Can low doses of radiation cause heart disease?

It is necessary to assess the epidemiological evidence of radiation effects other than cancer at low doses










Basic guideline: The basic tenet of radiation protection that radiation doses to workers should remain As Low As Reasonably Achievable remains.


Researchers at the Imperial College, London predict a link between low dose radiation exposure and heart disease (PLoS Computational Biology, October 2009). Their mathematical model suggests that the risk would increase as the dose increases.
Cardiovascular effect of high levels of radiation has been known in patients who underwent radiotherapy. Specialists found higher risk for cardiovascular disease among women treated for left-sided breast cancer when compared with women treated for right-sided breast cancer, during the period more than 10 years after diagnosis.
Emerging evidence
There is emerging evidence of excess risk of heart disease at much lower doses occurring after a long time after exposure among the A-bomb survivors included in the Life Span Study project and in some groups of radiation workers. The likely mechanism to explain the effect was not clear.
The US National Academy of Science’s Committee for Biological Effects of Ionizing Radiation (BEIR committee) in its latest report has acknowledged the existence of such effects; it asserted that the available data are inadequate to quantify the risk, if it exists.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in its latest report published in 2008, clarified that it is necessary to assess the epidemiological evidence of radiation effects other than cancer at low doses because the phenomena is potentially important for radiation risk assessment at these dose levels, and there is considerable lack of consistency among the available epidemiological data.
“The Committee considered it important to focus on cardiovascular disease as the major endpoint of interest, because cardiovascular disease is among the most common diseases in many populations worldwide and thus may be important for radiation risk assessment,” the report cautioned.
The Imperial College team suggested that radiation kills monocytes (a type of white blood cell) in the arterial wall, which would otherwise bind to monocyte chemo-attractant protein 1 (MCP-1). The resultant higher levels of MCP-1 cause inflammation which leads to cardiovascular disease.
According to the researchers, the predicted consequence of several small radiation exposures is to cause mean concentration of MCP1 to increase linearly with cumulative dose.
“The radiation-induced risks predicted by the model is consistent with those observed in a number of occupationally observed groups,” they claimed.
The implications
According to them, if their model is valid, it will have substantive implications in radiological protection, which currently does not take cardiovascular diseases into consideration.
In an interview to BBC, Professor Steve Jones, of Westlakes Research Institute who formerly worked for British Nuclear Fuels (BNF) and who has published his own research on the links between radiation and circulatory disease in nuclear workers conceded that the results of the mathematical model were interesting. He cautioned that its finding cannot be taken as definitive as it is based very largely on mathematical modelling.
“However it does propose a plausible biological mechanism and, most importantly, a mechanism that is testable by experiment.” he clarified to the BBC.
BBC quoted Professor Richard Wakeford, of the University of Manchester who also formerly worked for BNF, thus: “More research like this is needed if the results of epidemiological studies are to be properly understood, but there is still some way to go before it may be reliably concluded that low-level radiation can increase the risk of circulatory disease.”
According to BBC, Professor Dudley Goodhead, former director of the MRC Radiation and Genome Stability Unit, noted that this paper puts forward a highly complicated mathematical model, which makes many assumptions, to explore one possible causal mechanism.
“Such conclusions should not be drawn without laboratory validation of the key assumptions,” he asserted.
For many years, the model proposed by the Imperial college team may remain just that; a model with no practical implications.
The basic tenet of radiation protection that radiation doses to workers should remain As Low As Reasonably Achievable (ALARA principle) remains.
Scientists from the Regional Cancer Centre, Thiruvananthapuram and Bhabha Atomic Research Centre did not find any excess cancer in the high background radiation areas (HBRA) in Kerala. It will be worthwhile to look for excess cardiac diseases in HBRA.
K.S. PARTHASARATHY
RAJA RAMANNA FELLOW, DEPARTMENT OF ATOMIC ENERGY
ksparth@yahoo.co.uk
© Copyright 2000 - 2009 The Hindu

How safe is Madras Atomic Power Station?

South Asians Against Nukes (SAAN) , a Non Governmental Organization has claimed that the radiation levels are high in regions around the Madras Atomic Power Station. They measured the levels by using their own gamma monitor. The results indicate either that they were measuring the widely varying background radiation levels because of the presence of thorium in the soil or they wee using a defective instrument. Since they obtained abnormally high values, there instrument must have been defective!

The author had similar experience when another NGO claimed that the background radiation levels in Lucknow was very high. It turned out that the instrument they used was light sensitive!

K.S.Parthasarathy





How safe is Madras Atomic Power Station?







Within threshold: The releases from the Madras Atomic Power Station have not exceeded the limits prescribed by the regulatory agency.


Background radiation level at any place depends mainly on terrestrial radiation from natural radionuclides such as uranium, thorium and their decay products and potassium-40 present in soil and on cosmic rays (radiation from outer space).
The top one metre soil in a land of area 0.1 acre anywhere in the country may contain 1.28 kg of potassium-40, 3.6 kg of thorium and one kg of uranium.
The soil factor
In different soils these values may be higher or lower. The dose due to natural radiation varies from place to place.
The releases from the Madras Atomic Power Station (MAPS) have not exceeded the limits prescribed by the regulatory agency. The data collected from 1982 to date by the Environmental Survey Laboratory (ESL) at MAPS do not indicate high increases in radiation levels. Nuclear Power Corporation Limited should invite students and public to the ESL to reassure them. BARC scientists have measured outdoor natural gamma radiation levels at 214 locations in different parts of India continuously over a year by using special dosimeters and got an average annual value of 775 microgray.
They got the highest value of 26730 microgray at Chavara, Kerala. (Gray is a unit of radiation dose.
Energy absorbed
When the dose is one gray, the energy from ionizing radiation absorbed is one joule per kg; since gray is a big unit, submutiples such as milli-one thousandth or micro -one millionth-of a gray are usually used).
Using the geological data on the types of rocks and the abundance of uranium, thorium and potassium in these rocks, BARC scientists prepared a radiation map of the country in 1986.
The natural background radiation doses at Mumbai, Kolkata, Chennai and Bangalore are 484, 810, 790 and 825 microgray per year respectively.
The annual cosmic ray dose itself varies from 280 microgray in Chennai to 440 microgray in Bangalore which is 921 metres above the sea level.
Variation of a few hundred microgray is not unusual.
What is the extra contribution, if any, to radiation dose made by a nuclear power station at its fence post?
Data from 1982 to 2007 indicate that for the MAPS, the lowest extra dose was 7.2 microsievert per year and the highest 86.3 microsievert per year. (Sievert — Sv — is another unit. For all practical purposes, background radiation expressed in sievert or gray may be considered numerically equal). These are much less than the AERB limit of 1,000 microsievert.
The status is similar in other power stations.
Activity can escape only if several barriers (ceramic fuel, its cladding, coolant, coolant tube etc) are broken. These are of proven quality. Fail safe devices including redundant and diverse safety systems ensure that such uncontrolled releases do not happen.
In April 1994, an “environmentalist” measured high radiation levels at the MLAs’ hostel and other locations in Lucknow. “Radiation levels at some points are higher than those at Chernobyl,” he claimed. Many newspapers published the story.
Recorded normal
A team of scientists sent by the Atomic Energy Regulatory Board (AERB) found that his Geiger-Mueller counter —based instrument was defective. It was light sensitive. When the detector was made light-proof, the radiation levels recorded normal!
In 2005, Padmanabhan and Nakul of the South Asians Against Nukes (SAAN) claimed that while monitoring radiation levels around the Madras Atomic Power Station in places such as Coimbatore, Chenglepet, Mahabalipuram and Kalpakkam they came across several spots with gamma radiation levels as high as a few millisievert to above ten millisieverts per year. The highest level measured was 54.5 millisieverts.
The speculation
They speculated that the wide variations between the readings taken from the same spot indicated that the source of radiation is not on the ground but are “picoparticles” from uranium fission floating and flying in air! There are simpler explanations.
If they were using a defect-free instrument, they were recording radiation from thorium rich soil in the region. This is nothing unusual.
Since over 70 per cent of their readings were above 2mSv, I believe that they were experiencing the problem faced by the “environmentalist” in Lucknow!
K.S.PARTHASARATHY
Former Secretary, AERB
( ksparth@yahoo.co.uk )
© Copyright 2000 - 2009 The Hindu

Nuclear power: myths, realities

Nuclear power suffered because of accidents. But no one abandoned it because of accidents.Nuclear power seems to be an “unloved” industry, not because it is faulty. Mired in controversy, myths about nuclear power survive; the realities are unknown to many.Author highlights some of thew myths and the realities about this "unloved" industry
K.S.Parthasarathy



Date:15/10/2009 URL: http://www.thehindu.com/thehindu/seta/2009/10/15/stories/2009101550201400.htm Back Sci Tech



Nuclear power: myths, realities

Nuclear power suffered because of accidents. But no one abandoned it because of accidents

The impact of water used as coolant may extend up to about 500 metres from the discharge point

The doses to members of the public are too small and well within the AERB limit

The speakers at a well attended side event at the recently held International Conference on Peaceful Uses of Atomic Energy at Delhi (September 29-October 1) recommended a proactive, public awareness programme on issues related to energy, particularly nuclear energy.

International Atomic Energy Agency (IAEA), Department of Atomic Energy and Indian Nuclear Society jointly organized the meeting.

Nuclear power seems to be an “unloved” industry, not because it is faulty. Mired in controversy, myths about nuclear power survive; the realities are unknown to many.

Nuclear power suffered because of accidents. But no one abandoned it because of accidents at Three Mile Island (1979) and Chernobyl (1986).

U.S. electric companies connected 50 out of the currently operating 104 nuclear power reactors since 1979; nineteen of these after 1986. Canadian companies connected all the 14 operating nuclear power reactors to the grid after 1979. Of the fifty nine French reactors, 53 came on line after 1979.

Some European nations decided to phase out nuclear power. Since they are substitutes for fossil power stations (which are implicated in global warning), these nations are decisively moving away from their “phase out” decision.

Recently, “National Alliance of Anti-nuclear Movements (NAAM)” claimed that the nuclear plant at Kudankulam would lead to pollution in the near shore areas, affecting fish stocks. They alleged that this would impact on the health of fish-eating people in Kerala, Tamil Nadu and Sri Lanka (The Hindu, October 3). These allegations have no scientific basis. Pollution of sea shore is another myth!

Fish catch potential during 1994-98, in the Kalpakkam zone indicated variations. Central Marine and Fisheries Research Institute, Cochin, concluded that these variations are mere statistical variations with seasons.

The impact of water used to cool nuclear power reactors is limited to a mixing zone which may extend up to about 500 metres from the discharge point.

India has been operating nuclear power stations since 1969.

The Atomic Energy Regulatory Board (AERB) permits stations to release radioactivity up to certain prescribed limits. The scientists at the Environmental Survey Laboratory (ESL) outside each station use state-of-the-art methods to measure radioactivity in samples of air, water, soil, sediments and foodstuffs and look for trends, if any.

The doses to members of the public are too small and well within the AERB limit. They are within the variation of natural background radiation present everywhere even in the absence of the power station.

The radiation dose due to Kudankulam reactors will also be similar. An activist alleged that these reactors would trigger cancer and genetic disorders in the area (The Hindu, Oct, 3). This is a preposterous allegation.

The claim that iodine-131 released from Kalpakkam nuclear power station into sea and air is causing thyroid cancer in the area in another myth.

The release of iodine to sea is virtually zero. During 1983-2008, the annual releases into air were zero to 1.29 per cent of the AERB limit. The doses due to this were too trivial to cause cancer.

The Iodine-131 activity, if any, released from the station will get deposited on grass. It will appear promptly in goats’ thyroid. ESL scientists routinely measure iodine-131 from goats’ thyroid, an easily available sample.

They detected iodine-131 activities only twice, in 1976 during the aftermath of Chinese nuclear tests in the atmosphere and in 1986 shortly after the accident at the Chernobyl nuclear power station.

“The ESL Kalpakkam had found after the nuclear accident at Chernobyl in April 1986 that the incidence of thyroid related diseases in goats had registered an increase as a result of feeding on grass laced with Iodine-131”.

An activist wrote in a Chennai daily on October 18, 2008 (NUCLEAR FREE INDIA, December 2008).Obviously, he mistook why ESL scientists collect goats’ thyroid samples!

According to an activist, the scientific community was yet to come up with a safe nuclear waste management system (The Hindu Oct, 3). Another myth!

Nuclear wastes are managed safely. There is scientific consensus on safe management of high level nuclear waste; but that problem is mired in politics.

If you want nuclear power to thrive, dispel the myths, reveal the realities!

( ksparth@yahoo.co.uk )

K.S. PARTHASARATHY
FORMER SECRETARY, AERB

How safe are interventional cardiac procedures?

Radiation safety in interventional radiology practices are getting some attention now
The Hindu published an artcile on October 1, 2009
Dr K.S.Parthasarathy









Date:01/10/2009 URL: http://www.thehindu.com/thehindu/seta/2009/10/01/stories/2009100150441500.htm
________________________________________




How safe are interventional cardiac procedures?
— Photo: S. Thanthoni



Within threshold: Radiation risk is acceptably low when compared to risk of not carrying out the procedures when indicated.
Recently, radiation protection measures in interventional radiology especially in cardiology have been receiving special attention.
These are image-guided therapeutic techniques such as coronary angioplasty (to remove blockades in artery) and diagnostic techniques such as angiography (imaging the blood vessels using an x-ray contrasting agent).
These life-saving procedures require specially designed equipment and involve high radiation exposures to physicians, technologists and patients. Cardiologists must know the equipment specification and characteristics to use radiation effectively and optimally.
Risks compared
Radiation risk is acceptably low when compared to risk of not carrying out the procedures when they are medically indicated.
Recently, a survey supported by the International Atomic Energy Agency (IAEA) in 55 hospitals in 20 countries of Africa, Asia, and Europe indicated that many patients exceeded the dose threshold for erythema (skin reddening); a substantial number (62 per cent) of coronary angioplasty procedures exposed patients to doses above the recommended dose reference level. (American Journal of Roentgenology, August 2009). Though specially needed dose measuring instruments were in place in almost half the facilities, none had experience in its use.
Hundred out of 505 patients monitored, had peak skin doses above the 2-Gy threshold for deterministic effects (Gy is a unit of radiation dose; one Gy is equal to one joule per kg).
Inadequately trained
IAEA has noted that many physicians using interventional radiology techniques are not adequately trained in radiation safety or radiobiology. In a few cases, patients may suffer radiation-induced skin injuries which may go unnoticed. Younger patients may face an increased risk of future cancer.
Patients may ask their physicians about the radiation dose they are likely to get in the procedure. If they feel any changes in the exposed area of the skin later, they must report it to their physician. Though radiation dose is important, it is only one of the factors to be considered.
The dose to patients must be As Low As Reasonable Achievable (ALARA). Cardiac procedures are very complex, doses will be ALARA only if the cardiologists appreciate the importance of dose reduction; they must be constantly vigilant. If patient’s dose is reduced, occupational dose also will be reduced.
A few years ago, a medical physicist working in a corporate hospital introduced me to an eminent cardiologist who has been saving hundreds of lives. “When I have too many patients, I just remove the personnel monitoring badge”, he confessed. Unknown to him, he may become a victim of his carelessness.
Regular monitoring
Cardiologists must monitor their radiation doses regularly; they are among the category of radiation workers who have highest probability to get significant doses.
IAEA surveys conducted during training courses in which cardiologists from 56 countries participated showed that only 33 to 77 per cent of them use personnel dose measuring devices routinely.
During a workshop in Mumbai two cardiologists listed several telling deficiencies ( http://www.aerb.gov.in/t/newsflash/cathlab.pdf).
Cardiologists are not aware of the radiological safety precautions to be taken during angiography or angioplasty. They lack awareness of personal protective equipment, personnel dose monitoring devices and their proper use.
Lens of the eye is radiosensitive. Cardiologists remain near x-ray sources within high scatter radiation areas for several hours every day.
Preliminary results from the IAEA study called Retrospective Evaluation of Lens Injuries and Dose (RELID) indicate identifiable damage to the lens of those cardiologists not using eye protection.
A summary of the results of studies carried out in Colombia, Malaysia, Uruguay and Bulgaria during 2008-09 is freely available (http://rpop.iaea.org/RPOP/RPoP/Content/News/relid-activities.htm). Protracted eye lens dose of 4Gy over 3 months or 5.5 Gy delivered over five months may cause detectable opacities to the eye lens.
IAEA has been very active in the field of radiation protection. They offer educational material of inestimable value free at their web site (http://rpop.iaea.org/).
The International Commission on Radiological Protection has issued its publication No 85 titled “Avoidance of radiation injuries from medical interventional procedures” ( http://www.icrp.org/
educational_area.asp).
K.S. PARTHASARATHY
Former Secretary, AERB
( ksparth@yahoo.co.uk )
© Copyright 2000 - 2009 The Hindu