California warehouse fire leached chemicals into a nearby channel, releasing a 'rotten egg' smell that some residents say is making them sick

• Carson, California, smelled like rotten eggs for two months due to elevated hydrogen sulfide levels.
• The stench likely originated with a September fire that leached chemicals into a nearby waterway.

The putrid stench that wafted across Carson, California — just south of downtown Los Angeles — for nearly two months is no longer a mystery.

A local air pollution agency recently traced the fumes to a September warehouse fire, which leached chemicals from wellness and beauty products into the Dominguez Channel, a 15.7-mile river that empties into the ocean at the Port of Los Angeles. Exposure to the chemicals prompted the channel's vegetation and marine life to decay and release hydrogen sulfide, a colorless gas that smells like rotten eggs.

The air pollution agency investigating the smell, South Coast Air Quality Management District (AQMD), issued violations on Friday against four companies affiliated with the warehouse, including two companies that stored their products there: Virgin Scent and Day to Day Imports. The other two entities that received violations, Liberty Properties Limited Partnership, and its parent company, Prologis Inc., own the warehouse property.

South Coast AQMD also issued a fifth violation on Friday against Los Angeles County, which is responsible for maintaining the Dominguez Channel. Violations may come with civil penalties, such as fines, or ultimately lead to a civil lawsuit. Eight Carson residents have already filed a class-action lawsuit alleging that debris from a warehouse fire entered the channel, resulting in a noxious scent.

Virgin Scent and Day to Day Imports did not immediately respond to Insider's request for comment. Prologis told Insider that it "will continue to work with the Los Angeles County Fire Department in safeguarding the property against storm water runoff and cleaning up the fire debris."

In a statement to Insider, LA County Public Public Works Director Mark Pestrella said the county was "glad to see that Prologis, Inc. and Liberty Properties, LP — the parties the county believes are responsible for the anaerobic conditions that led to the release of hydrogen sulfide gas within the channel — are being held accountable."

Pestrella added that the county was working with state and federal regulators to investigate the incident. He did not directly address the violation issued against LA County.

Hydrogen sulfide can cause headaches, nausea, coughs, shortness of breath, and irritation of the eyes, nose, and throat at low concentrations. High concentrations, far higher than those detected at the Dominguez Channel, could potentially result in coma or death, according to the Centers for Disease Control and Prevention.

Some Carson residents experienced headaches and nausea from the fumes, Los Angeles County Supervisor Holly Mitchell said in an October statement. Other residents told The Guardian and the Los Angeles Times they experienced respiratory problems, like coughing and trouble breathing.

Monique Alvarez, a plaintiff in the lawsuit, told The New York Times that her three children broke out in welts after the hydrogen sulfide release. While the fumes recently subsided, she said, her kids still get bloody noses on occasion.

"People in our area are still getting sick," Alvarez said. "The symptoms are still here and our bodies are still saying something is wrong."

Levels of hydrogen sulfide were 230 times higher than California's public nuisance standard

The warehouse fire broke out on September 30. At the time, Sean Ferguson, an LA County fire inspector, told KTLA that the flames tore through crates of rubbing alcohol wipes. Pestrella also told The New York Times on Sunday that the warehouse contained hand wipes, bottles of hand sanitizer, and large vats of ethanol.

But it took roughly two months for investigators to associate the fire with the rotten egg smell. Local officials initially posited that a leaking pipeline had emitted the hydrogen sulfide, or that a September earthquake may have released the gas from a local refinery or chemical plant.

South Coast AQMD now alleges that the warehouse fire violated a California code, which prohibits the release of air contaminants that create a public nuisance. Offensive smells or public health hazards that affect an entire community or neighborhood are considered public nuisances in California.

The hydrogen sulfide levels in Carson reached upward of 7,000 parts per billion (ppb) — about 230 times the state nuisance standard. Hydrogen sulfide doesn't pose a risk of permanent health problems until people are exposed to 27,000 ppb for one hour, or 17,000 ppb for eight hours, The Guardian reported.

South Coast AQMD said in a press release that it has responded to more than 4,600 odor complaints from Carson and nearby areas since October 3. Residents described the smell as unbearable in posts on Facebook and Twitter, comparing it to vomit, body odor, and "the stench of death."

Since October, thousands of people have temporarily relocated to hotels to avoid the smell, with LA County reimbursing the cost of the rooms. Meanwhile, county officials have worked to eliminate the odor by spraying a biodegradable deodorizer and pumping oxygen into the channel — a process that inhibits the release of hydrogen sulfide.

Kerjon Lee, a spokesman for the county's public works department, told The New York Times that emergency work to get rid of the smell had already cost the county $54 million as of last week. Pestrella added that it could take up to two years to restore the channel's water conditions.