The primary pollution source of PM2.5 in Taiwan is the traffic emission.
According to Taiwan Environmental Protection Administration (TWEPA) publicized PM2.5 emission report of Taiwan, there are four primary sources: traffic emission accounts for 36% (about a third of the total), long range transport of East Asia's emission accounts for 27%(also about a third of the total), industrial emission account for 25% (about a fourth of the total), and natural events account for 12%. The 25% of industrial sources of PM2.5, can be specifically broken down into several categories: construction, chemical, electric power, steel, and other manufacturing industries. In particular, the 70,000 restaurants/diners in Taiwan account for about 6.2% of the total PM2.5 produced.
The chemical manufacturing industry has been misunderstood by the public. It actually only accounts for 2% of the total PM2.5. The electric power industry only accounts for 2.9% of the total PM2.5. These two add up to less than 5%, which is lower than that of the 6.2% coming from the restaurant industry. Therefore, it is unreasonable and incorrect to say that the industrial sector is the primary source of PM2.5.
The figure below shows a long-term trend spanning 8 years. The figure is the quarterly curve of PM2.5 from 2013 to 2020. As it can be seen, the curve was higher during the first quarter in 2013 and dropped during the second and third quarters. However, it rose again during the fourth and first quarter in 2014. This pattern repeated where the first and fourth quarters of each year are the declining periods. It is impossible for a factory that operates all year round to stop when the weather is good during the second and third quarters. The reason for the higher PM2.5 during the first and fourth quarters is mainly due to the influence of the northeast monsoon, which comes from long range transport sources.
Q1 & Q4 (in red) and Q2 & Q3’s (in blue) trends are now compared. The red line indicates that the decline rate of Q1 & Q4 is declining relatively high at about 3.2 μg/m3 per year. The blue line shows that even though there is a decrease, the slope is rather flat, declining at only about 1.7 μg/m3 per year. This indicates that the source of PM2.5 from long range transport has decreased. In other words, the air pollution in mainland China is improving, and its improvement is greater than Taiwan’s.
Looking at the national air quality, Taipei City’s air quality is the best, because Taipei is surrounded by mountains. Pollution from the outside cannot enter. Correspondingly, local pollution gets trapped inside. There are no large-scale industries in Taipei, therefore the biggest and only source of pollution is traffic, specifically, automobiles and motorcycles. Taipei is less affected by overseas sources of PM2.5, which is why the air quality in Taipei is relatively good.
The industrial sector cooperated with the government’s tight control over PM2.5 production to reduce the amount of PM2.5 produced. Since then, Taiwan's air quality has improved over the years.
The following figure is derived from the air quality monitoring report by the Environmental Protection Administration. The table shows that PM2.5 has gradually decreased from 34.5 μg/m3 in 2007 to only 15.1 μg/m3 in 2020. This indicates that Taiwan's air quality is indeed improving.
Some people and groups with questionable intentions have been emphasizing that Taiwan's air quality is not good and that it is the worst in the world. However, according to the following data surveyed by the World Health Organization and the data monitored by Taiwan, Taiwan's air quality is ranked No.17 in the world. Therefore, it is actually not worse than other countries. What's more, some data from other countries are inaccurate about Taiwan’s air quality. Taiwan definitely does not have the worst air quality in the world, as mentioned by some environmental groups. Taiwanese people should not belittle themselves.
(FPG, Sep 14, 2018)