Small increase in NO2 linked to increased heart and respiratory deaths

Even small increases in nitrogen dioxide (NO2) levels could be linked to a heightened risk of cardiovascular and respiratory deaths, according to a new study published by The BMJ today. 

A team of international researchers analysed daily concentrations of NO2 in 398 cities in 22 low to high-income countries over a 45-year period.

There were a total of 62.8 million deaths over the 45-year study period, 31.5% of which were cardiovascular-related and 8.7% of which were respiratory-related. 

The researchers found that on average, a 10 µg/m3 increase in NO2 concentration on the previous day was associated with 0.46% and 0.37% increase in the total, cardiovascular, and respiratory deaths, respectively.

The researchers have estimated that the proportion of deaths attributable to NO2 concentrations was 1.23% across the 398 cities.

These associations did not change after adjusting for levels of other air pollutants, including sulphur dioxide, carbon monoxide, ozone, and fine particulate matter.

The researchers have highlighted that this is an observational study, so they can’t establish cause, but have highlighted that it provides a significant insight into the public health benefits of reducing NO2 pollution. 

The authors said: ‘This analysis provides robust evidence for the independent associations of short term exposure to NO2 with increased risk of total, cardiovascular and respiratory mortality .. suggesting a need to revise and tighten the current air quality guidelines of NO2 for greater public health benefit, and to consider a regulation limit for daily mean NO2 concentration.

‘These findings contribute to a better understanding of how to optimise public health actions and strategies to mitigate air pollution.’