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Early Life Microplastic Exposure Impairs Mouse Incisor Enamel Formation
Summary
A new mouse study found that when pregnant mice and their babies were exposed to tiny plastic particles (microplastics) at low doses, the offspring's teeth didn't develop normally, their teeth came in later and had weaker, less mineralized enamel. Interestingly, the smallest plastic particles (1 micrometer, about the width of a bacterium) caused the most damage, suggesting tiny plastic fragments may be especially good at disrupting how enamel-forming cells work. While this is animal research and doesn't prove the same thing happens in people, it raises concern that early-life microplastic exposure could affect children's too
Microplastics (MPs) are pervasive environmental contaminants with growing evidence of systemic toxicity; however, their effects on tooth development during early life remain poorly understood. In the present study, we investigated whether early-life exposure to polystyrene microplastics (PS-MPs) affects tooth eruption, root formation, and enamel development in mice. Pregnant mice were administered 1, 4, and 10 μm PS-MPs (10 μg/kg/day) from gestation through lactation, and offspring continued exposure post-weaning. Mandibles were analyzed at postnatal days 14, 25, and 42 using micro-computed tomography, histology, scanning electron microscopy, and microhardness testing. Early-life MP exposure did not affect maternal outcomes or overall offspring growth. However, it significantly delayed molar eruption and root formation and produced incisor enamel defects, including reduced enamel length and volume, decreased mineral density, and decreased mechanical hardness. These effects exhibited particle size dependency, with 1 μm MPs causing the most significant changes. Histological analyses revealed increased proliferation of transit-amplifying cells in the labial cervical loop and postponed ameloblastic differentiation, accompanied by an incisal shift in enamel matrix deposition. Collectively, these findings demonstrate that early-life MP exposure disrupts tooth development in a size-dependent manner and identify developing dental tissues as sensitive targets of environmental MP exposure.