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Presence and hazard assessment of microplastics in mexican howler monkeys (Alouatta palliata ssp. mexicana) of the Los Tuxtlas Biosphere reserve, Mexico

Journal of Hazardous Materials Advances 2026
María Fernanda Alvarez‐Velazquez, Jaime Rendón-von Osten, Merle M. Borges-Ramírez, Colin A. Chapman, Andres M. López-Pérez, Ricardo J. Ortíz-Zárate, Juan Carlos Serio-Silva

Summary

Scientists found tiny plastic particles (microplastics) in the poop of endangered howler monkeys living in a protected rainforest reserve in Mexico—even though these monkeys live far from cities and don't drink from plastic bottles or eat processed food. This is a big deal because it shows plastic pollution has spread even into remote, protected wilderness areas, meaning there's likely no escaping it—for wildlife or for us. While this study didn't test human health effects directly, it adds to growing evidence that we're all constantly exposed to microplastics through our environment, food, and water.

• First study following established methods for the report of microplastics in wild American non-human primates. • Results show that even natural protected areas face plastic contamination. • Fecal samples are a non-invasive way to assess microplastic pollution in wild primates. • More studies on terrestrial mammals are urgently needed to protect endangered species. Microplastic pollution is an emerging conservation threat to wildlife in both terrestrial and aquatic habitats. However, little is known about its presence in terrestrial ecosystems. How microplastics threaten non-human primates remains poorly understood, and to our knowledge, no study following established methods has been conducted on the American continent. Therefore, this study aimed to detect the presence of microplastics in the feces of the endangered Mexican howler monkey ( Alouatta palliata mexicana ) from the Los Tuxtlas Biosphere Reserve, Veracruz, Mexico. We analyzed 66 fecal samples and found that more than 90% contained microplastics confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), with a mean abundance of 1.49 ± 1.63 particles/g dry weight (DW). The Polymer Hazard Index (PHI) for the polymer detected in fecal samples was calculated, and of the 31 polymer types identified, 12 fell into one of the hazard categories. PHI values ranged from 0.01 to 401.22 and were classified into hazard levels I to IV. These findings emphasize the urgent need for information on the presence and potential consequences of microplastic exposure in endangered terrestrial species.

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