County of Marin - News Releases - Warning for Shellfish Toxins

For Immediate Release
March 07, 2018

Public Health Warning for Shellfish Toxins

High levels of naturally occurring poison detected in waters of Drake Bay

San Rafael, CA – Marin County Public Health has issued a warning to people harvesting bivalve shellfish such as mussels, clams and oysters in Marin County  because of potentially lethal levels of a naturally occurring toxin, paralytic shellfish poison (PSP).

A pile of unopened shellfishPSP is a marine toxin that causes illness through the consumption of contaminated shellfish.
On March 6, the California Department of Public Health (CDPH) notified Public Health Officer Dr. Matthew Willis and other public health staff in Marin about a recent mussel sample from the Chimney Rock sentinel station, within Point Reyes National Seashore, that contained levels of PSP 37 times the “alert” level.

PSP is a marine toxin that causes illness through the consumption of contaminated shellfish. Changes in water conditions, including temperature, flow and salt content, can lead to surges in PSP. Cooking the shellfish does not alleviate the toxicity.

Anyone who experiences tingling, numbness, headaches, dizziness, nausea, rapid pain, or respiratory problems after ingesting any type of shellfish recently should seek medical attention immediately, Willis said.

There have been 542 reported illnesses and 39 deaths attributed to PSP in California over the past 90 years, according to state statistics. The PSP levels recorded this week are the highest levels detected in Marin in 20 years, and people up and down the California coastline are at risk, Willis said. However, no PSP-related illnesses have been reported recently in Marin.

The higher levels typically surface in the summer months, so the fact that they are occurring this early in the year is another sign of an increasingly unpredictable climate.

“Some PSP is detected regularly in the bay and the ocean, but the latest samples are showing record levels near Chimney Rock and points north of Stinson Beach,” Willis said. “Because these are potentially lethal levels, we want to make sure no one is out there collecting shellfish until it’s safe again. Please warn anybody who is out with boots and shovels looking for shellfish at low tide.”

Willis said the National Park Service has been notified to post warning signs at locations along Drakes Bay within the Point Reyes National Seashore.

The CDPH warning did not apply to commercially sold clams, mussels, scallops or oysters from approved sources. State law permits only state-certified commercial shellfish harvesters or dealers to sell those products. Shellfish sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins.

For the most current information on shellfish advisories and quarantines, call CDPH’s toll-free shellfish information line at 800-553-4133. For additional information, visit the CDPH marine biotoxin monitoring webpage.


Dr. Matthew Willis
Public Health Officer
Health and Human Services

3240 Kerner Blvd.
San Rafael, CA 94901
(415) 473-4163
Email: Dr. Matthew Willis
Marin HHS website