The U.S. EPA released a Draft Sewage Sludge Risk Assessment for PFOA and PFOS, open for public comment. The public comment for the draft, released in January 2025, has been extended until August 14, 2025.
This draft risk assessment reflects the EPA's latest scientific understanding of the potential risks to human health and the environment posed by the presence of PFOA and PFOS in sewage sludge that is land applied as a soil conditioner or fertilizer (on agricultural, forested, and other lands), surface disposed, or incinerated. The EPA defines Sewage sludge as the “solid, semi-solid, or liquid residue generated during the treatment of domestic sewage in a treatment facility.
One interesting point from the draft risk assessment relates to land application of sewage sludge. For the land application scenarios, the EPA modeled potential PFOA and PFOS exposures and estimated human health risks to those living on or near impacted properties under three hypothetical scenarios:
Application to a farm raising dairy cows, beef cattle, or chickens (pasture farm scenario),
Application to a farm growing fruits or vegetables (food crop farm scenario),[2] and
Application to reclaim damaged soils such as an overgrazed pasture (reclamation scenario). For the surface disposal scenarios, the EPA modeled potential PFOA or PFOS exposures via groundwater to those living near a lined or unlined surface disposal site ( e.g., sewage sludge monofill).
The EPA’s draft risk assessment indicates potential risks to human health for people living on or near impacted properties or primarily relying on their products from land application and surface disposal of sewage sludge containing detectable levels of PFOA or PFOS.
The potential risks highlighted by the EPA are dependent upon four factors:
The concentration of PFOA and PFOS in sewage sludge,
The specific type of management practice ( e.g., type of farm or presence of a liner in a monofill),
The local environmental and geological conditions ( e.g., climate and distance to groundwater)
The share of each product ( e.g.,food crop, drinking water) that is sourced exclusively from the impacted property, and other factors noted above.
As detailed by the EPA, the recommended analytical method is EPA Method 1633 to analyze PFAS in sewage sludge.
Merit Laboratories is a leading national PFAS environmental laboratory, analyzing drinking water, soil, wastewater, groundwater, and other sample matrices, including biosolids and sludge. Analytical methods performed by Merit for PFAS include drinking water by EPA 533, EPA 537.1, and EPA 537 rev. 1.1, soil and biosolids by ASTM D7968-17 with Isotopic Dilution, and wastewater, groundwater, and surface water by ASTM D8421 and ASTM D7979-19 with Isotopic Dilution and development of the new EPA 1633A method.