The nuclear crisis in Japan continues to remain in the news, but do we realise we are exposed to radiation in our day-to-day activities? GEETA PADMANABHAN opens our eyes to some of the risks
Asked why she quit her previous job, the dental assistant told Dr. Selvamuthukumar of Shakthi Dental: “Too much radiation in the X-ray room. All day I took X-rays, the clinic had no safe zone. The waiting room, outside a glass partition, wasn't much help.” In a recent television show, the popular Dr. Mehmet Oz said people who have more than five X-rays a year run a four-fold risk of developing thyroid cancer — “fastest-growing in women”. He recommended lead thyroid shields for patients and technicians. Dr. Carolyn Runowicz, a cancer specialist, said she would not go for dental X-rays just to check her teeth.
We debate a Fukushima-like meltdown in the neighbourhood, but willingly subject ourselves to medical radiation — for imaging and treatment. At airports, we walk through “intrusive” body-scanners. We watch kids needing braces get a series of X-rays. We undergo CT-scans, mammograms and radiation therapy. A New York Times study warns that a lot of dentists use outmoded (D-speed) X-ray film that needs high amounts of radiation. Sometimes, dentists increase exposure time — and radiation — to get clearer images. It quotes experts who say the new cone-beam CT-scanner, while producing “brilliant 3D images”, throws out “hundreds of times more radiation.” More than one scan and the lifetime risk increases with each exposure. How safe are we from radiation?
Use of X-rays
“X-rays form the first line of investigation,” says Dr. Jayaraj, Radiology Consultant, Apollo Speciality Hospital. “It's sometimes inconclusive. For the brain and spinal cord you need a CT scan.” The last few years have seen a four-fold increase in CT referrals, he says. The MDCT fast scanner is good for 30-40 times more exposure than ordinary X-ray, “but its risks have not been studied fully,” he adds.
Take that finger off the panic button. “The food we eat, the air we breathe, the water we drink are radioactive,” L.V. Krishnan, safety expert, informs us cheerfully. “We have instruments to detect the tiniest amounts of radium/uranium/plutonium anywhere. We've lived with radiation for centuries, probably at much higher levels earlier. You get it from ceramic tiles, at hill stations, on the beaches of Kerala and Tamil Nadu.” He breaks it down to numbers. “On average, we get two-and-a-half milliSieverts/year — half mSv from food, one from outside sources including cosmic rays, one from radon gas in the air.”
Chronic low-level radiation is manageable, says Krishnan. Body tissues repair damage from radiation as long as it's limited. Cancer from radiation occurs only when genetic mutation accumulates over time. We're moving towards technology where ultrasound replaces X-rays, MRI replaces CT-Scan. Digital X-rays use less radiation. There are efforts to find out if different people have different resistance levels to radiation.
Safety measures are in-built, explains Dr. Jayaraj, quoting the '10-day rule of radiography'. “For women in the child-bearing age, any non-urgent lower abdominal X-ray examination is done only during the first 10 days after the start of a menstrual period,” as the probability of pregnancy increases subsequently. Under the 28-day rule, radiological examination, if justified, is done throughout the cycle until a period is missed.
Radiation treatment of cancers is made safe, says Dr. Mahadev, Radio Oncologist, Apollo Speciality. “We use sophisticated, precise linear accelerators for radio therapy, so healthy tissues get less radiation.” The treatment is spread over many days giving healthy cells time for repair or replacement. Radiologists watch the treatment through a small aperture, monitor progress on CCTV.
Workers wear TLD that shows radiation levels. Technicians are checked, given leave periodically. There are safety regulators and lead aprons. “I have worked here 20 years, and feel fine,” he smiles. “Radiation is a useful tool, 60 per cent of cancers are treated with radiation at some point. There's 50-60 per cent cure even at stage three.”
“It's all about following rules,” says Dr. Selvamuthukumar. Like building clinics to specifications, seating one patient at a time in the X-ray room, or keeping chairs far apart. “The clinician analyses risks vs. benefits and decides on a minimal side-X-ray or the larger full-mouth one,” he says, but who will vouch for all of them? “Whether diagnosis or nuclear medicine, radiation has to be used within permissible limits,” says Dr. Jayaraj. “Medicos are expected to follow the ALARA (As Low As Reasonably Achievable) principle in Radiography. Studies have established the max limit.”
Keywords: Japan nuclear crisis