Black Carbon

Primary reference(s)

UNEP, 2019. Air Pollution in Asia and the Pacific: Science-based Solutions. Accessed 14 March 2025.

Annotations

Key relevant UN convention / multilateral treaty

UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP): Since 1979 the Convention on Long-range Transboundary Air Pollution has addressed some of the major environmental problems of the United Nations Economic Commission for Europe (UNECE) region through scientific collaboration and policy negotiation (UNECE, 1979). The Convention has been extended by eight protocols that identify specific measures to be taken by Parties to cut their emissions of air pollutants. The Convention, which now has 51 Parties, identifies the Executive Secretary of UNECE as its secretariat. In addition to

Arctic Council Fairbanks Declaration, 2017.(https://www.ccacoalition.org/resources/arctic-council-fairbanks-declara…)

Drivers

Black carbon is formed by the incomplete combustion of fossil fuels, biomass and biofuels. Sources include: mobile sources, particularly diesel driven road vehicles, nonroad mobile machinery and ships; residential heating in combustion facilities, particularly burning of biomass such as fossil fuel coal and wood; and open biomass burning, forest fires and agricultural waste burning (EEA, 2013). Household waste burning is also a source of black carbon (Ramadan et al., 2023).

Impacts

Black carbon is a major component of PM₂.₅ pollution, often making up 10–30% of measured PM₂.₅ concentrations. As a harmful air pollutant, black carbon significantly contributes to the 4 million premature deaths from outdoor air pollution, the 3 million deaths from household air pollution and the trillions of dollars of economic cost (6% of global GDP) each year. There is growing evidence on the health impacts of exposure to black carbon specifically, which builds on a plethora of evidence on PM₂.₅ more broadly. Assuming all components of PM₂.₅ are equally toxic, outdoor/ambient black carbon exposure is estimated to be responsible for 150,000 excess deaths annually worldwide. Black carbon can also worsen extreme heat conditions and increase the risk of heatwave-related mortality. Black carbon has been linked to the increased temperature of heatwaves. Also, exposure to elevated levels of air pollution and black carbon has been shown to increase the risk of mortality from heatwaves. It is estimated that when particulate matter concentrations were high, heatwaves caused 36% and 106% more deaths in the 75–84 and 85+ age groups, respectively (Muduchuru et al., 2024). Full implementation of the reduction of black carbon emission in all Arctic Council member and observer states could reduce the annual global number of premature deaths by 329,000 by the year 2030, which amounts to 9% of the total global premature deaths due to particulate matter (Kühn et al., 2020). 

Black carbon is a major contributor to the fine particulate (PM₂.₅) burden in the air. It is small enough to be easily inhaled into the lungs and has been associated with adverse health effects. The Near-Road Exposures to Urban Air Pollutants Study (NEXUS) evaluated that peat-burning wildfires release enormous amounts of particulate matter, including black carbon, which has been linked to increased risk of heart failure and respiratory hospital visits (US EPA, 2019). 

Black carbon emissions affect global warming, snow and ice melt, monsoon and weather patterns, flood risk, heat stress and public health. The potential benefits of reducing the emissions are felt most strongly close to the source. The dual nature of black carbon as a climate and air pollutant has resulted in neither of these fields taking full ownership. Therefore, black carbon remains largely absent from mainstream climate and health agendas (Muduchuru et al., 2024). More specifically, black carbon affects atmospheric radiative forcing through three distinct mechanisms: aerosol–radiation interactions, aerosol–cloud interactions, and snow darkening. Black carbon significantly influences regional surface temperatures, particularly in the Arctic, and has a substantial warming effect on the cryosphere, estimated to be approximately three times more potent than that of CO₂. Black carbon is also a significant contributor to regional precipitation changes and has been shown to drive the slowdown of the hydrological cycle, leading to drier conditions. 

The darkening of snow through the deposition of black carbon and other light‑absorbing particles enhances snowmelt. Sectors that emit large amounts of methane (agriculture and waste management) and black carbon (residential biofuel) are important contributors to warming over short time horizons of up to 20 years (Szopa et al., 2021).

Multi-hazard context

The figure below summarises common interactions between black carbon and other hazards. This information should be used with caution and not be solely relied upon in disaster risk management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.

Multi-hazard diagram

Risk Management

Control measures: recommended measures include requiring regular vehicle emissions tests, retirement, or retrofitting; banning or regulating slash-and-burn clearing of forests and burning of agricultural waste; requiring shore-based electrification/power of ships, regulating idling at terminals, and mandating fuel standards for ships seeking to dock; banning or regulating the sale of certain fuels and/or requiring the use of cleaner fuels; requiring permits to operate industrial, power-generating and oil-refining facilities, and periodic permit renewal and/or modification of equipment; and requiring filtering technology and high-temperature combustion for existing power generation plants (EEA, 2013).

The Climate and Clean Air Coalition (CCAC) is a voluntary partnership of over 190 governments, intergovernmental organizations, and non-governmental organizations founded in 2012, and convened within UNEP. Collectively and individually, partners who join the Climate and Clean Air Coalition are working to reduce powerful but short-lived climate pollutants (SLCPs) – methane, black carbon, hydrofluorocarbons (HFCs), and tropospheric ozone – that drive both climate change and air pollution. (https://www.ccacoalition.org/content/climate-and-clean-air-coalition).

The Clean Cooking Alliance (CCA) works with a global network of partners to build an inclusive industry that can make clean cooking accessible to all. Established in 2010, CCA is driving consumer demand, mobilising investment, and supporting policies that allow the clean cooking sector to thrive. (https://cleancooking.org/).

Monitoring

Air quality monitoring networks: the status of black carbon monitoring in Europe has been reported by the European Environment Agency (EEA, 2013).