Though every death is of concern, to date the World Health Organisation (WHO) believes Chernobyl has caused less than 50 deaths. Their estimate that 4,000 may die prematurely comes from a statistical disentangling of the effects of different sources of radiation, including natural ones, and then multiplying small percentages by large numbers.
Improvements in cancer therapy could still reduce the 4,000 number.
The causes and consequences arising from the explosion have, properly, been studied in great depth. As with any disaster the lessons learnt should ensure the risk of a repeat is infinitesimally small.
RICHARD BALMER (M), email@example.com