The World Health Organization is preparing for the potential that a nuclear catastrophe might occur as a result of the attacks on Iranian nuclear facilities conducted by Israel and the United States since February 28; such an event could result from either radioactive contamination released from a damaged nuclear facility, or the direct use of a nuclear weapon. Thankfully, no radioactive contamination has been reported from the stricken sites, but WHO officials remain “vigilant” for any type of nuclear threat that the Middle East might face.

While WHO staff are typically prepared for a nuclear incident in a “broader sense,” the organization is heightening its preparedness for a potential event in light of Israel and U.S. military strikes focusing on Iran’s nuclear infrastructure, including refreshing staff on response procedures.

If a release of radioactive material were to occur, it would expose people in the surrounding region to “significant immediate trauma to their lungs and skin, and heighten the danger of developing cancer and mental health problems,” according to WHO regional director for the eastern Mediterranean Hanan Balkhy.

Despite having reportedly “obliterated” Iran’s nuclear capabilities in June of last year, U.S. President Donald Trump has vowed to “eliminate the imminent nuclear threat posed by the Iranian regime,” even though no evidence that Iran was developing a nuclear weapon has been presented. Since the attacks were launched on February 28, the Atomic Energy Organization of Iran reported that its Fordow, Isfahan and Natanz facilities have been targeted.

“The worst-case scenario is a nuclear incident, and that’s something that worries us the most,” Balkhy stated. “As much as we prepare, there’s nothing that can prevent the harm that will come… the region’s way—and globally if this eventually happens—and the consequences are going to last for decades.”

Although the 1986 explosion of Chernobyl’s reactor number 4 resulted in the deaths of approximately 30 individuals within the first few months, the succeeding years saw a surge in the rate of thyroid cancers in the population living downwind from the site of the disaster; economically, the expense of containment and decontamination efforts—estimated to be over $6 billion in today’s dollars—essentially bankrupted the Soviet Union, hastening the former superpower’s collapse.

And despite having a combined yield of only 36 kilotons, the two nuclear weapons detonated by the U.S. over the Japanese cities of Hiroshima and Nagasaki in 1945 killed an estimated 200,000 people.

“I think those who read the history of previous incidents, whether intentional or accidental, are very aware of what we’re talking about,” Balkhy said.

Even if strikes against Iran’s nuclear facilities don’t result in the release of radioactive material, there is still the concern that a nuclear-capable player may detonate a nuclear warhead: Trump’s AI adviser David Sacks has stated that he’s worried about “Israel escalating the war by contemplating using a nuclear weapon,” a concern subsequently dismissed by the President.