Each year, most of Japan’s prefectures are affected by what is known as yellow dust, which appears as a yellow fog in the atmosphere for a few days, often in late winter and early spring. A mixture of des ert sand, arid topsoil and man-made pollutants from Central Asia, China and Mongolia, the annual yellow dust storms are a growing health hazard that have canceled or delayed flights in Japan and South Korea and, when mixed with rain, muddy the streets, creating an environmental headache for governments and individuals.

Q: What, exactly, are yellow dust storms and where do they come from?

A: Yellow dust and sandstorms originate mostly in Central Asia, China and Mongolia. The Takla Makan desert and the Gobi desert, as well as the Loess Plateau, are the main sources. The sand, dust and particles rise into the air and are driven across the Korean Peninsula to Japan by prevailing westerly winds. However, yellow dust from the storms has been found as far away as the U.S. Rocky Mountains.

Q: What causes the storms, and why have they been increasing of late?

A: Dust storms have been experienced in East Asia since ancient times, but over the past two decades Japanese government and academic data have shown that their frequency and intensity have been increasing. The storms, once thought to be exclusively a natural phenomenon, are now understood to be the result of the rapid spread of overgrazing, deforestation, soil degradation and desertification in Central Asia and parts of China. These developments, combined with changing weather patterns that include drier winters with less snowfall, result in massive quantities of dust being sucked into the atmosphere.

Q: What is the chemical makeup of the dust particles and how dangerous are they to human health?

A: Analysis by the Environment Ministry shows that the dust particles are primarily minerals like quartz and feldspar, as well as mica, kaolinite and chlorite. Ammonium, sulfate and nitrate ions have also been found in the particles and are said by meteorologists to originate in Chinese factories. These ions, in significant numbers, are hazardous to human health.

Q: What are the environmental standards, then, to determine how dangerous the yellow sand and dust really are?

A: The Japanese environmental standard for suspended particulate matter is 100 micrograms per cubic meter per hour. That means that the maximum amount of particle matter in the air considered safe is 100 micrograms per cubic meter as measured over a one-hour period. When the dust storms form over the deserts, the concentration levels can reach 90,000 per cubic meter per hour. By the time they arrive in Japan, according to the Environment Ministry, the concentration levels have dropped to 120 per cubic meter per hour, which is still more than the limit considered safe.

Q: When is the worst time for dust storms in Japan?

A: Dust from Asia blows across Japan throughout much of the year, but the worst storms have, over the past decade or so, been arriving in late winter and the spring months, usually between late February and mid-May. Western Japan, especially Kyushu, Chugoku and Kansai, have been particularly hard hit. In early March, a yellow sandstorm delayed flights at Fukuoka airport and, mixed with rain, left a brownish yellow film on the city streets and automobiles. Visibility in Kyushu on March 3 was less than 3 km. Past storms have reduced visibility to 2 km. The sand last month was also reported in Kansai and Tokyo.

The situation in early March was even worse in South Korea, though, as schools were closed due to the yellow sandstorms. The storms have caused billions of dollars in damage and many deaths, South Korean officials say.

Q: So what is being done about the problem?

A: To sound the warning against approaching yellow dust storms, there are 108 meteorological observatories throughout Japan that monitor air quality. Each day, there is a yellow sand update and a forecast at the Meteorological Agency’s Japanese-language Web page at www.jma.go.jp/jp/kosa

To tackle the long-term problem, the governments of Japan, China, South Korea and Mongolia launched a project in 2003 with several U.N. organizations and the Asian Development Bank to collect data on the yellow sandstorms and come up with countermeasures.

But while Japan and South Korea are moving ahead with early warning networks, long-term solutions to reduce the intensity of the storms are expensive, time-consuming and require close cooperation among the countries that are affected. Some technical and educational steps are being tried, such as reforestation, replanting of degraded land and introducing water-saving and water-management techniques to rural areas. Other measures, such as enforcing laws in China that prohibit land reclamation reducing the number of smoke-belching factories in the region require a combination of political and economic solutions that are much tougher to realize.

The weekly FYI appears Tuesdays (Wednesdays in some areas). Readers are encouraged to send ideas, specific questions and opinions to hodobu@japantimes.co.jp

The Weekly FYI appears Tuesdays (Wednesday in some areas). Readers are encouraged to send ideas, questions and opinions to National News Desk

In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.