Mystery sediment washes ashore following Los Angeles wildfires. Is it safe to swim and surf?

Yahoo

15-04-2025

LOS ANGELES – Residents and beachgoers along the Los Angeles County coastline have noticed dark and silty sediment washing up onto local beaches following recent California wildfires and subsequent storms.
The Los Angeles County Department of Beaches and Harbors (DBH), which operates and maintains 18 public beaches along the Pacific Ocean coastline from Malibu through San Pedro, said it has tested the debris and ash for fire-related substances and health risks, particularly at Will Rogers State Beach and Topanga Beach.
Samples provided to county health officials and other local and state agencies for analysis in February have offered some reassurance following the deadly devastating wildfires.
According to DBH, early test results indicate that the sediment does not appear to be hazardous material and poses no immediate threat to the environment or human health.
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This comes after a handful of wildfires in the Los Angeles metro raced through numerous neighborhoods after igniting in January. Tragically, over two dozen people were killed as wildfires razed upwards of 15,000 homes and businesses and created unhealthy air for millions of residents.
Storms then carried the ash and debris from the infernos into rivers and streams. Eventually, the ash and debris flowed into the ocean, where waves washed the material back onto the beach. This is a natural process after fires, especially during rainy or windy conditions, according to DBH officials.
"The test results for contaminants – including metals, petroleum hydrocarbons, chlorinated pesticides, polychlorinated biphenyls, volatile and semi-volatile organic compounds and asbestos – were below levels that would characterize the debris as hazardous waste," the agency notes.
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Initial tests found metal concentrations that are likely consistent with naturally occurring background levels, and importantly, no asbestos was detected. Other substances analyzed were either not found at all or present in only extremely limited and minor concentrations.
Additional testing is also planned in the coming months, with a target of completion before the Memorial Day weekend.
Despite the sediment's unusual appearance, county officials currently have no plans to remove it from the beaches.
"Removing it could harm the ecosystem by disturbing rocks, sand layers and marine habitats," the DBH said. "It could also erode the shoreline, potentially causing long-term environmental damage."
Instead, the current strategy is to allow natural processes to take their course. Officials anticipate that the natural action of tides and weather patterns will gradually clear the sediment away over time.
Last week, the Los Angeles County Department of Public Health lifted the ocean water advisories that were in place along the coastline following recent wildfires and subsequent runoff.
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Based on data collected in January and February, environmental advocacy group Heal the Bay (HTB) is cautiously optimistic that chemical contamination from the fires no longer poses a major risk for swimming and surfing in local waters.
While the water quality appears to be improving, authorities are urging continued vigilance due to the presence of physical debris in the water and along the shore.
"Because debris can include sharp objects, everyone should continue to use extra caution to avoid anything that looks like wildfire remnants, whether on the sand or in our coastal waters," HTB said in their April 10 update.
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Debris removal has begun on the 300 homes along Pacific Coast Highway that were lost in the fires.
"While this is great news for the bay, there may be a risk to human health within 250 yards of debris removal activity," HTB adds.
This activity can disturb contaminants, potentially releasing them into the air and water. Out of an abundance of caution, HTB is also highlighting that recreating within this 250-yard radius may pose an additional risk to beachgoers, swimmers and surfers.Original article source: Mystery sediment washes ashore following Los Angeles wildfires. Is it safe to swim and surf?