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Prevention & Control

How to Reduce Exposures and Prevent Illness

	health advisory sign

Permanent HAB health advisory sign in Oregon. Credit: Photo courtesy of Oregon Public Health.

It is not possible to know if an algal bloom is harmful just by looking at it. Additionally, toxins can be present even when an algal bloom is not visible.

Protect yourself and your pets from harmful algal blooms (HABs):

  • Avoid entering or playing in bodies of water that:
    • smell bad
    • look discolored
    • have foam, scum, or algal mats on the surface
    • contain or are near dead fish or other dead animals (for example, do not enter a body of water if dead fish have washed up on its shore or beach)
  • Follow local or state guidance if you are notified that your tap water contains algal toxins. Boiling water does not remove algal toxins and can increase the amount of toxin in the water. Be aware of advisories and health risks related to consuming contaminated fish and shellfish. For more information, see the Environmental Protection Agency's (EPA) Choose Fish and Shellfish Wisely web pages.

Health Promotion Materials

Preventing Freshwater Exposures

  • Do not drink directly from lakes, rivers, or ponds. Even if the water looks "safe," it might contain toxins or germs that can cause other types of illness.
  • Check your state or local environmental health website for beach or lake closures in your area before visiting.
  • Do not fish, swim, boat, or play water sports in areas that are experiencing a HAB 1. Do not let pets eat algae, get in the water, or go on the beach or shoreline.
  • Rinse pets off with tap water after they have been in a lake, river, or pond; do not let them lick their fur until they have been rinsed.
  • Do not fill pools with water directly from lakes, rivers, or ponds, as the water might contain toxins or germs that can cause other types of illness.
Reference
  1. Lopez CB, Jewett, EB, Dortch Q, Walton BT, Hudnell HK. Scientific assessment of freshwater harmful algal blooms. [PDF - 78 pages] Washington DC: Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science and Technology. Washington DC; 2008.

Preventing Marine (Salt) Water Exposures

  • Check your state or local environmental health website for beach closures in your area before visiting.
  • Do not fish, swim, boat, or play water sports in marine waters that are experiencing a HAB 1. Do not let pets eat algae, get in the water, or go on the beach or shoreline.
  • Rinse pets off with tap water after they have been in the ocean; do not let them lick their fur until they have been rinsed.
  • Avoid eating very large reef fish (especially the head, gut, liver, or roe). You can reference the FDA Reef Fish Guidance for more information on reef fish associated with unsafe levels of toxins.
  • Follow local guidance if you plan to eat any fish or shellfish that you harvest yourself.
Reference
  1. Lopez CB, Jewett, EB, Dortch Q, Walton BT, Hudnell HK. Scientific assessment of freshwater harmful algal blooms. [PDF - 78 pages] Washington DC: Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science and Technology. Washington DC; 2008.

Preventing HABs

Many large-scale efforts around the country are underway to reduce the occurrence of HABs, mainly by decreasing the amount of nutrients such as nitrogen and phosphorus that flow into our waters.

The Great Lakes Restoration Initiative (GLRI) has made it a priority to reduce phosphorus runoff in three major watersheds across four states: Indiana, Michigan, Ohio, and Wisconsin 1. In addition, the EPA, along with six other federal agencies, six states, and the District of Columbia, have collaborated to develop strategies to reduce nutrient inputs into the Chesapeake Bay 2.

To reduce the occurrence of HABs in your neighborhood:

  • Use only the recommended amount of fertilizers 3 on your yard. This will reduce extra nutrients from running off into nearby water bodies.
  • Maintain your septic system to prevent wastewater from leaking and seeping into nearby lakes and ponds 3. Wastewater is filled with nutrients that are food for algae.
References
  1. EPA, Great Lakes Interagency Task Force. Great lakes restoration initiative: Fiscal year 2012 report to Congress and the President. [PDF - 48 pages] 2012.
  2. Federal Leadership Committee for the Chesapeake Bay. Strategy for protecting and restoring the Chesapeake Bay watershed. 2010.
  3. Anderson DM. Approaches to monitoring, control and management of harmful algal blooms (HABs). Ocean Coastal Manag. 2009;52(7):342-347

What should I do if I have been exposed?

If you have any questions about symptoms that you are experiencing, call your local or state poison information center. The specialists might be able to provide information about HAB-associated illnesses.

Consult a healthcare provider for advice about how to relieve your symptoms. If you do consult a healthcare provider, please let them know that you might have been exposed to a HAB or that you have recently consumed fresh or marine water fish or shellfish that might have be contaminated with toxins. There are currently no available tests or special treatments for HAB-associated illnesses, but information about the suspected cause of your illness might help your healthcare provider to manage symptoms.

Contact your local or state health department if you suspect there is a HAB. Some local and state health departments have web forms or hotlines for reporting suspected HAB-associated illnesses directly to the health department. For more information about symptoms, visit Illness and Symptoms.

What should I do if my pet has been exposed?

If your pet has come into contact water that has an algal bloom, rinse them with tap water as soon as possible.

Seek veterinary care immediately if your pet has consumed or licked algae on its fur after swimming or playing in water that has an algal bloom.

While no HAB-associated human deaths have been reported in the United States, many pet deaths (especially dogs) have been reported after the animal swam in or drank from water bodies with ongoing cyanobacteria blooms. Also, there were anecdotal reports of dogs becoming ill after eating foam washed up on a beach during a Florida red tide. For more information on red tides, please visit Marine Environments. Between 2007–2011, thirteen states reported 67 cases of cyanobacteria toxin-related illness in dogs to CDC 1. Over half (58%) of these cases resulted in death 1.

Reference
  1. Backer LC, Landsberg JH, Miller M, Keel K, Taylor TK. Canine cyanotoxin poisonings in the United States (1920s-2012): review of suspected and confirmed cases from three data sources. Toxins. 2013;5(9):1597-628.

Reporting an Illness

  • Report any HAB-associated illness to your local or state health department. In some states, this can be done through an online form or a hotline. If not, call your local or state health department.
  • For reporting HAB-associated illness in pets, check with your local or state health department or your veterinarian.

State Resources

For the general public: Visit your state government website to find more information about water testing and beach closures in your area. Some states provide information on state laboratory testing, as well as environmental and/or health information related to HABs.

For state and local jurisdictions: CDC can provide technical assistance to state and local jurisdictions to develop their public health responses to HAB events. If you need technical assistance in response to a HAB event, please contact the Health Studies Branch at 770-488-3410 or email us at cleanwaterforhealth@cdc.gov.

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