The California Department of Public Health is warning consumers not to eat recreationally harvested Marin County mussels, clams, scallops or oysters due to dangerous levels of paralytic shellfish poisoning toxins. The warning does not apply to commercially harvested shellfish, which are tested regularly. Recent tests detected the presence of the naturally occurring toxins in mussels harvested in Marin. The toxins, which are not destroyed by cooking, can cause illness or death in humans by affecting the central nervous system. The health department imposes an annual quarantine on mussels from May through October, when cases of shellfish poisoning are most likely to occur. For updates on quarantines, call (800) 553.4133.