A new study published in the BMJ links nitrogen dioxide air pollution to increased cardiovascular and respiratory deaths.
- Researchers collected data from 398 cities in 22 countries/regions around the world for 45 years to estimate the long-term effects of nitrogen dioxide on human health.
- A 10 µg/m3 increase in nitrogen dioxide concentration is associated with an increase of 0.46% in total deaths, 0.37% in cardiovascular deaths and 0.47% in respiratory deaths.
- Researchers attribute 1.23% of recorded deaths to a nitrogen dioxide concentration above zero.
Highly harmful to the environment by causing, in particular, acid rain and by participating in the degradation of the ozone layer and the greenhouse effect, nitrogen dioxide (NO2) is also particularly harmful to human health. .
Released during the combustion of fossil fuels, in particular during motorway traffic, nitrogen dioxide is notably responsible for the formation of fine particles in the ambient air. Many studies have already shown that it is involved in respiratory disorders, chronic conditions such as asthma and in disturbances of oxygen transport in the blood, by binding to hemoglobin, which has the effect decrease lung function.
Nitrogen dioxide is measured in micrograms (one millionth of a gram) per cubic meter of air or µg/m3. World Health Organization (WHO) air quality guidelines currently recommend that nitrogen dioxide levels should not exceed an annual average of 40-40 µg/m3.
In a new study, published in the British Medical Journal (BMJ), an international team of researchers shows that the slightest increase in nitrogen dioxide levels in the air could be linked to an increase in cardiovascular and respiratory deaths.
1.23% of deaths attributable to nitrogen dioxide pollution
To reach this conclusion, the researchers studied the long-term effects of NO2 by recording total, cardiovascular and respiratory deaths in 398 cities in 22 low- and high-income countries/regions of the world. Their results are based on NO2 concentrations in these 398 cities, sampled daily from 1973 to 2018.
Daily weather data, including average temperature and humidity, was also recorded, and death records were obtained from local authorities in each country and/or region.
A total of 62.8 million deaths were recorded over the 45-year study period. 19.7 million (31.5%) were deaths related to cardiovascular disease and 5.5 million (8.7%) were respiratory deaths.
On average, a 10 µg/m3 increase in NO2 concentration the previous day was associated with a 0.46%, 0.37%, and 0.47% increase in total, cardiovascular, and respiratory deaths, respectively.
The researchers point out that these associations did not change after adjusting for levels of other common air pollutants, such as sulfur dioxide, carbon monoxide, ozone and fine particles of different sizes.
From all these data, the researchers therefore estimate that the proportion of deaths attributable to a concentration of NO2 above zero level was 1.23% in the 398 cities.
A need to strengthen air quality guidelines
The researchers point out that this is an observational study, and that it therefore does not establish with certainty a causal link. However, its realization on a very large scale, and over a period of 45 years “gives it enormous statistical power and guarantees the stability of the results, and the uniformity of the methods of analysis, which allows more reliable comparisons between different regions and populations”they point out.
The authors claim that their analysis “provides strong evidence for independent associations of short-term NO2 exposure with increased risk of total, cardiovascular, and respiratory mortality…suggesting a need to revise and strengthen current air quality guidelines of NO2 for greater benefit to public health, and to consider a regulatory limit for the average daily concentration of NO2”.
“These results contribute to a better understanding of how to optimize public health actions and strategies to mitigate air pollution”they conclude.
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