TAIPEI (Taiwan News) — Volcanic dust from an eruption on the Japanese island of Nishinoshima was responsible for a sudden turn for the worse in air quality on Taiwan’s sparsely populated east coast Thursday evening (Aug. 6), according to weather experts.

The counties of Yilan, Hualien, and Taitung are known for their fresh air and natural beauty, but late on Thursday the eastern sky turned gray and the air quality went from excellent to average, CNA reported. On the Facebook page WeatherRisk, Central Weather Bureau Director-General Cheng Ming-dean (鄭明典) said the change was not the result of simple environmental pollution but eruptions at the Nishinoshima volcano 2,000 km away.

The islet in the Ogasawara archipelago, also known as Rosario Island, has been growing for 40 years due to volcanic activity.

Due to the distance of the eruption, the ash and dust have become less dense, and their impact will gradually diminish over the course of Friday (Aug. 7), weather experts said. The dust first drifted west and then turned north before being blown south along Taiwan’s east coast by shifting winds.