Clean sex, wasteful computers and dangerous mascara. (Ask E).

Do condoms represent a significant portion of beach litter? Are there environmentally friendly condoms?--Wendy M., Olympia, WA

Condoms are often found discarded on beaches along with straws, bottles and other trash. About 900 condoms were found on Florida's beaches during a three-hour litter collection campaign in 1996. That's five condoms per minute. After conducting a 10-year study, Tidy Britain Group concluded that more than a third of the trash on west coast beaches arrives from North America. But Brits have little to boast about when it comes to prophylactic pollution. The British Environment Agency estimates Brits discard 61 to 100 million condoms per year, many of which end up in rivers, the sea and on beaches.

This litter not only detracts from shore beauty, it can cover coral reefs and smother sea grasses and other bottom dwellers, according to The Ocean Conservancy. Many animals confuse trash for food and try to eat it. Plastic and other materials can clog animals' intestines, causing them to starve, according to the Environmental Protection Agency (EPA).

Rubber rubbish prompted a German company called Condomi to develop a biodegradable condom. Except to say they are vegan-friendly, the company keeps the ingredients secret. CONTACT: Condomi, 49(0)221-50-04-400, www.condomi.com; The Ocean Conservancy, [phone], www.coastalcleanup.org.--Eve Hightower

Is it better to leave my computer on when I'm not using it, or to shut it off?.--E Reader, Norwalk, CT

The long-held belief that turning your computer on and off will stress its components just doesn't compute. According to the EPA's Energy Star program, powering down unused computers and monitors actually increases their longevity because it generates less heat, collects less dust and reduces mechanical stress. Computers that act as servers or run on networks that back up files or upgrade software at night must be left on, but in most homes, it's better ecologically--and economically--to shut down your machine when you're not using it.

If you only use your computer four hours a day, but leave it on all the time, you're wasting 20 hours of energy a day. If your computer consumes 300 watts of electricity, and electricity costs 8.5 cents per kilowatt-hour, that's 51 cents of wasted energy every day, not to mention nine pounds of the greenhouse gas carbon dioxide pumped needlessly into the atmosphere, according to the Alliance to Save Energy. Over one year, that unused computer will add $186 to your electricity bill and spew one and a half tons of carbon dioxide. Energy Star estimates the pollution averted by turning off your computer is like planting up to 6,000 square feet of trees or preventing up to four weeks of car emissions. CONTACT: Alliance to Save Energy, [phone], www.ase.org; Energy Star, www.energystar.gov.--Phoebe Hall

Does eye mascara contain toxic ingredients?--Amber Galt, Madison, WI

Some cosmetics companies throw petroleum distillates and other preservatives into the pot when stewing up lash thickener, writes Kim Erickson in her book DropDead Gorgeous. Ingredients like shellac and quaternium-22 can induce contact allergies; others, such as phenylmercuric acetate, may cause blisters. Though the Food and Drug Administration (FDA) restricts the use of this mercury derivative, cosmetic manufacturers are not required to register with the agency.

Eye products sometimes contain kohl, which is made of heavy metals. Also called al-kahl, kajal or surma, this color additive has been linked to lead poisoning in children and is not approved for cosmetic use in the U.S. However, the FDKs Center for Food Safety and Applied Nutrition (CFSAN) warns it can be found in imported mascaras. And be sure to check the label: Sometimes "kohl" indicates the shade of a product, not the actual contents.

Perhaps the most dangerous thing found in mascara is not meant to be included--bacteria. According to Dr. Andrew Weft, author of 8 Weeks to Optimum Health, airborne bacteria rush into the bottle every time you open it. Preservatives break down over time, losing their ability to prevent bacterial growth that can cause infection and, in rare cases, blindness. Doctors and beauty experts recommend replacing mascara every three months. Throw it out sooner if it develops an unusual texture or odor. CONTACT: CFSAN Cosmetics Program, www.cfsan.fda.gov/~dms/cos-toc.html; Dr. Andrew Weil, www.drweil.com.--P.H. and E.H.

Send your questions about environmental issues, from the personal to the political, to Ask E, P.O. Box 5098, Westport, CT 06881, or e-mail [e-mail]. Please keep your questions brief. Include your full name, address and a daytime phone number.