Biological life forms are exposed to radiation on a daily basis; the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR ) estimate the daily average exposure to radiation at 3.0 mSv/year, of which 80% of the annual dose is due to natural radiation from the cosmos, the earth and naturally occurring radioactive materials in consumed food and drink. Many parts of the world have background radiation levels that exceed the normal global average. Human exposure to ionising radiation also comes from industrial and medical facilities (WHO, 2011)
A study undertaken by the World Health Organisation (WHO) reflecting preliminary results for the anticipated scale of radiation exposure resulting from the Fukushima nuclear accident for the first year considered all major routes of exposure, including: external from cloud shine and ground shine; and internal from ingestion and inhalation. Conservative conclusions reflect data indicating the effective dose received by individuals in relatively high areas of exposure in the Fukushima prefecture within a dose range of 10 to 50 mSv; in these areas external exposure was the main contributor. In the remaining areas of the Fukushima prefecture the effective dose was estimated to be within a range of 1 to 10 mSv; the rest of Japan was estimated to be within a range of 0.1 to 1 mSv; and the rest of the world are below 0.01 mSv (WHO, 2011)
A study conducted by the Department of Civil and Environmental Engineering at Stanford University (Hoeve and Jacobson, 2012) concluded that external exposure, ingestion exposure and inhalation exposure of the public to radioactivity may result in 15 to 1300 cancer mortalities and 24 to 2500 cancer morbidities worldwide, most of which will occur in Japan. Initial radiation released from damaged reactors poisoned local water and food supplies and created a dead zone of several hundred square kilometres around the Fukushima site - which may not be safe to inhabit for centuries. Radiation was also detected as far away as North America and Europe. A number of studies have tracked the emission, transport and deposition of radionuclides using observational datasets and chemical transport models; they suggest that less than a quarter of the radioactivity was deposited over land in Japan, 1% reached Europe and over 80% of the radioactivity was advected over the Pacific Ocean.
Epidemiological studies indicate a statistically significant increase in stochastic cancer risks for radioactive emissions above 100 mSv, however, the US Nuclear Regulatory Commission (NRC) assumes that any amount of radiation may pose a health risk (Hoeve and Jacobson, 2012) thus, ongoing assessment and study of affected areas is obligatory.
Biological impacts of the Fukushima nuclear accident on the pale grass blue butterfly have demonstrated physiological and genetic deterioration, which is very likely attributed to the artificial radionuclides released into the environment (Hiyama et al, 2012). These observed abnormalities have increased over time, indicating a possible connection to a mutation accumulation caused by consistent exposure to low – dose radiation. Examination of adult morphology of various insects has indicated damage to testes, antennae and wings; frequent pupal and larval death has also been observed. Hiyama et al (2012) have empirically shown that the pale blue grass butterfly is sensitive to external radiation levels of 55 mSv and demonstrate heritable germ-line genetic damage caused by low dose radiation - this study serves as an important starting point in evaluating implications of the possible future effects of radiation on biological entities.
The Fukushima Da-ichi nuclear reactor will continue to emit radioactive elements into the environment, the extent of which is inherently difficult to quantify without extensive long term analysis and study. It is important to realise that as with most environmental scientific study there are no absolutes, however, current knowledge and scientific consensus indicates under worst case scenarios immediate localities will bear the brunt of the negative impacts, but regional and global arenas are relatively insulated due to the large dispersion factor of the Pacific Ocean.
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