How Long Does PFAS Stay in Soil? Years, Decades, Longer

No one can tell you a single number of years. What the sources do say is clear: PFAS do not break down in soil the way most pollutants do. The Minnesota Pollution Control Agency states that the carbon-fluorine bonds that define PFAS “do not break down in the environment.” Plan for a problem that lasts decades, and test before you assume it has faded.

This post explains what long-term studies show, what makes PFAS stay or move, and what a Missouri property owner should do first. For the basics, see our glossary entries on PFAS and forever chemicals.

Do PFAS break down in soil?

Not in a way that clears a site. PFAS can change into other PFAS, but the bond that gives them their staying power stays intact. The Minnesota Pollution Control Agency writes: “PFAS may transform to other PFAS, but the carbon-fluorine bonds characteristic of PFAS do not break down in the environment.” EPA scientists say the same thing in plainer words: because of the strong chemical bonds, PFAS “are difficult to destroy.”

That is why the nickname “forever chemicals” fits. AES’s own PFAS page says PFAS resist natural degradation and persist in soil and water for decades.

What does a long-term soil study show?

It shows that most of the mass stays put. ITRC’s PFAS guidance reports on a long-term lysimeter study. A lysimeter is a soil column that lets researchers collect the water that passes through. The soil was silty with some clay, and the rain was natural. ITRC writes that “even after 5 years, 96.88% and 99.98% of the mass of PFOA and PFOS, respectively, remained in the soil.”

Read the conditions before you reuse that number. It is one study, one soil type and one set of weather. It does not give a half-life for your yard. It does show that five years of rain did not flush out nearly all of two well-known PFAS. See the glossary for PFOA and PFOS.

The same study found that PFOA and shorter-chain PFAS traveled faster through the soil column than PFOS. So different PFAS behave differently at the same site.

What makes PFAS stay in soil or move to groundwater?

Water, soil makeup and the type of PFAS decide it. ITRC says the leaching potential “will be enhanced in areas with high water infiltration rates, which may include natural water sources such as precipitation or human-made sources such as irrigation.” Depth to the water table matters too. PFAS-specific effects can slow leaching, such as sticking to soil particles.

The table has a practical meaning. Soil that holds PFAS can act as a slow source. ITRC warns that “slow leaching of PFAS from shallow soils may contribute to a persistent groundwater plume.” Because the levels of concern in water are measured in parts per trillion, even a small steady release matters. Our glossary explains parts per trillion.

EPA describes the same path: PFAS can seep through the soil and migrate into groundwater, and the compounds can stick in the unsaturated zone and release slowly.

How long until PFAS in soil reach groundwater?

Possibly 1 or 2 years, possibly several decades or longer. ITRC says: “Time scales required for PFOS (and other PFAS that exhibit strong interfacial adsorption characteristics) to reach the underlying groundwater have been simulated to be from 1 or 2 years to several decades or longer.” Read the condition: these are computer simulations, not a measurement at your site. Climate and PFOS concentration change the answer.

Use the range to set expectations, not to predict one lot.

Where do PFAS in soil come from?

From places where PFAS products were made, used or burned. AES’s PFAS pages list firefighting foams, coatings and manufacturing processes as common uses. ITRC adds that releases often involve surface applications and air deposition, so soil can pick up PFAS near a source and at some distance from it.

Think about your property’s history. Was there a fire training area, an industrial plant, a plating shop, a landfill or a fire station nearby? Those questions guide where to sample. Our PFAS pages cover PFAS contamination and the facilities AES serves.

Does Missouri track PFAS in soil?

Not that we found for private lots. Missouri DNR says that since 2013 it has run PFAS occurrence monitoring “for public drinking water supplies through federal and voluntary sampling programs.” Its PFAS Viewer maps voluntary sampling in public water systems. That is useful if you are on city water. It tells you little about the soil on your own land.

If you own a former industrial site, a farm with biosolids history or land near a foam release, assume you need your own data. Do not rely on a nearby map point.

What should you do if your soil may have PFAS?

Work in order. Do not dig, haul or sell soil before you know what is in it.

1. Write down the site history. Note past uses, fires, spills and neighbors with industrial history.
2. Sample soil and groundwater. A plan should say where, how deep and how many samples. Our PFAS sampling and PFAS testing pages explain the process. The guide on PFAS testing for property owners walks through it.
3. Read the results with a professional. Units, detection limits and compound names matter, and a result in parts per trillion is not the same as one in parts per million.
4. Check water too. If a well is near the soil, test the well. See PFAS drinking water.
5. Compare cleanup options only after you have data. See PFAS soil treatment and soil remediation.

If the soil is also headed off site, talk about disposal rules early. Our page on PFAS waste disposal is a starting point. If your question is about the water side, read our post on whether PFAS can be removed from drinking water.

Can you wait it out?

Waiting does not fix a source that is still releasing PFAS. It can also let a groundwater plume grow. If your soil tests above a level that matters for your use, a lender, a buyer or a regulator, you need a plan, not a calendar.

Waiting may be reasonable for one case: a low result on a good sample, with no well nearby and no change planned for the land. Even then, keep the lab report and re-sample if the use of the land changes.

Next step

If you need PFAS soil testing or cleanup on a Missouri or Midwest site, start with our PFAS service page and call AES at (314) 865-2662, or send the details through /contact. AES quotes each job.