Abstract

The question of whether child acute leukaemia (ChAL) incidence in most contaminated countries has changed as a result of Chernobyl remains of great interest.

We present results of age-cohort-period analyses of IR trends of ChAL from 1979 to 2006 in Republic of Belarus. Number of cases was tabulated by age at diagnosis and period of observation (preaccident, 1979–1985) and postaccident: 1986–1992, 1993–1999, 2000–2006.

During first 7 years after the accident (1986–1992) we did not find any increase of ChAL incidence in the whole group of children (0–14 year old) (RR 1.03; 95% CI 0.92 to 1.14; p=0.61). However, the IR of infant AL (0–1 year old) increased significantly in this period—from 49 (IR 4.33) before Chernobyl to 67 cases (IR 6.36) in 1986–1992 (RR 1.47; p=0.04). Older age groups did not show any increase in ChAL rates.

Following 7-years period (1993–1999) revealed the statistically significant decrease of incidence of infant leukaemia: from 49 (IR 4.33) before Chernobyl to 16 cases (IR 2.29) in 1993–1999 years (RR 0.53; p=0.024).

During the following period (2000–2006) we found a further decrease of the incidence of infant leukaemia with only 3 cases (IR 0.47) in 7 years. It is highly significant when compared with 49 cases (IR 4.33) before Chernobyl (p =0.0 000 053, RR =0.11).

The carcinogenic effects of low dose radiation exposure may be restricted to children exposed in utero or in early infancy (0–12 months) during the first years after explosion. Following after dramatic decrease of IRs of infant leukaemia might be explained by the developing of adaptive response to chronic low dose ionising radiation exposure.