“Nowhere is truly ‘safe’ from fallout and other consequences like contamination of food and water supplies and prolonged radiation exposure.” That is the assessment of John Erath, the Senior Policy Director for the Center for Arms Control and Non-Proliferation, and one that has particular poignancy as the globe watches on at the deepening confrontation between Israel and Iran. The possibility of nuclear war, once a byproduct of the Cold War, again took center stage, and with it a new public interest in learning which areas of the United States would do best or least badly if the worst were to occur.
The method employed by the widely circulated fallout maps, such as those reviewed here by Newsweek and originally created for Scientific American, is based on the latest advances in atmospheric dispersion modeling. Researchers, including Sébastien Philippe and colleagues from Princeton University, have employed high-resolution forecasts of weather and computer simulations to simulate the effects of an imaginary nuclear attack on the US missile silo complexes primarily in Colorado, Wyoming, Nebraska, Montana, and North Dakota. The simulations forecast the course radioactive fallout would follow in the 48 hours after an attack, considering prevailing winds, population centers, and physical geography of the continent.
The outcomes are terrifying. A simultaneous attack on these silo fields would destroy all life in the neighborhood and make fertile agricultural land polluted for years, with acute radiation exposure alone causing a toll of millions if people are taken to shelter for at least four days. Without shelter, the number of deaths can be doubled. The danger does not stop at the blast zone radioactive particles carried by shifting winds might also infect over 300 million people in North America with doses of deadly radiation. The granularity of the model indicates that although the Midwest would suffer the worst, no contiguous US region is entirely safe.
Ranking criteria for US states based on relative safety during these events are straightforward but scientifically valid. States most distant from likely targets and prevailing fallout paths Maine, New Hampshire, Vermont, and much of the Northeast are least impacted. These regions, along with portions of the Southeast and Great Lakes, are shielded by distance and wind patterns. Nebraska, Montana, and North Dakota, states nearest to the missile fields, are ground zero for destruction, with neighboring Minnesota, Iowa, and Kansas also receiving high levels of fallout. The ranking is actually not fixed it depends on day-to-day wind patterns, as the simulations show, and even the most secure locations have a nonzero chance of receiving lethal doses in worst-case wind patterns. The science behind such maps was based on decades of fallout research, but advances now make the models much more precise.
Old models were based on mean seasonal winds and a few large radionuclides. State-of-the-art techniques, such as the “cocktail DCC” method in Health Physics, account for the full spectrum of radionuclides and radioactive progeny, using sophisticated algorithms to calculate dose rates from inhalation, groundshine, and immersion. This allows for quick, accurate estimates of risk from exposure, even as fallout plumes shift hours and days. The designs can have weapon yield, detonation height, and even aerosol-bound to noble-gas-bound ratio of fallout, all modifying the way radiation gets dispersed and lingered in the environment. A sample nuclear weapon aimed at a missile silo might have an 800-kiloton yield many times the Hiroshima bomb.
Ground burst would vaporize everything around it, lofting radioactive debris by the ton into the stratosphere. When the mushroom cloud rises, it carries entrained bomb material and soil with it, a motley package of activation isotopes and fission products. Within minutes, this radioactive cloud can move hundreds of miles, guided by upper-atmospheric winds. Fallout begins to fall within hours, contaminating everything that comes into contact with it water systems, soil, crops, infrastructure. The implication for emergency preparedness is immense.
Compared to nuclear power plant accidents, which are typically localized and give some lead time, a nuclear detonation would carry its radiation cocktail with little or no notice. Modern-day dispersion models emphasize the utmost significance of sheltering in place for four days or longer, because initial fallout is most dangerous during the first 48 hours. Nevertheless, as the Scientific American report notes, even maximal sheltering has its limits in the case of giant, multi-megaton attacks. The geopolitics in which such anxieties have been revived are grim.
Israel’s recent airstrikes on Iranian military and nuclear sites a “roll back the Iranian threat to Israel’s survival,” in Prime Minister Netanyahu’s words have invited Iranian counterattacks and an intensification of regional tensions. The United States, in an effort to withdraw from direct involvement, is however firmly entrenched in the security of the region. The specter of escalation, with both Iran and Israel possessing nuclear capabilities, has reinvigorated public debate regarding the doctrine of nuclear deterrence and its dangers. US nuclear policy, as stated in the SWP Berlin report, is based on a “counterforce” strategy striking at adversary military targets rather than cities, hoping to reduce civilian casualties.
But, as experts concede, unchecked fallout and escalation effects mean that the distinction between military and civilian targets soon vanishes. The doctrine’s reliance on a wide range of nuclear alternatives, including low-yield ones, is designed to provide flexibility but always lurking is danger of accidental or sudden escalation. As John Erath told Newsweek, “Administrations of both parties have long understood nuclear weapons are only for defense and deterrence, not for starting a nuclear war. We would all do well to remember former President Ronald Reagan’s words, recently reaffirmed by President Joe Biden ‘A nuclear war cannot be won and must never be fought.'”
The policy and scientific consensus is clear although sections of certain US states may be less affected in a hypothetical nuclear conflict, no section of the country is safely protected from fallout, contamination, and social upheaval. The models and maps are not survival blueprints, but reminders of common dangers and the ongoing need to avoid nuclear war entirely.
