You may have heard recent media reports raising concerns about the fact that people with certain types of cancer and other diseases are "radioactive" (meaning that they emit radiation from their bodies) for up to a week after being treated for their illness with radioactive materials. This raises some disconcerting questions -- for instance, is it dangerous to share a bedroom or a bathroom with people who have had radiation therapy? To stand next to them at choir rehearsal? Is it safe to sit near such folks on a train or plane? Theres no question that radioactive materials used to treat cancer and certain other diseases stay in the body and, for a period of time, are theoretically powerful enough to be dangerous to other people. But how dangerous... and when? To get some perspective on this, I called Henry Duval Royal, MD, professor of radiology at Washington University School of Medicine, who had some helpful advice to offer. Why Are We Worried? This issue grabbed headlines in recent months when it became the focus of a congressional report. While the federal Nuclear Regulatory Commission (NRC) once required hospitals to quarantine radioactive patients after treatment, that requirement was dropped in 1997. However, some legislators have reason to believe that stricter measures should be in place -- which is what led to the new report. Concerns were raised when patients treated with radioactive materials caused alarms to go off in public transportation systems and on bridges and in tunnels in New Jersey . Alarms also were triggered in landfills in Maryland and Massachusetts by household waste from patients being treated with radiation. The congressional report found that more than 10% of outpatients being treated with radioactive materials arent being appropriately educated about what they should do to avoid exposing family members to radiation. On the other hand, 7% choose to minimize the danger to family members and others with whom they interact daily by staying in hotels for several days, a move Dr. Royal calls "unnecessarily conservative." How dangerous is this? After the NRC rescinded its patient release regulation, researchers conducted a study measuring the radioactivity of patients receiving outpatient radioactive iodine therapy for thyroid cancer. Thirty patients and 65 family members (and their 17 pets) agreed to be monitored continuously for 10 days. For two days after radiation treatment, the patients were instructed to sleep alone and avoid prolonged close personal contact with others -- after that they could resume normal activities. The researchers learned that while family members were indeed exposed to radioactivity from the iodine, the amount was well below the limit of 5 millisieverts (mSv) per exposure determined to be safe by the NRC. The study was reported in the Journal of the American Medical Association in May 2000. Note: Though the study is now more than 10 years old, Dr. Royal said the radiation treatments have remained the same, so the findings are still valid. It sounds frightening, but according to Dr. Royal, the risk posed by being within a few feet of someone who has recently had radioactive iodine treatment actually is quite small -- especially when you take pains to avoid prolonged contact. Dr. Royal emphasized that risk is measured by the strength of each radiation dose, not by whether radiation sets off an alarm, and he added that it is important to realize that radiation detectors are designed to be very, very sensitive. Protect Your Loved Ones Nonetheless, Dr. Royal agreed that it makes sense to do what you can to minimize exposure to radiation. To err well on the side of safety, Dr. Royal said that patients should sleep in a separate bed for two weeks, which he said is "the absolute longest amount of time that there is any reason for concern." Other measures patients can take to protect their loved ones include... Keep physical contact brief. Dont hug or cuddle kids or pets for prolonged periods for the first two days following treatment, though it is fine to be in the same room with them. Be a bit standoffish. Keep a distance of three to six feet from others while seated at the table or on a couch... avoid letting anyone come in contact with your bodily fluids... dont share plates, eating utensils or cups... and dont kiss. If you want to be extra careful, he said, you may want to use a separate toilet and flush multiple times and wash clothing separately. Put most succinctly, Dr. Royal said his advice is to "pretend that you have a cold, and youll do all the right things." Source(s): Henry Duval Royal, MD, professor of radiology at Washington University School of Medicine and associate director of the Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, St. Louis .