Background radiation No evidence of ill effetcs

Date:24/05/2007 URL: http://www.thehindu.com/thehindu/seta/2007/05/24/stories/2007052400111700.htm Sci Tech



Background radiation: no evidence for ill-effects

Cancer occurrence not consistently higher in monazite-rich areas

RECENTLY, A section of the media published stories about excess cancer deaths in the high background radiation areas (HBRA) in Kerala and Tamil Nadu.

But scientific studies do not substantiate such claims. The natural radiation levels are high in these areas primarily because of the presence of monazite (thorium ore) in soil.

Ionising radiation can cause mutations in all parts of the cell including the DNA. Dr Lucy Forster from the University of Cambridge and her team analysed mitochondrial DNA from 248 families (mostly over three generations) that have been exposed to natural radiation throughout their lives.

Widely published

They found 22 mutations in individuals from the high radiation areas and one in persons from areas of low radiation (Proceedings of the National Academy of Sciences, 2002).

The media widely published the results as the authors, during interviews, suggested that people exposed to even low levels of radiation may be at risk of cancer.

BBC's headline was `cancer risk for radiation workers.' Responding to my queries, Ray Dunne, Health Reporter, BBC news online agreed that BBC did not suggest that that was the conclusion of the original research.

BBC focused on it as it was of more relevance to more people. It was purely speculative. A mutation to manifestation of cancer involves several steps.

Low doses

Responding to my e-mail query, Prof K.Sankaranarayanan, Professor Emeritus, Leiden University Medical Centre, The Netherlands, stated that at the current state of knowledge, we cannot attach any importance to these mutations from the standpoint of adverse health effects at low doses of radiation.

He must know as he wrote all the reports on genetic effects of radiation for the United Nations Scientific Committee on the Effects of Atomic Radiation!

"It might be worth considering whether to lower the allowed limits for radiation workers of reproductive age," Dr Peter Forster, one of the authors, warned.

Exposed populations

"It is premature to try to draw any conclusion concerning cancer risk from the study, let alone to call for a reduction in dose limits etc... " After all, our risk estimates (which form a part of the basis for dose limitation) are computed from epidemiological data on populations exposed to radiation. In other words, although we may have been unaware of this particular mechanism, its contribution to the total risk due to the combinations of mutations is already taken into account, automatically," Dr Jack Valentin, a geneticist and Scientific Secretary of the International Commission on Radiological Protection — the agency which recommends dose limits, clarified in an e-mail response.

Survey result

In a thorough health survey of about 400,000 people (100,000 from HBRA), researchers from the Regional Cancer Centre and Bhabha Atomic Research Centre did not see that cancer occurrence is consistently higher because of external gamma radiation exposure in the monazite-rich areas (Radiation Research, 1999).

Scientists did not observe significant differences in any of the reproductive parameters between the two population groups based on monitoring of 26,151 newborns from HBRA and 10,654 from areas of normal background radiation in the Kerala coast.

The stratification of newborns with malformations, still births or twinning showed no correlation with the natural radiation levels in different areas. (Radiation Research, 1999)

Critical review

In a critical review, of the health studies at HBRA carried out by different authors till 1981, Dr K.S.B. Rose, UK Atomic Energy Research Establishment, Harwell concluded that none of them produced any reliable evidence that the high level natural radioactivity in the area has a detectable adverse effect on the inhabitants (Nuclear Energy, 1982). More recent studies published in peer reviewed journals led to the same conclusion.

Further studies

The studies at HBRA carried out by different agencies have been scattered and limited. Epidemiology must complement molecular genetics, which currently employs tools of unparalleled sensitivity.

India, with advanced technology, must build a national institute at HBRA, modelled more or less like Radiation Effects Research Foundation, Hiroshima, to carry out "research in clinical medicine, epidemiology, statistics, genetics and molecular biology"; an advanced school of radiobiology and allied sciences may be a spin-off from the institute.

K.S.PARTHASARATHY

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

© Copyright 2000 - 2006 The Hindu

ORNL reactor refurbished

EurekAlert Public release date: 17-May-2007
ORNL NEWS
Contact: Mike Bradley
bradleybk@ornl.gov
865-576-9553
DOE/Oak Ridge National Laboratory
Revamped, renewed, restarted -- Oak Ridge High Flux Isotope reactor back on line
OAK RIDGE, Tenn., May 17, 2007 -- The research reactor at the Department of Energy’s Oak Ridge National Laboratory is back in action and better than ever.
After $70 million in renovations and more than a year of meticulous system checks, ORNL’s High Flux Isotope Reactor was restarted this week, taken to 10 percent power, and reached its peak power of 85 megawatts Wednesday.
"The restart has gone well," said Kelly Beierschmitt, HFIR executive director. "This reactor’s design is rigorous and robust. Its performance has been stellar from both an operational and a safety perspective.
"We still have work to do, but we are extremely pleased with our progress so far."
Built in 1966, HFIR is internationally known as a neutron source for materials studies and isotope production. The reactor returns with a suite of new experiment instruments, beam lines to channel neutrons, a new beryllium reflector, and other upgrades.
In October, powerful refrigeration systems were added to cool the reactor’s neutron beams to minus 425 degrees Fahrenheit. The intense cold slows the neutrons and lengthens their wavelength, allowing scientists to study "soft" materials such as proteins and polymers and to analyze materials with certain magnetic properties.
The restart marks HFIR’s 408th cycle. Each cycle represents about 25 days, the time it takes for the reactor to use up its uranium fuel.

Greg Smith, who leads ORNL’s Low Q Neutron Scattering Group, said 49 science experiments are scheduled for this summer, including:

• Experiments to create new materials with beneficial properties, based on polymer nano-composites, which are "hard" nanoparticles surrounded by a "soft" polymer matrix.
• Studies to make crystals from membrane proteins, which determine interaction and communication between living cells, to better understand the membrane proteins’ structure and function.
• Examination of how high-pressure carbon dioxide is absorbed by and migrates through different types of coal to help develop new, more efficient ways to sequester CO2 to reduce greenhouse gas emissions.

"We anticipate eventually providing neutron beams for eight to ten reactor cycles per year and no major shutdown for a beryllium reflector replacement until after 2020," Smith said. "In the meantime, HFIR users will soon be able to access thermal and cold neutron beams of world-class brightness."

Neutrons are vital to research in physics, chemistry, engineering and other materials-related fields. At room temperature, they are ideal for use in special instruments to illuminate the atomic structure and dynamics of hard, dense materials.
HFIR’s cold source will complement the capabilities of ORNL’s recently completed Spallation Neutron Source, the world’s premier neutron science facility.
While SNS also has cold-neutron capabilities, the continuous neutron flow from a reactor such as HFIR, as opposed to pulsed beams from accelerators like SNS, offers advantages for certain types of neutron experiments.

The new cold neutron source is part of an Office of Science-funded renovation that represents a major new direction for the reactor and revitalizes its role to the nation’s science and research community.

The fully instrumented HFIR will include 15 state-of-the-art neutron-scattering instruments, seven designed exclusively for cold neutron experiments; new computer control systems; and a new guide hall facility. Particularly prominent in the guide hall are the two new small-angle neutron scattering instruments, each terminating in a 70-foot long evacuated cylinder containing a large moveable neutron detector.
The reactor also produces radioisotopes used in nuclear medicine. HFIR is the only domestic source of californium-252, an isotope used in industrial analysis. These nuclear materials are processed and refined at the nearby Radiochemical Development and Engineering Center.

###
Oak Ridge National Laboratory is managed by UT-Battelle for the Department of Energy.
NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.ornl.gov/news.

MRI scanner under scanner

Date:03/05/2007 URL: http://www.thehindu.com/thehindu/seta/2007/05/03/stories/2007050300371600.htm Sci Tech
— Photo: K. Pichumani


MRI scanner under scanner

MRI with a gadolinium-based contrast agent may cause a sometimes fatal condition

# Free unbound gadolinium (a paramagnetic heavy metal) is very toxic
# Dialysis a must after recieving the gadolinum based agent for moderate to end stage kidney patients



UNIQUE TOOL: Many MRI uses are unique and a few of them tend to be irreplaceable.

MAGNETIC RESONANCE imaging (MRI), a non-invasive technique used to characterise and discriminate tissues using their physical and chemical properties, finds applications in cardiology, neurology and oncology.

Many MRI uses are unique and a few of them tend to be irreplaceable. But now the scanner itself has come under the scanner.

The press release

A report by Dr T. Grobner in January 2006 and a press release, dated May 29, 2006 from the Danish Medicines Agency (DMA) described patients with renal failure who developed a rare, potentially life-threatening condition called Nephrogenic Systemic Fibrosis/Nephrogenic Fibrosing Dermopathy (NSF/NFD).

These patients had gadolinium-enhanced Magnetic Resonance Angiography (MRA) procedures a few weeks to a few months before developing NSF/NSD.

Health advisory

The US Food and Drug Administration (FDA) posted two advisories on the topic in June 2006 and December 2006. The agency warned that patients with moderate to end-stage kidney disease who receive an MRI or MRA with a gadolinium-based contrast agent may get NSF/NFD, a debilitating and sometimes fatal condition. When such a patient needs an imaging study, physicians should select methods other than MRI or MRA with a gadolinium-based contrast agent for the study whenever possible, FDA cautioned.

If these patients must receive a gadolinium-based contrast agent, the physicians must consider arranging prompt dialysis following the MRI or MRA.

The UK Commission on Human Medicines (CHM) together with the European Pharmaco-vigilance Working Party (PhVWP) of the Committee for Medicinal Products for Human Use (CHMP) and Health Canada issued appropriate health advisories on NSF during February and March this year.

Signs of the disease

FDA reported the following signs of the disease: burning, itching, swelling, hardening and tightening of the skin; red or dark patches on the skin; yellow spots on the whites of the eyes; stiffness in joints with trouble moving or straightening the arms, hands, legs or feet; pain, deep in the hip bones or ribs; and muscle weakness. NSF patients develop swelling and tightening of the skin over a period of days to several weeks (Journal of American Medical Association-JAMA- January 17, 2007). Often, the thickening of the skin inhibits joint movement. In severe cases, the patient cannot walk. Fibrosis may lead to multiple organ failure and death.

Physicians identified NSF/NFD for the first time in1997. In 2000, Dr Shawn Cowper at Yale University School of Medicine described the condition (Auntminnie.com, March 27, 2007).

NSF/NFD has no known treatment; improved renal function (spontaneous or via kidney transplant) appears to slow down or arrest its development and may even yield a gradual reversal of the condition (FDA, December 22, 2006).

Middle-aged affected

NSF appears to affect males and females nearly equally. Children and the elderly suffer from it. It tends to affect the middle-aged most commonly. Specialists identified it in patients from different ethnic backgrounds and from North America, Europe, and Asia. In 2006-2007, six papers in prestigious medical journals dealt with NSF.

The ACR Guidance Document on Safe MR Practices from the American College of Radiology (American Journal of Roentgenology, March 1, 2007) specifically addressed NSF calling "gadolinium administration a necessary factor in the development of NSF at this time". This 27-page document deals with all issues of MRI safety.

Free unbound gadolinium (a paramagnetic heavy metal) is very toxic; but in the contrast agent it is chelated with a ligand; then its safety profile improves dramatically, resulting in a 500-fold increase in renal excretion (Kramer, ACR, 2007).

Initiating the process

In patients with poor kidney function, gadolinium may disassociate from the ligand and may deposit in tissue beds and initiate the fibrotic process. Specialists have isolated gadolinium from biopsy specimens of NSF patients.

Dr Christopher M. Kramer, an MRI specialist estimated that nearly 200 million patients have received a magnetic resonance imaging examination using gadolinium-based contrast agent since 1988.

"The NSF registry currently contains over 215 worldwide cases, it is reasonable to assume that NSF is largely under-recognized", Dr Kramer said

Dr Shawn Cowper who set up a world registry of NSF patients also felt that what is recorded is only a small fraction of actual cases.

Physicians should consider the advisories from different agencies before carrying out MRI screening

K.S PARTHASARATHY

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

© Copyright 2000 - 2006 The Hindu