In early September 1949, Jack Healy, an employee for the Health Instrument Divisions (HIDs) of the Hanford, Washington, nuclear facility was monitoring air filters on the nearby, picturesque Rattlesnake Mountain. These filters were set up at a high elevation to study how radioactive contamination varied with altitude, which fitted with the HIDs overall responsibility for radiological safety.

However, when he checked these filters, Healy discovered something unexpected. He observed anomalous radioactive readings that, after noting their rapid decay, suggested some sort of recent nuclear test. Little did Healy know, he had just detected the radioactive debris from the first Soviet nuclear test that took place at the Semipalatinsk Test Site in Kazakhstan, on August 29, 1949.

For some time, the US Air Force had suspected that nuclear tests could be detected through traces of radioactive materials in the air, but they had not had a chance to prove it. As such, Healy’s discovery offered them a chance to investigate further.

Soon after news of his assessment reached the capital, the Air Force sent specialists to examine Healy’s samples and data. Then, on September 23, 1949, President Harry Truman announced to the world that the Soviet Union had indeed detonated their first atomic bomb and had the ability to make more. At the same time, the announcement confirmed that nuclear tests could be detected from the other side of the planet.

What followed is one of the darkest, most shortsighted, and lesser-discussed stories from the early nuclear age, one that ultimately contributed to the distrust many American citizens feel towards the government and some scientific institutes today.

Detection at any cost

With the realization that the Soviet Union knew how to make nuclear weapons, the US faced uncertainties surrounding a new nuclear threat. How many weapons did the Soviets have? How strong were they? How much fissile material – the core of a nuclear weapon – did they have and how much were they capable of producing?

One way to answer these questions was with the detection of radiation in the atmosphere. When nuclear weapons are tested, especially above ground, they send radioactive materials high into the atmosphere. Over time, larger particles will fall to the ground, while lighter ones, as well as gases, continue to travel into the upper atmosphere. This is essentially nuclear fallout, which consists of hundreds of different radionuclides. As particles of fallout are spread across the world by winds and weather patterns, their traces can then be identified by sensitive instruments that are located great distances away from the original detonation.  

The detection of radionuclides in the atmosphere is an important feature of the world’s current systems designed to confirm that a nuclear weapon has been tested somewhere on the planet, but in 1949, the idea was still largely untested. To make it a reliable and trusted way to determine the nature of a secret nuclear test, the US Air Force needed to experiment with ways to detect known radioactive gases.

As such, they turned their attention to the nuclear facility at Hanford, which had been providing plutonium – one kind of fissile material used in nuclear weapons – to the Manhattan Project since 1942. The site was located in the beautiful landscape surrounding the Columbia River in southeast Washington state, which supplied it with the freshwater it needed to cool its nuclear reactors. The nearby towns of Richland, Kennewick, and Pasco then became successful boom towns, as their economies depended on the secretive activities taking place at Hanford.

At first, the Air Force attempted to sample radionuclides from Hanford and at Oak Ridge, Tennessee, by flying planes over them, but they could only detect radionuclides at close distances. This, obviously, was not useful for trying to monitor nuclear activities on the other side of the planet. To overcome this, representatives from the US Air Force, the Atomic Energy Commission (AEC), and others met at Hanford on October 25, 1949, and planned to release large quantities of radioactive material from the site so that it could be used in detection tests.

The experiment took place on December 3, 1949. The staff at Hanford began to process fission products from the reactors that had only been cooling for 16 days, rather than the typical 90 to 125 days. This meant the fuel contained much higher quantities of radioactive iodine-131 and xenon-133 than normal, as these isotopes would usually decay during longer cooling periods.

This was intended to replicate the amounts of radionuclides that were detected in the Soviet’s earlier test. The highly radioactive fuel was referred to as “green” in HID reports, which gave the whole experiment the name “Green Run”.

Green Run: A massive mistake

To say the Green Run is an example of how clever thinking can go wrong is a significant understatement. The researchers involved had initially predicted that around 4,000 curies of radioactive iodine-131 would be released as part of the test. In reality, it released roughly 8,000 curies of the isotope into the atmosphere. To be sure, this level of release only equated to around 1 percent of the total radioiodine released from the site in the years between 1945 and 1947, but it nevertheless represented the largest amount released in a single instance.

The test’s success also relied on very specific and stable weather conditions that would allow the released radionuclides to be measured effectively and to limit local contamination. Obviously, the weather had other ideas in mind. Rather than being held aloft in the low altitude by a layer of cold air on the ground, as was expected, the temperatures were higher, which allowed the emissions to pool in the local area for several days before they were blown towards the north-northeast by a storm front, ultimately dispersing them across Washington state.

Contrary to the team’s plans, the released radionuclides ended up contaminating the ground, vegetation, and the local water. HIDs staff who carried out the monitoring of the release detected at least 400 times the tolerable amount of iodine-131 that would otherwise risk injury to livestock. Thankfully, this contamination was only temporary, but it was still a sizable problem, especially as this level also represented a threat to human health.   

A toxic legacy

Given how serious this incident was, you would imagine extensive efforts were taken to evacuate the local communities living near Hanford. However, this was far from the case. In fact, news of the radiation release was kept secret for over 40 years. What’s even more disturbing is that this was not an isolated incident, although it is one of the better-known examples.

In 1994, the Department of Energy formed the Advisory Committee on Human Radiation Experiments (ACHRE) to investigate and report on the use of humans as experiment subjects in federally funded research using ionizing radiation. The ACHRE report revealed the full extent of the Green Run experiment, as well as many other secret tests carried out across the US during the Cold War. In fact, a year later, ACHRE determined that in the years between 1944 and 1970, there were several hundred secret, intentional releases of radioactive materials carried out at sites including the Army’s Dugway Proving Ground in Utah, Bayo Canon, New Mexico, AEC sites in Nevada and Idaho, and the Alaskan wilderness.

Those exposed to this radiation, as well as that from other releases, are known as “Downwinders” and represent an often overlooked and ultimately unwitting group of human test subjects. But did their exposure to radiation have any significant impacts on their health? This is uncertain but appears to be unlikely.

According to bioethicist and historian, Jonathan D. Moreno, who was also a senior staff member on the ACHRE investigation, the Green Run and its “cousins” probably had minimal health impacts as dose reconstruction studies of radiation releases have not shown cause for concern. It seems the Green Run may have increased the chances of fatal thyroid cancer by 0.04 percent, which would result in less than a single extra death.

Although the Green Run emissions were considerably high, they were nothing compared to the overall amount of radiation released by Hanford between 1944 and 1972. This has now been estimated to be around 739,000 curies of iodine-131.

But as Moreno stated in his influential book, Undue Risk, “numerical estimates are cold comfort to people who have lived and raised their children on contaminated soil.” Not only were Downwinders unable to give their consent for this experiment, they were not even aware it had happened. When information was eventually begrudgingly released, decades had passed and the shadow of the whole affair seriously undermined trust in the government.

“That the possible health effects from the Green Run and other intentional releases are so slight that they cannot be distinguished from other sources of disease is small comfort to ‘downwinders’ who were put at risk without their knowledge”, the ACHRE committee report stated.

“These costs include, first, the anxiety and sense of personal violation experienced by those who have discovered that they have intentionally and secretly been put at risk, however small, by a government they trusted. But they also include the consequences for that government, and its people, of the attendant distrust of government that has been created.”