Are period underwear actually better for the environment? What the life-cycle research does and does not say

What the research measured, and what it did not

The most thorough public review is the UN Environment Programme and Life Cycle Initiative report "Single-use menstrual products and their alternatives: Recommendations from Life Cycle Assessments" (2021). It compared the life-cycle studies that existed for single-use tampons, single-use pads, reusable cloth pads and menstrual cups, and its headline conclusion is unambiguous: "In all circumstances, reusable menstrual products have substantially lower environmental impacts than commonly available single-use options." For cups the difference was enormous - under 1% of the impact of single-use options over a year of use in two of the four studies, with the cup paying back its footprint within roughly 12 to 20 tampons, or one to two months.

Period underwear was not one of the products studied. The report names it twice as a gap the studies "do not cover." Its only statement about period underwear is an inference: reasoning from a separate review of reusable nappies, it says that efficient washing makes reusables beat single-use and that this is "likely" true of period underwear too. That is a reasonable inference from a credible body, and it is still an inference. One peer-reviewed life-cycle study that appears to include period underwear has since been published (Fourcassier and colleagues, Cleaner Environmental Systems, 2022); we could not read its full text, so we cite no figures from it. Anyone quoting a precise footprint for a pair of period underwear is quoting a brand's own estimate or a guess.

The single-use side, in numbers

The disposable side is better measured. The UNEP report, citing a 2019 Zero Waste Europe analysis, puts single-use menstrual products at about 19 billion a year in the US and 49 billion in the EU, with roughly 80% (US) and 87% (EU) ending in landfill, and notes that a conventional pad can contain up to 90% plastic. The widely repeated figure that a person uses 11,000 to 14,000 tampons or pads in a lifetime is not a brand invention: UNEP takes it from two 2019 reports (Zero Waste Europe's, by Cabrera and Garcia, and a study by Peberdy, Jones and Green) that build it from products per period, periods per year and years of menstruation. Treat it as an estimate with visible assumptions, which is more than most numbers in this category can say.

Why washing decides the answer

The reusable products' footprint comes overwhelmingly from use, not manufacture. For cups the driver is boiling water to sterilize; for the one reusable-pad study in the review, the result was "strongly dependent on how the pad is washed." The report's washing guidance, which names period underwear directly, is the whole lever: pre-rinse in cold water, wash in an energy- and water-efficient machine with a full load, and line-dry; or hand-wash in lukewarm water with minimal detergent. A pair washed alone in a hot cycle and tumble-dried after every wear can erase much of its advantage. A pair cold-rinsed, washed with the rest of the laundry and air-dried keeps nearly all of it.

That guidance is the same routine that makes a pair last. Heat and softener shorten a pair's life; cold water and air-drying extend it. The care rules and the environmental rules are one list.

Lifespan is the other lever

A reusable earns its footprint back by replacing single-use products over time, so the number of periods a pair serves matters as much as how it is washed. Most brands estimate around two years or 40-plus washes with proper care. A pair that lasts that long replaces several hundred disposables; a pair killed in six months by hot dryer cycles replaces far fewer while carrying the same manufacturing footprint. Buying one pair, proving it fits and holds, and then building a rotation you will actually wear is both the cheaper path and the lower-impact one - a drawer of pairs that never get worn helps nobody.

What we cannot tell you

Three things stay open. First, the pair itself: most period underwear is nylon, polyester and elastane with a synthetic barrier, and no menstrual-product life-cycle study has weighed those fibers against cotton pads or against each other. Second, chemistry: PFAS finishes are an environmental question as well as a health one, and the PFAS guide covers what has and has not been found in period underwear; no study we could read puts an environmental number on it. Third, end of life: a worn-out pair is several bonded fabrics, which is what fiber recycling struggles with, so most retired pairs end in general waste after their two years. The lifespan guide covers the realistic disposal options.

The honest bottom line

Our reading of the evidence: a pair of period underwear worn for two years and washed cold, in full loads, and air-dried almost certainly has a substantially lower footprint than the disposables it replaces, because every reusable the research did measure did, and because the mechanism - a few hundred single-use items replaced by one washable one - is the same. How much lower has not been measured for period underwear specifically, and the answer depends more on your laundry habits than on the brand. Buy a pair that fits and holds, wash it the cheap way, keep it for years, and the environmental case takes care of itself.

Sources

The research facts above trace to:

• The reusable-versus-single-use findings, the washing guidance, and the statement that period underwear was not covered: UN Environment Programme and Life Cycle Initiative, "Single-use menstrual products and their alternatives: Recommendations from Life Cycle Assessments," 2021. Full report read 2026-09-04.
• Single-use volumes, landfill shares, plastic content and the lifetime figure: as cited in that report from Zero Waste Europe (Cabrera and Garcia, 2019) and Peberdy, Jones and Green (2019).
• A peer-reviewed life-cycle study that appears to include period underwear, cited here only as existing: Fourcassier and colleagues, Cleaner Environmental Systems, 2022, doi 10.1016/j.cesys.2022.100096. We could not read its full text and quote no figures from it.