ASN Report 2015

radiation (nuclear industry workers, medical personnel,

medical diagnostic exposure, etc.).

Low-dose risks are assessed for risk-management

purposes by extrapolating the risks observed at higher

doses. This calculation gives an estimate of the risks

entailed by exposure to low doses of ionising radiation.

For these estimates, the prudent hypothesis of a linear

no-threshold relationship between exposure and

the number of deaths from cancer has been adopted

internationally. This hypothesis implies that there is

no dose threshold below which one can assert that

there is no effect. The legitimacy of these estimates and

of this hypothesis nevertheless remains scientifically

controversial, as very large scale studies would be

necessary to further support the hypothesis.

On the basis of the scientific syntheses of UNSCEAR

(see box page 49), the International Commission on

Radiological Protection – ICRP (see publication ICRP 103,

chapter 3, point 1.1.1) has published risk coefficients for

death from cancer due to ionising radiation, showing a

4.1% excess risk per sievert (Sv) for workers and 5.5%

per sievert for the general public.

The evaluation of the risk of lung cancer caused by

radon (radon is a naturally occurring radioactive gas

– a decay product of uranium and of thorium – which

emits alpha particles and is classified by the IARC as a

definite human carcinogen) is based on a large number

of epidemiological studies performed directly in the

home, in France and internationally. These studies have

revealed a linear relationship, even at low exposure

levels (200 becquerels per cubic metre (Bq/m

)) over a

period of 20 to 30 years. TheWorld Health Organisation

(WHO) has synthesised the studies and recommends a

maximum annual exposure level of between 100 and

300 Bq/m

for the general public. The ICRP

(Publication 115)

compared the risks of lung cancer

observed through studies on uraniumminers with those

observed on the general population and concluded that

there was a very good correlation between the risks

observed in these two conditions of exposure to radon.

The ICRP recommendations confirm those issued by

the WHO which considers that, after tobacco, radon

constitutes the highest risk factor in lung cancer.

In metropolitan France, about 19 million people

spread over some 9,400 municipalities are potentially

exposed to radon. According to InVS (French Health

Monitoring Institute) figures from 2007, between

1,200 and 2,900 deaths from lung cancer can be attributed

each year to radon exposure in the home, that is to say

between 4 and 10% of deaths due to cancer. A national

action plan for managing radon-related risks has been

implemented since 2004 on the initiative of ASN and is

updated periodically (see point 3.2.2).

The latest publication of the International

Agency for Research on Cancer – IARC (2015)

on cancer mortality rate of workers employed

in the nuclear industry*

The publication in 2015 by the WHO (IARC, Lyon,

www.iarc.fr)

of the cancer mortality rate for French, American

and British workers employed in the nuclear industry

(fuel preparation, research, electricity production, spent fuel

reprocessing) and having worn personal dosimeters, has provided

greater insight into the external irradiation risks which, although

low, accumulate over the working life. The studied population

included nearly 300,000 workers, of which the French cohort

comprised 59,000 workers from Areva NC, CEA and EDF.

The average monitoring time of these workers was twenty-

seven years. The average dose is 25 mSv cumulated over the

working life (fifteen years on average). The mean annual dose

is less than 2 mSv. 94% of the individuals had a cumulative

total of less than 100 mSv. Among the 6% of individuals whose

cumulative dose exceeded 100 mSv, 75 % started working in

the 1970’s and their mean cumulative dose is 223 mSv.

A first publication in June 2015 showed an increase in the risk

of leukemia as a function of the cumulative dose. A second

publication in October 2015 shows that the risk of cancers

other than leukemias also increases as a function of the

cumulative dose, that is to say about 4% for an increase of

100 mSv.

These results were observed from a total of 66,600 deaths,

of which 19,064 were due to cancers other than leukemias.

From the estimated dose-risk relationship, it appears that the

proportion of deaths that can be attributed to external exposure

to radiation within this population of workers is about 1% of

all the observed 19,064 deaths due to cancers other than

leukemias.

The observed relationship is stable (little heterogeneity between

the countries, small-amplitude variations in the sensitivity

analyses). To evaluate the existence of a potential bias due to

tobacco, lung cancers were excluded from the analysis; this

exclusion had little impact on the risk estimate.

The dose-risk relationship observed is consistent with those

observed in other studies, particularly those of the Hiroshima

and Nagasaki survivors and shows that the risk at low doses

spread over time does not differ from that observed for the

same irradiation dose received in a few seconds.

TO BE NOTED

* The new results concerning the risk of death by cancer other

than leukemia were published in the

British Medical Journal

;

those on the leukemia risk were published in the

Lancet

CHAPTER 01:

NUCLEAR ACTIVITIES: IONISING RADIATION AND HEALTH AND ENVIRONMENTAL RISKS

ASN report on the state of nuclear safety and radiation protection in France in 2015