What it is
Cotton, linen and hemp are cellulose fibres harvested from plants; wool is keratin protein grown by sheep. Spun and woven essentially as nature made them — unlike synthetics, which are extruded from molten plastic. Since polyester bedding is plastic you sleep inside, this category is the exit.
Why it’s safer
The decisive numbers are about what happens after shedding. NC State measured both sides: cotton and rayon microfibres reached ~76% and ~62% biodegradation in 243 days in aquatic conditions — versus 4% for polyester, which “is expected to persist” (Marine Pollution Bulletin, 2019) lab. Wool likewise biodegrades in marine settings (Water, Air & Soil Pollution, 2024 — noting much wool research is industry-funded) lab. A cotton fibre in dust is lint; a polyester fibre in dust is a permanent resident.
The honest caveats
Natural fibres shed MORE, not less. In the same NC State study, cotton and rayon released 0.2–4 mg of fibre per gram of fabric per wash versus 0.1–1 mg/g for polyester lab. The win is degradability, not a cleaner lint screen.
They end up in bodies too. Cellulosic fibres sit alongside plastic ones in human lung tissue (1998; 2022 μFTIR study) human obs. — and natural fabrics carry dyes and finishes (easy-care formaldehyde resins, water repellents), so “natural” isn’t automatically “untreated”. Blends still shed their polyester half.
“Bamboo” is almost always viscose. Bamboo sheets and socks are bamboo dissolved with solvents (classically carbon disulfide) and re-extruded as regenerated cellulose — the US FTC requires the label “rayon made from bamboo” and has fined major retailers over the claim (FTC) agency. Honest placement: as a fibre it behaves like the rayon above — sheds, then biodegrades — so it beats polyester in the wash. But the “natural bamboo” halo is marketing, the solvent chemistry has a real occupational history, and bamboo’s antibacterial claims don’t survive processing. My bamboo sheets stay; my illusions about them don’t.
What I do
Over 2025 the bedroom and bathroom went natural-fibre: bamboo-viscose and Egyptian cotton sheets, merino wool quilts, cotton mattress protectors, bamboo-cotton towels, cotton everything underneath. Dish cloths are moving from microfibre to organic cotton as they wear out. It’s the single largest category in the kit — about a third of everything I’ve spent — because you spend eight hours a night breathing next to it.