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Understanding the links between nitrogen dioxide (NO2) and our health
Nitrogen dioxide (NO2) is a gas which mainly gets into the air from the burning of fuel, including from vehicles and power stations. Breathing air with a high concentration of NO2 can cause or worsen respiratory problems. People with conditions such as asthma, and children and older people are at greater risk.
In order to gain a better understanding of the links between NO2 and our health, COMEAP has examined studies undertaken in a number of countries, as well as the UK. This report builds on previous statements published by COMEAP on NO2 in March and December 2015. It examines the effect that long-term exposure to NO2 might have on length of life.
We have attempted to develop an approach that could be used by government and others when developing and implementing policies to reduce air pollution so that the public health impact of these policies can be factored into their decisions.
We encountered a number of challenges in preparing this report. Firstly, there were differences between the studies, making it hard to compare them. In addition, other air pollutants, such as particulate matter, are also harmful when inhaled. These are often emitted from the same sources as NO2 (for example, traffic), leading to difficulties in assessing the effect of NO2 itself, on people’s health.
Therefore, not all of our conclusions are unanimous. This report presents the views of committee members who dissent from the majority view, as well as the views of the majority of members, to reflect this.
Despite these difficulties, we are recommending an approach that can be used, with caveats, by policymakers to estimate the size of the effect of NO2 on public health and to assess the impact of policies designed to reduce this.
We have applied expert judgement to develop this approach but it is based on a degree of speculation as well as hard evidence and so should be regarded as an approximation only.
COMEAP’s previous estimate of the mortality burden of human-made air pollution in the UK is an annual effect equivalent to nearly 29,000 deaths. The methodology of this present report allows for calculations to be made on the basis of either particulate matter known as PM2.5 (fine particles which are produced by power generation, vehicle engines and reactions in the atmosphere) or NO2, and using the higher of the two estimates. The results should not be added together as this would lead to an over-estimation of the effects.
The report also includes exploratory calculations based on both PM2.5 and NO2, using information from studies in which the overlap of effects associated with the 2 pollutants has been accounted for.
Using these 2 approaches, the range of estimates of the annual mortality burden of human-made air pollution in the UK is estimated as an effect equivalent to 28,000 to 36,000 deaths.