Since at least the beginning of October, the Dominguez Channel, a 15.7-mile storm drain that prevents flooding, has been emitting elevated levels of hydrogen sulfide, a foul-smelling gas, into Carson, Gardena, Long Beach, Redondo Beach, Torrance, Wilmington and other Los Angeles County communities.

After breathing this air, thousands of people began suffering a variety of symptoms including headaches, eye, nose and throat irritation, sneezing, dizziness, insomnia, nausea, and even vomiting or diarrhea. Authorities determined that the stench was most concentrated by South Avalon Boulevard near the 405 Freeway in Carson.

Officials have attributed it to the decay of organic matter, such as vegetation, within the Dominguez Channel. Hydrogen sulfide was a byproduct of the decay, which would normally occur for short periods of time at much lower concentrations in the channel. Authorities, as well as other non-governmental parties, are still investigating why hydrogen sulfide levels reached higher levels for a prolonged period.

To better understand this air quality crisis, the Long Beach Post created this timeline of events related to the Dominguez Channel.

Coding and design support by Dennis Dean.