Dutch Study Reveals Soil-Dwelling Worms Drive High PFAS Levels in Backyard Chicken Eggs

Overview

A study by the Dutch National Institute for Public Health and the Environment (RIVM) has confirmed widespread PFAS contamination in backyard chicken eggs across the Netherlands. The research identified a critical bioaccumulation pathway: soil-dwelling worms ingest PFAS from contaminated soil, chickens eat the worms, and the PFAS compounds accumulate in eggs at concentrations that exceed food safety standards. This pathway operates independently of drinking water quality, meaning that properties with clean groundwater and scheme water supplies can still produce eggs with unacceptable PFAS levels if the soil is contaminated.

For Australian environmental professionals, this study has immediate relevance for the assessment and management of PFAS-contaminated residential and peri-urban sites. It demonstrates that standard risk assessment approaches focused on direct soil contact, dust inhalation and groundwater ingestion may underestimate actual human exposure where ground-foraging poultry is present.

Key details

The RIVM study tested eggs from backyard chickens at properties across the Netherlands, including areas near known PFAS point sources and locations with only diffuse, background-level PFAS contamination. The results showed that PFAS concentrations in eggs frequently exceeded European food safety limits, even at sites with relatively low soil PFAS concentrations.

The key finding was the identification of earthworms as the primary bioaccumulation vector. Worms living in PFAS-contaminated soil accumulate these compounds in their tissues at concentrations significantly higher than the surrounding soil. When free-range chickens consume these worms as a routine part of their diet, the PFAS transfers into the hen’s body and concentrates in the egg yolk. The bioconcentration factor through this soil-to-worm-to-egg pathway was substantially higher than what would be predicted from direct soil ingestion alone.

Notably, the study found that PFOS (perfluorooctane sulfonate) was the dominant compound in egg samples, consistent with its known tendency for bioaccumulation. However, shorter-chain PFAS compounds were also detected, indicating that the bioaccumulation pathway is not limited to legacy long-chain compounds.

Australian context

The implications for Australian contaminated land practice are significant. Under the NEPM 2013 framework, Schedule B4 provides guidance for site-specific health risk assessments including the development of Conceptual Site Models. The secondary exposure pathway of soil to invertebrate to poultry to human is acknowledged in risk assessment theory but is often underestimated or excluded from practical CSMs for residential sites.

The PFAS National Environmental Management Plan (NEMP 3.0) recognises multiple exposure pathways for PFAS, but specific guidance on the backyard poultry pathway remains limited. State guidelines in Queensland, New South Wales and Victoria do not currently mandate assessment of this pathway as standard practice for residential PFAS assessments.

This is particularly relevant for peri-urban and semi-rural areas across Australia where keeping backyard chickens is common. Suburbs on the fringes of Sydney, Melbourne, Brisbane, Adelaide and regional centres often feature larger residential lots where hobby poultry keeping is permitted under local council regulations. If these areas are located near former defence bases, airports, industrial sites or firefighting training grounds with known PFAS contamination, the egg ingestion pathway could represent a significant and uncharacterised exposure route for residents.

Local councils in PFAS-affected areas may need to consider whether development consent conditions should address ground-foraging poultry on sites with residual PFAS contamination. Environmental management plans for residential subdivisions on remediated PFAS sites may require specific provisions addressing this pathway.

Practical implications

For contaminated land consultants and risk assessors working on PFAS-impacted sites in Australia, the RIVM study supports several practical recommendations:

• Conceptual Site Models: CSMs for residential and peri-urban PFAS-impacted sites should include the soil-to-invertebrate-to-poultry-to-human pathway where land use permits backyard chickens. This should be assessed as a potentially complete and significant pathway.
• Site-specific risk assessments: Where low-level PFAS soil impacts remain at residential sites, practitioners should evaluate whether site-specific risk assessments are necessary to quantify the egg ingestion pathway, rather than relying solely on generic soil screening criteria.
• Environmental management plans: For developments on former PFAS sites, EMPs should consider including formal advice against ground-foraging poultry, requirements for raised coops with clean imported fill, or ongoing egg monitoring programs.
• Soil disposal and remediation: The findings reinforce the importance of achieving thorough remediation of PFAS in soil at residential sites, as residual contamination below generic screening levels may still present unacceptable risks through secondary pathways.
• Council and community advice: Local councils and health authorities in PFAS-affected areas should consider issuing specific guidance about backyard egg consumption, particularly where soil PFAS concentrations are known to be elevated.

References and related sources

• NL Times: Backyard chicken eggs across Netherlands contaminated with PFAS, study finds
• RIVM – Dutch National Institute for Public Health and the Environment
• PFAS National Environmental Management Plan (NEMP)
• NEPM 2013 – Assessment of Site Contamination

How iEnvi can help

iEnvi delivers specialist contaminated land assessment and remediation services for PFAS-impacted sites across Australia. Our team has extensive experience developing Conceptual Site Models that account for complex bioaccumulation pathways, conducting site-specific human health risk assessments and preparing environmental management plans for residential developments on former contaminated sites. We work with developers, local councils and state regulators to ensure PFAS risks are properly characterised and managed.

This is an iEnvi Machete news summary. Prepared by iEnvi to summarise the source article for contaminated land, groundwater, remediation, approvals and site risk professionals.

Need advice on this topic? Speak to an iEnvi expert at hello@ienvi.com.au or 1300 043 684, or contact us online.