On 25 November, the US Environmental Protection Agency (EPA) received a petition signed by over 100 consumer advocacy groups calling for the EPA to develop a monitoring program for microplastics in drinking water. If successful, this petition could lay the framework for the official regulation of microplastics and further reinforce the EPA’s plans to address the plastic pollution crisis under the newly released National Strategy to Prevent Plastic Pollution, impacting both producers and users of plastics. The petition claims that the ubiquity of microplastics in the environment and the threats that this broad class of substances pose to human health justify the monitoring of microplastics under the Unregulated Contaminant Monitoring Rule (UCMR) and warrant future regulation. New UCMRs, which are required every five years under the Safe Drinking Water Act (SDWA), outline monitoring programs for up to 30 unregulated substances and are intended to inform decision-making about substances that should be regulated under the SDWA. The next UCMR proposal is due in 2025.

This petition comes on the heels of numerous lawsuits alleging harm arising from exposure to microplastics due to their presence in bottled spring water, leaching from baby bottles and sippy cups, and many other sources. Although several of these suits have been dismissed, and the US Food and Drug Administration recently stated the “current scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in food pose a risk to human health,” the call for monitoring of microplastics under the UCMR is demonstrative of the need to better understand any alleged environmental and human health implications of these ubiquitous substances. Several challenges that the EPA is likely to encounter if the decision is made to include microplastics in the next UCMR include the chemical and structural diversity of this broad class of substances and the lack of standardized methods for the detection, quantification, and characterization of microplastics.