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PFAS Biomagnified From Insects Into Barn Swallows, With the Highest Estimated Risk Just After Hatching

Two newly hatched barn swallow chicks and three eggs in a mud nest
Conservation · Threats

Per- and polyfluoroalkyl substances, or PFAS, became more concentrated as they moved from insects into barn swallows (Hirundo rustica) at a tropical rural site in South China. Researchers measured 33 PFAS compounds in environmental samples, insects, eggs, guano and chicks from one to 20 days old.

PFAS biomagnified from insects into the swallows

Biomagnification factors from insects to swallows were greater than one, indicating trophic magnification. The analysis also pointed to water and soil ingestion as additional sources of some long-chain perfluorocarboxylic acids, a subgroup of PFAS, so insect prey was not the only route by which the birds accumulated the chemicals.

Concentrations fell during early growth and rose again after day 13

PFAS concentrations followed a U-shaped pattern from eggs through chick development. As chicks grew from day one to day 13, the increase in body mass diluted measured concentrations. Between days 13 and 20, dietary exposure outweighed this dilution and concentrations rose again. The estimated total amount in the body showed a similar age pattern for most compounds, although perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) differed, reflecting compound-specific exposure sources and metabolism.

Estimated risk was highest just after hatching

Hazard quotients — ratios comparing measured exposure with toxicological reference values — indicated substantially higher potential risk during the first days after hatching than in eggs or older nestlings. The paper also identifies guano as a possible route by which barn swallows can carry PFAS from agricultural fields into buildings and create potential exposure for residents.

Sources and image credit

  1. Sun, C., Yao, J., Xu, Y., Zeng, J., Tian, L., Zheng, X., Mai, B., & Qiu, R. (2026). Bioaccumulation and age-dependent risks of per- and polyfluoroalkyl substance (PFAS) in tropical barn swallows (Hirundo rustica) from South China. Avian Research, 17, 100367. https://doi.org/10.1016/j.avrs.2026.100367Primary open-access research article published 17 March 2026. The study quantified 33 PFAS compounds in environmental media, insects, barn swallow eggs, guano and chicks aged 1–20 days at a tropical rural site in South China, and assessed trophic magnification and age-dependent exposure risk.

Image: Alpsdake — two newly hatched barn swallow chicks and three eggs of Hirundo rustica gutturalis in a mud nest; Wikimedia Commons; cropped to 16:9; representative early-life image, not birds from the South China PFAS study · CC BY-SA 4.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

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