札幌市的空气质量

What is the air quality index of Sapporo?

Sapporo is situated on the Japanese island of Hokkaido. It is the capital of the prefecture and the Ishikari Subprefecture. In February 2020 it has an estimated population of almost 2 million people.

In early 2021, Sapporo was enjoying a “Good” quality of air with a US AQI figure of 50. This is based on the recommendation by the World Health Organisation (WHO). Other levels of pollutants suspended in the air were: PM2.5 - 12 µg/m³, PM10 - 10 µg/m³, nitrogen dioxide (NO₂) - 18.8 µg/m³ and sulphur dioxide (SO₂) - 5.2 µg/m³. These figures are expressed in microns per cubic metre. With air quality as good as this, the advice is to open doors and windows to let the fresh air in and to get outside and enjoy outdoor activities.

Sapporo attained the WHO target figure for air quality in 2019 with a mean annual figure of 8.1 µg/m³. Only in February and March did the figure rise above the 10 µg/m³ when it reached a “Moderate” level of 13.6 and 13.9 µg/m³, respectively. In 2017 it also attained the WHO target with a figure of 8.4 µg/m³ and in 2018 it was 7.3 µg/m³.

What is the history of Sapporo’s polluted air?

In the mid-1950s, coal was used as the main fuel. During the winter, the sky in Sapporo would be filled with "dust" that was emitted when coal burned and the atmosphere was very dirty. In the following decade, the energy source changed from coal to oil. Heavy oil used in factories and contained large amounts of sulphur, so when it was burned, a pollutant called sulphur oxide (SO) was generated. They were being discharged from the factory chimneys. However, heavy oil with a low sulphur content began to be available and, as such, the air quality has improved.

In the 50s, studded tyres were used during the winter months to provide extra traction on the snow-covered roads. This caused "car powder" to be generated by scraping the asphalt on the road, and it became a social problem. Now that studless tires are used, this problem can be solved.

Is air pollution in Sapporo getting better or worse?

In recent years, PM2.5, a fine particulate matter, has become a problem. It can be blown in from overseas and is also a residual from the combustion of fossil fuels. These come from the exhaust gases from vehicles and also from coal-fired power stations. PM2.5 has a grain size of 2.5 microns or less and is one of the smallest particulate matter in the atmosphere. Its size is about 1/30^th the thickness of a human hair. Therefore, it is a real health hazard because it is easy to get into the base of the bronchial tubes when inhaled. It is thought to be the cause of asthma, respiratory illness, and heart attacks because it easily can be transferred to the bloodstream.

The rise in PM2.5 in Sapporo from the end of February 2019 was caused by a large-scale forest fire in the Russian Far East from northern China, and it was said that it was blowing over Hokkaido Island on a westerly wind. The level of PM2.5 concentration in Hokkaido and Sapporo rose to nearly 200 at that time and was noticeable in the air when moving outdoors.

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

Due to the cold climate, fuel consumption for heating homes and other buildings increases in winter, so the air environment tends to be worse in winter than in summer. In particular, when an “inversion layer” that hinders air convection and suppresses the diffusion of pollutants is generated, it becomes difficult for pollutants in the atmosphere to diffuse in the wind.

The temperature of the atmosphere is usually higher the closer it is to the ground and lower the higher it is. However, on the contrary, a layer having a temperature higher than the temperature near the surface of the earth may be formed in the sky, and that layer is called an inversion layer. When this layer is formed, the air near the surface of the earth stagnates and the diffusive power of the atmosphere weakens, so that soot and toxic gas in the air drift low, and pollution may become severe and prolonged.

With the tightening of regulations on automobile exhaust gas and the reduction of air pollutant emissions, substances emitted from sources other than exhaust pipes (for example, fuel evaporation gas, brake and tyre dust, etc.) are also attracting attention. In addition, with the improvement of chemical analysis technology, it is possible to measure trace components that could not be quantified until recently.

In 2015, the carbon dioxide (CO₂) reduction target for 2030 was announced. . The transportation sector emits about 20 per cent of carbon dioxide in Japan as a whole, of which the automobile sector accounts for about 90 per cent, and it is necessary to implement reduction measures. Carbon dioxide reduction measures in the automobile sector include comprehensive measures such as improving fuel efficiency and popularising next-generation vehicles, as well as improving traffic congestion and making effective use of private cars.

What are the effects on health through breathing in Sapporo’s polluted air?

Carbon monoxide (CO) mainly comes from fossil fuels that are not completely burned. Most of the carbon monoxide in the air in Sapporo comes from the exhaust emissions from vehicles on the city roads. Carbon monoxide will reduce 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 how much is inhaled. The average person feels headache, dizziness and fatigue when inhaling low levels of carbon monoxide. When inhaling high concentrations though it can cause blurred vision, loss of coordination, and even death.

Of course, not everybody is affected by polluted air in the same way. A strong, healthy person is going to be able to cope with polluted air far better than someone who is already suffering from respiratory problems. Pregnant women, children under the age of 14 years and senior citizens must take extra care when venturing outside when the air is badly polluted.