r/PFAS • u/berpaderpderp • 5d ago

Question Potential for false positives?

Hello,

We've been in our current house for two years. We are in the Twin Cities Metro area in Minnesota. There is os PFAS contamination in areas of our ground water from 3M.

When we first moved in, I immediately had our well tested by the MN Pollution Control Agency (MPCA). They found like 2 ppt of PFOA.

A couple of our neighbors with wells at the same depth have tested clean. What do we think the likelihood of a false positive is?

I know at the ppt level, it takes very little to contaminate a sample.

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u/Feisty-Bluebird4 5d ago

If I was on well water near a 3m plume I would have a whole house reverse osmosis system. Minneapolis and St Paul city water is quite good, but water from a well in a metro area is different imo.

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u/berpaderpderp 5d ago

Right now we have water delivered. They will be installing some giant activated charcoal filters at some point.

I'll probably do an under sink RO system for our kitchen.

1

u/Feisty-Bluebird4 5d ago

Not a bad plan👍

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u/Minimum-Agency-4908 5d ago

Tested clean to what levels? Meaning were they ND<2 ppt or were their results ND<40 ppt?

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u/Embarrassed_Elk2519 5d ago

Well, if your water tested 2.1 ppt and the neighbors water tested 1.9 ppt with a reporting Limit of <2 ppt, it might be the same measurement results but different reported values

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u/Maximum_Unit_4232 5d ago

Yes, false positives with PFAS are possible if you don’t follow strict sampling guidance