2019 美国 AQI平均值
PM2.5浓度 2019年日本达到1倍以上 世界卫生组织污染暴露建议值
|2019 日本空气最清洁的城市||Obihiro, Hokkaido|
Japan is an island nation spanning an archipelago of around 7000 islands. There are five main islands which are Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa. It is situated in the northwest pacific area and is classed as part of East Asia. Tokyo is the capital city where the metropolitan area has a population of around 37.5 million residents.
At the beginning of 2021, Japan was enjoying relatively good quality air with a US AQI reading of 47 which classified it in the “Good” category according to recommended figures by the World Health Organisation (WHO). The average PM2.5 figure for 2019 was 11.7 µg/m³ which, again, placed it in the “Good” category. For three months of that year, it attained the WHO target figure of 10 µg/m³ or less. Four months classed it as “Good” with readings between 10 and 12 µg/m³. The remaining 5 months called it as “Moderate” with figures between 12.1 and 35.4 µg/m³. Looking back over the previous years, the air quality can be seen to be improving. In 2017 it was 13 µg/m³ and in 2018 it was 13.1 µg/m³ whilst the levels in 2019 were 11.7 µg/m³.
The istory of air pollution in Japan goes back to the Meiji government's policy era of encouraging the rapid development of industry, where pollution was not considered, but the problem intensified from the period of high economic growth in the 1950s. A large amount of oil and coal were burned in order to provide the energy which was necessary for post-war reconstruction and to boost the national income. Pollution centred on sulphur oxides (SOx) which was becoming serious. As a result of this, in industrial cities all over the country, many people suffered from respiratory disorders which became known as Yokkaichi asthma.
As people became more aware of the poor quality air, the anti-pollution movement intensified nationwide and measures related to pollution control were promoted, since then, various regulations such as the introduction of the Air Pollution Control Law and promotion of resource saving and energy saving have been encouraged, and the air quality has improved significantly.
In recent years, air pollution derived from automobiles has increased, and cross-border air pollution from the rapidly growing Asian region has also become noticeable. In response to these problems, the government has introduced various regulations such as tightening automobile emission regulations, but the current situation is that the environmental standards set by the government for the protection of health and the environment are still insufficient.
There are three main sources of air pollution in Japan which are as a result of industrial production activities, vehicle emissions and cross-border air pollution.
Although there has been a marked improvement compared to the period of high economic growth, air pollutants such as sulphur oxides (SOX) and nitrogen oxides (NOx) are still emitted from factories and thermal power plants. Since these air pollutants are regulated by the Air Pollution Control Law, each company is obliged to have a dust collector installed that separates and removes particulate matter in gas, and smoke exhausts that remove sulphur oxides and elementary oxides in the exhaust gas. Further reductions are sought after in order to reduce it by using technologies such as desulphurisation and flue gas denitrification.
According to the final energy consumption by sector of the Agency for Natural Resources and Energy, it decreased only slightly between 2010 and 2017. Technology to reduce air pollutants is advancing annually, but in order to reduce pollutants further, it is required to reduce energy consumption during the production phase.
Air pollution in Japan is also caused by the exhaust gases given off from vehicles, the increase in the number of cars owned, and the concentration of traffic in big cities.
The government is introducing tighter regulations on automobile exhaust gases, but the current situation is that the achievement of environmental standards is unsatisfactory.
In 2017, according to the Ministry of the Environment's air pollution condition, the achievement rate of fine particulate matter or PM2.5 environmental standards had decreased by 1.9 per cent from the previous year at the Automobile Emissions Measurement Bureau, and ground-level ozone (O3) was an extremely low level with an increased rate of 0 per cent.
However, the achievement rate of other air pollutants such as suspended particulate matter (PM10) and nitrogen dioxide (NO2) is 100 per cent or very close, and PM2.5, which normally has a poor achievement rate, is also emission-regulated. It is expected that it will be improved by strengthening the system and developing new technologies.
Air pollution caused by fuel consumption in thermal power plants, factories, automobiles, etc. in the Asian region where industrial development is progressing, is also affecting Japan.
Combustion of fossil fuels releases air pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) into the environment which produces harmful ozone (O3). In Japan, these pollutants are decreasing annually due to source regulations, but it is thought that cross-border air pollution is the main reason why ground-level ozone does not decrease in significant numbers.
According to the National Institute for Environmental Studies, the rate of increase in nitric oxides (NOx) and volatile organic compounds (VOCs) emissions in Asia from 1980 to 2003 was 2.8 times for NOx in Asia, 2.6 times in East Asia, and 2.1 times for VOC in Asia. In East Asia, it is 2.4 times.
In particular, it can be seen that China has increased significantly, with NOx 3.8 times and VOC 2.5 times.
The Ministry of the Environment will comprehensively promote measures such as emission control measures from factories and business establishments, automobile exhaust emission controls, and the encouragement of the use of low-emission vehicles in order to continue to achieve and maintain environmental standards.
This will also include the strengthening and creation of measures to control the emission of air pollutants, which are the source of fine particulate matter and photochemical oxidants, analysing the current situation and organising information, and reassess the situation if progress is slow.
Imari, Saga has the most polluted air according to the Swiss air monitoring company, IQAir.com with a US AQI figure of 63. This is possibly due to the widespread manufacture of porcelain in and around this area. Imari porcelain is exported worldwide and is of very high quality.
The cleanest city in Japan is Obihiro, Hokkaido with a recorded level of 24 which classifies it as being “Good”. In 2008, Obihiro was designated a "model environmental city" in Japan. There is a large agricultural community surrounding Obihiro and not too many factories which are the main cause of pollution.
Currently, the two main sources of air pollution in Japan are fixed sources such as factories and business establishments and mobile sources such as automobiles and aircraft.
In particular, air pollution caused by nitrogen oxides (NOx) emitted from automobiles, which are the source of mobility, is serious, and national measures such as automobile emission regulations and promotion of the spread of low-emission vehicles are being promoted.
In order to control sulphur oxides (SOx) and nitrogen oxides (NOx) emitted from thermal power plants, electric power companies use petroleum fuels with low sulphur content and take measures such as installing flue gas desulphurisation equipment.
For those who use automobiles and motorcycles for commuting, simply switching the means of transportation to public transportation, walking, or biking would help significantly in reducing emissions and would make a big difference to environmental pollution.
Exhaust gas is not only emitted when the car is running but also when the vehicle is idling such as waiting in a queue at traffic lights.
Fine particulate matter (PM2.5) or micro particulate matter is suspended in the air during standby and is characterised by a fairly small diameter of 2.5 microns. It is known to be generated mainly from the combustion of fossil fuels which cause soot and dust from sources such as factories, automobiles, ships, and aircraft.
The big problem is that fine particulate matter is microscopic and if it is inhaled into the lungs where it penetrates deeply and lodges at the base of the bronchial tubes. Therefore, it is thought to increase the risk of respiratory diseases such as asthma and bronchitis.
Spring is the season when the concentration of PM2.5 rises and is at its highest. A daily average of 70 μg / m3 may have detrimental health effects.
Overall, the annual average concentration of PM2.5 in Japan is declining due to regulations on soot and smoke generating facilities such as factories and business establishments, together with automobile emission regulations. However, PM2.5 concentration fluctuates depending on the season, and the concentration tends to increase from March to May every year. There are also differences depending on the region and the weather conditions at the time.
Short term symptoms resulting from exposure to air pollution include itchy eyes, nose and throat, wheezing, coughing, chest pain, headaches, nausea, and upper respiratory infections such as bronchitis and pneumonia. In some cases it can also cause a rash to form on the skin but, of course, this depends on the contents of the air and the susceptibility of the individual. It also exacerbates asthma and emphysema. Long term effects may include lung cancer, cardiovascular disease, chronic respiratory illness, and developing allergies. Air pollution is also associated with heart attacks and strokes.
The effects are very dependent on the state of health of the individual. Pregnant women, children under the age of 14 years and the elderly will be more susceptible than young healthy people with no pre-existing medical problems. The level of concentrations and the length of exposure also play an important role.
The achievement rate of environmental standards for fine particulate matter has improved from 89.9 per cent for general stations and 86.2 per cent for self-exhaust stations to 93.5 per cent for general stations and 93.1 per cent for self-exhaust stations. However, there were some areas in the Kanto region, the urban areas in the Kansai region and coastal areas that did not meet the environmental standards.
General stations are measuring stations which have been installed for the purpose of measuring air pollutants in general living spaces such as residential areas. Self-exhaust stations are measuring stations which monitor the pollution status from automobile exhausts.
In the transportation, railway, and aviation industries, new regulations with regards to air pollutant exclusion standards are being introduced together with the development and introduction of low-emission vehicles and energy-saving aircraft. In logistics, curbing carbon dioxide (CO2) and nitrogen oxide (NOx) emissions through a “modal shift” that shifts freight transportation to railroads and shipping are being gradually phased in, which have less impact on the environment.
All efforts are being made based on the "Automobile NOx / PM Law", a special law aimed at reducing pollutants emitted from vehicles, but the spread of electric vehicles is particularly attracting attention as a countermeasure to nitric oxides (NOx). Since electric vehicles run on motors using electricity stored in batteries, they do not emit any exhaust gas and emit fewer pollutant substances and carbon dioxide (CO2) than ordinary gasoline-powered vehicles.
Furthermore, if charging with renewable energy such as solar cells becomes common, it will become unnecessary to consider emissions from power plants, and nitric oxides (NOx) and carbon dioxide (CO2) emissions from automobiles can be reduced to zero. In this way, electric vehicles are highly expected, but there are problems to overcome, such as high vehicle prices and maintenance costs, a relatively short-range, and lack of charging stations, and further technological development for full-scale popularisation.
Recently, the number of passenger cars used for private use has increased from gasoline cars to eco-energy cars that use hydrogen and electricity, and "hybrid cars" that use both eco-energy and gasoline.