Is cotton sustainable? Water, pesticides and chemical finishes

Cotton grows as fiber, isn’t plastic and breaks down when it’s thrown away. In lake water, cotton yarn biodegraded by more than 70% in lab tests, while polyester barely changed. That doesn’t make every cotton shirt a clean one. The costs show up in three places: the water, the farm chemicals, and the finishes added at the mill.

Water

Cotton is a thirsty crop where it’s irrigated. Averaged over the world, a kilogram of cotton lint takes about 9,100 liters of water, according to a global study of crop water use. About 5,200 liters of that is rain, 3,000 is irrigation, and 1,000 is the water needed to dilute the pollution it causes.

How much of that comes from rivers and aquifers depends on where it’s grown. Between 2020 and 2024, 44% of the world’s cotton land was irrigated. The other 56% was rain-fed and grew more than 45% of the crop. The worst case is the Aral Sea: water diverted for cotton and rice from the 1960s on left it with about a tenth of its former area.

Figure you’ll see	Where it comes from	What it means
2,700 liters per T-shirt	A 2006 study, 1997–2001 data	2,720 liters for a 250 g shirt, of which 1,230 liters is irrigation and the rest is rain and dilution water
20,000 liters per kg	No global source found	Close to one study’s figure for India, not a world average
16% of insecticides	2003 sales data	Outdated; the latest estimate is 10.51%

Pesticides

Conventional cotton is grown on 2.3% of the world’s arable land and takes 4.0% of its pesticides and 10.51% of its insecticides, according to the cotton industry’s own international body, working from pesticide maker Bayer’s sales figures for 2018 to 2022. The people who apply them pay first. In a 2016 survey in Benin, 42% of conventional cotton farmers reported pesticide poisoning symptoms in the previous year. Organic rules ban most synthetic pesticides; see organic vs regular cotton.

Chemical finishes

A lot of what makes a cotton shirt behave like a polyester one is sprayed on. “No-iron,” “wrinkle-free,” “permanent press” and “easy care” finishes are made by cross-linking the cotton with compounds built from urea, melamine, glyoxal or formaldehyde, and the European Commission’s technical reference on textile mills notes they can release formaldehyde.

When the US Government Accountability Office tested 180 shirts, sheets and other skin-contact items in 2010, 10 had more formaldehyde than the strictest limits in force abroad, between 75.4 and 206.1 parts per million, and more than half of those 10 were labeled durable press. Japan limits formaldehyde to 16 ppm in clothing for babies up to 24 months and 75 ppm in underwear and nightwear.

Formaldehyde is classified by IARC as carcinogenic to humans, with sufficient evidence for cancer of the nasopharynx and myeloid leukemia. On skin, the concern is allergy. Textile formaldehyde resins have caused allergic dermatitis in sensitive people, though dermatologists disagree about modern finishes: one review found no proven case at today’s lower levels.

Water- and stain-repellent finishes are the other big one. In a 2022 investigation, 72% of products marketed as water- or stain-resistant contained PFAS. New York banned new clothing with intentionally added PFAS from January 2025. Antimicrobial “odor control” finishes often use silver, and in one study between 1% and 45% of a fabric’s silver washed out in a single wash.

What more sustainable cotton looks like

The cotton itself is the easy part. Organic cotton cuts the pesticides, and cotton from rain-fed farms uses far less irrigation, although labels rarely say which farms the cotton came from. The finishes are easier to control. GOTS-certified products are processed without formaldehyde, PFAS or synthetic antimicrobial finishes, and you can skip any garment sold as no-iron or stain-proof.

Fibers in this guide

• Cotton: not plastic