Is it Safe to Take a Dip in Michigan’s Lakes?

By Susan Goldhaber MPH — Jun 03, 2024
Announcement: “Michigan Dept. of Health and Human Services recommends Michigan residents and visitors avoid foam on Michigan waterbodies such as lakes, rivers, and streams.” As a former Michigander, I wondered about the scientific basis for avoiding lake foam in all the lakes across Michigan.    
Sea Foam

According to the state of Michigan, perfluoroalkyl substances (PFAS) can occur in high levels in the foam from waterbodies and pile up along its shores. If you touch the foam, you should rinse it off and bathe as soon as possible. Michigan warns us not to swallow the foam, although specific health effects are not provided.

“Some studies have found that high exposure to some PFAS in linked to high cholesterol and liver damage, among other health effects.”Michigan Department of Health and Human Services    

With 11,000 inland lakes, more freshwater shoreline than any other state in the nation, and tens of thousands of miles of rivers and streams, Michigan’s waterbodies play a critical role in the state’s economy. Tourism accounted for $22.8 billion in spending last year, with much of it centered on Michigan’s lakes, streams, and rivers. The Michigan Dept. of Health and Human Services telling residents and tourists to avoid lake foam throughout Michigan sends an extremely strong message that should be supported by compelling scientific evidence across the state.

What is Lake Foam?

Lake foam is a natural process that occurs primarily from the die-off of aquatic plants. Plants, made up of organic substances, contain oils that are released and float to the water's surface. Wind and waves push them to the shore, and the oils change the physical nature of the water, creating foam. The bubbles are formed when air from wind is introduced into the water, which contains high levels of organic substances.

“Synthetic foams” result from spills, discharges, or runoff contaminated with PFAS, cleaning agents, de-icing solution, or other chemical substances. According to the State of Wisconsin, the color of both natural and synthetic foams can vary from white to brown; both natural processes and synthetic substances can contribute to foam formation, and it is difficult to determine if foam formed on a waterbody contains natural or synthetic products or both. [1]

PFAS Contamination 

PFAS contamination has been identified in 266 sites across Michigan. Unsurprisingly, contamination is localized to areas where PFAS was used extensively. The main PFAS sites in Michigan are located near the following sources: (the number of sites out of 266 is provided in parentheses):

  • Landfill (90)
  • Industrial (transportation-related, chemical, and other manufacturing) (55)
  • Plating (25)
  • Wastewater (20)
  • Airport (19)
  • Military (14)
  • Fire-related (13)
  • Laundromat/Dry Cleaner (7)
  • Paper Manufacturing (7)

Although military sites make up a small percentage of the total sites in Michigan, there have been some severely contaminated sites near current or former military bases nationally due to the use of PFAS in fire-fighting foam over many years. This was the situation for Van Etten Lake, Oscoda, Michigan, near a former military base heavily contaminated with PFAS, where the public health alert was based on a 2019 risk assessment of PFAS.

Van Etten Lake Risk Assessment

Van Etten Lake is near the former Wurtsmith Air Force Base, which operated from 1924 to 1993 and was heavily contaminated with PFAS from its former use of fire-fighting foam. PFAS has been found in high levels in drinking water, fish, and deer near the base. The Air Force agreed to install two treatment systems to stop the flow of groundwater contaminated with PFAS into Van Etten Lake.  

The risk assessment that formed the basis of the Michigan advisory calculated how much PFAS would be absorbed in the body after skin contact with water or foam and incidental swallowing of water while swimming or playing in lake water or foam. The amount of PFAS absorbed was compared with an acceptable daily dose, the Minimal Risk Level or MRL, from the Agency for Toxic Substances and Disease Registry (ATSDR). When the “Hazard Quotient” (HQ) ratio is greater than one, it indicates a potential public health risk; a HQ less than one suggests no risk.    

The risk assessment used data from Van Etten Lake collected from 2011 through 2018. PFAS concentrations detected in the lake ranged from none to 131 nanograms per liter (ng/L) for PFOA and none to 497 ng/L for PFOS. [2]

The risk assessment for both water and foam used worst-case assumptions by evaluating the highest concentrations of PFAS detected and assuming:

  • Three hours of swimming per day
  • 60 days per year (the summer months)  
  • Swallowing 0.049 liters of water per hour – 5 ounces for three hours of swimming  

The risk assessment concluded that incidental swallowing or extended skin contact with Van Etten Lake water is not a public health risk to children or adults. In contrast, contact with Van Etten Lake foam is a public health risk.

The assumptions put into context how likely or unlikely an actual public health risk exists. Michigan reported a public health risk in a lake near a highly contaminated military site only after swimming or playing in foam, not the water, for three hours per day for 60 days. Parents should be reassured that their children can swim in water near a military site without harm, although I know of no children who can swim for three hours straight without constantly running in and out of the water. The risk for children swimming or playing in lake foam for three hours a day strains the limits of credibility and is a scenario that the state of Michigan might want to discard.       

The fundamental problem with the Michigan advisory, issued for the entire state, based on old data (2011-2018) from one heavily PFAS-contaminated lake, is unrealistic assumptions. This is an example of a situation where science does not support the conclusions. It would be appropriate if it were focused on Van Etten Lake, but it is inappropriate and misrepresents the situation regarding PFAS throughout Michigan waterbodies.   

Old data from one highly contaminated lake does not reflect the situation throughout Michigan and contributes to the unwarranted hysteria about PFAS that has taken root across this country.  

 [1] Michigan disagrees, stating that natural foams are easily distinguishable from PFAS foam, with natural foam being off-white or brown and having an earthy or fishy smell, while PFAS foam usually is bright white, sticky, and tends to pile up like shaving cream.   PFAS Foam

[2] A nanogram per liter equals one part per trillion (ppt). One ppt equals one drop of ink in 20 Olympic-sized swimming pools.

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