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Yoga should bring inner peace and enlightenment, not environmental pollutants or unsightly foot ailments. The production of polyvinyl chloride (PVC) plastic, a common ingredient in cheaper mats, releases cancer-causing dioxins into the atmosphere. Furthermore, hormone-disrupting phthalates, often mixed with carcinogenic lead or cadmium, are added to soft PVC products to make them more pliable but are released over time. And rental yoga mats pose their own individual threats. "Fungus thrives in moist, dark and warm environments, like the folds of a yoga mat," says Timothy McCall, M.D., medical editor of Yoga Journal. "I've never seen anything as disgusting as the yoga mats at a gym I used to belong to." Even podiatrists are seeing more cases of plantar warts and athlete's foot on mat renters.

Mat renters, BYO cleaning supplies: Stirlen Chi mat refresher wipes ($15/20 wipes) are free of harsh chemicals and preservatives, and mats dry relatively quickly after use (www.stirlenchi.com, 888-515-4509). Vermont Soap Organics USDA certified-organic yoga mat cleaner comes in a handy 2-ounce bottle ($5.99, $39.99/1 gal. refill; www.vermontsoap.com, 866-SOAP-4U2).

Better still, show a little eco enlightenment at your next yoga class with a PVC-free mat. "We want everybody who practices yoga to think a little bit more about the environment," says Kumiko Buckman of Jivamukti Yoga School in New York, so they supply Harmony's PVC-free Jade yoga mats as rentals (or buy for $39 and up at www.jadeyoga.com). A few more options: natural dried grass yoga mats with a natural latex backing ($49.95; www.healthandyoga.com, 732-203-7146); Eco Yoga Mat, made of jute and backed with natural rubber ($42; www.jivamuktiyoga.com/boutique, 877-IAMYOGA); organic cotton Vinyassa yoga rug, made under fair-trade conditions in Egypt ($60; www.intentusa.com, 866-669-7108); AgoyUSA's PVC-free and latex-free Earth Mat made from a recyclable thermoplastic elastomer ($67; www.agoyusa.com, 866-500-2469); and Gaiam's 100-percent natural rubber yoga mat ($40; www.gaiam.com, 877-989-6321).