Fukushima Daiichi nuclear disaster led to radioactive contamination crisis was resulted from a series of system failures, nuclear meltdown and radioactive material releases, following the 9.0 magnitude of earthquake and tsunami on March 11, 2011. The objectives of this study were; to investigate the movement of radionuclides based on oceanography and morphology of Pacific Ocean and Southeast Asia (Malaysia); to estimate the time for radionuclides to reach Malaysia and to calculate the amount of total absorbed dose rate for selected marine biotas namely benthic fish and pelagic fish. ERICA code system was used because it has the ERICA integrated approach to assess the radiation risk of biota. The estimations of radionuclide discharge from Fukushima Daiichi nuclear disaster were based on Cs-137 (half-life of 30.17 years), I-131 (half-life of 0.02 years). The parameters such as discharge rate of radionuclides (Bq/s), water depth (m), the distance between the target coast of Malaysia and radionuclide release point (m), the distance between the receptor and radionuclide release (m) and the velocity of the water/ocean currents (m/s) were studied. The results showed that the minimum estimated arrival time of radionuclides to reach Malaysia is located in Sandakan, Sabah, which is approximated at 4.82 years (Dec 2015) with an average of 5.039±0.310 years after the accident. Meanwhile, maximum estimated arrival time of radionuclides to Malacca is 5.87 years (Jan 2017) with an average of 5.527±0.480 years. The lowest estimated total absorbed dose rate by benthic fish is 0.0583 μGy/h with an average of (6.33±0.71) × 10-2 μGy/h in Malacca whereas the highest estimated total absorbed dose rate by benthic fish is 0.0751 μGy/h with an average of (7.11±0.57) × 10-2 μGy/h in Sandakan, Sabah. Pelagic fish in Malacca shows the lowest estimated total absorbed dose rate of 0.00149 μGy/h with an average of (1.62±0.18) × 10-3 μGy/h whereas Sandakan, Sabah showed the highest estimated total absorbed dose rate of 0.00193 μGy/h with an average of (1.83±0.15) × 10-3 μGy/h. The total absorbed dose rate and risk quotient of ERICA code system show that for all reference organisms, the probability of exceeding the selected screening dose rate of 400 μGy/h by aquatic biota is below the probability selected. Therefore, no measurable population of chronic exposure effects would occur at this stage. Nonetheless, a normal experimental analysis of fish samples should be performed in order to monitor the radiation effects to marine ecosystem.
The aims of this study are to estimate the equivalent dose to the skin, eyes and thyroid in intra- and extra-oral imaging examination and to compare the dose-area product (DAP) derived from the calculation method with Diagnostic Reference Levels (DRL) that has been provided by the Malaysian Ministry of Health (MOH). Dose equivalent is measured by placing Thermoluminescence Dosimeter (TLD-100H) in the anthropomorphic RANDO phantom. Exposure is performed using intra-oral X-ray machine ActeonSatelec X-Mind® and extra-oral X-ray machine InstrumentariumOP300®, and the value is compared to the equivalent dose of the International Commission on Radiological Protection (ICRP) dose limit. DAP value for both examinations was obtained by using formula and comparing them with the DRL from MOH. The average dose equivalent of intra- and extra-oral radiographic examination is lower than the ICRP dose limit. The doses derived from both examinations did not exceed the prescribed levels when compared with DRL. The doses calculated for intra-oral examination of molar maxillary, molar mandibular and interproximal (bitewing) was 0.880 mGy while periapical examination of the anterior maxillary and mandibular was 0.688 mGy and occlusal examination was 1.100 mGy. For the panoramic examination the dose was 0.011 mGy.m2 while lateral cephalometric examination was 0.0054 mGy.m2. The doses obtained from this study were within the dose limit and predetermined level. This shows that a patient receives the minimum dose for both dental radiographic examinations with the optimum level of safety which meets the ALARA concept.
Mathematically, the human alimentary tract organs were simplified in the model structure as separate compartments with
pathways of transfer that are kinetically homogenous and equally distributed. The development of gastro-compartment
model follows the first order kinetics of differential equations to describe cadmium absorption, distribution and elimination
in the human digestive system. With the aid of in vitro DIN assay, an artificial gastric and gastrointestinal fluid were
prepared using water leach purification (WLP) residue as a sample that contained toxic metals cadmium. The Simulation,
Analysis and Modelling II (SAAM II) V2.1 software is employed to design models easily, simulate experiments quickly and
analyze data accurately. Based on the experimental inputs and fractional transfer rates parameter incorporated to the
gastro-compartment model, the concentration of cadmium against time profile curves were plotted as the model output.
The curve presented concentration of cadmium in both gastric and gastrointestinal fluid where initially absorption phase
(first hour) occurred followed by the distribution phase (second to third hours) and elimination process (third to fifth
hours). The concentration of cadmium obtained from the simulated model structures was in good agreement with the
fitted model predicted measurements as statistical t-test conducted showed the values were not significantly different.
Therefore, modeling approach with SAAM II software gave realistic and better estimation of cadmium dissolution into
the human gastrointestinal tract.