It has been 25 years since the worst nuclear power accident in history at the Chernobyl plant in Ukraine, and we still aren’t certain what health damage it may ultimately cause. That gap needs to be filled by a vigorous research program — both to improve readiness to cope with another bad nuclear accident and to enhance understanding of the long-term effects of low doses of radiation.

Although Chernobyl is rightly synonymous with disaster, international health authorities have found the damage from fallout downwind to be far less than originally feared. The latest evaluation — a United Nations committee in 2008 — concludes that emergency workers who struggled to bring the plant under control suffered great harm but the wider public was barely affected.

In the three countries hit with the most fallout — Belarus, Ukraine and parts of the Russian Federation — the committee found that the only significant harm was several thousand cases of highly curable thyroid cancer among people who were exposed as children, mostly by drinking contaminated milk. Only a handful have died.

Critics have long contended that such estimates downplayed the dangers. Now a panel of experts assembled at the request of the European Commission is also calling for a wider look. It cited scattered reports, many appearing in leading scientific journals, suggesting that Chernobyl’s radiation might be increasing the risk of breast cancer, various other cancers, and immunological abnormalities, among other effects.