Recreationally harvested Marin County mussels, clams and scallops have been found to contain dangerous levels of paralytic shellfish poisoning toxins, the California Department of Public Health announced late Wednesday. The warning does not apply to commercially harvested shellfish. The naturally occurring toxins, which are not destroyed by cooking, can cause illness or death in humans by affecting the central nervous system. For updates on shellfish poisoning and quarantines, call (800) 553.4133.