If you are what you eat, you may want to check where your food's been before you take a bite. In this hour of To the Best of Our Knowledge, our toxic environment. Beef contamination is only the beginning, as we learn the dangerous truth about our polluted food chain. And a survivor tracks the source of her illness upstream.

SEGMENT 1

Americans have no idea how unsafe their food is. Nicols Fox is out to change that with her book "Spoiled: The Dangerous Truth about a Food Chain Gone Haywire." She tells Steve Paulson that E Coli 0157H7 is not the ubiquitous bug of the past; that many food industry practices favor profits over public health; and that food poisoning outbreaks happen all the time and are often deadly.

SEGMENT 2:

Sandra Steingraber is a cancer survivor and the author of "Living Downstream: An Ecologist Looks at Cancer and the Environment." She tells Jim Fleming how toxins make their way into groundwater, and directly into the bloodstream from environmental pollutants; about the links to human disease; and the availability of non-toxic alternatives. Also, Stephen Hall tells Steve Paulson about his work in immunotherapy. Hall thinks vaccines can be used to trigger the immune system to resist some malignancies. Hall writes for the New York Times Magazine and is the author of "A Commotion in the Blood: Life, Death and the Immune System." His article "Vaccinating against Cancer" appeared in the Atlantic Monthly in April, 1997.

SEGMENT 3:

Surgeon Sherwin Nuland celebrates the beauty of the living organism in his new book "The Wisdom of the Body." He tells Anne Strainchamps that operating room staff work quietly and with great intensity and that it is ultimately the patient's own body that fights disease. Nuland teaches medical history and bioethics at Yale, and is the author of the best-selling "How We Die."

Distribution dates:

• week of 08/31/97 - hour 2
• week of 07/12/98 - hour 2