Cotton itself is not toxic. It’s a natural plant fiber that humans have worn and used for thousands of years. But the journey from cotton plant to finished product involves pesticides, chemical dyes, formaldehyde-based finishes, and other treatments that can leave residues in the fabric you wear, sleep on, or use in personal care products. The real question isn’t whether cotton is toxic, but whether the chemicals added to it pose a risk.
Chemicals Added During Processing
Raw cotton is soft and absorbent, but it wrinkles easily and doesn’t hold color on its own. To fix that, manufacturers treat it with a range of industrial chemicals. Formaldehyde-based resins have been applied to cotton since the 1920s to make it wrinkle-resistant, and they’re still used today in “permanent press” and “easy care” finishes. Formaldehyde is a known skin sensitizer and, at high concentrations, a carcinogen.
The EU limits formaldehyde in clothing that touches skin to 75 mg/kg, the same threshold required by the widely used OEKO-TEX Standard 100 certification. Stricter certifications like the EU Eco-label set the limit at 30 mg/kg. Baby textiles have the tightest restrictions, with limits as low as 16 to 20 mg/kg depending on the standard. Testing of commercially available garments has generally found formaldehyde levels well below these thresholds, often 10 times lower than the concentration at which adverse effects begin to appear. Still, new clothes with a strong chemical smell can contain higher levels, and washing before wearing reduces exposure significantly.
Beyond formaldehyde, cotton processing uses ammonia, petroleum-based scours, softeners, flame retardants, and antimicrobial agents like triclosan and chlorhexidine. Some of these are known to cause allergic contact dermatitis in sensitive individuals. The preservative thiazolinone, sometimes used in textile finishes, is another documented skin sensitizer.
Dyes and Heavy Metals
Colored cotton clothing contains dyes that may carry trace amounts of heavy metals like chromium, lead, and cadmium. Testing of printed T-shirts found chromium levels highest in yellow-colored samples (about 5.2 mg/kg) and black samples (about 3.8 mg/kg). Lead was highest in red (3.4 mg/kg) and blue (2.7 mg/kg) fabrics. Cadmium levels were low across the board, ranging from 0.011 to 0.277 mg/kg.
These concentrations are generally small, but they add to your overall exposure from other sources. Azo dyes, which can break down into compounds linked to cancer, are banned in certified organic cotton processing but still permitted in some conventional manufacturing. If you have sensitive skin or a history of textile dermatitis, lighter-colored or undyed cotton is less likely to cause a reaction.
Pesticide Residues in Cotton
Conventional cotton is one of the most pesticide-intensive crops. Glyphosate, the active ingredient in Roundup and classified as a “probable carcinogen” by the World Health Organization, made up more than a third of all pesticide use on U.S. cotton in 2019. Other commonly applied chemicals include organophosphates, pyrethroids, and neonicotinoids.
Newer genetically modified cotton varieties are engineered to resist multiple herbicides at once, including glyphosate, glufosinate, dicamba, and 2,4-D. This means more types of chemicals may be applied during growing. Most pesticide residue washes out or degrades during processing, so finished cotton clothing typically contains very little. The greater concern is environmental: runoff from cotton fields contaminates water supplies and soil in farming communities, and farmworkers face direct exposure.
Cotton in Tampons and Pads
One area that draws particular concern is cotton used in menstrual products, since tampons contact mucous membranes that absorb chemicals more readily than skin. Multiple studies across the U.S., Europe, and Asia have tested tampons and pads for dioxins, furans, glyphosate, phthalates, and polycyclic aromatic hydrocarbons (PAHs).
The results are mostly reassuring but not entirely clean. Trace amounts of dioxins have been detected in tampon products in nearly every study, a byproduct of the chlorine bleaching process. A Swiss study also found low levels of PAHs and glyphosate in some products. A Belgian analysis detected glyphosate in both pads and tampons, along with small amounts of phthalates and other industrial chemicals. However, the concentrations were consistently described as negligible by most research teams. A French government review concluded there was no health risk from these trace amounts but recommended manufacturers work to eliminate substances with carcinogenic or endocrine-disrupting potential from their products.
Cotton Dust and Lung Disease
For people who work with raw cotton in textile mills, the fiber itself poses a genuine respiratory hazard. Inhaling cotton dust over time can cause byssinosis, commonly called “brown lung disease,” a permanent and disabling condition. Short-term effects include chest tightness, difficulty breathing, and coughing up mucus. Long-term exposure can also trigger occupational asthma.
The National Institute for Occupational Safety and Health recommends that airborne cotton dust stay below 0.2 milligrams per cubic meter over a 10-hour workday. This is a concern for factory workers, not for people wearing cotton clothing. Consumers are not exposed to cotton dust at levels that would affect lung health.
Cotton Microfibers in Water
When you wash cotton clothing, tiny fibers break off and enter wastewater. These microfibers eventually reach rivers, lakes, and oceans. Cotton is biodegradable, unlike polyester microfibers, which persist in the environment for decades. But “biodegradable” doesn’t mean harmless. Lab research has shown that both cotton and polyester microfibers cause developmental delays in freshwater invertebrates at concentrations of 500 fibers per liter. Cotton microfibers can also carry whatever chemical treatments were applied to the fabric, delivering those substances into aquatic ecosystems.
How Organic Cotton Differs
Organic cotton, particularly when certified under the Global Organic Textile Standard (GOTS), is grown without synthetic pesticides and processed without many of the chemicals used in conventional manufacturing. GOTS specifically bans ammonia, azo dyes, heavy metal-based dyes, flame retardants, formaldehyde, and petroleum-based softeners. The formaldehyde limit under GOTS is 16 mg/kg for all textiles, stricter than most other standards.
OEKO-TEX certifications take a different approach. Rather than banning chemicals outright, they set maximum allowable concentrations for hundreds of substances. The 2025 updates tightened limits on bisphenol A (dropping from 100 to 10 mg/kg), certain UV stabilizers, and PFAS compounds. An OEKO-TEX label doesn’t mean a product is organic, but it does mean it’s been tested for harmful residues and falls within safety thresholds.
If you’re looking to minimize chemical exposure from cotton, choosing GOTS-certified organic products is the most reliable option. For conventional cotton, washing new items before first use removes a significant portion of chemical residues, especially formaldehyde and loose dye. This simple step makes the biggest practical difference for most people.