Besides smoke haze, ash emissions from volcanic eruptions in the region may also affect the air quality in Singapore. This was the case for the eruption of Mount Pinatubo in Luzon Island, Philippines in June 1991. During Mt Pinatubo’s powerful eruptions on 14 June 1991, enormous amount of ash clouds and gases were injected into the stratosphere (above 45000 feet). The ashes were blown westwards over the South China Sea and the surrounding region under the influence of upper-level easterly winds. Singapore was affected by the ash fall between 17 and 19 June 1991, and the air quality on these 3 days were in the moderate range (PSI: 50 (17 June), 70 (18 June), 57 (19 June)).
January 1, 1991