High levels of naturally occurring poison detected in waters off Marin coast
San Rafael, CA – Marin County Public Health has confirmed a case of paralytic shellfish poison (PSP), a naturally occurring toxin found in bivalves such as mussels, clams and oysters that are harvested in uncontrolled conditions.
One person, an adult who will not be further identified, consumed mussels harvested Sunday in Dillon Beach and was hospitalized for neurological symptoms consistent with shellfish poisoning. Public Health Officer Dr. Matthew Willis said the County’s public health staff was notified of the illness Tuesday.
“The person is getting better,” Willis said. “Fortunately, the clinician was aware of the elevated PSP levels in locally sport-harvested shellfish and made a timely diagnosis.”
On March 6, the California Department of Public Health (CDPH) notified Marin County Public Health 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. The County distributed a news release to warn the public on March 7.
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 last week were the highest levels detected in Marin in 20 years, and people up and down the California coastline are at risk, Willis said. In Marin, the highest levels were near Chimney Rock and points north of Stinson Beach.
“Because these are potentially lethal levels, we want to make sure no one is out there collecting shellfish until it’s safe again,” Willis said on March 7.
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.