Which City Has the Lowest AQI?

Air pollution is a serious concern around the world, with more than seven million people losing their lives prematurely due to exposure to contaminated air. In fact, it’s estimated that over 90% of the global population breathe dirty air on a daily basis! Significant advances in urban air quality monitoring have revealed that an overwhelming majority of our towns and cities are plagued by poor quality air.

Having said that, there are certain parts of the globe where geographical topography, cultural norms and governmental initiatives have contrived to improve the air breathed in by the local residents. Here’s a quick rundown of four cities with least polluted air worldwide, as collated by the US Air Quality Index (AQI). According to this sophisticated system of collecting, assimilating and presenting air quality data, the lower the value, the cleaner the air – and these four metropoles boast some of the cleanest around.

Honolulu, Hawaii

In 2019, the Hawaiian capital of Honolulu posted a median AQI score of 29, with a record 339 days of “Good” air quality and not one single “Unhealthy” or “Hazardous” day. In fact, the highest the AQI ever reached in 2019 was 98, meaning it never even ventured beyond “Moderate” air quality. That makes it the cleanest city in the US and one of the cleanest in the world in terms of air pollution. The reason? The strong trade winds which carry contaminants out to sea, alongside the dearth of local industry and the remoteness of the islands from other industrial epicentres.

Zurich, Switzerland

In 1986 – long before many other supposedly progressive parts of the world woke up to the imminent dangers posed by poor air quality – the Swiss government introduced a number of traffic-calming and pollution-curbing measures in Zurich and other cities around the country. Since that year, the quality of the air breathed by Zurich citizens has steadily improved and stayed constant over recent times, regularly achieving an annual certification of “Good” from the US AQI. This has largely come about due to the affordability and availability of public transport and the excellent waste management systems in the city.

Stockholm, Sweden

Famed for their forward-thinking outlook in many facets of life, it’s hardly surprising to see a Scandinavian country near the top of the list in terms of clean air. Stockholm has taken concerted steps to reduce its emissions and improve its air quality over the last couple of decades, including the introduction of clean air zones and the promotion of electric vehicles (EVs) among their populace. Meanwhile, the recent installation of catalytic converters on buses, trucks and other HGVs has reduced nitrogen dioxide concentrations in the last few years.

Helsinki, Finland

Although not part of Scandinavia, Finland is another Nordic country with excellent environmental credentials. At the outset of the 21^st century, the Helsinki authorities realised that real world emissions data from vehicle exhausts was the key to better management of their urban air quality and since then, have taken a wide-ranging approach to cleaning up the emissions produced from transport. Part of that has relied on promoting the use of bicycles over cars, with over 2,400 miles of cycle lanes currently in place around the city.

Those interested in learning more about how local authorities are implementing measures to tackle ambient pollution would do well to attend this year’s Air Quality and Emissions (AQE) Show in Telford in the UK. Scheduled to take place over two days, the event will showcase the latest innovations and developments in the air monitoring sector.