Air quality in Tokyo

Is Tokyo a polluted city?

Tokyo, or officially Tokyo metropolis, is the capital city of Japan and the most populous city in the country, with some 14 million inhabitants living there. Formerly known as Edo, it was once a fishing village that came to major political and cultural prominence due to the Tokugawa Shogunate making it its seat of power in the early 17^th century. Nowadays Tokyo is a very technologically advanced city, being the leader in Japan's business and finance sector.

In regards to its air pollution levels, Tokyo came in with PM2.5 readings of 11.7 μg/m³ as an average over the year of 2019, putting it into the ‘good’ ratings bracket of air quality, which requires a PM2.5 reading of anywhere between 10 to 12 μg/m³ to be classified as such, a grouping that has a very fine margin of entry. This reading is a somewhat respectable one, with many months out of the year coming within the World Health Organizations target goal of 10 μg/m³ or less on the PM2.5 readings chart.

Its yearly average of 11.7 μg/m³ was enough to place it in 1924^th place out of all cities ranked worldwide, as well as 225^th place out of all cities ranked in Japan. This is a very respectable placing, with a good year round quality of air, although it can be said that the air quality is not yet perfect, with some months rising up by several units into the ‘moderate’ ratings bracket. As such, whilst Tokyo is very clean, it has some pollutive issues that may need addressing, but overall has a good quality of air for its citizens to breathe.

What are the main causes of pollution in Tokyo?

Due to rapid urbanization and industrialization that occurred over the last century, Tokyo has undergone vast changes to its urban geography, and whilst the levels of pollution may have lowered when compared to its more heavily industrialized time, there are still many causes of pollution that are remnants of this era, with many factories and industrial areas responsible for putting out larger amounts of pollution, thus raising the PM2.5 and PM10 count in the air, as well as emitting other noxious chemicals such as nitrogen dioxide (NO₂) and sulfur dioxide (SO₂).

So, with this in mind, one of the main causes of pollution in Tokyo would be emissions from factories, particularly ones that still run on forms of fossil fuels such as coal, although this is significantly less prominent than other countries, due to the more stringent regulations that Tokyo authorities place on fuel standards. Nevertheless, these emissions still add to the year round ambient pollution levels.

Lastly, the other main source of pollution in Tokyo would be that of vehicular emissions, with some 4 million vehicles being registered in the city in 2014, and as such would have grown significantly since. Whilst rules for what fuels can be used are very strict, the large amount of vehicles on the road would still lead to a heavy increase in pollution levels, far greater than what would be recorded if there were to be less cars and other automobiles on the road.

When is Tokyo’s air at its most polluted?

Observing the data taken over 2019, it can be seen that Tokyo is subject to some quite sporadic readings of PM2.5, with three different groupings coming in over the course of the year, including the WHO’s target goal, the ‘good’ rating bracket as well as the ‘moderate’ ratings bracket, which requires a PM2.5 reading of anywhere between 12.1 to 35.4 μg/m³ to be classed as such.

To see a pattern emerge, it appears that despite its sporadic and random nature, the months of January through to August came in with the highest readings of pollution, as well as December falling in line with these months.

The most polluted month of the year by far was February, with a PM2.5 reading of 17.4 μg/m³, followed by March and December with readings of 13.9 μg/m³ and 13.4 μg/m³ respectively.

When is Tokyo's air quality at its cleanest?

In contrast to the previous question, the months that came in with the cleanest readings of pollution were towards the end of the year, with the exception of December which came in with a relatively high reading despite its proximity to the cleanest months of the year.

September through to November were the months that came in with the lowest levels of pollution, with readings of 9.4 μg/m³, 8.9 μg/m³ and 9.8 μg/m³ respectively, making October the cleanest month out of the year, with a good quality of air for its inhabitants to breathe.

Have pollution levels in Tokyo improved?

Observing data taken over the last few years, it can be seen that Tokyo's pollution levels have made some good improvements, and although they may be marginal in terms of the amount of PM2.5 units involved, when pollution levels are as low as ones such as in Tokyo and other similar clean cities, these minute changes can make a world of difference.

In 2017, Tokyo came in with a PM2.5 reading of 13 μg/m³, placing it in the moderate ratings bracket. This was followed in 2018 by a reading of 13.1 μg/m³, showing a slight increase in pollution levels. In more recent times the aforementioned reading of 11.7 μg/m³ was shown in 2019, that moved the cities reading down by a whole bracket from moderate to good.

If this trend is to continue, with the right initiatives in place (which are already being efficiently implemented), then hopefully Tokyo may be able to reduce its pollution levels further to the point that it finds itself within the WHO’s target goal for clean air year round.

What are some pollutants found in the air in Tokyo?

With the main sources of pollution being vehicle fumes as well as factory emissions, the main pollutants would be the ones such as the previously mentioned nitrogen dioxide and sulfur dioxide, with nitrogen dioxide being particularly prominent in areas that see high volumes of traffic.

Other pollutants would include fine particulate matter such as black carbon, a major component in soot and a dangerous form of PM2.5, having both carcinogenic and climate changing properties. Volatile organic compounds would also be present, released from cars, factories as well as industrial materials or even household items such as paints, varnishes, lacquers and combusted material such as coal or fuel.

Some examples of these would include benzene, toluene, formaldehyde and ethylene glycol. All of these have numerous detrimental effects on human health, and as such when pollution levels are higher in the air, preventative measures such as the wearing of fine particle filtering masks and avoiding outdoor activities or sports may become of increased importance.