January 1, 2014
Updated: January 2,
2014 04:02 IST
Is
working in a nuclear power plant risky?
K.S. PARTHASARATHY
APNuclear power plant workers receive low doses
of radiation.
TOPICS
Several studies of nuclear power plant workers have shown that
work in a nuclear power plant is not a risky occupation
A
24-year-old man who was about to join the Nuclear Power Corporation of India
Limited (NPCIL) and his parents were troubled by what they saw on a TV channel
about the alleged damage to DNA by radiation. TV channels often go overboard
and make unsubstantiated claims.
A
63-year-old person asked this writer whether the throat malignancy, which, his
33-year-old daughter was suffering from, was likely due to the possible
radiation exposure he might have received while working in a nuclear power
plant when he was 28 years old. The explanations offered appeared to have
dispelled their doubts.
Is work
in a nuclear power plant risky?
Several
extensive epidemiological studies of nuclear power plant workers have shown
that work in a nuclear power plant is not a risky occupation.
Radiation
workers in nuclear industry like other radiation workers form a unique group.
They are adult workers whose radiation doses received at work are regularly
measured; these records are maintained.
Radiation
protection specialists accept that ionising radiation at high dose levels can
cause cancer. Nuclear power plant workers receive low doses of radiation.
Cancer
induced by radiation is indistinguishable from those caused spontaneously or by
other cancer-causing agents. Since there are no unique biomarkers for
radiation-induced cancer, specialists depend on statistical methods to predict
cancer incidence in a group of exposed workers.
Specialists
have carried out long-term studies of these workers in many countries. Most of
these studies have low statistical power.
To get
statistically respectable population groups, specialists carried out a pooled
study of radiation worker populations from 15 nations. The participants in this
international collaborative study included 407,391 workers whose external
radiation doses were individually monitored; the total follow up was about 5.2
million person-years.
The
study published in Radiation
Research in 2007
quite unexpectedly showed statistically significant increased risks per unit of
occupational ionising radiation dose for mortality from solid cancer and from
all cancers excluding leukaemia, compared to those of A-bomb survivors.
The
observation that the radiation risk at low doses is more than that at high
doses attracted wide attention. In the pooled analysis, Canadian workers had
the highest cancer radiation risk estimates among the 15 countries. None of the
other 14 country cohorts individually had significantly raised cancer mortality
risk estimates. Exclusion of Canadian workers (4 per cent of the sample) from
the pooled analysis changed the findings to statistically non-significant.
Critics
questioned the data and the analytical validity of the study because of the
apparent difference in the results between the Canadian and the 15-country
studies.
A
recent paper dispelled the disproportionate alarm caused by the pooled study.
A paper
published on November 13, 2013 inthe British
Journal of Cancer, indicated that the significantly increased risks for early
AECL workers are most likely due to incomplete transfer of AECL dose records to
the National Dose Registry.
Researchers
reported that the analysis of the remainder of the Canadian nuclear workers
(93.2 per cent) provided no evidence of increased risk; also the risk estimate
was compatible with estimates that form the basis of radiation protection
standards.
“Study
findings suggest that the revised Canadian cohort, with the exclusion of early
AECL workers, would likely have an important effect on the 15-country pooled
risk estimate of radiation-related risks of all cancer excluding leukaemia by
substantially reducing the size of the point estimate and its significance,”
the researchers clarified.
Workers
in nuclear power plants will receive some radiation dose. Nuclear Power
Corporation of India Limited (NPCIL) has strict procedures in place to keep the
doses to workers within the limits prescribed by the Atomic Energy Regulatory
Board (AERB).
The
AERB Annual Report of 2012-2013 published at (www.aerb.gov.in) indicates that
in 2012 no radiation worker in any nuclear power plant exceeded the dose limits
prescribed by AERB.
The
average radiation dose varied from 0.35 mSv to 2.84 mSv, a fraction of the AERB
annual dose limit of 30 mSV. Conclusions were similar in earlier years. At
these doses, radiation risks, if any, are insignificant.
Since
the dose limits are based on conservative assumptions, it is inconsequential if
anyone receives, occasionally, a dose above the limit.
Radiation
protection standards are based on studies by scholarly bodies such as the US
National Academy of Sciences (NAS), Biological Effects of Ionizing Radiation
Committee, the International Agency for Research on Cancer (IARC) and United
Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR).
They
indicate that at low doses — similar to those received by nuclear power plant
workers — radiation risks, if there are any, are negligibly small. Such risks
are no risks at all. Work in a nuclear power plant is not a risky occupation.
K.S.
PARTHASARATHY
Former
Secretary, Atomic Energy Regulatory Board
(ksparth@yahoo.co.uk )
Keywords: Nuclear power plant, NPCIL, ionising radiation, radiation risks
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