From the Lab by ETR Laboratories

For years, researchers have been publishing studies on microplastics in drinking water. The findings have been consistent and increasingly alarming, and for just as long, the regulatory response has been essentially nothing. That changed in April 2026.

On April 2nd, the EPA formally designated microplastics as a priority contaminant group for the first time, adding them to the draft Sixth Contaminant Candidate List. This is the agency’s formal mechanism for identifying unregulated contaminants that may require national drinking water standards. Being added to this list triggers additional research, monitoring requirements, and data collection as a precursor to potential regulation.

It’s a significant step. It’s also, depending on how you look at it, an acknowledgment of how far behind the regulatory framework has fallen.

What we already know

Microplastics are tiny fragments of plastic, generally defined as particles under five millimeters, that break off from larger plastic materials as they degrade. They’ve been found in oceans, in soil, in rainfall, in food, and in drinking water, both bottled and tap. They’ve also been found in human blood, lung tissue, and most recently, brain tissue.

A study published in 2025 found that concentrations of nanoplastics in human brain tissue appeared to increase measurably between 2016 and 2024. The long-term health implications of this are still being studied, but the trajectory of the research is not reassuring.

People who drink primarily bottled water have been estimated to consume roughly 90,000 additional microplastic fragments per year compared to those who drink tap water. This is one of the more counterintuitive findings in the field: the product marketed as a cleaner alternative to tap water is, by the measure of plastic particle ingestion, significantly worse. The plastic bottle itself is the source.

What the watch list designation actually means for you

Being added to the contaminant candidate list does not mean microplastics are now regulated in drinking water. There is no maximum contaminant level. There is no enforcement mechanism. What it means is that the EPA has formally acknowledged that microplastics warrant serious attention and has started the process that could eventually lead to standards. That process typically takes years.

In practical terms, this means that for the foreseeable future, no public water system is required to test for microplastics or remove them. No bottled water company is required to disclose microplastic levels. The gap between what the science shows and what regulations require is wide, and you are in that gap right now.

This is exactly the situation where independent testing and informed filtration decisions matter most.

Tap water vs. bottled water on microplastics

The instinct to switch to bottled water when concerned about tap water quality is understandable. In many situations, for certain contaminants, it makes sense. Microplastics are the exception. The plastic bottle is the problem. Water stored in plastic, often for months in warehouses and trucks, accumulates plastic particles from the container itself. Heat accelerates the process. Age accelerates it. The longer water sits in plastic, the more plastic ends up in the water.

The better path, as we’ve written about in the context of phthalates as well, is a quality home filtration system using glass or stainless steel for storage. Reverse osmosis systems have shown effectiveness at reducing microplastic concentrations in drinking water. But the right filtration approach depends on what else is in your water beyond microplastics, which is why testing before filtering is still the right sequence.

Where this is going

The EPA’s designation is the beginning of a regulatory arc that will likely take years to result in enforceable standards. In the meantime, microplastic contamination in drinking water is not going away. If anything, the volume of plastic in the environment continues to increase, and the research connecting plastic particle exposure to health outcomes is getting more specific, not less.

Staying ahead of this means not waiting for regulation to catch up. It means understanding what’s in your water now, making informed choices about filtration, and not assuming that because something isn’t regulated, it isn’t present.

At ETR Laboratories, we stay current on emerging contaminants and the testing methods used to detect them. If you have questions about what a comprehensive water test covers or want to understand your options, a free consultation is a good place to start. You can also browse our water testing options here.

Sources

EPA — Draft Sixth Contaminant Candidate List (CCL 6), April 2, 2026

Nature Medicine, 2025 — Bioaccumulation of Microplastics in Decedent Human Brains

Environmental Science & Technology, 2019 — Human Consumption of Microplastics (Senathirajah et al.)

EPA Press Release — EPA Takes Bold Action to Ensure Drinking Water is Safe from Microplastics