The analysis, for 2023, is part of the 6th Annual Report on Air Quality in the World, carried out by IQAir, a Swiss technology organisation whose mission is to empower people, organisations and governments to improve air quality.

IQAir used data from 30,000 air quality monitoring stations in 7,812 locations in 134 countries, territories and regions.

In last place, comes Bangladesh, followed by Pakistan, India, Tajikistan and Burkina Faso.

To prepare the list, the organisation's main indicator is the so-called fine particles (PM2.5), measured in micrograms per cubic meter. They are linked in particular to combustion engines and have significant impacts on human health.

According to the report, Bangladesh had 79.9 micrograms per cubic meter of annual average, more than 15 times higher than that approved by the World Health Organization (WHO), which recommends a maximum of five micrograms.

In the European Union, the maximum permitted levels are 25 micrograms.

On the map of countries, on a color scale where the best positions are in green, there are more than 90 with a less than good classification.

Russia (10 micrograms, in position 94) is the first nation in green, followed by others such as Spain (9.9 micrograms), France in position 99 (9.5 micrograms), and the United Kingdom (7 .7 micrograms). Portugal, in position 118, accounts for 6.8 micrograms.

The best classification goes to French Polynesia, in place 134, with 3.2 micrograms of fine particles per cubic meter.

This means that only 16 countries/regions have better air than Portugal, in the list now released.

By capital cities, New Delhi, in India, is the most polluted, followed by Dhaka, in Bangladesh, and Ouagadougou, in Burkina Faso. Rome, Berlin and Paris are on the yellow list and Lisbon appears on the green list, ahead of other green capitals such as London, Madrid, Copenhagen or Luxembourg.