Health effects of black carbon

Warning - Black carbon can seriously damage your health. Photo: Esther Simpson / Creative Commons

Reducing people’s exposure to PM_2.5 containing black carbon should lead to a reduction in the health effects associated with PM.

Exposure to black carbon is linked to health impacts such as cardiopulmonary morbidity and mortality, and reducing people’s exposure to particles containing black carbon will therefore also reduce such adverse health impacts, according to a recent report published by the World Health Organization (WHO).

Prepared for the Task Force on Health Aspects of Air Pollution under the Convention on Long-range Transboundary Air Pollution, the report was produced as input to the revision of the Convention’s Gothenburg Protocol (see article on front page), and it presents the results of a systematic review of evidence of the health effects of black carbon in ambient air.

The report concludes that toxicological studies suggest that black carbon may operate as a universal carrier of a wide variety of chemicals of varying toxicity to the human body, and that reducing people’s exposure to particulate matter containing black carbon should reduce its effects on their health.

Black carbon (BC) is said to be an operationally defined term, which describes carbon as measured by light absorption, and as such it is not the same as elemental carbon (EC), which is usually monitored with thermal-optical methods. As yet, there are no generally accepted standard methods to measure BC or EC in atmospheric aerosol, so there is a need for standardisation.

The main sources of black carbon emissions are diesel-driven combustion engines (in road vehicles, non-road mobile machinery and ships), residential burning of wood and coal, power stations using heavy oil or coal, field burning of agricultural wastes, as well as forest and vegetation fires.

Due to the location of these sources, the spatial variation of BC in ambient air is greater than that of PM2.5, but in general ambient measurements or model estimates of BC are said to reflect personal exposures reasonably well and with similar precision as for PM2.5.

The review was carried out by a number of experts selected by the WHO. After reviewing the available time-series studies, as well as information from panel studies, it was concluded that these provided sufficient evidence of an association of short-term (daily) variations in BC concentrations with short-term changes in health (all-cause and cardiovascular mortality, and cardiopulmonary hospital admissions). Furthermore that cohort studies provided sufficient evidence of associations of all-cause and cardiopulmonary mortality with long-term average BC exposure.

Studies of short-term health effects showed that the associations with BC are more robust than those with PM_2.5 or PM₁₀, suggesting that BC is a better indicator of harmful particulate substances from combustion sources (especially traffic) than undifferentiated PM mass. The evidence from long-term studies was however inconclusive – in one of the two available cohort studies using multi-pollutant models in the analysis, the effect estimates for BC were stronger than those for sulphates, while an opposite order in the strength of relationship was suggested in the other study.

According to the report, there are not enough clinical or toxicological studies to allow an evaluation of the qualitative differences between the health effects of exposure to BC or to PM mass (for example, different health outcomes), or to allow quantitative comparison of the strength of the associations or identification of any distinctive mechanism of BC effects.

The review of the results of all available toxicological studies suggested that BC (measured as EC) may not be a major directly toxic component of fine PM, but it may operate in particular, as a universal carrier of a wide variety of combustion-derived chemical constituents of varying toxicity to sensitive targets in the human body such as the lungs, the body’s major defence cells and possibly the systemic blood circulation.

Based on these findings, the Task Force on Health agreed that a reduction in exposure to PM_2.5 containing BC and other combustion-related PM material for which BC is an indirect indicator should lead to a reduction in the health effects associated with PM. The Task Force therefore recommended that PM_2.5 should continue to be used as the primary metric in quantifying human exposure to PM and the health effects of such exposure, and for predicting the benefits of exposure reduction measures. It also recommended that the use of BC as an additional indicator may be useful in evaluating local action aimed at reducing the population’s exposure to combustion PM.

Christer Ågren

Health effects of black carbon. By Nicole AH Janssen, Miriam E Gerlofs-Nijland, Timo Lanki, Raimo O Salonen, Flemming Cassee, Gerard Hoek, Paul Fischer, Bert Brunekreef and Michal Krzyzanowski. Available from WHO: http://www.euro.who.int/en/what-we-publish/abstracts/health-effects-of-black-carbon

In this issue

Editorial: Still a long way to go

In early May, after five years of negotiation, countries in Europe and North America agreed to take on new emission reduction commitments for the major air pollutants, by adopting a revised Gothenburg Protocol to the Convention on Long-range Transboundary Air Pollution ..

Health effects of black carbon

Reducing people’s exposure to PM_2.5 containing black carbon should lead to a reduction in the health effects associated with PM.

Air pollution from traffic kills 5000 a year in UK

Premature deaths due to PM_2.5 are estimated to cost the UK between €7.5-77 billion every year, corresponding to 0.4-3.5 per cent of the country’s gross domestic product.

Ozone levels still much too high

In the summer of 2011, the threshold for protecting human health from ozone was exceeded on more than 25 days in a significant part of Europe.

Europe’s most polluting power plants

Eight of the twelve largest single sources of carbon dioxide in Europe are found in Germany.

The arrival of a new EU sulphur law

The sulphur content of ship fuels will be cut to 0.1% from 2015 in the Baltic Sea and the North Sea, and to 0.5% from 2020 in other EU waters. As a result, emissions of sulphur dioxide from shipping in Europe will come down by more than 80 per cent.

Welcome to the golden age of fracking

Fracking, exploitation of gas from shale, is growing fast. This is game-changing both for energy policy and climate policy. There is now more, and dirtier fossil gas around. The resistance is also growing, and fracking is banned in some countries.

Biggest environmental cause of mortality

A new OECD report says that by 2050 air pollution will become the biggest cause of premature death, killing an estimated 3.6 million people a year.

New Danish energy agreement

A massive expansion of wind power, reforms to promote biomass and an expansion of mandatory energy savings are the main features of the Danish energy agreement. The measures combined are estimated to reduce carbon dioxide emissions by 34 per cent by 2020.

Improvements from the revison

Emission cuts under the new Gothenburg Protocol are expected to reduce health damage in Europe from PM_2.5 and ozone by 27 and 11 per cent, respectively, between 2000 and 2020.

New Gothenburg Protocol adopted

Between 2005 and 2020 the EU member states must jointly cut their emissions of sulphur dioxide by 59%, nitrogen oxides by 42%, ammonia by 6%, volatile organic compounds by 28% and particles by 22%.

Main menu

Health effects of black carbon

In this issue

Editorial: Still a long way to go

Health effects of black carbon

Air pollution from traffic kills 5000 a year in UK

Ozone levels still much too high

Europe’s most polluting power plants

The arrival of a new EU sulphur law

Welcome to the golden age of fracking

Biggest environmental cause of mortality

New Danish energy agreement

Improvements from the revison

New Gothenburg Protocol adopted

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The 100 largest industry emitters in EU-27

Road to Nowhere

Bioenergy CCS – too little, too expensive, and not net negative

Direct air carbon capture and storage - A waste of time and energy

Carbon emissions from the cement industry can be reduced without CCS

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