Hawai'i Volcanoes National Park
Sulfur Dioxide (SO2) Advisory Program
Volcanic activity at Hawai'i Volcanoes National Park is a source of the gaseous air pollutant sulfur dioxide (SO2). This gas can pose a threat to human health, animal health, and plant life. High levels of SO2 can cause breathing difficulty and respiratory illness and aggravate existing heart disease in sensitive groups. Groups sensitive to air pollution include people with asthma who are active outdoors, children, the elderly, and individuals with heart or lung disease. This gas can also react with other chemicals in the air and convert to a small particle that can lodge in the lungs and cause similar health effects. These sulfate particles can also create haze and reduce visibility in national parks. Sulfur dioxide can chemically convert to acids in the atmosphere and deposit out in rain, snow, fog or as dry particles. Such atmospheric deposition can damage vegetation, affect soils, acidify lakes and streams, and ruin memorials, buildings, and statues at our national cultural monuments.
A sulfur dioxide air pollution advisory program was established at Hawai'i Volcanoes National Park to provide timely information about potentially unhealthy air pollution conditions that could affect the health of visitors, island residents, and park personnel. The sulfur dioxide and weather data used in this program are collected by the National Park Service at the Jaggar Museum and Kilauea Visitor Center monitoring sites.
High levels of SO2 at the park are dependent on the intensity of volcanic activity and the wind direction. When the prevailing trade winds carry the volcanic plumes away from the monitoring stations, the concentrations drop to or near zero.
However, locations that are directly downwind of the plume are likely to see higher SO2 concentrations than those being measured at the monitoring stations. When the trade winds are disrupted and winds flow from the east and south transporting the pollution to the monitors, the measured SO2 concentrations can be significantly greater.
Visitors, residents, and park staff downwind of the plume may be exposed to unhealthy levels of pollution. Because it is not possible to control volcanic activity, the National Park Service developed this sulfur dioxide advisory program and issues warnings to limit the exposure of people to unhealthy levels of this gaseous pollutant. Graphical displays both at the park and here at this web site alert visitors and employees of the areas where the SO2 volcano emissions are being transported and therefore should be avoided. The graphical display includes current measurements of SO2 concentrations and wind speed and direction, the advisory level, and a simple representation of the size and direction of the volcanic plumes transporting the pollution downwind.
The SO2 concentrations measured at the two monitoring sites are reviewed every 15 minutes and one of four advisory levels of health concern are assigned for that 15-minute period for each site. The four possible advisory levels are Good (with an associated advisory color of green), Moderate (yellow), Unhealthy for Sensitive People (Orange), and Unhealhy (Red). Each advisory level is associated with an increasing level of concern for human health. The meaning of the four levels are:
|Good||Unusually sensitive individuals may want to limit their exposure in this area.|
|Moderate||Sensitive individuals may want to limit outdoor exertion, or stay indoors or in an air conditioned environment.|
|Unhealthy For Sensitive People||Physically active and sensitive individuals may want to limit outdoor exertion, or stay indoors or in an air conditioned environment.|
|Unhealthy||All individuals should limit or avoid outdoor exertion, or stay indoors or in an air conditioned environment.|
|Very Unhealthy||All individuals should avoid outdoor exertion and remain indoors.|
|Hazardous||All individuals should avoid outdoor exertion and remain indoors. Leave the area if directed by Civil Defense.|
Sensitive individuals can include children, the elderly, people with asthma or heart or lung disease.The advisory level is determined every 15 minutes and is initally set based on the current 15-minute average SO2 concentration at each monitoring site. The table below outlines the levels and the criteria used to set the levels.
|Criteria for Setting the Advisory Condition Level|
|Good||< 0.2 ppm||15-minute average||Can be > 0.2 ppm for single 15-minute average|
|Moderate||≥ 0.2 ppm||15-minute average||Requires just one 15-minute average|
|≥ 0.4 ppm||15-minute average||Requires just one 15-minute average|
|Unhealthy||≥ 1 ppm||15-minute average||Requires just one 15-minute average|
|Very Unhealthy||≥ 3 ppm||15-minute average||Requires just one 15-minute average|
|Hazardous||≥ 5 ppm||15-minute average||Requires just one 15-minute average|
The advisory color/level resulting after these checks are performed and the current 15-minute average SO2 concentration are posted on the Hawai'i Volcanoes Current Conditions web page.