IMPERIAL COUNTY- The South Coast Air Quality Management District has issued an odor advisory today for the Coachella Valley due to elevated levels of a gas that smells like rotten eggs. That gas – hydrogen sulfide – is associated with natural processes occurring in the Salton Sea.
Hourly average concentrations of hydrogen sulfide (H2S) peaked last night at 106 parts per billion immediately downwind of the Salton Sea – at a monitor close to the shore, in an area with little population. The levels then quickly dropped to the normal range.
The monitor in Mecca, a more populated community further downwind, did not exceeded the state standard of 30 parts per billion. High H2S levels are not expected today, but if southeasterly winds do occur, areas in the Coachella Valley may briefly experience the odors.
The state standard for outdoor levels of hydrogen sulfide is 30 parts per billion averaged over one hour. At that level individuals may experience symptoms such as headaches and nausea.
However, the symptoms associated with this level of exposure are temporary and do not cause any long-term health effects. Humans can detect hydrogen sulfide odors at extremely low concentrations, down to a few parts per billion.
SCAQMD monitors hydrogen sulfide at two locations in the southeastern Coachella Valley – one very close to the Salton Sea and the other in the community of Mecca.
There is potential for Salton Sea odors to occur as the winds shift, especially in the late summer months in the early morning and late afternoon, or as thunderstorms occur.
SCAQMD is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.