Microplastics in urban environments: The dog as a bioindicator of exposure and human gastrointestinal risk.

INTRODUCTION: Microplastics, particles smaller than 5 mm, are an environmental and public health concern due to their widespread presence in domestic environments. They affect humans and animals that share water, food, and environments. In Santo Domingo (Ecuador), companion dogs can act as environmental sentinels, reflecting exposure to these contaminants and their potential association to health problems. OBJECTIVE: To evaluate microplastics in dog feces in Santo Domingo and their possible relationship with domestic plastic waste and gastrointestinal diseases in their human tutors. MATERIALS AND METHODS: Feces from 27 domestic dogs were analyzed using potassium hydroxide (KOH) digestion and microscopy to identify and quantify microplastics. Daily production of plastic waste in contact with food and the presence of gastrointestinal diseases in tutors were recorded. Statistical analyses were applied to evaluate correlations and associations, considering a significance level of α = 0.05. RESULTS: Fecal samples from 21 dogs contained microplastic particles, with an average of 288.89 microplastic particles per gram, predominantly plastic fibers. The northeastern and northwestern areas showed the highest levels. No significant correlation was found between plastic waste generation and microplastics load (p = 0.194), but a significant association was found with gastrointestinal diseases in tutors (p = 0.027; Cramer's V = 0.463). CONCLUSIONS: Dogs reflect domestic exposure to microplastics, and its study provides evidence of shared risks to both human and animal health. The need to control plastic pollution and promote inter-sectorial preventive research and actions under the One Health approach is reinforced.