The oceans can affect our health in many ways. They contain many types of microscopic organisms, some of which produce toxins when conditions are right. Toxins from harmful algal blooms, sometimes called red tides, can contaminate shellfish such as clams and mussels. Eating the contaminated seafood may cause serious illness. Harmful algal blooms are unsafe to touch or swallow, and they can produce airborne toxins that cause health problems when inhaled.