京都的空气质量

What is the air quality index of Kyoto?

Kyoto which is sometimes known as Kyoto City is the capital of the prefecture of the same name. It is located in the Kansai region of Honshu Island. In 2018 the population was recorded as being 1.47 million people.

At the start of 2021, Kyoto was experiencing “Moderate” air quality with a US AQI figure of 73. This is according to the suggested levels by the World Health Organisation (WHO). Other recorded pollutants were PM2.5 with a concentration level of 22.5 µg/m³ and nitrogen dioxide (NO₂) at 17.9 µg/m³. At these levels of pollution, the advice is to close doors and windows to stop the ingress of dirty air and those of a sensitive disposition should reduce outdoor activity until the air quality gets better.

What is the main source of Kyoto’s polluted air?

As in most major cities anywhere in the world, air pollution in city centres usually comes from two sources transportation and the production of energy. Car ownership is on the rise as people become richer and are therefore able to afford to buy and run a private car. Nitrogen dioxide (NO₂) and PM2.5 are the main pollutants from vehicle emissions. These can cause the production of ground-level ozone (O₃). Kyoto also suffers from air pollution which is “imported” from other areas across East Asia. China is close enough for its polluted air to be blown across the sea to Kyoto and to Japan in general.

Ozone (O₃) does not decrease easily. Ozone is generated from photochemical reactions in the atmosphere as a result of human activity. It does not come directly from the vehicle exhaust emissions. It is the NO_x or nitrogen oxide, that is produced when things burn and VOCs (Volatile Organic Compound). It is generally known that ozone is produced when these two photo-react in the atmosphere, and it is a major premise that these must be reduced. The level of ozone often increases during the day as it needs UV sunlight to be produced.

This is an environmental problem in cities in developed countries, as it occurs not only in Japan but also in cities in Europe and the United States. Air pollution is severe even in cities in emerging countries, but it is the same as pollution in Japan around 1970, and reducing the causative substances has a great effect on reducing oxidants. Scientists are helping to make a law together with the government by clarifying what substances should be reduced and how much to clean the atmosphere.

Is air pollution in Kyoto getting better or worse?

Air quality in Kyoto City has been almost flat or shown a gradual improvement in recent years in terms of the concentration levels of each substance. Looking at the achievement status of environmental standards set by the government, sulphur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), suspended particulate matter (PM10) and fine particulate matter (PM2.5) have achieved the standards at all measuring stations. However, photochemical oxidants do not meet the standards at all measuring stations, as is the case with national trends.

Kyoto is located in an inland basin surrounded by mountains on three sides and has the characteristic that the atmosphere tends to stay topographically, so the concentration of air pollutants tends to increase, especially in winter. Because of its location, the winds are not strong enough to blow the pollutants away so they hang in the air.

What can be done to improve the air quality in Kyoto?

The way forward would be a city centre with zero carbon emissions, but that will take several years to come to fruition. The increased usage of electric vehicles is particularly attracting attention as a countermeasure to nitric oxides (NO_x). Since electric vehicles run on motors using the energy stored in batteries in the form of electricity, they do not emit any exhaust gas and emit fewer pollutant substances and carbon dioxide (CO₂) than ordinary vehicles. In addition, if charging with renewable energy from solar cells becomes common, it will not be necessary to consider emissions from power plants, and NOx and CO₂ emissions from automobiles can be reduced to zero.

The government is promoting eco-energy conversion while taking measures such as automobile emission regulations and eco-car tax cuts, but in reality, it is not enough to make noticeable differences.

Electric vehicles certainly seem to be the way forward, but there are issues such as the initial high vehicle prices and high maintenance costs when compared to traditional gasoline/diesel-powered vehicles. They also currently suffer from a short mileage range, and a lack of charging stations, and further technological development for full-scale popularisation. As technology improves so does the attractiveness of owning and using an electric vehicle.

Walking and cycling are also excellent ways of reducing air pollution and are good for the body too as a means of exercise.

What are the effects of breathing in Kyoto’s poor quality air?

Carbon monoxide (CO) mainly comes from fossil fuels that are not completely burned. Most of the carbon monoxide in the air in Kyoto comes from the exhaust from vehicles. It reduces the oxygen-carrying capacity of red blood cells, and its impact on health depends on the length of time the body is exposed to it and the concentration of the gas inhaled. The average person may experience headaches, dizziness and fatigue when inhaling low levels of carbon monoxide. When inhaling high concentrations, it can cause blurred vision, loss of coordination, and eventual death.

Suspended particles come from many sources and can be produced by human activities and can also occur naturally. The burning of fossil fuels such as the exhaust from vehicles and power plants and the burning of living organisms such as from wildfires are the main sources. Generally speaking, suspended particles are a complex mixture of solid and liquid organic and inorganic substances in the air. The microscopic PM2.5 particles are particularly dangerous as they can easily bypass the body’s defence mechanism due to their very small size. They are easily inhaled into the lungs where they lodge themselves in the alveoli which are the tiny air sacs responsible for the oxygen/nitrogen exchange in the respiratory system.