PFAS vs. microplastics: what's the difference?

You've probably seen PFAS and microplastics in the same headline, sometimes in the same sentence, as if they were one problem. They aren't. They come from different places, behave differently, and need different tests. Here's what each one is, where it comes from, what the research links it to, and how to figure out which one is worth your attention.

What PFAS are and where they come from

PFAS (per- and polyfluoroalkyl substances) are a family of thousands of synthetic chemicals built around chains of carbon bonded to fluorine. That carbon-fluorine bond is one of the strongest in chemistry¹. It's why PFAS repel grease and water so well, and why they barely break down, in the environment or in the body^2–4. That's where the nickname "forever chemicals" comes from.

Because they stick around, they build up. PFAS are detectable in the blood of nearly all Americans⁵, and an estimated 45% of U.S. tap water contains at least one type⁶.

Nonstick pans get most of the attention, but PFAS also show up in firefighting foam, water-resistant clothing and gear, and, before major phaseouts, grease-resistant food packaging like microwave popcorn bags^7–9. For most homes, drinking water is the exposure that's easiest to test and act on, and it can be the biggest source in areas with contaminated water¹⁰.

What microplastics are and where they come from

Microplastics are pieces of plastic smaller than 5 millimeters, about the size of a grain of rice or much smaller¹¹. Unlike PFAS, they aren't one family of chemicals. They're physical particles made from many kinds of plastic, often carrying their own mix of additives¹².

Some are made small on purpose. Most come from bigger things wearing down: packaging and containers, synthetic clothing in the wash, tires on the road, plastic waste breaking apart outdoors. Because plastic is everywhere, microplastics have been found in air, water, food, soil, household dust, and human tissue samples¹³.

How they're alike, and how they're not

They get lumped together for a reason. Both are widespread, both are persistent, and both can reach your home in several ways.

The difference is what they are. PFAS are chemical compounds that can dissolve in water or sit inside products and food. Microplastics are particles that vary in size, shape, and makeup. That changes how you measure them.

What the research links them to

PFAS have been studied for decades. Exposure to certain PFAS is associated with changes in cholesterol, immune function, and liver health, with effects on reproduction and development, and with some cancers^15–17. How much any of that applies depends on which PFAS, how much, and for how long.

Microplastics are a much younger field. Researchers are looking at whether the particles contribute to inflammation, oxidative stress, and other changes in the body, and whether the chemicals they carry play a role^18,19. They've been found in several parts of the body. What nobody can say yet is what level of exposure meaningfully affects health²⁰.

What to do first

Start with the one you can measure and act on. If you're on a private well, live near an airport, military base, or manufacturing site, or just want to know, a water test tells you whether PFAS are in your tap water and at what levels. If PFAS shows up, the right filter can reduce them²¹. Test first, then pick the fix.

Sources

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4. 4.Li, Y. et al. Half-lives of PFOS, PFHxS and PFOA after end of exposure to contaminated drinking water. Occup. Environ. Med. 75, 46–51 (2018).
5. 5.Calafat, A. M., Wong, L.-Y., Kuklenyik, Z., Reidy, J. A. & Needham, L. L. Polyfluoroalkyl chemicals in the U.S. population: data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and comparisons with NHANES 1999-2000. Environ. Health Perspect. 115, 1596–1602 (2007).
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13. 13.Thompson, R. C. et al. Twenty years of microplastic pollution research-what have we learned? Science 386, eadl2746 (2024).
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15. 15.National Academies of Sciences, Engineering, and Medicine et al. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. (National Academies Press, Washington, D.C., DC, 2022). Link
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19. 19.Marfella, R. et al. Microplastics and nanoplastics in atheromas and cardiovascular events. N. Engl. J. Med. 390, 900–910 (2024).
20. 20.Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health. (2022). Link
21. 21.Herkert, N. J. et al. Assessing the effectiveness of point-of-use residential drinking water filters for perfluoroalkyl substances (PFASs). Environ. Sci. Technol. Lett. 7, 178–184 (2020).

Nestwell screens your home environment. Results describe your water, air, or dust and are not a medical diagnosis.