Sewage Spill Lawsuit Update #2:
Elevated Hydrogen Sulfide Levels Recorded in El Segundo

In the days following the Hyperion Sewage Spill on July 11, the South Coast Air Quality Management District (AQMD) found increased levels of hydrogen sulfide in the El Segundo community.  Thus far, AQMD has issued thirty-two (32) Notices of Violation for creating a public nuisance as a result of the noxious odors and one (1) Notice of Violation for the release of visible emissions.

LA Sanitation (LASAN)’s air quality monitoring system at the Hyperion fenceline has shown the highest levels of hydrogen sulfide in the El Segundo community to date.

Exposure to hydrogen sulfide could have detrimental effects on the health and well-being of nearby residents.

What Is Hydrogen Sulfide?

Hydrogen sulfide (H₂S) is a colorless, flammable, and extremely hazardous gas with a characteristic “rotten egg” smell.  Hydrogen sulfide occurs naturally in crude petroleum and natural gas, but it can also be produced when bacteria break down organic materials and human waste in sewage.  Hydrogen sulfide is a common byproduct of wastewater treatment facilities like the Hyperion plant.

How Does It Affect My Health?

Hydrogen sulfide is both an irritant and a chemical asphyxiant, affecting both your use of oxygen and your central nervous system. The gas has been known to aggravate existing health conditions, particularly those that cause breathing problems.

Symptoms of hydrogen sulfide exposure include:

  • Headaches
  • Dizziness
  • Nausea
  • Eye, nose, and throat irritation
  • Respiratory distress
  • Anxiety, depression, and emotional distress

According to the CDC, exposure to hydrogen sulfide may be even more severe for children. Not only do children breathe faster and more often than adults, but hydrogen sulfide exposure is more likely to occur closer to the ground, where children breathe and play.

How Serious Was the Exposure?

The World Health Organization (WHO) states that hydrogen sulfide levels should not exceed an average of .005 ppm (or 5.02 ppb) in 30 minutes. This standard was developed around minimizing and preventing symptoms from the noxious odors. Following the Hyperion Sewage Spill, hydrogen sulfide levels in the El Segundo community were well over this WHO standard.

AQMD is monitoring air quality from St. Anthony Church, located northeast and within a mile of the Hyperion facility. SCAQMD’s data shows at least 10 days of excess hydrogen sulfide recorded at this station. Many El Segundo residents are even closer to the Hyperion facility than St. Anthony Church and could face more severe exposures.

Additionally, LASAN itself monitors the air quality at the Hyperion facility’s fenceline. LASAN’s fenceline monitors revealed hydrogen sulfide levels as high as 657 ppb on July 27, 2021. As recently as September 15, these same monitors have continued to show hydrogen sulfide levels exceeding the WHO’s limit for hydrogen sulfide exposure.

Curiously, LASAN is not doing any fenceline testing at night for hydrogen sulfide.  During the night, hydrogen sulfide is less likely to dissipate into the atmosphere and more likely to reach people living further inland. 

No one should have to endure noxious odors at these levels.

What Is PARRIS Doing About It?

PARRIS attorneys are closely monitoring the air quality data in El Segundo. We have strongly encouraged the South Coast AQMD in a series of letters to inform El Segundo residents of the abnormal hydrogen sulfide levels in their community, and Hyperion’s violations of the WHO limits for hydrogen sulfide. We also called for air quality testing between the Hyperion fenceline and St. Anthony Church, which will help better record hydrogen sulfide levels impacting residents closer to Hyperion.

As we move forward in our legal action against LASAN, we are committed to keeping the public informed of any and all exposure to hydrogen sulfide.

How Can I Protect My Rights?

If you live near the Hyperion plant and you’ve experienced (a) noxious odors in your home and (b) abnormal or worsened medical symptoms since July 11, then you may have a case against LASAN.

You may be entitled to damages for any of the following:

  • Relocation expenses
  • Air conditioning units and increased electrical costs
  • Air purification systems and increased electrical costs
  • Medical expenses (past and future)
  • Loss of the enjoyment of your home
  • Income losses
  • Emotional injuries (anxiety or depression) and
  • Physical injuries (skin rashes, eye/nose irritation, nausea, and headaches).


If you think you have a case against LASAN, call PARRIS Law Firm today at 310-362-3921. We’ll fearlessly fight for you until you see justice.  Filing a claim is the best way to protect your rights and ensure a disaster like this never happens again.