Frequently Asked Questions About Monitoring Water Quality at Beaches

The water quality at beaches in Massachusetts is required to be monitored. This page answered frequently asked questions about beach monitoring in the state.

Table of Contents

Why are beaches tested?

In the United States, most swim-related illnesses are associated with disease-causing organisms (pathogens) that are linked to fecal contamination. To protect public health, the Massachusetts Department of Public Health (MDPH) requires that certain “indicator organisms”, or specific microscopic bacteria that indicate harmful pathogens may be present.  This monitoring data helps local health officials determine when to close a beach due to unsafe conditions and to notify the public so that beach visitors can make informed decisions about swimming at the beach.

What are indicator organisms?

Indicator organisms share similar characteristics and life cycles as pathogens, disease-causing organisms that can make humans sick. Pathogens in the water are difficult to measure directly, so indicator organisms are used to predict the presence of pathogens associated with fecal contamination. Enteric bacteria are a type of indicator organism found in the intestines of warm-blooded animals and humans and are often associated with fecal contamination.

The bacteria used as indicator organisms to test the waters at beaches are Enterococci and E. coli.  Marine beaches are tested for the presence of Enterococci. Freshwater beaches are tested either for the presence of E. coli or Enterococci.

Are all beaches in Massachusetts monitored?

Over 1,100 public and semi-public beaches in Massachusetts are monitored.  Each beach is monitored for a specified period where it is considered officially open for swimming.

Public and semi-public beaches are required by state and federal regulations to monitor indicator bacteria during their operational dates. Private beaches that are owned by individuals and/or families are not subject to these regulations.

A “Public beach” is beach open to the general public that permits access to bathing waters.  A “Semi-public” beach is a beach with common access and shared use by a group or organization (e.g., beaches at hotels/motels, summer camps, clubs, condominiums, or neighborhood associations).

How do bacteria get in beach water?

Bacteria in the water can come from a variety of sources. These include:

  • Stormwater (rain) run-off
  • Failing or malfunctioning septic systems
  • Combined and sanitary sewer overflows
  • Leaking sewer pipes
  • Illegal sewer hookups
  • Wildlife and pet waste
  • Agricultural runoff

What are the risks associated with bacteria in beach water?

Swimming in unsafe waters may result in illnesses with the following characteristics:

  • Gastrointestinal symptoms - nausea, vomiting, diarrhea, and abdominal pain
  • Respiratory symptoms - sore throat, cough, runny nose, and sneezing
  • Dermatological symptoms - skin rash and itching
  • Eye and ear symptoms - irritation, earache, itching
  • Flu-like symptoms - fever and chills

Most of these symptoms are minor, but occasionally a more serious illness may occur. Children, the elderly, and those with weakened immune systems are at greater risk for illness.

How is beach water tested?

Local boards of health, Barnstable County Department of Health and the Environment, and the Massachusetts Department of Conservation and Recreation collect the majority of water samples in Massachusetts. Samples are collected in three feet of water at a depth of 12 inches below the surface water. Testing is done at accredited laboratories using laboratory methods approved by the U.S. Environmental Protection Agency (EPA).  The laboratory testing takes about 24 hours to perform, so water quality results are typically reported the next day.

How often is beach water tested?

Depending on the beach, water is tested anywhere from daily to monthly.  The majority of beaches in Massachusetts are tested once a week following sampling frequency guidelines from the US EPA.  Testing frequency depends on how likely the beach is to have water quality issues. Low-use beaches or beaches with few, if any, water quality issues are tested less often. High-use beaches or beaches with historic water quality issues are tested more often.

Why do beaches close?

When levels of Enterococci or E. coli exceed the limits set for beaches, it is called an exceedance. Water is considered unsafe for swimming at a majority of beaches in Massachusetts when two exceedances occur following one after another without an interruption (consecutive days). Beaches with a history of multi-day exceedances are required to post after a single exceedance.

Beaches can be closed to swimming for reasons not related to bacteria. When there are concerns for other physical or chemical hazards, including riptides, poor visibility within the water, cyanobacteria and harmful algae blooms, heavy rainfall, combined sewer overflow events, or hazardous materials like PFAS, beach closures may also occur.

At marine beaches, the accepted level of Enterococci for a single sample is 104 colony forming units per 100 milliliters (cfu/100 ml) of water or below.

At freshwater beaches, the accepted level of Enterococci for a single sample is 61 cfu/100 ml or below. The freshwater limit is stricter because elevated levels of bacteria within a smaller body of water (such as a lake versus the open ocean) can pose higher risks of illness. Freshwater beaches can also be tested for E. coli instead of Enterococci. The accepted level of E. coli for a single sample is 235 cfu/100 ml of water or below.

MDPH also has a limit for the last 5 test results at a beach known as the geometric mean, or geomean for short. The geomean is intended to reflect water quality found during a previous time frame (typically a month). At marine beaches, the geomean for Enterococci is 35 cfu/100 ml. At freshwater beaches, the geomean for E. coli is 126 cfu/100 ml and the geomean for Enterococci is 33 cfu/100 ml.

When will the beach re-open?

Beaches remain posted until test results from laboratory analysis show indicator bacteria levels are back within the acceptable range for water being safe to swim. Laboratory analysis for all beach samples takes approximately 24 hours, so it is common for a beach closure to last a day or two following an exceedance.

How do I know if it is safe to swim?

Know before you go.  Find out from your local health department or MDPH if the beach you want to go to is monitored regularly and posted for closures. MDPH maintains a list of beach postings during the swimming season.

Look for signs posted at the beach. Check for any warnings or beach closures indicating that the water is not safe because of bacteria, riptides, or other hazards.

Swimming conditions can also vary throughout the day. Below are a few recommendations for deciding when and where to swim:

  • Check the weather
  • Avoid swimming after heavy rain events - bacterial levels tend to rise due to runoff after heavy rains
  • Watch for "signs" of water pollution such as discolored, fast flowing, and strong-smelling water
  • Avoid swimming next to drainpipes, outlets, or other obvious sources of pollution
  • Do not swim near trash or street litter floating in the water
  • Avoid swallowing the water - when waterborne pathogens are present, most swimmers are exposed when they swallow the water. You will be less likely to get sick if you wade or swim without putting your head under water.
  • Swim only in areas designated as "swim beaches". Do not swim in rivers or streams unless they are designated swim beaches.

Can I still go to the beach if it is posted closed to swimming?

A beach posting does not mean that a person cannot go to a beach, or that a posting prevents anyone from entering onto a beach. If a beach is posted, it simply means swimming is not allowed. There are plenty of safe recreational activities people can still do at the beach that don’t involve contact with the water, including walking along the shore; sunbathing; collecting seashells/sea glass; and playing sports such as paddleball, volleyball, football, frisbee, etc.

If I accidentally swam at a closed beach, and now feel sick, what should I do?

For any health-related symptoms and concerns, please contact your primary health care provider.

How can I keep beaches clean?

Everyone can take steps to help reduce contamination and pollution at the beach.

  • Clean up after your pets
  • Do not feed birds – this only encourages the birds to hang out at the beach, which increases the risk of fecal matter
  • Use public restrooms
  • Pick up and throw away trash using public waste bins
  • If there are no public waste bins – pack up your trash and properly dispose of at home
  • Do not enter the water if you are ill/not feeling well
  • Change diapers and put plastic/rubber pants (e.g., swim diapers) on diapered children before allowing them in the water
  • Dispose of boat sewage at onshore sanitary facilities
  • Do not dump anything down storm drains; water moving through storm drains do not get treated at a wastewater facility and flows directly into our lakes and streams
  • Avoid using fertilizers and pesticides on your yard – these chemicals are easily carried into our surface waters during rain events and snowmelt
  • Use walkways and do not walk on dunes – this helps reduce erosion and preserve vegetation that filter out pollutants from runoff before they reach the beach

Help Us Improve  with your feedback

Please do not include personal or contact information.