Fungi that live off radiation at Chernobyl

Fungi that live off radiation at Chernobyl

It was shown how ionising radiation encourages growth of melanised fungi

Like chlorophyll, melanin uses a part of the electromagnetic spectrum to benefit the fungi

The phenomenon may be useful to astronauts, who may harvest the fungi as a food source

Occasionally, the lowliest of the lowly beings get global attention by being at the most unexpected places.

This was what happened to some microorganisms including Cladosporium sphaerospermum (CS). This tongue-twisting name belongs to a type of humble fungus.

Five years ago, Dr. Arturo Casadevall, Albert Einstein College of Medicine, New York, U.S., read in the web that a robot sent into the still highly radioactive damaged reactor at the Chernobyl nuclear power station, returned with samples of black fungi, which were growing on the reactor’s walls. (PhysOrg.com, May 23, 2007).
Habits revealed

It appeared that these fungi were feeding on radiation. They can no longer keep their radiation feasting habits away from the prying eyes of researchers.

These fungi contain melanin, a high molecular weight pigment, the same colouring agent in our skin.

Until now, the biological role of melanin has been a mystery (PHYSICS.ORG, 2007). In a 13-page paper in the Public Library of Science Journal (PLoS ONE, May 23, 2007) Dr Casadevall and other researchers explained the physico-chemical tests and in vivo experiments with three genetically diverse fungi and four measures of cell growth; they demonstrated lucidly how ionising radiation brings about changes in melanin and encourages the growth of melanised fungi.

An elegant and simple hypothesis may explain the behaviour of melanised fungi.

“Just as the pigment chlorophyll converts sunlight into chemical energy that allows green plants to live and grow, our research suggests that melanin uses a different part of the electromagnetic spectrum to benefit the fungi containing it”, Dr Ekaterina Dadachova, one of the co-authors of the paper, explained.
Providing energy

Dr Casadevall admitted that it is pure speculation but not outside the realm of possibility that melanin could be providing energy to skin cells. They grew some melanised fungi and others without the pigment and exposed them to gamma radiation.

The dark fungi grew better when irradiated (The New Zealand Herald May 27, 2007).

Certain types of fungi grew significantly faster when scientists exposed them to ionising radiation levels nearly 500 times more than the background; they gained more dry weight biomass.

People despise fungi because they assume that the main job of fungi is to decompose matter into other chemicals!

The melanin-containing microorganisms are often the dominating species in certain extreme environments (PLoS ONE 2007) such as the abandoned contaminated regions at Unit 4, the stricken reactor at Chernobyl.
Living happily

They live happily in soil contaminated with radionuclides, at high altitudes and in hostile Arctic and Antarctic regions!

There are indications that melanins are ancient pigments that have probably been selected as they enhance the survival of melanised fungi in diverse environments and, perhaps incidentally in many hosts (PLoS ONE, 2007).

Casadevall and his co-workers believe that despite the high prevalence of melanotic microorganisms in radioactive environments, it is unlikely that they synthesise melanin for the purposes of protection (shielding) from ionising radiation.

They noted that in the high altitude regions inhabited by melanotic fungi, the background radiation levels are about 500-1,000 times higher than at sea level.

Since most fungi, whether melanised or not, can withstand 17,000 times more energy, the authors consider that there is apparently no need for melanin to remain as a radio-protective agent.

But biological pigments play a major role in photosynthesis; they convert light energy to chemical energy.
Properties changed

Since melanin can absorb visible and UV light of all wavelengths, the authors suggested that exposure to ionising radiation would change the properties of melanin and affect the growth of melanized microorganisms.

They could convincingly demonstrate their expectations. The capability of fungi to live off radiation and make biomass may be useful to astronauts, who may be able to harvest the fungi as a food source.

The fungi can produce food by using enhanced levels of ionising radiation present in outer space.
Nature’s capriciousness

Nature is very capricious in revealing its resourcefulness. Lowly beings such as fungi can teach enterprising humanity a lesson or two in harnessing energy while surviving in unendurable environments.

K.S. PARTHASARATHY

Former Secretary, AERB
ksparth@yahoo.co.uk

© Copyright 2000 - 2007 The Hindu

Routine use of CT to screen for lung cancer risky

Routine use of CT to screen for lung cancer risky

Routine use of this unique tool on symptomless individuals is potentially hazardous

Photo: K.R. Deepak



Need for caution: Population based screening for lung cancer is not recommended and may, ultimately put the patient at risk for further complications. — .

The American College of Chest Physicians (ACCP) oppose the use of low dose computed tomography (CT) for general screening of lung cancer (EurekAlert, September 10).One hundred multi-disciplinary panel members developed and published the new evidence-based guidelines in a supplement to the September issue of CHEST, ACCP’s peer reviewed journal.

Mortality unaffected

Dr. W. Michael Alberts, Chief Medical Officer, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida, cautioned that even in high risk populations, currently available research data do not show that lung cancer screening alters mortality outcomes.

“Population [based] screening for lung cancer is not recommended and may, ultimately, put the patient at risk for further complications,” said Dr.Gene L. Colice, Director, Pulmonary, Critical Care and Respiratory Services, Washington Hospital Center, Washington DC and vice chairman of the ACCP lung cancer guidelines.

He clarified that during screening, physicians may commonly find nodules; however, to determine whether they are cancerous or not requires fairly invasive and extensive additional testing. The patient may have to face needless risk, both physically and psychologically.

‘Diagnosis and Management of Lung Cancer: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition)’ contains 260 of the most comprehensive recommendations related to lung cancer prevention, screening, diagnosis, staging, and medical and surgical treatments. Some of these apply to computed tomography screening.

“There is little evidence to show that lung cancer screening impacts mortality in patients, including those who are considered at high risk for the disease” an ACCP press release asserted.

CT screening of symptom-free individuals is controversial. Peter B. Bach and his co-workers analysed lung cancers in 3,246 asymptomatic current or former smokers screened for lung cancer from two academic centres in the U.S. and one in Italy and found that screening for lung cancer with low dose CT may increase the rate of lung cancer diagnosis and treatment, but may not meaningfully reduce the risk of advanced lung cancer or deaths from lung cancer (JAMA, March, 7).

They argued that until more conclusive data are available, asymptomatic individuals should not be screened outside clinical research studies that have a reasonable likelihood of further clarifying the potential benefits and risks.
Conclusions opposed

These results contradict the conclusions of the International Early Action Lung Cancer Programme, which claimed that CT screening of high risk individuals could prevent 80 per cent of lung cancer deaths (New England Journal of Medicine, 2006).

After reviewing these two papers, Drs William C. Black and John A. Baron concluded thus: “Although expensive and time consuming, rigorous trials for cancer screening are far more cost-effective than what might be the alternative — widespread adoption of costly screening interventions that cause more harm than good” (JAMA, March, 7, 2007).

The unambiguous ACCP guidelines must settle the issue. The ACCP Thoracic Oncology NetWork, the Health and Science Policy Committee, the Board of Regents, and external reviewers from the journal CHEST reviewed and approved these guidelines.

The American Association for Bronchology, American Association for Thoracic Surgery, American College of Surgeons Oncology Group, American Society for Therapeutic Radiology and Oncology, Asian Pacific Society of Respirology, Oncology Nurses Society, Society of Thoracic Surgeons, and the World Association of Bronchology also endorsed them.

Over 2,200 CT scan units are used in India. These are beneficial tools only in clinically indicated diagnostic tests.

Each CT scan exposes patients to radiation doses equal to a few hundreds of chest x-ray examinations. Routine use of this unique tool on symptomless individuals is potentially hazardous.
Panel of specialists

Professional associations in India must develop robust guidelines. In the absence of such efforts, the Health Ministry must urgently set up a panel of specialists with representatives from Indian Council of Medical Research, the Atomic Energy Regulatory Board and professional associations to review the ACCP recommendations and other similar guidelines.

The panel may be asked to examine the applicability of these guidelines in the Indian context and make appropriate recommendations.

K.S. PARTHASARATHY

Former Secretary, AERB
( ksparth@yahoo.co.uk)

© Copyright 2000 - 2006 The Hindu

Safety factors considered in nuclear powerplant location

Safety factors considered in nuclear power plant location

A detailed analysis revealed that a postulated fault at Kalpakkam did not exist

The AERB Code of Practice on Safety in Nuclear Power Plant Siting prescribes 48 criteria

The doses to public due to radioactive releases during normal operation are within AERB limits

While addressing a public meeting organised by the Rotary club in a metro city, one of the speakers asked the audience whether they prefer to have a cattle farm or a nuclear power plant in their backyard.

The voice vote clearly favoured a cattle farm! The reasons for the “Not In My Backyard (NIMBY) view” are not far to seek. Public distrusts nuclear industry.
Previous accidents

The accidents at the nuclear power station at Three Mile Island in the U.S. in 1979 and that at the Chernobyl nuclear power Station in Ukraine in the former Soviet Union in 1986 did not help.

The discerning public may blame the nuclear establishment, if the NIMBY attitude continues. NIMBY will become In My Backyard (IMBY), if the public realises the steps taken to ensure safety in nuclear power plants.

These include the choice of the right site; construction of reactors of proven technology; institution of sound quality assurance measures; provision of diverse and redundant reactor control and protection systems of high reliability; defence-in-depth philosophy; proven operating procedures by qualified and trained staff; continuous review and feedback of operating experience; well rehearsed emergency prepared plans among others.

The AERB (Atomic Energy Regulatory Board) Code of Practice on Safety in Nuclear Power Plant Siting prescribes 48 criteria; thirty of them are mandatory; seven are desirable. Eleven criteria belong to the rejection category.

The AERB reviews the effect of natural events such as earthquakes, winds, floods, tides, slope instability, etc and man-induced events such as air-crash, oil slick, blasting, mining etc. on the plant.
Outright rejection

A few seismic criteria prescribe outright rejection of certain sites. Other factors include prescribed grade elevation above tide level, location of airfields, military installations storing ammunition, architectural or historical monuments and pilgrimage or tourist centres. Sites will be acceptable only if they satisfy AERB Codal requirements.

The desirable parameters specified by AERB Code include distance from the site to the facilities, if any, handling/storing inflammable, toxic, corrosive or explosive material and any mining activities, the terrain features and the population density within specified distances.

A site selection committee of specialists appointed by the Central Government chooses the sites for locating nuclear power plants from the sites proposed by the State Governments.

AERB issues siting clearances valid for a specific period after reviewing the recommendations of its Site Evaluation Committee (SEC) and a senior level Advisory Committee for Project Safety Review (ACPSR).

Recently, the SEC recommended installation and operation of a five-station micro earthquake monitoring network at the Prototype Fast Breeder Reactor (PFBR). It is operational now. AERB recommended a detailed analysis and field check to ascertain the status of a postulated fault at Kalpakkam.
Coastline stable

The study revealed that the fault does not exist. On the recommendation of SEC, National Institute of Oceanography (NIO) studied the shore line stability at Kalpakkam. NIO found that the coastline was stable. A detailed study for evaluation of tsunami hazard in Kalpakkam area is in progress.

Nuclear power reactors produce large amounts of radioactivity during their operation.
Design features

Design features and safety measures ensure that the radiation doses to workers are well within the limits prescribed by the AERB. AERB may argue that there is scope for reduction.

The doses to public due to radioactive releases during normal operation are too low to be measured directly and are within AERB limits.

They are within the variations of the natural background radiation present everywhere even in the absence of nuclear power plants. The safety performance of Indian reactors is reassuring.
Recent survey

A recent survey in the U.S. organised by the Nuclear Energy Institute, a nuclear advocacy group, among 1,100 adults, revealed that 71 per cent would be willing to see a new reactor near them (World Nuclear News, August 21), a probab le response in France, as it generates 78 per cent of its electricity from nuclear reactors.

The French are very proud of their nuclear programme. If the recent awareness on nuclear issues is an indication, NIMBY attitude among the Indian public will hopefully turn into IMBY during the next few years!

K.S.PARTHASARATHY

Former Secretary, AERB
ksparth@yahoo.co.uk

© Copyright 2000 - 2006 The Hindu