutional | 63,000 | 70,000 | 68,000 | 67,000 | 68,000 | 62,000 | 59,000 | 62,000 | 58,000 |
Incineration And Waste | 6,700 | 6,700 | 7,900 | 4,300 | 4,400 | 5,200 | 4,600 | 4,600 | 3,700 |
Paints and Solvents | NA | NA | 35 | 15 | 51 | 40 | 35 | 140 | 140 |
Dust | NA | NA | NA | NA | NA | NA | NA | NA | NA |
Fires | 7,500 | 1,400 | 890 | 600 | 670 | 530 | 520 | 1,200 | 230 |
Grand Total | 2,200,000 | 2,700,000 | 2,300,000 | 1,400,000 | 1,400,000 | 1,300,000 | 1,200,000 | 1,200,000 | 1,200,000 |
Notes:
Totals may not add up due to rounding.
0.00 Indicates emissions were truncated due to rounding.
NA Indicates no emissions.