PFOS and PFAS levels in US sewage sledge may exceed risk levels

Draft risk assessment guidance published by the US Environmental Protection Agency (EPA) suggests levels of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) in sewage sludge being spread on fields are exceeding safe levels.

Preliminary findings reveal risk posed by forever chemicals

While the findings are only preliminary, they reveal the current levels of PFOS and PFAS in sewage sludge applied to 'the land for beneficial reuse or surface disposed' is potentially exceeding risk threshold levels.

Currently, the assessment is only focusing on people living near farms using 'impacted' farms and those who 'rely on their products'. The draft assessment does not examine exposure among the wider population.

Why is the EPA concerned about the presence of PFOA and PFOS in sewage sludge?

Although domestic manufacturing of PFOA and PFOS have been phased out and their uses restricted, multiple activities still result in PFOA, PFOS, and their precursors being released to wastewater treatment plants in the US.

Traditional wastewater treatment technology does not remove or destroy PFOA or PFOS, which results in the chemicals typically accumulate in the sewage sludge. And while new technologies for capture, or capture and destroy are being developed all the time, at the time of the report none have been deployed at scale.

The strong chemical bonds in PFOA and PFOS make it almost impossible for the to naturally break down in the environment or in the human body. Once on the land, the chemicals can move from soils to groundwater or nearby lakes or streams, and be taken up into fish, plants, and livestock.

It is for this reason the EPA is assessing potential risks associated with the presence of PFOA or PFOS in sewage sludge and the effect is has on land where it is applied as a soil conditioner or fertilizer (on agricultural, forested, and other lands), surface disposed, or incinerated.

What sewage sludge can be applied to the soil in the US?

The EPA currently designates sewage sludge as the solids that separated from liquids after sewage from households and businesses is treated at a wastewater treatment plant. Any sludge intended for land application is referred to as a biosolid.

Federal rules allow biosolids to be applied to pastures, feed crops, and crops for direct human consumption. They can also be applied to forests, tree farms, golf courses, turf farms, and other types of land. In other cases, biosolids are bagged and sold at stores to the general public and are often used on lawns or in home gardens.

What does the draft sewage sludge risk assessment suggest?

Based on the modelling in the draft sewage sludge risk assessment, the EPA's draft assessment finds that there may be human health risks exceeding the EPA's acceptable thresholds for some modelled scenarios when land-applying sewage sludge that contains 1 part per billion (ppb) of PFOA or PFOS.

The EPA also finds that there may be human health risks associated with drinking contaminated groundwater sourced near a surface disposal site when sewage sludge containing 1 ppb of PFOA, or sewage sludge containing 4 to 5 ppb of PFOS is disposed in an unlined or clay-lined surface disposal unit.

These assessment makes clear that these figures are not seen as conservative, partly because they do not include other forms of exposure to PFOS and PFAS, and only reflect median scenarios.

Concerned communities

The EPA has recognised that its draft assessment may raise concerns among affected communities. It has advised people to contact their local USDA Service Center, local government, state environment agency, or the local wastewater treatment plant to find out more about progress being made on identifying and removing the chemicals from land-applied sludge.

What is the EPA doing to tackle the risks?

The EPA has provided the US equivalent of over €19.3 million in research funding through the Evaluation of Pollutants in Biosolids and Research for Understanding PFAS Uptake and Bioaccumulation in Plants and Animals in Agricultural, Rural, and Tribal Communities grants.

Along with other EPA regulations covering PFAS, the EPA is working towards restricting industrial PFAS discharges to WWTPs using Effluent Limitations Guidelines. Current actions include:

• Revising the Organic Chemicals, Plastics, and Synthetic Fibers Effluent Limitation Guidelines (ELGs) to address wastewater PFAS discharge from PFAS manufacturing facilities
• Revising the Metal Finishing and Electroplating ELGs to address wastewater discharge of PFAS from metal finishing and electroplating operations focusing on facilities using PFAS-based fume suppressants and wetting agents
• Revising the Landfills ELGs to address PFAS discharges from landfill leachate.

Moving toward a full risk assessment and action

Once finalised, the risk assessment will provide information on risk from use or disposal of sewage sludge and will inform the EPA's potential future regulatory actions under the Clean Water Act (CWA).

The EPA has committed to partnering with states, Tribes, territories, and wastewater treatment plants (WWTPs) to reduce risks from PFOA and PFOS that may occur through the management of sewage sludge, including the land application of sewage sludge.