WILDFIRE AFTERMATH: IS OUR WATER SAFE?
In the aftermath of the Los Angeles megafires, there is an increased risk of dangerous debris and pollutants reaching the Santa Monica Bay and its shoreline. Heal the Bay has been monitoring all incoming water quality data from the Los Angeles Regional Water Quality Control Board to determine any potential impact on human health.
UPDATE – NEW DATA COLLECTED ON MAY 1, 2025 – Results are consistent with previous sampling efforts (i.e. no exceedances of risk screening levels). Get the full update below.
What You Need to Know:
- There are no existing guidelines to determine human health risk from swimming or surfing in the ocean after an urban fire. This makes it challenging to determine risk to public health from contaminants entering the bay from the burn areas. Heal the Bay used the EPA Risk Screening Tool to evaluate risks to public health.
- Recent water testing does not reveal any urgent, lethal threats. Data appears to be below the calculated risk-thresholds for human health.
- Acquiring missing data is key to ensuring safety. Previous data did not include testing for specific — and particularly concerning — types of arsenic and chromium: Inorganic Arsenic or Hexavalent Chromium (also known at Chromium-6), both of which can be harmful in lower concentrations.
- UPDATE: Hexavalent Chromium was included in the more recent testing, but Inorganic Arsenic was not. More details below.
- Key Findings:
- Arsenic: All samples were analyzed for Total Arsenic, which is a combination of Organic Arsenic and Inorganic Arsenic.
- Inorganic Arsenic is highly toxic but health impacts are most common with exposure from drinking water or contaminated foods.
- Total Arsenic levels exceed the median background (i.e. pre-existing) concentration (1.490 µg/L), suggesting elevated levels potentially resulting from the fire.
- UPDATE: Inorganic Arsenic was not included in the latest round of sampling by the LA Regional Water Board. Since our last post, we have been meeting with a group of toxicologists and public health experts. These toxicology experts do not believe testing for inorganic arsenic is warranted because inorganic arsenic is primarily hazardous when ingested; dermal contact is not considered a significant route of exposure under typical environmental conditions.
- Heal the Bay continues to advocate for testing of inorganic arsenic. It will provide a more in-depth understanding of risk, and can also provide peace of mind for beach visitors.
- Chromium: The Los Angeles Regional Water Quality Control Board analyzed for Total Chromium, which includes Trivalent Chromium (an essential nutrient with no known health risks) and Hexavalent Chromium. While there is no human health risk threshold for Total Chromium, the risk threshold for Hexavalent Chromium is 0.1 µg/L.
- Hexavalent Chromium, also known as Chromium 6, is usually produced by an industrial process, such as hardening alloy steel, and is known to cause cancer and can target the respiratory system, kidneys, liver, skin, and eyes.
- Until now, water samples have only been tested for Total Chromium. Although Hexavalent Chromium was not specifically analyzed during that time, results consistently showed Not Detected (ND) for Total Chromium. However, the detection limit for Total Chromium was approximately 16 µg/L, while the median background concentration was only 0.37 µg/L. Thus, even if Hexavalent Chromium were present at harmful levels, it would go undetected.
- In the May 1st samples, Hexavalent Chromium was tested for the first time, and results were reported as “Not Detected (ND)”. However, these results are inconclusive because the detection limit was not provided and the Reporting Limits were higher than the human health risk threshold for Hexavalent Chromium which is 0.1 µg/L. Without knowing how low the analytical method can detect, we cannot determine whether Hexavalent Chromium is below the risk threshold.
- While we don’t have any information that would point to the likelihood of chromium in our coastal waters, Heal the Bay urges caution and recommends retesting all locations for Hexavalent Chromium using methods with detection limits below the risk threshold of 0.1 µg/L. Future testing should ensure methods are sensitive enough to detect concentrations below the human health risk threshold.
- Heal the Bay is planning to collect sand and water samples from three beaches with stormdrain outfalls, including Rustic Creek Outfall. We are reaching out to labs and will plan to include inorganic arsenic and hexavalent chromium.
- Arsenic: All samples were analyzed for Total Arsenic, which is a combination of Organic Arsenic and Inorganic Arsenic.
What’s Next?
- More Water Testing. Heal the Bay plans to conduct additional water quality testing and will provide updates when that data is available. Stay tuned.
- Recommendations for new public health risk-thresholds for water contamination from climate disasters. Heal the Bay is part of the Southern California Coastal Water Research Project Task Force, which is developing new guidelines for fire-related water quality monitoring efforts.
Keeping Yourself and Your Families Safe
- Health risk appears to be low for people swimming and surfing in Santa Monica Bay, based on comparisons to risk-thresholds calculated using EPA’s risk-screening level calculator, and the currently available data.
- Because we don’t have data on Inorganic Arsenic and debris removal is actively occurring along PCH, which can impact air quality and send debris into the water, we are advising the following precautions for the time being:
- Avoid swimming and surfing within 250-yards of active debris removal. While the US Army Corp of Engineers (USACE) completed their debris removal in May, some properties opted out of this program and active debris removal by private contractors may still be occurring on properties between Carbon Beach and Topanga Creek.
- Don’t enter the water for at least 72-hours after a rain event.
- Keep an eye out for debris in the water.
- Risk tolerance is a very personal decision, we are providing data to help inform your decisions.
- Bacteria, unrelated to the fires, can still make people sick. Please check our Beach Report Card (or download our app on your iPhone or Android) for the latest bacteria data at your favorite West Coast beach.
How We Assessed Potential Risk
- Heal the Bay used the EPA Risk-Screening Level Calculator to determine health risk from swimming and surfing.
- Tested scenario: 4 hours/day in water, 180 days/year, across all age groups (including infants).
- We evaluated water quality data from various sites along Santa Monica Bay from Malibu to Malaga Cove collected by Heal the Bay scientists and Los Angeles Regional Water Quality Control Board between January 27 and May 1, 2025.
Heal the Bay’s testing locations.