Exceptional Event Data

The Department of Health (DOH) monitors the ambient air quality in Hawaii. The DOH compares the air quality to the National Ambient Air Quality Standards (NAAQS), numerical thresholds below which no health impacts are expected. When an area has pollutant levels lower (i.e., better) than the standards, that area is said to be in “attainment” of the NAAQS.

In some cases, an Exceptional Event, an event that is not reasonably preventable or controllable, may cause pollutant levels to exceed those standards. An Exceptional Event is caused by human activity that is unlikely to recur at a particular location or is a natural event. A good example is the volcanic activity on the Big Island which has caused the levels of sulfur dioxide (SO2) and particulate matter to exceed the standards in some areas.

Data that is influenced by exceptional events can be flagged and excluded when determining an area’s attainment status with the NAAQS. The DOH has made a request to the U.S. Environmental Protection Agency that Exceptional Event data from the 2012-2014 exceedances of the SO2 annual NAAQS at the Hilo, Mountain View, Ocean View and Pahala air stations be excluded from this determination. The request is supported by the Documentation for Natural Event Excluded Data (PDF).


Related Topics

Please click on the following links to learn more about related topics:

Get background information and see the list of Notifications of Exceedances of the NAAQS.

Visit the Hawaii Air Quality Data Books page and select the most recent data book to learn more about DOH monitoring, air pollutants and the NAAQS.

View Hawaii Ambient Air Quality Data. Please note that the data has not been validated for quality assurance and is provided for information only.

Read the FAQs on Vog from Kilauea Volcano on the Big Island.