The best prevention for radiation sickness is to minimise the exposure dose or reduce the dose rate. Increasing distance from the radiation source reduces the dose according to the inverse-square law for a point source.
RADIATION-GUSHING: Tokyo Electric Power Co’s Fukushima Daiichi Nuclear Power Plant’s No.1, 2 and 3 (from right) reactors are located in northeastern Japan. — Reuters photo
AS soon as Doris crossed the threshold of her house, her siblings and parents dashed for cover. Her mother, who had scurried into a bedroom, yelled at her: “Go for a shower!”
The family’s fear was not without ground — Doris had just returned from a visit to an aluminum smelter plant.
After all, radiation leaks have been the tenor of grave concern since the nuclear power plants in Japan were crippled by a 9-magnitude earthquake-tsunami.
But aluminum smelter plant? Radiation? Isn’t aluminum smelting free from radiation?
“Strictly speaking, it’s not,” said Dr Ting Chek Ming, who earned his PhD dissertation in radar remote sensing from the US. He specialises in applied electromagnetics and radiation.
“Even though the aluminum smelter process does not produce much radiation, an aluminum smelter uses prodigious amounts of electricity.
“Whenever there is an AC current, there is a electromagnetic (EM) field associated with that current. So it’s not free from radiation even though the EM radiations are due to the current.
“When the current terminates, the EM fields go away. So radiation stops.”
According to Dr Ting, the concern over aluminum smelter plants is not so much radiation as toxic emission.
Aluminum smelting, he explained, is the process of extracting aluminum from its oxide alumina, generally by the Hall-Heroult process.
Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery. This is an electrolytic process, so an aluminum smelter uses prodigious amounts of electricity; it tends to be located very close to large power stations, often hydro electric ones, and near ports since almost all of them use imported alumina.
In some countries, coal is used to fire the power station to drive the aluminum plant.
On toxicity emission from aluminum, Dr Ting said emission from aluminum smelter plant was generally categorised under Class 3 Indicators.
“It’s extremely hazardous, carcinogenic, teratogenic, mutagenic, highly toxic. In short, it has high potential to cause cancer among workers or general population living nearby the plant.
“Therefore, it’s the toxicity that is the major concern. Radiation effect from the current is minimal,” he reiterated.
In the furtherance of knowledge and understanding on radiation, Dr Ting said too much radiation exposure is harmful.
“The degree of radiation injury depends on the amount of radiation received and the time involved. In general, the higher the amount, the greater the severity of early effects (occurring within a few weeks) and the greater the possibility of late effects such as cancer.”
According to him, regardless of where or how an accident, involving radiation, happens, three types of radiation-induced injury can occur:
l External irradiation
l Contamination with radioactive materials
l Internal or incorporation of radioactive material into body cells, tissues or organs.
External radiation
External exposure is exposure which occurs when the radioactive source (or other radiation source) is outside (and remains outside) the organism which is exposed. Example: A person who places a sealed radioactive source in his pocket.
Contamination
The second type of radiation injury involves contamination with radioactive materials. Contamination means that radioactive materials in the form of gases, liquids or solids are released into the environment and contaminate people externally, internally or both.
An external surface of the body, such as the skin, can become contaminated, and if radioactive materials get inside the body through the lungs, gut or wounds, the contaminant can become deposited internally.
Internal or incorporation
Internal exposure occurs when the radioactive material enters the organism, and the radioactive atoms become incorporated into the organism.
In general, radioactive materials are distributed throughout the body based on their chemical properties. Incorporation cannot occur unless contamination has occurred.
According to Dr Ting, these three types of exposure can happen in combination and be complicated by physical injury or illness.
In such a case, serious medical problems always have priority over concerns about radiation such as radiation monitoring, contamination control, and decontamination.
Radiation is invisible, Dr Ting cautioned.
“You cannot taste it, smell it or feel it on your fingers.”
There are four primary kinds of ionizing radiation which is light with enough energy to ionize an atom, that is making it into a charged particle.
Alpha particles are relatively heavy and, when emitted, cannot penetrate human skin or clothing but are harmful if they get into the body.
Beta radiation can cause skin injury and are also harmful to the body internally. Gamma and X-rays are high-energy invisible light that can damage tissue and are most hazardous to humans.
Radiation is all around us, according to Dr Ting.
Quoting the National Council on Radiation Protection and Measurement US, he said the average radiation exposure a person got from natural sources was about 3.1 millisieverts.
The limit for occupational radiation exposure among workers who deal with radioactive material is 50 millisieverts.
“To give you a sense of what that means, a chest X-ray delivers a dose of about .02 millisieverts, and a CT to the abdomen carries 8 millisieverts.
“But note that these procedures don’t last very long; prolonged exposure would be more dangerous.
“The farther away you are from the source of radiation, the less exposure you will have to damaging high-energy light beams such as gamma rays,” he explained.
Radiation sickness
Generally, the greater exposure you’ve had, the faster and more intense the symptoms of radiation sickness will be.
Nausea and vomiting are usually the initial symptoms of radiation sickness. A very severe exposure can lead to them within 10 minutes — dizziness, weakness, and low blood pressure may begin immediately.
If the radiation exposure is mild, a person might not start experiencing these symptoms for up to six hours.
The simple removal of clothes and shoes eliminates about 90 per cent of external radiation contamination, and washing with soap and water takes radiation off the skin.
This lowers your risk of breathing or ingesting radiation particles, or having them get into open wounds.
Big difference
There is a big difference between the effects of the atomic bombs dropped in Hiroshima and Nagasaki at the end of World War II and possible spread of nuclear radiation from malfunctioning nuclear power.
“The atomic bomb — it was whole body exposure that lasted less than a second. The radiation travelled through the body, similar to how X-rays behave.
“For the reactors, it’s a gradual exposure over time. It might include radioactive elements such as iodine and cesium, which may be ingested,” Dr Ting said.
Long term exposure
According to him, longer term exposure to radiation at doses less than that which produces serious radiation sickness, can induce cancer as well-cycle genes are mutated.
The probability cancer will develop is a function of radiation dose. In radiation-induced cancer, the disease, the speed at which the condition advances, the prognosis, the degree of pain, and every other feature of the disease are not functions of the radiation dose to which the person is exposed.
Radiation sickness is generally associated with a sudden single large exposure.
Prevention
Dr Ting said the best prevention for radiation sickness is to minimise the exposure dose or reduce the dose rate.
Increasing distance from the radiation source reduces the dose according to the inverse-square law for a point source.
Distance can sometimes be effectively increased by means as simple as handling a source with forceps rather than fingers.
He also pointed out that the longer humans were subjected to radiation, the larger the dose would be.
Dr Ting said potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or attack at a nuclear power plant, or the detonation of a nuclear explosive.
KI, he cautioned, would not be effective against a dirty bomb unless the bomb happened to contain radioactive iodine, and even then, it would only help to prevent thyroid cancer.
Will it affect Malaysians?
Dr Ting, who is now a lecturer at University Selangor (UNISEL), said Malaysia is too far from Japan and even if radioactive particles reached Malaysia, the quantity would be too small to cause a major uproar.
With that, the family of Doris had perhaps been unduly suspicious of the radiation risk they were exposed to.
Much as they would like to play safe, they had definitely over reacted – more so when Doris was returning from a visit to an aluminum smelter plant — not Japan.