News

Childhood thyroid cancers rise 10-fold in the Ukraine

BMJ 1999; 319 doi: https://doi.org/10.1136/bmj.319.7203.145a (Published 17 July 1999) Cite this as: BMJ 1999;319:145

Elevated leukemia rates in Chernobyl accident liquidators

Elevated leukemia rates in Chernobyl accident liquidators

 

 

Editor - Following the Chernobyl accident of April 26, 1986,
two main population groups were exposed to radiation: emergency workers
involved in mitigation of the accident consequences (liquidators) and residents
of contaminated territories.

A dramatic increase in
thyroid cancer incidence among residents exposed as children has been apparent
since 1992.1,2 However, there remains considerable uncertainty about
the existence of radiation-related health effects in liquidators (average dose
of external radiation about 100 mGy).3

Our data demonstrates that
there has been a significant increase in the incidence of leukemia other than
chronic lymphocytic leukemia (CLL) among liquidators
with external radiation dose estimates of 150 to 300 mGy.

We studied a cohort of 71,870
Russian-resident males who were engaged in recovery operations within the 30-km
zone between 1986-1990 and for whom individual external radiation dose estimates
were available (average dose 107 mGy)4. A
total of 58 morphologically verified leukemia cases (ICD9 204-208) were
diagnosed in this cohort between 1986 and 1998, from which we excluded 16 cases
of CLL. While leukemia is a well-known early consequence of acute radiation
exposure,5 various studies3 indicate that CLL rates are
not increased by radiation exposure.

We considered the
relationship between leukemia incidence rate and absorbed radiation dose based
on both external and internal comparisons. For the external comparison we used
age-specific Russian male population rates for this time period to compute dose
category-specific standardized incidence ratios (SIRs).
The internal comparisons were based on using estimates of both
category-specific relative risk and excess relative risk (ERR) per Gy. Parameter estimates, confidence intervals and significance
tests were computed using the Poisson regression methods.6 The results
are summarized in Table 1. Both the external (SIR=2.5, P<0.001) and internal
comparisons (RR=2.2, P=0.03) indicate significantly elevated risks in the
150-300 mGy dose group.

 

Table 1.
Results of analysis of leukemia incidence among Chernobyl accident liquidators

 

Liquidators of 1986-1990

Liquidators of 1986-1987

Dose group (mGy)

0-

45-

90-

150-300

0-

45-

90-

150-300

Mean dose

17

66

103

208

19

72

104

208

Mean age at exposure (years)

32.8

33.2

34.0

34.3

33.1

33.7

34.0

34.3

Cases

9

4

7

22

4

2

7

22

PYR

154718

113033

144171

205394

67264

82790

137650

203929

External comparison

Expected cases

5.8

4.4

5.9

8.9

2.7

3.3

5.6

8.9

SIR

1.6

0.9

1.2

2.5

1.5

0.6

1.2

2.5

90% CI

(0.9, 2.6)

(0.4, 1.9)

(0.6, 2.1)

(1.7, 3.4)

(0.6, 3.0)

(0.1, 1.6)

(0.6, 2.2)

(1.7, 3.5)

Internal comparison

Relative risk

1.0

0.6

0.8

1.8

1.0

0.4

0.9

1.8

90% CI

-

(0.2, 1.6)

(0.4, 1.9)

(1.0, 3.6)

-

(0.1, 1.6)

(0.3, 2.6)

(0.8, 5.0)

Pooled comparison group

1

2.2

1

2.4

90% CI

-

(1.3, 3.7)

-

(1.4, 4.3)

ERR/Gy

6.7 (90% CI 0.8, 23.5)

10.7 (90% CI 1.3, 81.4)

 

It should be emphasized that
similar results were obtained for the liquidators of 1986-1987 who are provided
with better than usual health care by the law of the Russian Federation (Table
1).

Our results suggest that
liquidators with doses in excess of 150 mGy (about
30% of all Chernobyl liquidators) should be regarded as having elevated risks
of developing non-CLL leukemia.

 

Viktor Ivanovresearch
deputy director

nrer@obninsk.com

Anatoly Tsybdirector

Anton Gorskysenior
statistician

MaratMaksioutovsenior researcher

Svetlana Khaitsenior
researcher

Medical Radiological Research Center of Russian Academy of Medical
Sciences, Korolevstr. 4, Obninsk, Kaluga Region, 249020, Russia

Dale Prestondepartment chief

Department of Statistics, Radiation Effects Research Foundation,
Hiroshima 732, Japan

Yoshisada Shibatadepartment chief

Department of Radiation
Epidemiology, Nagasaki University School of Medicine, Nagasaki 852-8523, Japan

 

References

1.   Josefson
D. Childhood thyroid cancers rise 10-fold in the Ukraine. BMJ 1999; 319: 145.

2.   Kazakov
VS, Demidchik EP, Astakhova
LN. Thyroid cancer after Chernobyl. Nature
1992; 359: 21.

3.   UNSCEAR, 2000
report, E.00.IX.4. New York: United Nations, 2000.

4.   Ivanov
VK, Tsyb AF, Ivanov SI, Souchkevitch GN. Low doses of ionizing radiation: health
effects and assessment of radiation risks for emergency workers of the Chernobyl
accident. Souchkevitch GN, Repacholi
MN, editors. Geneva: World Health Organization, 2001.

5.   Preston D, Kusumi S, Tomonaga M, Izumi S,
Ron E, Kuramoto A, Kamada
N, Dohy H, Metsui T, Nonaka H, Thompson D, Soda M, Mabuchi K. Cancer incidence
in atomic bomb survivors. Part III: Leukemia and Multiple Myeloma,
1950-1987. Radiation Research 1994; 137
(Suppl.): S68-S97.

6.   Breslow
N, Day N. Statistical methods in cancer research. Lyon: IARC, 1987.

Competing interests:  
None declared

Competing interests: nrer@obninsk.com

15 April 2003
Victor Ivanov
research deputy director
Anatoly Tsyb, Anton Gorsky, Marat Maksioutov, Svetlana Khait, Dale Preston, and Yoshisada Shibata
Medical Radiological Research Center, Korolev str. 4, Obninsk, Kaluga Region, 249020, Russia
Click to like:
21