Press Release

BALTIMORE, MARYLAND (June 1, 2011) – With summer approaching, the Maryland Department of the Environment, your local health department, and the Department of Health and Mental Hygiene encourage swimmers to enjoy Maryland waters and be sure to check beach advisories and take some simple steps to stay healthy and protect our beaches.

Information on beach closings and advisories is posted on and on many local health department websites. The Maryland Healthy Beaches website also includes tips for preventing water-related illnesses.

Last year, there were reports about a number of infections associated with Vibrio, which is an organism that naturally occurs in many waterways, including Maryland waters, when water temperatures elevate in the summer. Some species of Vibrio are potentially harmful to human health. The National Oceanic and Atmospheric Administration, in partnership with Maryland and others, has developed a new method to help predict when Vibrio bacteria are likely to be present in Chesapeake Bay waters.

Beach monitoring

MDE joins with other federal, state, and county government agencies to help keep swimmers healthy. The public should swim only at monitored beaches. Swimming in other natural waters could present a health or safety risk from bacteria or such physical dangers as submerged debris.

Before each beach season local health departments conduct sanitary surveys around beaches to identify and evaluate pollution sources that potentially contribute to high bacteria levels. Identified problems are immediately acted upon.

Last year, local health departments monitored water quality at 204 designated swimming beaches in Maryland. While swimming in natural waters is never risk-free, regular monitoring for indicator bacteria helps identify potential health risks. The frequency of monitoring is based on the frequency and nature of the use of the beach, the proximity of pollution sources, and the effects of storms.

When indicator bacteria levels exceed Maryland and U.S. Environmental Protection Agency standards, an advisory is issued by the local health department. An advisory is a recommendation against swimming or water sports. These indicator bacteria are not usually harmful and are commonly found in the gut of humans and warm blooded animals in very high numbers, and are quick, easy and inexpensive to identify in the laboratory.  The assumption is that if these bacteria are present then potentially harmful human pathogens may also be present.

During the 2010 beach season (from Memorial Day to Labor Day), Maryland beaches were not under an advisory 96 percent of the time. Beaches are only closed when the waters are affected by a sewage spill or overflow or other harmful contaminants.

The Maryland Healthy Beaches website includes a Google Earth application that provides color-coded status reports on beaches throughout the state and daily updates on rainfall at individual beaches. The public is always advised to avoid swimming following a significant rain event because potentially harmful bacteria concentrations may rise after heavy rains due to polluted stormwater runoff.

Maryland’s recent actions to reduce stormwater pollution, including the Stormwater Management Act of 2007, a new general permit to control stormwater discharge during construction, and new municipal stormwater permits now being issued for Maryland’s 10 largest counties, are estimated to reduce urban stormwater by 20 to 30 percent when fully implemented.

Vibrio bacteria

Vibrio are bacteria that occur naturally in the Chesapeake Bay and estuarine and marine waters worldwide. Vibrio vulnificus and Vibrio parahaemolyticus are two species that can cause infection if someone has an open wound while swimming, wading, or fishing (including crabbing). Not all strains of Vibrio bacteria cause illness or infection. Since their presence is not necessarily due to pollution the indicator bacteria used for beach advisories is not useful for determining the presence of Vibrio. The primary environmental factors controlling Vibrio concentration are temperature, salinity, and chlorophyll. Vibrio can also be transmitted by eating raw or undercooked seafood, and this risk can be avoided by proper cooking.

Scientists with the National Oceanic & Atmospheric Administration have developed models that can predict the likelihood of V. vulnificus and V. parahaemolyticus in the Chesapeake Bay. The models are not suitable for determining the individual risk for Vibrio-related illness and should not be used to guide decisions about swimming or other activities in the Chesapeake Bay. The models are useful for estimating the likely extent of vibrio bacteria in Maryland waters during the summer.

Due to the complex relationship between exposure, dose, and an individual’s vulnerability for infections, there is no known threshold or standard that determines risk of infection from Vibrios. People can take precautions to avoid or reduce the risk of infection. These precautions include: covering wounds with waterproof bandages; having hand sanitizer or access to soap and water to cleanse wounds that occur while swimming, fishing, or crabbing; and showering following swimming in natural waters and washing hands before eating.

Play it safe

Here are some tips to keep well when visiting a beach and to help keep your beach clean:

  • Be sure to avoid swimming within 48 hours of a heavy rain event.
  • Try not to swallow beach water.
  • Avoid swimming if you feel ill or have open cuts or sores. If water contact can’t be avoided, cover your open cut or sore with waterproof bandages.
  • Pick up waste left by pets and dispose of it in the trash.
  • If they are available, use diaper-changing stations in restroom facilities, or change diapers away from the waters’ edge. Remember to properly dispose of used diapers.
  • Wash your hands with soap and warm water after using the bathroom or changing diapers.
  • Pick up your trash.
  • Remember not to feed seagulls or other wildlife.
  • When boating, use an approved marina pump-out station for boat waste disposal.
  • If you have a septic tank, keep it maintained and in good working order.
  • If you see any unsafe or unhealthy conditions, be sure to report them to a lifeguard or beach manager.

Remember to check the Google Earth Beach Notification System on, or your county website, for water quality information about your beach.


This press release was updated since first published.