Air Quality

The news about air quality from the Big Island seems to get worse every day. The amount of SO2 rises with as lava flow increases. Rock and steam explosions eject ash. Lava falling into the sea creates clouds of laze, a mixture of glass particles and hydrochloric acid. However, these are mostly problems local to the volcanic area because the trade winds typically blows these pollutant out to sea before they get to the more populated areas of the island.

Here is an example when the SO2 was very high due to fresh lava on May 20. Note that the Green air has some SO2, but less than 0.1 ppm, and is considered good. Yellow is moderate air but still considered okay. Orange air is USG, Unhealthy for Sensitive Groups. Red air is considered unhealthy for the general population.

Consider Hilo, which is just 21 miles northwest of Leilani Estates, the source of most of the SO2. Because the trade winds blow from the northeast, Hilo generally has better air than Kona, 71 miles from Leilani Estates. There was one day, May 17, that Hilo got some Orange SO2 air because the trade winds failed. The history of SO2 measurement on the Big Island can found HERE.

The trade winds can wrap around the south point of the island and blow on the southwest coast, Kona and below. However, Kona has only gotten Green SO2 air so far, even on May 17. This is because of the long distance, about 150 miles, in the round about path that the SO2 has to travel to get to Kona. SO2 reacts with water and dust in the air to form sulfate particles. These particles get larger with time. So the dominant air quality concern in Kona is PM2.5, particles smaller than 2.5 um. The current PM2.5 reading on the Big Island can be found HERE. The PM2.5 AQI, Air Quality Index, uses the same color code as SO2 readings.

Vog is a mixture of SO2 and sulfate particles. Even if the vog in Kona is mostly PM2.5, it can still be bad. I have been watching the PM2.5 AQI for Kona since the start of the eruptions. It has mostly been Green or Yellow, but today it is Orange. Nevertheless, it is easier to filter PM2.5 than SO2 which will be the topic for a future post. 

Needless to say, a filter that works on PM2.5 sulfate should also work on ash and glass particles. The filter may not work on hydrochloric gas from laze, but the amount should be minute relative to SO2. The media has reported that the laze plumes could extend 15 miles along the coast. The lava entry point to the ocean is 70 miles from our condo.