Air pollution responsible for more than 1 in 10 deaths in Delhi
A new study has found that across ten major cities in India, around 7% of all deaths can be linked to air pollution, a figure that rises to 11.5% in Delhi.
The team had access to a dataset of 3.6 million deaths across the ten cities and generated daily average PM2·5 concentrations at 1 km2 spatial resolution, from 2008 to 2020, using a hybrid ensemble averaging approach.
Using population-weighted exposure metrics, they were able to generate causal estimates for the association between PM2·5 and mortality.
The results showed a clear association between daily PM2·5 exposure and increased risk of mortality, with a total of 7.2 % of all deaths in these cities, (33,000 per year) linked to PM2.5 levels above the World Health Organization limit value.
It was found that a 10 μg/m³ increase in PM2.5 levels over two days increased the number of deaths by 1.42%, a figure that rose to 3.57% when a causal modelling approach was used, isolating the impact of local sources of air pollution, such as transport and industries.
Petter Ljungman, senior researcher at the Institute of Environmental Medicine, Karolinska Institutet and one of the study’s main authors said: ‘Interestingly, we found that local sources of pollution are likely to be more toxic than more distant sources, pointing to the importance of addressing both local and regional air pollution levels.
‘Our findings have implications for policymakers dealing with this highly relevant threat to human health. Year-round, nationwide action will be required to address the problem.’
In a country where the limit value for PM2.5 is four times higher than the WHO limit (60 μg/m³ as opposed to 15 μg/m³) it is worrying that the mortality risk was seen to increase rapidly at lower pollution levels before levelling off.
The WHO limit value was found to have been exceeded on 99.8% of days across the study period.
Many cities in India have introduced Graded Response Action Plans, a set of emergency measures that are triggered as air quality deteriorates. However these action plans kick in at high levels of air pollution (often above 150 μg/m³) which, they say, would only yield marginal benefits with respect to daily mortality, with negative health effects continuing to accrue even at lower pollution concentrations
Jeroen de Bont, postdoctoral researcher at the Institute of Environmental Medicine, Karolinska Institutet and one of the study’s main authors said: ‘Air pollution in India is extremely high and our study clearly shows how day-to-day variations in pollution levels can be linked to increased mortality. The results show that there is no safe threshold for air pollution but underscore that the limit value in India needs to be reviewed.’
The fell research can be read here
