Backyard eggs contaminated: worms found to be major PFAS source
Your homegrown eggs may contain dangerous levels of PFAS, a harmful chemical. New research reveals worms from soil are the main culprit, posing health risks for those consuming backyard eggs regularly.
| Key Data Point | Details |
|---|---|
| Contaminant | PFAS (per- and polyfluoroalkyl substances) |
| Primary Source | Worms from soil consumed by chickens |
| Affected Eggs | Backyard eggs from hobby chickens |
| PFAS Levels | Higher than in commercial eggs |
| Other Contributors | Water, soil, straw, sawdust, and wood from chicken coops |
| PFAS Exposure Risk | Exceeds health-based guideline value in the Netherlands |
| Research Body | RIVM (National Institute for Public Health and the Environment) |
| Research Focus | Identifying sources and reducing PFAS exposure |
The RIVM is the Dutch National Institute for Public Health and the Environment, responsible for researching environmental contaminants like PFAS. It advises the government on health risks and potential measures to protect citizens from harmful substances in food and the environment.
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Worms are a major source of PFAS in backyard eggs
In April 2025, the RIVM concluded that in the Netherlands, backyard eggs may contain far more PFAS (per- and polyfluoroalkyl substances) than commercial eggs. New RIVM research confirms that this is mainly due to the worms that chickens pick up from the soil.
The RIVM investigated the source of PFAS (per- and polyfluoroalkyl substances) in backyard eggs. Backyard eggs come from chickens kept as a hobby, for example in gardens, vegetable plots, animal pastures, and care and children’s farms.
Worms are a major source
The highest levels of PFAS were found in eggs from free-range hobby chickens. The RIVM frequently detected large amounts of the same PFAS in worms as in the eggs. Therefore, the RIVM concludes that worms are a major source of PFAS in backyard eggs. Other soil-dwelling animals also contain high levels of PFAS. The RIVM did not investigate the origin of PFAS in the soil at the locations where the hobby chickens were kept.
In addition, water, soil, straw or sawdust, and wood from chicken coops may contribute to the amount of PFAS in eggs, although far less PFAS was found in these materials than in soil-dwelling animals.
PFAS levels vary per measurement
Many chickens lay no or fewer eggs in winter. It was expected that this would result in significantly higher PFAS levels in the first eggs laid after winter. However, this was not the case. The amount of PFAS detected varies per location and can differ every day. This study did not find an explanation for these differences. Therefore, the result of a single measurement only provides information about the eggs tested at that specific time.
Research into current PFAS exposure
PFAS is present in the environment throughout the Netherlands, due to emissions from industry and consumer products. Once in the environment, PFAS hardly breaks down at all.
People in the Netherlands ingest more PFAS through food and drinking water than the health-based guideline value. PFAS in backyard eggs can lead to a significant additional exposure.
As part of the PFAS research programme, the RIVM is investigating how much PFAS people in the Netherlands are currently exposed to. The RIVM is also researching the sources of this PFAS. The aim is to determine which measures can help reduce exposure to PFAS.