Bergen, Norway, is an example of a city surrounded by mountains where the air quality can get very bad, terrible for asthmatics. This phenomenon is called inversion. Before the symptoms begin, the asthmatic person may alleviate the symptoms by measures such as traveling to locations with inversion during summer and observing bad geographic landscapes so avoiding them altogether such as strong winds blowing directly to valleys with clouds very low, hardly seeing sun. Instead of asking directly list-style question "What are cities in the world that asthmatics should avoid due to poor air quality?":

What are the measures an asthmatic traveller can make to choose new travelling locations not affected by inversion?

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    There is a list of world's most polluted list of cities. That is a place to start from. And winter exacerbates pollution.
    – DumbCoder
    Mar 13, 2016 at 10:47
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    The particular effect you've mentioned is caused an [inversion](en.wikipedia.org/wiki/Inversion_(meteorology). I've linked to the Wikipedia article. I thought Denver also had issues (but it's not on the list.
    – mkennedy
    Mar 13, 2016 at 19:24
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    The problem in Bergen seems to be caused by wood stoves, not cars. "Recently, the Norwegian Institute for Air Research (NILU) published statistics showing that “particulate matter from log burning in cities is more dangerous than pollution from traffic”. Research by Statistics Norway (SSB), meanwhile, concluded that 61% of the particulate matter in Norway’s air stems from its 1.7 million existing log fires, compared to 39% from private vehicles, buses and lorries." Mar 13, 2016 at 20:54
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    @mkennedy LA is more complicated. The northern part is in the San Fernando Valley, surrounded by mountains, and the central part is in the LA Basin, with mountains to the NW, N, and NE. The LA basin as a whole has mountains on all sides but the SW (facing the ocean). Also, in my limited experience, Denver is much windier than LA, especially at the edge of the front range. But I've never been there in the summer, and an image search for "Denver smog" yields some pretty impressive pictures, so maybe it should be on the list.
    – phoog
    Mar 14, 2016 at 19:40
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    Avoid France, there is no regulation at all about wood burning. Anyone can burn his trash in his woodstove without any risk (villages are the worst). And avoid especially the French Alpes, the air pollution is literally deadly (you won’t hear about it because these info would greatly damage the French tourism revenues. Some French have been threatened on their own life to talk about it in the Alpes, because of that. One of these guys was a doctor.)
    – JinSnow
    Apr 17, 2016 at 5:35

2 Answers 2


I would recommend looking at this live and historical dataset of air quality, mapped out globally. Values over 100 indicate the air quality could be problematic for sensitive groups, such as asthmatics. . It's important to note that air quality varies a lot based on time of year, weather, etc. so look at the values for the same dates as you plan to travel will give you a good idea of what cities to avoid.


The Air Quality Index

There are several air quality monitoring websites out there. These use an Air Quality Index (AQI) ranging from 0 to 500, where a 0 indicates good air quality, and 500 indicates hazardously unhealthy air, as detailed in the table below:

Air Quality Index colours explained

Worldwide Air Quality Monitors

The World Air Quality Index Team runs an online real-time world map of air quality. They are a China-based organisation which collaborates with Chinese, American, and worldwide Environment Protection Agencies to gather and publish air quality data.

Another tool is provided by CITEAIR who runs a website showing a comparison on air quality in European cities.

The World Health Organisation maintains an Global Urban Ambient Air Pollution Database whose summary data can be downloaded and analysed.

You could also look at the data collected and published by the US Environment Protection Agency, which provides both raw and summary data. The EPA website also allows you to generate data plots for easier visualisation.

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