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Patagonia PBL Merino Wool
Photo: Tetsuya Ohara

If you take a close look at wool fibers under a microscope, you’ll see small, barbed scales covering their surface. When the wool fibers are machine-washed and dried, their scales can interlock, causing the wool to felt and shrink. That’s why many wool garments require hand-washing or dry cleaning to prevent interlocking.

To make wool garments machine-washable, the barbed scales are typically pretreated with chlorine, then coated with a thin polymer. This makes the wool fibers smooth and allows them to slide against each other without interlocking. Millions of pounds of wool are processed this way each year.

Unfortunately, this method results in wastewater with unacceptably high levels of absorbable organ halogens (AOX) – toxins created when chlorine reacts with available carbon-based compounds. Dioxins, a group of AOX, are one of the most toxic substances known. They can be deadly to humans at levels below one part per trillion. Wastewater from the wool-chlorination process contains such high concentrations of chlorinated chemicals, that most wastewater treatment facilities in the United States will not accept it. Therefore, most chlorinated wool is processed in other countries, then, imported to the United States. There are other ways of removing the tips of the barbed scales without using chlorine. Ozone and hydrogen peroxide are two alternatives that break down into oxygen and water when their wastewater is treated.

Garments made from chlorine-treated wool do not pose any risk to the wearer. The final product is not the issue, but rather the environmental impacts of producing it. That’s why we use chlorine free and AOX-free methods to produce machine-washable wool garments such as our merino baselayers.

For more information about chlorine, visit the industry website

For a report about chlorination byproducts, visit the nonprofit research organization Environmental Working Group

Chlorine-Free Wool

Raw, untreated wool has scales that make it itchy and coarse and cause it to shrink, so most wool fabrics are treated with chlorine to reduce the scales. But chlorine is a pervasive pollutant that’s especially harmful to organisms living in water and soil. We remove the scales from our merino wool fibers using a unique chlorine-free process that’s bluesign® approved.

Chlorine-Free Wool Products

Men's Styles

Women's Styles