Radioactive contamination in steel: a wake-up call

Frequent appearance of contaminated steel products has been reported from many countries.It appears that three companies made the contaminated steel products from imported scrap.Regulatory bodies have reported that there must be control on scrap imported in to the country.
K.S.Parthasarathy



Date:26/02/2009 URL: http://www.thehindu.com/thehindu/seta/2009/02/26/stories/2009022650061400.htm
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Radioactive contamination in steel: a wake-up call

Regulatory authorities have identified Indian steel products contaminated with cobalt-60 in the U.S., Germany, France and Sweden. The events occurred at disturbingly high rates.
“Overall, 123 shipments of contaminated goods have been denied entry to U.S. ports since screening began in 2003, according to Homeland Security data.
Of those, 67 originated in India, 23 came from China and 20 were from Canada” (The Los Angeles Times, November 13, 2008). We cannot ignore this wake-up call.
150 incidents
In the last three years, out of the 500 incidents, involving uncontrolled radiation sources, which the International Atomic Energy Agency (IAEA) came to know, 150 were related to sources found in scrap metal or contaminated goods.
The finding in Germany is attracting more attention. On August 19, last year customs officers identified a container of contaminated stainless steel bars from India on way to Russia. They ordered that the container be put back on the ship immediately and be sent back to India (SPIEGEL ONLINE, February 16).
There were several such findings later; The German Environment Ministry received 19 findings which included radioactive bars, steel cables, chippings and valve housings from 12 states. SPIEGEL reported that a total of 150 tons of contaminated steel has been seized.
Some of it, about 85 tons, according to a reliable source, have been sent back to India. Rest of it remains in Germany pending a decision on its safe disposal.
One of the possible practices is to use the items depending on their radiation levels in fencing or in bridges where the occupancy is less.
Imported metal scrap
After a thorough survey, the Atomic Energy Regulatory Board (AERB) concluded that the steel products in the recent incidents were made out of imported metal scrap which contained radioactive material. India imports more than 80 per cent of stainless steel metal scrap for recycling in the steel industry. Also most of the contaminated material was exported.
The health consequences from these products were negligible, as the radiation levels were low. But the presence of even low radiation levels is not desirable.
We do not have any estimate of the humongous economic losses including loss of business suffered by the industry. In some instances, the defaulters had to ship back the rejected material for safe disposal.
In spite of regulatory control, radioactive sources get lost occasionally. These may be melted along with other metal scrap. The steel products include handle bars, manhole covers, metal straps, steel wires, lift buttons, metal strips used in leather bags etc.
Sources licensed for use in India are unlikely to get into metal scrap, because of regulatory measures in place. However since there were a few instances of loss of control of sources, there is no room for complacency.
Presently, we have no firm assurance that contaminated imported scrap will not enter the country. Several measures including the plan to install radiation monitors at shipping ports through which bulk of the imported scrap metals enter the country must be implemented swiftly.
Precautions
Every importer of metal scrap should obtain a certificate from the exporting country that the scrap is free from radioactivity. A multilayer radiation check system proposed by AERB should be followed to prevent the import and export of radioactive contaminated material.
During this week, over 300 specialists from 62 countries including India are attending a five day International Conference on Control and Management of Inadvertent Radioactive Material in Scrap Metal, organized by the IAEA at Tarragona, Spain. The delegates asserted “that further steps are needed to protect people from radioactive material that can end up in junks and scrap yards,” (IAEA release, Feb 23).
All agencies must wake up before it is too late. Not long ago, explosion of live shells in imported metal scraps led to loss of life in India. Import of scrap laced with high levels of radioactivity is a possibility we must be concerned with.
K.S. PARTHASARATHY
FORMER SECRETARY, AERB
© Copyright 2000 - 2008 The Hindu

Monazite sand does not cause excess cancer incidence

The long awaited study on the cancer incidence among populations living in the high background radiation areas of Kerala has been published in the January 2009 issue of the Health Physics. The study showed that monazite sand does not cause excess cance incidence.

Dr K.S.Parthasarathy







Date:01/01/2009 URL: http://www.thehindu.com/thehindu/seta/2009/01/01/stories/2009010150131600.htm Back Sci Tech



Monazite sand does not cause excess cancer incidence






— Photo: C. Suresh Kumar

Cancer risk: The study found that there is no excess cancer risk to people living in the area of high natural background radiation in Kerala.

Now it is official. In the January 2009 issue of the Health Physics Journal, researchers from the Regional Cancer Centre (RCC), Thiruvananthapuram, and their collaborators have shown that there is no excess cancer risk to people living in the area of high natural background radiation in Kerala from exposure to terrestrial gamma radiation.

The Journal highlighted the importance of the paper by carrying a photo of the beaches in its cover page.
Gamma radiation

The coastal belt of Karunagappally, Kerala, is known for high background radiation (HBR) from thorium-containing monazite sand.

In the coastal panchayats, the median outdoor gamma radiation levels are more than 4 mGy y{+-}{+1} and in certain locations, the levels are as high as 70mGy y {+-}{+1}.(Gy is a unit of radiation dose; mGy is one thousandth of a Gy; the annual gamma radiation level in normal locations is on an average one mGy).

During 1990-97, survey teams collected data on 359,619 subjects in 71,674 households using a standardised questionnaire which covered socio-demographic factors, lifestyle, dietary habits and tobacco and alcohol use.
Follow up study

Based on radiation level measurements, by a method perfected by scientists of the Bhabha Atomic Research Centre, they chose a radiation sub cohort consisting of 173,067 residents and analysed the cancer incidence in the sub cohort, aged 30 to 84y (N=69958 followed up for 10.5 years).

They estimated the cumulative radiation dose to each individual in the age group based on the radiation doses received indoors and outdoors and taking into account how long and where they stayed during the period.

By the end of 2005, they identified 1379 cases of cancer including 30 cases of leukaemia.

The results

Statistical analysis of the data showed no excess cancer risk from exposure to terrestrial gamma radiation.

In site-specific analysis, they did not find any cancer site or leukaemia to be significantly related to cumulative radiation dose.

“Although the statistical power of the study might not be adequate due to the low dose, our cancer incidence study, together with previously reported cancer mortality studies in the HBR area of Yangjiang, China suggests it is unlikely that estimates of risk at low doses are substantially greater than currently believed,” the researchers concluded.

It appears that the researchers were in a hurry to publish the paper. They did not use the complete data but selected four coastal panchayats (Chavara, Neendakara, Panmana and Alappad) which had HBR and two control areas (Oachira and Thevalakkara) which have relatively low natural radiation levels.

They estimated the excess risk as -0.13 Gy{+-}{+1} (95 per cent confidence limit:-0.58, 0.46). The authors pointed out that the upper limit of 95 per cent confidence limit was lower than 0.97, which other researchers got for pooled analysis for nuclear workers from 15 countries (BMJ, 2005) and slightly lower than 0.47 Gy{+-}{+1} reported in the study of atomic bomb survivors in Hiroshima and Nagasaki (Radiation Research, 2007)

Authors highlighted some unique features of their data. Unlike the nuclear workers study, RCC study included smoking habits, an important contributing factor. The estimate of atomic bomb survivors is a sex-averaged estimate for solid cancer unlike the RCC study. The currently accepted radiation risk estimate is mostly based on atomic bomb survivor study.

Regrettably, the researchers did not estimate the substantial contribution of airborne radon and thoron daughters to the individual radiation dose. This may not affect the main conclusion that there is no excess cancer in areas of high natural background radiation.
The limitations

Though the analysis limited to six panchayats cannot be faulted scientifically, they should use complete data including internal dose from all panchayats for a reanalysis to do justice to the project and to examine whether precise radiation risk estimate can be arrived at from this study

Highlighting the negative radiation risk coefficient of -0.13 Gy{+-}{+1}, proponents of those who believe in the beneficial effects of radiation (hormesis theory) may argue that low level radiation is helping to lower cancer risks!

They may not agree that lack of statistical power may be the reason for the negative result.

K.S. PARTHASARATHY
FORMER SECRETARY, AERB

ksparth@yahoo.co.uk

© Copyright 2000 - 2008 The Hindu

Cancer risk not high in radiation workers

The latest issue of the British Journal of Cancer published an epidemiological study of radiation workers in the United Kingdom. It showed that cancer risks to radiation workers increase with dose; the magnitude of the risk estimates are consistent with international consensus. The study will not have any impact on the standards recommended for radiological protection.
Dr.K.S.Parthasarathy


Date:05/02/2009 URL: http://www.thehindu.com/thehindu/seta/2009/02/05/stories/2009020550011300.htm Back Sci Tech

Cancer risk not high for radiation workers

Radiation doses to workers in various professions studied

Cancer incidence among 1,74,541 workers studied

A study published in the latest issue of the British Journal of Cancer (BJC, Vol.100, 2009) by the researchers at the UK Health Protection Agency (HPA) concluded that the risk of developing cancer among radiation workers increases with the dose of ionizing radiation they are exposed to.

This study and the latest research on cancer risks to populations residing in high background radiation areas in Kerala reported in the January 2009 issue of the Health Physics Journal (The Hindu, Jan 1, 2009) are reassuring.

The results of these studies will have no impact on radiological practices, as the observed cancer risks are consistent with the international scientific consensus on radiation protection.

The dose limits to workers are based on such consensus.

The UK study is the third analysis of deaths and cancer incidence among 1,74,541 radiation workers whose occupational histories are maintained in the National Registry for Radiation Workers from 1976. The present study relative to earlier analyses had longer follow-up (to 2001) and cancer registration data and gives more precise information on the risks of occupational radiation exposure. The registry covers virtually all radiation workers from all the main organizations involved in nuclear and related research and industrial sectors in the UK

“This is a continuation of a study started in 1976 and it provides reliable information on the health of people working with ionizing radiation.

The results confirm the cancer risk estimates observed in other studies even though, overall, radiation workers have lower cancer risks than the general population” an HPA release quoted Dr Colin Muirhead from the Health Protection Agency and the lead author of the paper.

This indicates the so called “healthy worker effect”. Usually, workers exhibit overall death rates lower than those of the general population due to the fact that the severely ill and disabled are ordinarily excluded from employment (biology-online.org October 2005).

Scientists who believe in the beneficial effects of radiation may argue that this is an indication of hormesis, a view which will be stoutly rejected by mainstream specialists.

Within the cohort, death from and incidence of both leukaemia excluding chronic myeloid leukaemia and the groupings of all cancers excluding leukaemia (CLL) increased to a statistically significant extent with increasing radiation dose (BJC, January 2009).

It is known that radiation does not induce CLL. The trend in risk was similar to those for the Japanese A-bomb survivors.

The researchers noted that some evidence of an increasing trend with dose in mortality from all circulatory diseases may, at least partly, be due to smoking, a known confounding factor.

So far, specialists have studied the health effects of ionizing radiation on over fifty groups of about two million persons; but the estimates of the long-term health risks from radiation are based largely on studies of the survivors of the atomic bombings at Hiroshima and Nagasaki and of groups exposed for medical reasons.

The dose rates in these instances were high and other exposure conditions were also not similar to those faced by radiation workers.

Radiation workers get exposed to low doses of radiation at relatively low rates.

The UK study is ideal as it represented the typical radiation doses to workers in various professions.

Data collected from employers consist of individual identifiers, factors such as date of birth, gender and industrial classification, and radiation dose histories (BJC, January 2009).

“Continued follow-up of these workers will be valuable in determining whether radiation-associated risks vary over time or by age, and enables the study of specific cancers and causes of death in more detail” HPA argued in a release (HPA release January 7).

In a separate paper in the same issue of the BJC, researchers at the Childhood Cancer Research Group at the University of Oxford and the Health Protection Agency have shown that their study does not support an earlier finding of a raised risk of cancer in children of female radiation workers.

In a subgroup of women who worked with radiation during pregnancy, a weak statistical association was found between maternal radiation work and childhood cancer, but the evidence is limited by the small numbers involved and the result may be due to chance (BJC release January 7, 2009)

Let us hope that HPA does not suffer any resource crunch which may adversely impact on such research.

K. S.PARTHASARATHY
FORMER SECRETARY, AERB

ksparth@yahoo.co.uk

© Copyright 2000 - 2008 The Hindu