Derry has been named among 40 cities in the UK which are at or have exceeded air pollution limits set by the World Health Organization (WHO).
The WHO data shows 31 areas have fine particle air pollution levels above 10 micrograms per cubic metre, with another 15 at that limit.
The report lists Derry as having a figure of 11.
Areas that exceeded the level include London and Manchester, with the Welsh steelworks town Port Talbot the worst.
Dirty air can cause debilitating diseases and hasten death.
Fine air particle pollution is particularly bad for us, penetrating deep into the lungs and cardiovascular system, causing diseases including stroke, heart disease, lung cancer and respiratory infections, the WHO says.
The world's most polluted city in 2015, according to the WHO, was Muzaffarpur in India, with a figure of 197 micrograms per cubic metre - although that figure is under revision.
Pasakha in Bhutan, Delhi in India, and greater Cairo, Egypt, also had very high levels.
Many of the recordings were made in 2015 or earlier.
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