To better understand the levels set by INES, some instances will be useful here.
The radioactive incident of 1987 in Goinia, Brazil where Cs-137 SRS was distributed in an area was a level 5 risk whereas level 7 risks involved Chernobyl nuclear
disaster and Fukushima Daiichi nuclear disaster. It is estimated that 6000 mSv of
radiation exposure was found within a month of Chernobyl nuclear disaster, and in
case of Fukushima, 400 mSv per hour was recorded on 14 March, and it was the
maximum recorded value to this date though it fell down later. Apart from the
immediate deaths on aftermath of Chernobyl nuclear disaster, till date there are many
cases of thyroid cancers reported. According to a UNSCEAR (United Nations
Scientific Committee on the Effects of Atomic Radiation) report, around 6000
cases of thyroid cancer were reported related to Chernobyl disaster till 2005. The
predicted cause for this sudden increase in incidence of thyroid cancer attributed to
overexposure of 131-I due to the fallout of Chernobyl nuclear disaster. In contrast, in
Fukushima incidence, the level of radioactive exposure or contamination remains
uncertain though the estimated radioiodine exposure is 1% to that of Chernobyl
accident (Lee et al. 2013). Nuclear accidents are the sole reason of major contamination of environment. Also Chernobyl nuclear disaster was able to increase the
radioactive contamination of soil of Europe 3500 times compared to beforehand of
the disaster. Most radionuclides which get dispersed in a nuclear disaster involve
131I, 137Cs, 90Sr, 239Pu and 240Pu (Steinhauser et al. 2014). Major contaminants
from Fukushima Daiichi nuclear disaster involved 134Cs and 137Cs which were
mostly found in soil samples 32 km from the incident site. Furthermore, in the same
soil, other radionuclides like 110mAg, 129Te, 129mTe, 131I and 140La were also
detected. The outer cover of leaves of cabbage, bamboo and grasses were also found
to have radioactive contamination along with soil (Tazoe et al. 2012).
13.2 Microbes-Assisted Bioremediation of Radioactive
Wastes
Enormous volumes of radionuclides and lethal metals containing wastes are generated from atomic fuel cycle and nuclear weapon generation agencies, medical
research institutes, mining, etc., and causing adverse effects on earth is a significant
concern (International Atomic Energy Agency 2010). As the physical and chemical
methods of remediation are much expensive and also generate secondary pollutants,
development of new low-cost inventive treatment and remediation advancements,
including bioremediation utilizing microorganisms for adjustment or evacuation and
recuperation of the contaminants, got much attention (Coelho et al. 2015; Francis
2006).
A wide range of microorganisms including bacteria, fungi and algae showed
efficient results in the field of bioremediation of different types of pollutants.
Microbial bioremediation of radioactive wastes depends upon the complex interaction of microbes and pollutants (Lloyd and Renshaw 2005). Different types of
13 Role of Microbes in Bioremediation of Radioactive Waste
337
The radioactive incident of 1987 in Goinia, Brazil where Cs-137 SRS was distributed in an area was a level 5 risk whereas level 7 risks involved Chernobyl nuclear
disaster and Fukushima Daiichi nuclear disaster. It is estimated that 6000 mSv of
radiation exposure was found within a month of Chernobyl nuclear disaster, and in
case of Fukushima, 400 mSv per hour was recorded on 14 March, and it was the
maximum recorded value to this date though it fell down later. Apart from the
immediate deaths on aftermath of Chernobyl nuclear disaster, till date there are many
cases of thyroid cancers reported. According to a UNSCEAR (United Nations
Scientific Committee on the Effects of Atomic Radiation) report, around 6000
cases of thyroid cancer were reported related to Chernobyl disaster till 2005. The
predicted cause for this sudden increase in incidence of thyroid cancer attributed to
overexposure of 131-I due to the fallout of Chernobyl nuclear disaster. In contrast, in
Fukushima incidence, the level of radioactive exposure or contamination remains
uncertain though the estimated radioiodine exposure is 1% to that of Chernobyl
accident (Lee et al. 2013). Nuclear accidents are the sole reason of major contamination of environment. Also Chernobyl nuclear disaster was able to increase the
radioactive contamination of soil of Europe 3500 times compared to beforehand of
the disaster. Most radionuclides which get dispersed in a nuclear disaster involve
131I, 137Cs, 90Sr, 239Pu and 240Pu (Steinhauser et al. 2014). Major contaminants
from Fukushima Daiichi nuclear disaster involved 134Cs and 137Cs which were
mostly found in soil samples 32 km from the incident site. Furthermore, in the same
soil, other radionuclides like 110mAg, 129Te, 129mTe, 131I and 140La were also
detected. The outer cover of leaves of cabbage, bamboo and grasses were also found
to have radioactive contamination along with soil (Tazoe et al. 2012).
13.2 Microbes-Assisted Bioremediation of Radioactive
Wastes
Enormous volumes of radionuclides and lethal metals containing wastes are generated from atomic fuel cycle and nuclear weapon generation agencies, medical
research institutes, mining, etc., and causing adverse effects on earth is a significant
concern (International Atomic Energy Agency 2010). As the physical and chemical
methods of remediation are much expensive and also generate secondary pollutants,
development of new low-cost inventive treatment and remediation advancements,
including bioremediation utilizing microorganisms for adjustment or evacuation and
recuperation of the contaminants, got much attention (Coelho et al. 2015; Francis
2006).
A wide range of microorganisms including bacteria, fungi and algae showed
efficient results in the field of bioremediation of different types of pollutants.
Microbial bioremediation of radioactive wastes depends upon the complex interaction of microbes and pollutants (Lloyd and Renshaw 2005). Different types of
13 Role of Microbes in Bioremediation of Radioactive Waste
337