International comparison: air pollutant emissions in selected countries

Sulphur oxides

Key results

In 2021, Canada:

• saw a decrease of 47% in sulphur oxides (SO_X) emissions from 2011 levels
• ranked 4th highest in SO_X emissions among OECD member countries
• had the 3rd highest ratio of SO_X emissions to gross domestic product among the top 10 emitting OECD member countries

Sulphur oxides emissions and emissions intensity of the top 10 emitting member countries of the Organisation for Economic Co-operation and Development, 2011 and 2021

How this indicator was calculated

Note: Definitions of pollution sources and estimation methods may differ from country to country. Comparisons should be made with caution. Gross domestic product values are in millions of constant United States dollars, constant purchasing power parity, for the base year 2015. The use of purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.
Source: Organisation for Economic Co-operation and Development (2024) OECD.Stat.

Although Canada's SO_X emissions declined by 563 kilotonnes from 2011 to 2021, Canada ranked as one of the highest emitters among OECD member countries, behind Türkiye, Australia, and the United States. Of the top 10 emitters, the United States experienced the largest decrease (4 088 kilotonnes, or 71%), driven by reduced emissions from the coal-fired electricity production industry. Except for Türkiye, all of the other top 10 emitting member countries experienced declines in emissions between 2011 and 2021.

In terms of the ratio of SO_X emissions to gross domestic product, all top 10 emitting member countries reported declines ranging between 30% and 76% from 2011 to 2021.

Note that, in 2011, South Korea and Colombia were the 7th and 9th highest in SO_X emissions among OECD member countries with 434 kilotonnes and 401 kilotonnes, respectively. Since no data was available for 2021, South Korea and Colombia are not represented in the comparison as the top 10 emitting countries are based on 2021 emissions.

Nitrogen oxides

Key results

In 2021, Canada:

• saw a decrease of 27% in nitrogen oxides (NO_X) emissions from 2011 levels
• ranked 3rd highest in NO_X emissions among OECD member countries
• had the 2nd highest ratio of NO_X emissions to gross domestic product among the top 10 emitting OECD member countries

Nitrogen oxides emissions and emissions intensity of the top 10 emitting member countries of the Organisation for Economic Co-operation and Development, 2011 and 2021

How this indicator was calculated

Note: Definitions of pollution sources and estimation methods may differ from country to country. Comparisons should be made with caution. Gross domestic product values are in millions of constant United States dollars, constant purchasing power parity, for the base year 2015. The use of purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.
Source: Organisation for Economic Co-operation and Development (2024) OECD.Stat.

In 2021, Canada ranked as one of the highest emitters among OECD member countries, behind the United States and Australia, despite a reduction of 483 kilotonnes in NO_X emissions between 2011 and 2021. Of the top 10 emitting members, the United States experienced the largest reduction over that period (6 268 kilotonnes, or 48%). In 2021, emissions from Australia and Türkiye were higher than in 2011 (+22% and +3%, respectively).

Emissions intensity, the ratio of NO_X emissions to gross domestic product, was lower in 2021 than it was in 2011 for all top 10 emitting member countries. The reductions in intensity were between 3% and 58%.

Note that, in 2011, South Korea was the eighth highest in NO_X emissions among OECD member countries with 1 040 kilotonnes. Since no data was available for 2021, South Korea is not represented in the comparison as the top 10 emitting countries are based on 2021 emissions.

Carbon monoxide

Key results

In 2021, Canada:

• saw a decrease of 27% in carbon monoxide (CO) emissions from 2011 levels
• ranked 2nd highest in CO emissions among OECD member countries
• had the 2nd highest ratio of CO emissions to gross domestic product among the top 10 emitting OECD member countries

Carbon monoxide emissions and emissions intensity of the top 10 emitting member countries of the Organisation for Economic Co-operation and Development, 2011 and 2021

How this indicator was calculated

Note: Definitions of pollution sources and estimation methods may differ from country to country. Comparisons should be made with caution. Gross domestic product values are in millions of constant United States dollars, constant purchasing power parity, for the base year 2015. The use of purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.
Source: Organisation for Economic Co-operation and Development (2024) OECD.Stat.

In 2021, the United States was the highest CO emitting country, followed by Canada. Except for Japan, all the top 10 emitting member countries of the OECD experienced declines in emissions between 12% and 39% in 2021 from 2011 levels.

Declines were also observed in the ratio of CO emissions to gross domestic product between 2011 and 2021; they ranged from 4% to 63% for the top 10 emitting countries.

Volatile organic compounds

Key results

In 2021, Canada:

• saw a decrease of 21% in volatile organic compounds (VOC) emissions from 2011 levels
• ranked 3rd highest in VOC emissions among OECD member countries
• had the 3rd highest ratio of VOC emissions to gross domestic product among the top 10 emitting OECD member countries

Volatile organic compounds emissions and emissions intensity of the top 10 emitting member countries of the Organisation for Economic Co-operation and Development, 2011 and 2021

How this indicator was calculated

Note: Definitions of pollution sources and estimation methods may differ from country to country. Comparisons should be made with caution. Gross domestic product values are in millions of constant United States dollars, constant purchasing power parity, for the base year 2015. The use of purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.
Source: Organisation for Economic Co-operation and Development (2024) OECD.Stat.

Although Canada's VOC emissions declined by 366 kilotonnes between 2011 and 2021, Canada ranked as one of the highest emitters among the member countries of the OECD, behind the United States and Chile. Most of the top 10 emitting member countries experienced declines in emissions between 2011 and 2021, with the exception of Türkiye whose emissions increased by 9%.

The reductions in emissions intensity range from 5% to 36% between 2011 and 2021 for the top 10 emitting member countries.

Fine particulate matter

Key results

In 2021, Canada:

• saw an increase of 5% in fine particulate matter (PM_2.5) emissions from 2011 levels
• ranked 2nd highest in PM_2.5 emissions among OECD member countries
• had the highest ratio of PM_2.5 emissions to gross domestic product among OECD member countries

Fine particulate matter emissions and emissions intensity of the top 10 emitting member countries of the Organisation for Economic Co-operation and Development, 2011 and 2021

How this indicator was calculated

Note: Definitions of pollution sources and estimation methods may differ from country to country. Canada and the United States include open sources such as dust from roads, prescribed forest burning and agriculture in their PM_2.5 emissions. These sources are not always reported by other OECD member countries. Comparisons should be made with caution. Gross domestic product values are in millions of constant United States dollars, constant purchasing power parity, for the base year 2015. The use of purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.
Source: Organisation for Economic Co-operation and Development (2024) OECD.Stat.

Of the top 10 emitting member countries, Canada is the only country that experienced an increase in PM_2.5 emissions from 2011 to 2021. Despite this increase in emissions, all the top 10 member countries experienced declines in their emissions intensity, which decreased between 8% and 46%, from 2011 to 2021.

Canada and the United States include open sources^{Footnote 1}  such as dust from roads, prescribed forest burning and agriculture in their PM_2.5 emissions. These sources are not always reported by other OECD member countries.

Note that, in 2011, Colombia was the 8th highest in PM_2.5 emissions among OECD member countries, with 191 kilotonnes. Since no data was available for 2021, Colombia is not represented in the comparison as the top 10 emitting countries are based on 2021 emissions.

At the time of this update the OECD.Stat database contained emissions data up to the end of 2021, reflecting delays in the collection and aggregation of international data. Data are collected for each member country from the following sources:

• the Centre on Emission Inventories and Projections database (as of August 2023) of the Convention on Long-Range Transboundary Air Pollution
• the National Inventory Submissions 2023 (as of August 2023) of the United Nations Framework Convention on Climate Change
• the replies to the OECD Questionnaire on the State of the Environment and comments from member countries received before September 2023

The OECD.Stat database indicates the source used to report emissions for each country, pollutant, and year.

Air pollutant emissions indicators

Emissions for each member country are estimated or measured using one or several of the following methods:

• continuous emission monitoring systems
• predictive emission monitoring
• source testing
• mass balance
• site-specific emission factors
• published emission factors
• engineering estimates
• special studies

Generally, each country compiles and estimates its air pollutant emissions combining facility-level emissions (aka point sources) with sector-level emissions (or area sources).

Canada's data are derived from the annual Convention on Long-Range Transboundary Air Pollution submission to the Centre on Emission Inventories and Projections database. The submitted air pollutant emission data are based on Canada's Air Pollutant Emission Inventory. This includes information reported by facilities to the National Pollutant Release Inventory as well as emission estimates compiled for non-reporting facilities, non-reporting sources such as motor vehicles or non-reported pollutants (in-house emissions estimates).

Air pollution emissions per unit of gross domestic product

The emissions intensity indicators are expressed in tonnes of pollutants emitted per million United States dollars using constant gross domestic product at purchasing power parity for the base year 2015. Purchasing power parity is a weighted average of the relative prices, quoted in national currency, of comparable items between countries. Using purchasing power parity facilitates international comparison of gross domestic product by creating an equivalent purchasing power basis for each country compared.

Countries included in the comparison

The indicators include all member countries of the OECD as of February 2024. The data presented in the indicator reflect data completeness in the OECD.Stat database at the time of reporting.