If you’re one of the 15.8 million Americans who practice yoga, you know there’s nothing better than to relax into savasana after a long day at work. But next time you hit the sticky mat, you might want to ask, what exactly am I sticking to?

In most cases the answer is polyvinyl chloride, or PVC. But the manufacture of that rubbery plastic, which helps keep your hands in place for downward dog, generates the proven carcinogen dioxin as a by-product. And PVC also leaches phthalates, which may be hormone disruptors.

Fortunately, as yoga’s popularity grows, so do the nontoxic alternatives to PVC. The best advice is to emulate the Indian hatha yoga practitioners of the fifteenth century and use organic cotton rugs, although the weave can be rough on sensitive skin and cotton does have a tendency to slip on hardwood floors. The next best option is open-cell natural rubber mats, whose main downside is that they contain latex, to which some people are allergic. But they do maintain a good grip in intense sessions. A natural rubber-and-jute blend is another possibility.

For ideas on buying a new mat for your next session, useful Web sites include jadeyoga.com, greenyoga.org, and intentusa.com.

Illustration by David Semple