Photo by JIm Hyde

Vermont is blessed with over 800 lakes and ponds, more than 284 of which are larger than 20 acres. Many are available and accessible for recreational use by swimmers, boaters, fishermen and even divers.

However, Vermont lakes and ponds face environmental challenges from bacteria, pesticides and phosphorus-rich agricultural runoff. We’ve also seen recent cases, for example in Burlington, in which sewage treatment systems have been overwhelmed by torrential rains and equipment failures and have dumped raw sewage into Lake Champlain. According to a June 20 story in Seven Days, eight million gallons of sewage and wastewater have been released into the lake so far in 2018, triple the amount for all of 2017.

These events, combined with environmental changes, increased rain fall, rising temperatures and air pollution, are threatening our water quality today. Vermont’s Department of Environmental Conservation (DEC) along with a number of private sector partners have been actively engaged in monitoring these threats to the state’s lakes, ponds and streams. The Inland Lake Score Card as well as the Lake Champlain monitoring program provide valuable up-to-date information for all concerned with Vermont water quality. 

These developments are also having an impact on the health of recreational users. Let’s look at three important biologic risks.

Swimming
Aside from obvious threats—concealed objects, hidden rocks and logs, and drowning—use of open waters poses certain biologic risks. A range of bacteria, parasites and viruses, as well as toxins and chemical agents, can be found even in Vermont waters. Some are introduced through surface and ground water pollution, some by natural processes, but most of these hazards are the result of human activity, including intensive development near watersheds, and through the careless disposal of human and industrial waste products. 

Vermont-specific data are scarce. However, on July 1 of this year, the CDC reported on 140 recreational water-associated outbreaks representing over 5,000 cases from 35 states.  Eighty-seven percent of the cases were caused by enteric pathogens (“bugs” from the gut) from either humans or animals (one reason dogs are often not allowed at town and park beaches). Two percent of cases were from chemicals and toxins, while in 35 percent of cases the cause of illness was unidentified. Three findings are especially relevant for Vermonters: 1) the majority of outbreaks occurred from June to July; 2) 36 percent and 32 percent of the outbreaks occurred at public parks and beaches respectively; 3) and interestingly, many of the pathogens that caused these outbreaks rarely cause outbreaks in treated recreational settings, such as pools, due to the effectiveness of chlorination. 

What does this mean?
Swimming in one-of-a-kind secluded or open spots—such as the center of Lake Champlain—is likely to pose little risk. However, public beaches and other places where groups of people are swimming may pose risks from fecal contamination from other swimmers, storm water runoff or blue-green algae blooms (more on this later). Fecal contamination can come from other swimmers recently or currently suffering with a diarrheal illness, diapered children swimming nearby, pets and wildlife or even malfunctioning septic systems. Be especially careful about swimming shortly after torrential or tropical-type rains, which have occurred in recent weeks. These events have the tendency to flush all sorts of material into streams, ponds and lakes.

The Vermont Department of Health (VDH) as well as common sense suggest the following guidelines for swimmers:

  • make sure that animal waste is properly disposed of near beaches
  • do not go swimming if you have recently had diarrhea
  • do not feed birds and wildlife near swimming areas and beaches
  • do not swallow beach water, and instruct your children not to do so as well
  • it’s a good idea as well to wash off if at all possible after swimming in areas used by large numbers of people
  • check the health status of beaches at lakes and ponds prior to swimming (see below).

Blue-green algae (cyanobacteria)
Cyanobacteria are naturally occurring organisms that are found in fresh water ponds and lakes. Some of these bacteria produce toxins that can cause a wide range of symptoms, such as sore throat, skin rashes, diarrhea and other gastrointestinal symptoms. These symptoms can affect both humans and pets. Children have been shown to be at a special risk as they have a greater tendency to swallow contaminated water. (Vets also warn that pets can lick and swallow cyanobacteria caught in their fur). Blue-green algae “blooms” are enhanced by phosphorus-rich runoff, and they tend to occur more commonly in the late summer and fall. 

The good news is that there is active weekly monitoring of conditions at many (but not all) beaches and public swimming areas around the state. View a regularly updated interactive map of blue-green algae conditions on Lake Champlain, including Charlotte, Shelburne and Ferrisburgh. If you are planning on visiting one of the state parks check out their website for an up-to-date report. Finally, visit the Lake Champlain Basin Program website for additional information on beach and swimming conditions on the lake.

A word of caution: Observational reports or lab reports may lag by two or three days the appearance of an algae bloom or a pollution event. This is why it’s important to understand the conditions that pose the most risk to swimmers and act accordingly. A terrific video produced by VDH will provide you with important information you will need to recognize blue-green algae. 

Fishing
Sadly, one aspect of this wonderful pastime and sport, namely eating fish that are caught, needs to be mentioned. The problem stems from the tendency of fish to ingest and concentrate methylmercury into their flesh. Mercury in its various forms has serious adverse health implications for humans and animals, causing developmental and neurological damage of varying degrees depending on exposure levels. The sources of mercury include industrial waste, air pollution and naturally occurring mercury compounds. Children and pregnant women are especially vulnerable to these effects. Importantly, mercury once ingested tends to accumulate in the body. Researchers are still intent on understanding the effects of varying levels of mercury in the body, but as with lead there appears to be no “safe” level. 

VDH provides a very thorough and specific listing of which fish species at which locations in Vermont pose the highest risk. For example, pregnant women and children under 15 are advised not to eat lake trout from Lake Champlain, whereas yellow perch pose far less risk. Further complicating matters is the fact that store-bought and restaurant fish meals also contain mercury, resulting in the need to include those meals in your calculations.

Summertime in Vermont is a magic time in part because of the opportunity to get out and enjoy our lakes, ponds and streams. As with most of the enjoyable things in life, however, it comes with risks. Be mindful of, rather than paralyzed by, those risks. 

Jim Hyde is professor emeritus of public health at the Tufts University School of Medicine. He lives in Charlotte.

Web-based resources
Swimming
Vermont Department of Health (VDH) Recreational Water Use
Vermont Department of Environmental Conservation—Inland Lakes Score Card
Lake Champlain Basin Program  
Vermont State Parks
Cyanobacteria (what it is, where it comes from, adverse effects) what can be done about it, guidance. 

Fishing and mercury contamination 
Vermont Department of Health
Centers for Disease Control