People suffering from otherwise unexplainable medical problems such as headaches, fatigue, shortness of breath, and even chest pains may have everyday chemicals to blame. Multiple Chemical Sensitivity (MCS) is a medical condition whereby such symptoms can be attributed to the combined exposure to synthetic pollutants commonly found in detergents, perfumes, pesticides, solvents and even some foods and medicines.

While MCS goes by other names--including "Environmental Illness" and "Total Allergy Syndrome"--perhaps none captures its essence as well as "20th Century Disease." Between 1940 and 1980, the global production of synthetic organic chemicals rose from less than 10 billion pounds per year to more than 350 billion.

No longer rare, MCS reportedly affects 10 percent or more of Americans in varying degrees of severity. Nevertheless, the medical community rarely takes the condition Seriously. "Traditional medicine has not known how to explain it," writes Dr. Peter Montague in Rachel's Environment and Health Weekly. "This has left MCS sufferers in limbo. Told they are crazy, or imagining their disease, they are passed from physician to physician without any satisfactory answers and often without relief from their very real distress."

According to the federal Occupational Safety and Health Administration (OSHA), "There is insufficient scientific evidence to confirm a relationship between any of these possible causes and symptoms." Even so, OSHA may offer some relief by regulating the use of cleaning products and other air quality contaminants. But some of the most ubiquitous MCS offenders, perfumes and air fresheners, are not subject to testing for toxins and are largely unregulated.

"It's oxymoronic to talk about fragrances that can be used by people with chemical sensitivities," says Albert Donnay, director of Multiple Chemical Sensitivity Referral & Resources. In order for perfumes and air fresheners to work, he explains, they must contain volatile organic compounds, even if they are all-natural. "People with MCS have to give up perfumes, and people who do wear them need to be sensitive to the needs of others," says Donnay. CONTACT: OSHA, (800)321-6742, www.osha.gov; Multiple Chemical Sensitivity Referral & Resources, (410)889-6666, www.mcsrr.org.

I've heard that some foods are now being irradiated. Why is this and what are the implications for our health and safety?--Emily Worden, Monroe, CT

Food irradiation is used to kill bacteria and parasites and to retard spoilage. The U.S. FDA approved irradiation in 1963 to rid flour of insects, and to block potato sprouting. It later approved irradiation of spices and meat.

The U.S. Centers for Disease Control and Prevention and the World Health Organization (WHO) endorse food irradiation, and more than 40 nations have approved it. WHO says it is "badly needed in a world where food-borne diseases are on the rise."

The FDA says irradiation is safe, but critics charge otherwise. Irradiation does not make food radioactive, but it can create toxic byproducts and "unique radiolytic products" that haven't yet been identified or tested, says John W. Gofman of the University of California. "Our ignorance about these compounds makes it a fraud to tell the public 'we know' irradiated foods are safe," he says. The Organic Consumers Association claims irradiation saps food's nutritional value, deactivates enzymes and encourages fats to turn rancid.