Biotoxins - Myths and Misconceptions

What do you know about biotoxins? Does your knowledge contain myths? Misconceptions? Some common beliefs are listed here...and not all of them are true.

PSP is only present in red or muddy colored water.

Misconception. PSP is often associated with the term "red tide", which is misleading. Red or muddy colored water is no indication of PSP. Occasionally the water is red when PSP levels are high; there is a type of toxic algae that turns water a reddish color. However, most of the red-colored algae in Washington are not toxic. The fact is, high levels of toxin can be present in water that is crystal clear.

Toxic shellfish look different than non-toxic shellfish.

Myth. There are no visual clues to tell you when shellfish are toxic. They look exactly the same as shellfish that are safe to eat.

A good test to see if shellfish are toxic is to touch one to your tongue. If your tongue tingles, it's toxic. If it doesn't, it's ok to eat.

Myth. This is not a reliable test, in fact it's a very risky practice. If your tongue doesn't tingle, the shellfish can still contain high enough levels of toxin to make you sick. If your tongue does tingle, the shellfish is extremely toxic and you may have just made yourself seriously ill. Please don't try this!

If I develop symptoms of biotoxin poisoning*, I shouldn't worry too much. Antidotes are readily available.

Myth. There are no antidotes for biotoxin poisoning. The only treatment for severe cases is to be placed on life support systems (such as a ventilator) until the toxin passes from your system. This is why it's so important to call 911 or your health care provider if you have symptoms of PSP or ASP. Time is of the essence. Deaths have occurred from PSP in less than thirty minutes.

I should view the Shellfish Safety Map or call the Hotline a few days before I go to the beach to make sure the area is safe to harvest shellfish.

Half right. You should check these resources, but do so just before harvesting to make sure the area you're going to is safe. Biotoxin levels can change rapidly, and there can be several closures in the course of one day.

Before digging shellfish, I should call the county health department.

True. The county where you're planning to dig will have current information on beaches closed for pollution or other problems.

You know shellfish are safe to eat if you see seagulls or other wildlife eating them and they don't look sick or have any symptoms.

Myth. The tolerance level for biotoxins in wildlife species is not known. Observing birds or other animals that have eaten shellfish will not tell you if the shellfish are safe to eat.

Cooking shellfish in boiling water will remove toxins, making them safe to eat.

Myth. Biotoxins are not destroyed by cooking. Only pathogens such as Vibrio and Norovirus are destroyed with proper cooking.

Biotoxins are related to water pollution.

Myth. There is no correlation between biotoxins and pollution. Biotoxins can be present in otherwise pristine waters, and even heavily polluted waters can be biotoxin-free.

You should only harvest shellfish in months that have the letter "r."

Misconception. Shellfish can be toxic (or safe) at any time of the year. In our state, there have been high levels of biotoxins in September, October, get the idea. And May, June, July, etc. are often completely safe for shellfish harvesting.

How did this belief get started?

This misconception was actually law at one time, first enacted in 1719 by the legislature in New Jersey. The law was passed in an attempt to address a spoilage issue. In the warm summer months (those without an "r" in the name), shellfish would spoil on the way to market because there was no refrigeration. (Imagine horse-drawn oyster wagons heading to town on a hot summer day!) Although modern refrigeration methods make the law obsolete, this misconception is still popular today.

More Resources


Diarrhetic Shellfish Poisoning (DSP)

Paralytic Shellfish Poisoning (PSP)

Amnesic Shellfish Poisoning (ASP)

Other Illness Causing Pathogens in Shellfish



Know before you dig!

Shellfish Safety Map - View status of recreational beaches on maps.

List of Public Beaches and Status by County

Recorded Hotline for Biotoxin Closures: 1-800-562-5632

List of Biotoxin Beach Closures by County

Shellfish Identification

Questions? Call us at 360-236-3330 or the local county health department during weekday business hours.