County Recommends Avoiding Prolonged Outdoor Activities Between 9 p.m. and 8 a.m. Around Dominguez Channel

Los Angeles County officials have been working since Oct. 6 to investigate and address the pungent odor affecting communities in the area of Dominguez Channel in the City of Carson. A multi-agency response — including the County departments of Public Works, Public Health, Fire and the Office of Emergency Management and the South Coast Air Quality Management District — was mobilized in response to this incident and to provide rapid relief to residents and businesses that have been affected.

The Los Angeles County Department of Public Health or Public Health has updated the health recommendations for residents impacted by odors reported in Carson and surrounding communities to avoid prolonged outdoor activities between the hours of 9 p.m. through 8 a.m., based on patterns seen with air monitoring results, and whenever odors are strong to reduce exposure.

South Coast AQMD is continuing to conduct air monitoring in Carson and the surrounding areas using technologies, including handheld hydrogen sulfide (H2S) monitors, grab samples, and mobile monitoring.

Monitoring efforts are focused on schools and senior centers in communities impacted. Community monitoring has shown H2S levels to be within typical background levels. However, elevated H2S levels have been detected at various locations along the Dominguez Channel that exceed state nuisance thresholds, but not at levels determined by health experts to be imminently dangerous.

A fixed air monitor was set up last week at the intersection of E. 213th St. and Chico St., near a residential neighborhood adjacent to the Channel, to supplement the monitoring network. The monitor has shown high H2S levels in overnight readings obtained from Oct. 14 through Oct. 16. The highest 1-hour average concentrations over those three days were 3.7 ppm, 6.2 ppm, and just under 7.0 ppm, respectively.

South Coast AQMD inspectors conducted 24-hour operations through the weekend and obtained instantaneous readings near residences that were significantly lower than the levels detected at the 213th & Chico monitor. The agency continues to provide data to public health professionals. Additional outreach efforts were conducted by DPH and Hazmat at residences closest to the Channel in an abundance of caution.

On Oct. 17 and 18, readings obtained at the 213th & Chico monitor and through handheld monitoring were drastically lower. The highest readings at the fixed monitoring site over the last two nights were 1.1 ppm and 0.8 ppm. Further information regarding South Coast AQMD’s monitoring efforts can be found on the agency’s website, www.aqmd.gov.

Solutions to Channel Odors

A specialized team of scientists and engineers has been working aggressively to develop solutions to address conditions within the channel, alleviate the smell and restore the waterway to a healthy estuary.

On Oct. 15, LA County Public Works maintenance crews began spraying a natural, water-based and biodegradable deodorizer in the channel to neutralize the odor. The community should expect a noticeable reduction in the smell within 3-5 days.

A bubbler system was installed Oct 19, to inject millions of tiny oxygen bubbles into the water to increase the levels of dissolved oxygen and prevent the creation of additional hydrogen sulfide gas.

Residents and Businesses

For businesses that may be impacted by the foul odors, if you have noticed strong odors inside your building during the last week when opening in the morning, Public Health recommends businesses run their air-conditioning units 1 to 2 hours, if possible, before on-site operations begin. Doing so will increase air flow inside your business and help reduce any odors present that may have built up overnight.

Although the odor has also been detected by those in surrounding communities, the smell is reportedly stronger and higher levels have been detected in the late evening and early morning in the areas next to the Channel. The levels noted can cause notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, the effects are not expected to be disabling, but are expected to be transient and reversible as the exposure decreases or stops. 

The source continues to be considered as naturally decaying organic material (vegetation and marine life) at the bottom and sides of the Channel in Carson. As air monitoring of the surrounding areas continues, no other point sources for the hydrogen sulfide have been identified. South Coast AQMD, County Fire Hazardous Materials (HazMat), and Public Health continue to evaluate and monitor hydrogen sulfide concentrations and mitigate health impacts.

Public Health Recommendations

While the effort to get rid of the odor continues, Public Health recommends residents take the following actions to lessen their exposure and any symptoms experienced and to protect the health of themselves, their family, and their pets:

1. If symptoms feel life threatening, seek immediate medical care.
2. If symptoms are persistent, worrisome, or worsening, seek medical attention. Relocate to another area until odors go away. For assistance, call 2-1-1.
3. Avoid prolonged outdoor activities between the hours of 9 p.m. through 8 a.m. and whenever odors are strong to reduce exposure.
4. Keep doors and windows closed as much as possible to prevent outdoor odors from entering the residence or business. Air out the home/business when odors are not present.
5. If residents have a central heating, ventilation, and air conditioning (HVAC) system, contact an air conditioning specialist, if needed, to determine if the air filters in the system may be replaced with High Efficiency Particulate Air (HEPA) or MERV-rated filters with activated charcoal (carbon) to improve the air quality inside. If residents notice odors are stronger or symptoms are worse in the late evening or early morning hours (9 p.m. to 7 a.m.), residents should try running their central HVAC system throughout the night, if they have not already. Temporarily relocating may be best if this does not help.
6. Use a certified portable HEPA indoor air filter with activated charcoal to improve air quality in their home. If residents notice odors are stronger or symptoms are worse in the late evening or early morning hours (9 p.m. to 7 a.m.), residents should try running their portable indoor air filter throughout the night, if they have not already. Temporarily relocating may be best if this does not help.
7. Keep pets indoors. If residents notice any of the following in their pets, they should contact their local veterinarian: difficulty breathing, vomiting, lethargy, or nausea.

Hydrogen sulfide is a colorless gas that has a very strong odor (like “rotten egg”). Its smell can be detected and cause temporary mild to moderate symptoms even below the minimum detection limit of 1 part per million (ppm) or 1000 parts per billion (ppb) of typical equipment used to detect it. Everyone should take steps to reduce their exposure when the odors are present. People experiencing persistent, worrisome, or worsening symptoms from the odors are encouraged to contact their health care providers, especially if they have any chronic health conditions. People should also ensure that they have adequate supplies of their medications, especially if they have heart or lung conditions. In addition, Public Health recommends temporarily leaving the area where odors are present to alleviate health impacts.

For more information contact the Public Health Community line at 626-430-9821 and leave a message with your contact information and your call will be returned. The message line will be checked every hour between 7 a.m. to 10 p.m. every day while odors persist.

If you live in the areas of Carson or West Carson, or the surrounding vicinity, County Public Works has a reimbursement program for the purchase of HVAC air filters, portable HEPA air filters, or for temporary relocation. during this public nuisance event. 

Review the recommendations and guidance on “Air Cleaners and Filters to Improve Indoor Air Quality and Remove Odors” below before purchasing filters. Visit https://lacounty.gov/emergency/dominguez-channel for more information on the reimbursement program. Residents can click here to submit for reimbursement. For assistance, they can call 2-1-1.

In addition, residents should continue to call South Coast AQMD to report odors at 1-800-CUT-SMOG (1-800-288-7644) or use the agency’s On-line Complaint System.