Hello and thank you for your inquiry.

I wanted to quickly let you know that I reached out to a colleague at Michigan State University who has contacted the Michigan  Department of Health and Human Services to get some more information and recommendations regarding this concern. I will get back to you about his as soon as I hear back.

In the meanwhile, have you reached out to the Grand Traverse Health Department for information about your concern?
https://www.gtcountymi.gov/781/Environmental-Health

Hi Marie,

Sorry for the delay, but was just waiting to hear back from the toxicologists from the Michigan Department of Health and Human Services. This is the comprehensive response they they put together based on your inquiry:

• PTA (ptaquiloside, also known as PTQ in some cases) seems to be the contaminant that is focused on when it comes to bracken fern water contamination and PTA is an emerging contaminant, so there is not a lot known.
• I did not find info on bracken fern water contamination from other state health department websites or any fact sheets on this topic.
• With the information known/what I could find it does not seem likely that the bracken fern would cause colon polyps/cancer from drinking water. Here is one resource with more info on this: https://www.sciencedirect.com/science/article/pii/S<personal data hidden>11794?via%3Dihub
  that states "Limited epidemiological data have suggested links between the consumption of bracken fern and human oesophageal and gastric cancer as well as upper digestive and urinary bladder cancers in cattle."


• Additionally, this resource states that "While PTQ may be relatively stable in separate groundwater matrices (Wu et al., 2021), it has never been found in deep groundwater (>20 m or 65.5 feet) but has been detected in shallow groundwater (O'Driscoll et al., 2016; Mrkajic et al., 2021)." The resident indicated that their well is 68 feet deep, so it does not seem likely that PTQ from bracken fern would be a concern for them. Other illudane glycosides could be a potential concern still though according to the resource that the person inquiring had (https://enveurope.springeropen.com/articles/10.1186/s1<personal data hidden>6-y).


• There does not seem to be much info on filters that would be effective for PTA. There was one resource that predicted granular activated carbon (GAC) could be helpful, but in general there is not much info or certainty on this.
• There does not seem to be info on a resident being able to test their drinking water for PTA or other illudane glycosides. Our lab does not test for PTA, caudatoside (CAU) and ptesculentoside (PTE). It can be difficult to link a particular exposure to a specific cancer, however, there could be other contaminants of concern in drinking water potentially linked to colon cancer (for example Exposure to widespread drinking water chemicals, blood inflammation markers, and colorectal cancer - ScienceDirect). MDHHS has recommendations for well water testing that does include chemicals, such as nitrate, that the resident could test for: Protect Against the Unknown: Test Your Drinking Water from Your Well (michigan.gov)
• Bottled water could also be used for drinking and cooking in the meantime while waiting to have the water tested.
• Here is additional guidance on water filters and water treatment options: Choosing a Home Water Filter and Other Water Treatment Options (michigan.gov)
  
• To be safe, the bracken fern could also be removed.

Sorry again for the delay, and please know that understand why you are frustrated with the lack of solid information on this topic. I did check with another resources at MSU who works in the area of drinking water quality and unfortunately, there just isn't much on treatment. There is a little bit of information about biological sand filter and heat treatment (boiling). Reverse Osmosis (RO) might work however there are other potential issues. Installing a whole house RO system could lead to the leaching of metals from household plumbing if they have metal plumbing throughout. If they have a septic system and discharge the reject (wastewater) stream to the septic system it could lead to the creation of a "looped" system between the septic field and the well. (seen this with softening waste streams). If you were to put in an RO system, the recommendation would be to select an under-the-sink unit in the kitchen, followed by plastic plumbing.
HOWEVER, since not much research has been done in this area and hence not much is know about what will work and what won't, there is NO way to know the efficacy of RO or activated carbon.

We've now shared pretty much all that is known on this topic, which as you can attest, is very little.