Recreational water quality and health: Hazards

Learn about hazards that may be present in natural waters.

On this page

• Pathogenic microorganisms
• Swimmer's itch
• Cyanobacterial blooms
• Waves, currents, depths and visibility
• Litter and debris
• Cold, heat and sun exposure
• Chemical contaminants

Pathogenic microorganisms

Pathogenic microorganisms are extremely small organisms that may cause disease, and include:

• bacteria
• viruses
• parasites

Many different kinds can be present in the water and sand at recreational water areas. Most come from human and animal waste that enters waterways from:

• swimmers
• runoff from farms
• discharges of sewage and stormwater

Some pathogens live naturally in the water and can become a problem if they are present in high enough numbers.

Pathogens can cause infections if you swallow contaminated water or if it gets into your eyes, ears, nose or open cuts or wounds.

The most common types of illnesses associated with swimming or playing in recreational waters are:

• skin, ear or eye infections
• gastrointestinal illness, such as:
  • diarrhea
  • vomiting

Some pathogens that commonly cause illness include:

• noroviruses
• Cryptosporidium
• pathogenic Escherichia coli (also known as E. coli)

Some pathogens can cause more serious illnesses. For example, Naegleria fowleri causes an extremely rare meningitis that is almost always fatal. It occurs when a person inhales water containing the microorganism. It's commonly found in warm lakes and ponds in tropical and subtropical climates. Most cases are in the southern US, but some have occurred in northern states where water temperatures are similar to those found in parts of Canada. No cases have been reported in Canada to date.

Swimmer's itch

Swimmer's itch is caused by parasites that are released into the water by infected snails. They are most often found in shallow waters close to the shoreline where there are many aquatic plants.

The swimmer's itch parasite cannot survive in humans. When it comes into contact with a swimmer, it tries to penetrate the outer layers of skin but quickly dies. This causes an allergic reaction and rash. Swimmer's itch is not contagious and cannot spread from one person to another.

Symptoms of swimmer's itch are:

• an itching, burning or tingling of the skin
• small reddish pimples that may develop into small blisters or a rash

The severity of the symptoms varies from person to person. Because swimmer's itch is an allergic reaction, the reactions can be faster and more intense each time you are exposed to contaminated water. The condition can last from a few days up to 2 weeks.

Cyanobacterial blooms

Cyanobacteria (also known as blue-green algae) are naturally occurring bacteria that can contain toxins that are harmful to humans and animals.

Learn more about:

• Cyanobacteria

Waves, currents, depths and visibility

Some beach characteristics can increase the risk of injury or drowning, such as:

• rough waves
• changing tides
• deep waters close to the shoreline
• strong currents, including rip currents
• shallow waters in areas where swimmers may try to dive
• cloudy waters or thick plant growth that make it hard to spot hazards or swimmers in distress

Litter and other debris

Litter and other debris can be a hazard on the beach or in the water. Examples include:

• logs
• cans
• rocks
• sticks
• bottles
• broken glass

They can easily cause cuts or punctures, mostly on the feet and legs.

Cold, heat and sun exposure

In Canada, cold water temperatures are more of a concern than warm water temperatures. Sudden exposure to cold water temperatures (15°C or lower) can result in:

• gasping and cold shock
• being unable to keep swimming
• hypothermia

Even at comfortable swimming temperatures (20 to 30°C), your body loses heat over time. Prolonged contact can cause symptoms of cold water exposure.

Hot waters, such as those found in natural hot springs, can reach temperatures above 37°C. Prolonged exposures can lead to overheating, with symptoms including:

• nausea
• dizziness
• weakness
• headache
• increased or decreased heart rate

High air temperatures during recreational activities can lead to heat illness, and overexposure to the sun's UV (ultraviolet) rays can be harmful.

Sun safety basics

Fact Sheet: Staying Healthy in the Heat

Chemical contaminants

Recreational water areas may sometimes contain chemical contaminants. Sources include wastes from industries and runoff from farms and cities. Generally, the health risks from exposure to chemicals in Canadian recreational waters are low.