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division of radiation safety and environmental management

Marine Biotoxin Monitoring Program

The Environmental Management Branch manages the Marine Biotoxin Monitoring Program for bivalve shellfish in California.  Other CDPH agencies participating in the program are the Food and Drug Branch, Division of Communicable Disease Control, the Microbial Diseases Laboratory, the Food and Drug Laboratory, and the Office of Public Affairs. 

California has the longest-standing biotoxin monitoring program in the U.S., beginning in 1927 in response to a massive paralytic shellfish poisoning (PSP) episode. That event resulted in several deaths and over 100 illnesses that were associated with mussel consumption. In the fall of 1991, another natural neurotoxin called domoic acid was discovered in the California marine environment in several species, including shellfish. Domoic acid poisoning involves a wide range of symptoms, including severe neurological effects that have been referred to as amnesic shellfish poisoning (ASP).

Because PSP and domoic acid toxicity represents a serious ongoing public health threat that requires year-round attention, the CDPH has implemented a prevention program that has traditionally been comprised of six basic elements: (1) a coastal phytoplankton monitoring program for early detection of toxigenic species that could impact shellfish resources;  (2) a coastal shellfish monitoring program that serves to protect recreational harvesters and serves as an early warning for harmful algal blooms (HABs) that could be transported into the bays and estuaries used for commercial shellfish aquaculture; (3) frequent monitoring of commercial shellfish growing areas; (4) an annual statewide quarantine on sport-harvested mussels (from May 1 through October 31); (5) mandatory reporting of disease cases; (6) public information and education activities.

The shellfish monitoring component of the Marine Biotoxin Monitoring Program relies on participation of people from a wide variety of local, state, and federal agencies, Tribal biologists, educational organizations, researchers, and, increasingly, citizen volunteers. Program participants collect shellfish samples, primarily mussels, and ship them to the CDPH laboratory in Richmond, California where they are tested for the PSP toxins and domoic acid. Commercial shellfish growers, who account for approximately two-thirds of the total number of samples, are required to submit shellfish samples at least weekly for toxin testing as a condition of their certification by CDPH.

CDPH initiated a volunteer-based phytoplankton monitoring program in 1991 to detect an initial increase of a toxin-producing species before shellfish and other seafood resources are impacted. This program draws on a wide range of participants as detailed for the shellfish sampling program. Phytoplankton monitoring participants are provided nets for collecting concentrated seawater samples, which are sent to the CDPH laboratory for examination under a microscope. This effort allows CDPH to focus additional attention on those coastal areas experiencing an increase in toxin-producing phytoplankton or an increase in toxins in shellfish.

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