Bloom sometimes receives the question, “If I apply biosolids five times in a year, am I adding five times the PFAS to my soil?”
The reality is PFAS are now ubiquitous in the environment, meaning they are already present in nearly all soil and are routinely detected in rainwater. Each application of Bloom does add a very small amount of PFAS, but in practice, biosolids are applied at agronomic rates (the modest amount that matches what your plants actually need), typically once a season or less, not repeatedly throughout the year. And how much matters enormously: the amounts are extremely small, most of them stay in place, very little reaches the food you grow, and it is a tiny part of your everyday PFAS exposure. Here is the full picture:
1. Our biosolids are exceptionally low in PFAS
DC Water produces Bloom, which is a Class A Exceptional Quality (EQ) municipal biosolids material that is tested monthly. The current combined PFOS + PFOA monthly average concentration is 14 parts per billion (ppb). This is well below the regulated thresholds that Maryland and Virginia (<25 ppb), as well as several other states, have set for unrestricted land application. It’s also dramatically lower than the PFAS concentrations in industrially impacted sludge on farms that you might have heard about in Maine and Texas, which have garnered high-profile media coverage in the last couple of years.
Like any soil amendment, Bloom should be applied at agronomic rates (the amount matched to your plants’ nutrient needs), which naturally keeps each application modest. Overall PFAS concentrations in Bloom are very small – especially when compared to biosolids made with industrial residuals. The Bloom blends commonly used by home gardeners (Bloom Woody Blend and Bloom Sandy Blend) have even lower concentrations of PFOA and PFOS and are comparable to other compost products on the market. For example, Woody Blend was tested at 6.8 ppb PFOS + PFOA.
2. Small inputs that stay put, not a runaway buildup
Field research shows that when biosolids come from municipal sources without significant industrial inputs, PFAS accumulation in soil remains very low. At an Arizona site studied after 35 years of continuous annual application, researchers found PFAS in the treated soil averaged about 4 ppb, and in some samples was not detectable at all. Just as telling, neighboring farmland that never received biosolids measured in a similar range. Bloom’s PFOS and PFOA levels are lower than the material used in that study, which means decades of use at recommended rates would be expected to add only small amounts of PFAS to soil, keeping overall soil concentrations in the same general range as those commonly found in many agricultural soils.
In addition, PFOS and PFOA bind tightly to soil organic matter, and the longer-chain compounds bind the most strongly. Researchers consistently find these compounds staying in the top layer of soil rather than washing downward. Organic-rich, woody material (exactly the kind of blend we produce) actually helps hold PFAS in place. It does not multiply on itself or surge through your soil; it is simply the sum of small inputs, most of which stay put where they land.
3. PFAS rarely reaches the edible parts of plants
So far, years of research (including field studies by Dr. Linda Lee of Purdue University, a leading national expert on PFAS in biosolids-amended soils) show that plant uptake from municipal biosolids is very low. When uptake does occur, the longer-chain PFAS like PFOS and PFOA tend to stay in the roots. The implication for urban food crops is that the edible portions of most vegetables, especially fruiting crops (tomatoes, peppers, beans), are less likely to accumulate PFAS than root vegetables or leafy greens, and even in those cases, the concentrations observed with municipal biosolids applied at agronomic rates are very small.
4. PFAS is already all around us, including in rain
PFAS is unfortunately universal now. It’s found in rainwater across the globe, even in remote regions. Studies measuring PFAS in U.S. precipitation detect it in the large majority of samples, and rainwater in populated areas often carries PFOA and PFOS above EPA drinking-water health advisory levels. Your yard receives PFAS from the atmosphere every time it rains, independent of any amendment you add. Our biosolids are one small, well-measured input against a background that is already everywhere.
5. Everyday exposure comes from many other sources too
PFAS exposures can often come from common household items like grease-resistant food packaging, cosmetics, stain-resistant carpets and fabrics, and household dust. If you want to reduce your family’s PFAS exposure, those everyday sources are likely to give you far more leverage than a low-PFAS soil amendment on your yard.
Bottom line: Applying our biosolids more than once does add PFAS in the arithmetic sense, but you are adding very small amounts of a substance that is already in your rain, that binds tightly to your soil instead of accumulating exponentially, that rarely reaches the edible parts of your plants, and that is a fraction of your overall exposure. We regularly test our material to confirm our levels remain exceptionally low.
And it’s worth remembering the bigger picture: Bloom returns nutrients and carbon to depleted soils, cuts reliance on energy-intensive synthetic fertilizers, improves soil health and water retention, and keeps material out of landfills and incinerators, a huge benefit for the climate and a healthier earth.
