Air quality in Osaka

Does Osaka have polluted air?

Osaka is the capital city of the Osaka prefecture in Japan, being a considerable financial hub as well as home to many large multinational electronics companies, such as Panasonic. It has a long history of being an important cultural and economic center for the country, and this continues on today. As with all economic areas with well developed infrastructure, there often comes issues of pollution, mainly based off of industry as well as the mass movement of people, particularly regarding day to day commutes. Of note is that Osaka and indeed much of Japan has taken many steps to improve its pollution levels following its industrialization during the previous century.

Regarding it pollution levels taken over 2019, Osaka came in with a yearly average PM2.5 reading of 13.5 μg/m³, placing it into the ‘moderate’ pollutions rating bracket, which requires a PM2.5 reading of anywhere between 12.1 to 35.4 μg/m³ to be classed as such. This shows that whilst Osaka came in on the lower end of this moderate rating bracket, being only 1.5 units away from moving down to the ‘good’ air quality bracket (requiring 10 to 12 μg/m³ for classification), it still has some pollutive issues, as any PM2.5 reading over the World Health Organizations target goal of 10 μg/m³ may cause health issues to those exposed to poorer air quality, particularly if done over extended periods of time as well as on vulnerable demographics, such as the young, elderly, expectant mothers as well as those with preexisting health conditions or compromised immune systems.

What are the main causes of pollution in Osaka?

Alongside many major economic and industrial cities in Japan, Osaka sees much of its pollution arising from similar sources. Among the two main ones are fumes coming from the use of vehicles, and with some 2.6 million inhabitants living in the city, there would undoubtably be a large amount of pollution stemming from the use of personal cars, motorbikes, as well as more heavy duty vehicles such as lorries, trucks and buses, some of which are still running on diesel fuels.

Whilst Osaka has considerable amounts of public transportation infrastructure, rush hour traffic and any vehicle usage will result in the inevitable build up of certain pollutants, as well as photochemical pollutants arising as a result of these chemicals being exposed to strong sunlight during summer months, which often results in the coined term of ‘smog’.

Other forms of pollution in Osaka would be from the numerous factories around the city’s limits. Whilst they would have more stringent rules in place than other far more polluted cities in Asia, once again it is inevitable that any factories that rely on combustion (particularly of fossil fuels such as coal) and release any kind of industrial smoke related to the product being made (as an example, certain product facilities or even plastic recycling plants inevitably release burnt plastic fumes, although with containment protocols this can be limited). To summarize, the two main sources are vehicular and factory based emissions.

When is pollution at its worst in Osaka?

Once again observing the data taken over 2019, the months that came in with the highest readings of PM2.5 were recorded at the very end of the year in December, and continuing on into the earlier months of the year, coinciding with the colder winter months, often due to the increased demand for heating for both homes and businesses, with Osaka experiencing some fairly drastic cold spells during its winter, and as such the subsequent demand for heating would rise significantly. From January through to May is when pollution levels were on average at their worst, with the first three months of the year showing the highest readings of PM2.5, coming in at 15.1 μg/m³, 22.5 μg/m³ and 16.3 μg/m³ respectively, making February the most polluted month of the year in Osaka, more than double that of its cleanest months.

When is air quality cleanest in Osaka?

In contrast to the previous question, the cleanest months fell within the summer and autumnal seasons, with the pollution levels showing their aforementioned decline during the coldest times. From June to November is when the air quality levels showed significant improvements, with less smoke, haze and pollutants permeating the atmosphere.

In June the PM2.5 reading was 13 μg/m³, followed by 11.6 μg/m³ in July, an improvement and also a drop from the ‘moderate’ pollution bracket down into the ‘good’ ratings one. August came in with a slightly worse reading of 12.2 μg/m³, followed by the cleanest months of the year, September and October, both of which fell within the WHO's target goal for clean air quality, with readings of 9 μg/m³ and 9.4 μg/m³ respectively, making September the cleanest month of the year and with a great quality of air, although a further reduction bringing its number closer to 0 would of course be most optimal.

November also showed a decent rating, coming in within the ‘good’ bracket rating at 11.1 μg/m³, before declining quickly again in the final month of the year as mentioned before.

What are the main pollutants found in the air in Osaka?

With much of its pollution arising from the use of vehicles, the pollution would be largely associated with these activities. Chemical compounds and fine particulate matter released from associated fumes would include ones such as nitrogen dioxide (NO₂) and sulfur dioxide (SO₂), with nitrogen dioxide being the most prominent out of the two, often being found in high concentrations in any areas that see high volumes of traffic, so much so to the point that concentrations of NO₂ can accurately be used to predict how much pollution is being caused by vehicular use alone.

Oxides of nitrogen can also undergo the photochemical reactions when exposed to sunlight, creating pollutants such as ozone (O₃) to permeate the air at ground level. Whilst this is a vital compound in the upper stratosphere, when on the ground level it can have highly negative effects on human health, causing significant damage to the lungs and triggering off respiratory problems such as reduced lung function and asthma attacks. Other pollutants would include fine particulate matter such as black carbon, and volatile organic compounds (VOC's) such as benzene and formaldehyde, both of which have palpable risks to human health.