TO ensure the safety of occupationally exposed workers, as well as potential victims in the event of a nuclear or radiological emergency, researchers from the Department of Science and Technology – Philippine Nuclear Research Institute (DOST-PNRI) continue to study blood samples for any signs of radiation exposure beyond the allowable regulatory limits.
Monitoring radiation exposure becomes even more important considering the increasing variety of nuclear and radiation-related technologies in factories and firms. In the Philippines, most workers who are regularly exposed to radiation are from the industrial and medical sectors.
In addition to the local users of radioactive materials, a growing number of overseas Filipino workers (OFWs) trained in non-destructive testing also use radiation in aircraft maintenance and other industries – and safety requirements for their continued employment abroad includes an assessment of their radiation exposure.
International standards on chromosomes analysis
help our “bagong bayani” (modern hero) monitor their radiation doses, PNRI researchers use cytogenetic biodosimetry to analyze the chromosomes in their white blood cells to see if there are any aberrations that would serve as signs of radiation damage.
Most chromosomes look like the letter “X”, consisting of two arms connected by one centromere. But dicentric chromosomes instead have two centromeres which means that they are affected by ionizing radiation. From there, the researchers can approximate if a worker has exceeded his or her dose levels which is proportional to how high the number of dicentric chromosomes are.
As the regulatory body for nuclear and radioactive materials and facilities, PNRI also adopts the international standards for radiation protection, including the limits of radiation exposure for workers as well as the general public. This is measured in Sieverts, which is the SI unit for the dose of ionizing radiation absorbed by the human body.
According to the Code of PNRI Regulations, radiation workers are only allowed up to 50 millisieverts per year, or an average of 20 millisieverts per year of radiation spread out over five years. In contrast, the general public is only allowed to be exposed up to 1 millisievert per year.
While many of our medical and industrial professionals wear dosimeters to monitor their exposure, analyzing chromosomes provide a more direct assessment of the effects of radiation in a person’s body.
Dicentric chromosome assay is the “gold standard” in biological dosimetry because it is specific to ionizing radiation, sensitive and cheap.
Cytogenetics can also be used in emergency preparedness and response, as researchers can assess the absorbed radiation doses of people who are involved in nuclear or radiological incidents.
After the 2011 Fukushima Nuclear Power Plant accident, PNRI has since worked hard to improve their capabilities for cytogenetics. Researchers recently published their output on the established dicentric chromosome response curve of white blood cells against different doses of gamma radiation accomplished by sampling a small population of healthy donors and counting their dicentrics after experimental radiation exposure. This dose response curve is used to extrapolate the absorbed dose of people suspected to have been exposed to radiation.
Apart from monitoring radiation exposure, PNRI also collaborates with the Department of Radiotherapy of Jose Reyes Memorial Medical Center to study the application of cytogenetics in determining the radiosensitivity of cancer patients aimed to improve the radiotherapy outcomes of cancer patients. (✓)