gardent with beet shoots and a hand reaching down over a short fence to do weeding

Sludge in the Garden

Published on May 25, 2021

Toxic PFAS in home fertilizers made from sewage sludge

Many home gardeners buy compost or commercial soil amendments to enhance soil nutrition. But new tests reveal concerning levels of toxic chemicals known as PFAS in fertilizer products which are commonly made from sewage sludge. These “forever chemicals” were found in all of the nine products tested by the Ecology Center of Michigan and Sierra Club and marketed as “eco” or “natural” and eight of the nine exceeded screening levels set by the State of Maine. PFAS in fertilizers could cause garden crops to be a source of exposure for home gardeners. 


Maine's PFOS screening limits exceeded for 8 of 9 fertilizers

Product Name PFOA (ppb) PFOS (ppb)
Cured Bloom 23.8 22.1
Earthlife Natural Fertilizer 2.75 17.3
EcoScraps Slow Release Fertilizer 1.2 16.9
GreenEdge SlowRelease Fertilizer 1.39 13.5
GreenEdge SlowRelease Fertilizer 1.66 12.9
Menards Premium Natural Fertilizer 1.01 9.05
Milorganite ® 6-4-0 Fertilizer 0.67 8.66
Pro Care Natural Fertilizer 0.94 14.9
Synagro Granulite Fertilizer Pellets 0.95 3.71
TAGRO Mix 7.51 7.92

Biosolid limits: PFOA: 2.5 ppb, PFOS: 5.2 ppb

PFAS are per- and poly-fluoroalkyl substances are a class of widely used industrial chemicals that persist for decades in the environment. Many are toxic to people. In most places industries are allowed to flush PFAS-containing waste into wastewater drains that flow to treatment plants. The chemicals are not removed during sewage treatment and instead settle in solid materials that are separated out from liquids in the treatment process. 

Americans generate massive quantities of sewage waste each day. Nearly half of sewage sludges are treated to kill pathogens and then spread on farms, pastures and wildlands for disposal, where nutrients like nitrogen improve soil productivity. The wastewater industry and EPA call these “biosolids.” Unfortunately, biosolids carry a variety of persistent and toxic chemicals (in addition to PFAS) that can threaten our food supply and contaminate water sources. 

The Sierra Club and the Ecology Center identified dozens of home fertilizers made from biosolids. We purchased 9 fertilizers: Cured Bloom (Washington DC), TAGRO Mix (Tacoma, WA), Milorganite 6-4-0 (Milwaukee, WI), Pro Care Natural Fertilizer (Madison, GA), EcoScraps Slow-Release Fertilizer (Las Vegas, NV), Menards Premium Natural Fertilizer (Eau Claire, WI), GreenEdge Slow Release Fertilizer (Jacksonville, FL), Earthlife Natural Fertilizer (North Andover, MA), and Synagro Granulite Fertilizer Pellets (Sacramento area, CA). 

Our tests reveal that American gardeners can unwittingly bring PFAS contaminants home when they buy fertilizer that is made from sludge-biosolids. All of the tested products contained two chemicals: PFOS and PFOA. Maine, the state with the most robust action on PFAS in biosolids, has set acceptable standard levels for these two chemicals in agricultural soils in the state. Eight of the nine products exceeded Maine's screening limits for PFOS. Three of the nine products exceeded Maine's screening limits for PFOA. Of the 33 PFAS compounds analyzed in the products, 24 were detected in at least one product. Each product contained 14 to 20 detectable PFAS compounds. Additional tests showed they also contained 2 to 8 times greater mass of precursor compounds and hundreds to thousands of times more unidentifiable, synthetic fluorine compounds.

Our testing provides a snapshot of PFAS levels in complex wastewater systems. The findings are in line with national surveys of PFAS in sludge-biosolids, and academic studies testing biosolids-based fertilizers and composts. Available evidence suggests that PFAS and related chemicals in sewage sludge could jeopardize the safety of the commercial food supply and home gardens. We recommend home gardeners do not purchase biosolids-derived fertilizers for use on fruit and vegetable beds. For the large-scale problem of disposing of sewage waste, however, simple solutions are elusive. The federal government and most states have done little to study the issue, let alone address it.

Our test results suggest that urgent changes are needed to halt the unnecessary uses of PFAS in commerce, and minimize the amounts that are discharged into our wastewater system. EPA Administrator Michael Regan has pledged immediate action to reduce the threats posed by PFAS uses. But the agency’s anemic responses thus far, as well as structural barriers created by key environmental laws make quick action unlikely and hinder even the most common sense measures to contain the chemical crisis.

The EPA and states must take immediate action to keep PFAS and other persistent chemicals out of the wastewater system, biosolids, and the food supply. This means preventing industrial polluters from discharging PFAS in their wastewater drains. Agencies must survey the hazard of food production on highly contaminated soils, and regulate land application of biosolids with high levels of PFAS and other chemicals. Industry must pay for the damages that PFAS production and use poses to people and the environment, including costly cleanups of contaminated places. The most efficient and effective way to protect people from the growing threat of PFAS exposure is to end the use of PFAS with limited exemptions.