Field evidence for transfer of plastic debris along a terrestrial food chain

TLDR

Plastic pollution is global, yet the transfer of micro‑ (<5 mm) and macro‑plastic (5–150 mm) to terrestrial species that humans consume has not been examined. The study measured micro‑ and macro‑plastic in soil, earthworm casts, chicken feces, crops, and gizzards from traditional Mayan home gardens. Micro‑ and macro‑plastic accumulated from soil to earthworms to chicken feces and gizzards, with gizzards containing the highest concentrations and crops showing no micro‑plastic, demonstrating that these plastics can enter terrestrial food webs.

Abstract

Although plastic pollution happens globally, the micro- (<5 mm) and macroplastic (5-150 mm) transfer of plastic to terrestrial species relevant to human consumption has not been examined. We provide first-time evidence for micro- and macroplastic transfer from soil to chickens in traditional Mayan home gardens in Southeast Mexico where waste mismanagement is common. We assessed micro- and macroplastic in soil, earthworm casts, chicken feces, crops and gizzards (used for human consumption). Microplastic concentrations increased from soil (0.87 ± 1.9 particles g-1), to earthworm casts (14.8 ± 28.8 particles g-1), to chicken feces (129.8 ± 82.3 particles g-1). Chicken gizzards contained 10.2 ± 13.8 microplastic particles, while no microplastic was found in crops. An average of 45.82 ± 42.6 macroplastic particles were found per gizzard and 11 ± 15.3 macroplastic particles per crop, with 1-10 mm particles being significantly more abundant per gizzard (31.8 ± 27.27 particles) compared to the crop (1 ± 2.2 particles). The data show that micro- and macroplastic are capable of entering terrestrial food webs.