Unexploded WW I and WW II Bombs Growing ‘Much More Sensitive’

Leftover bombs hidden in the ground decades after World Wars I and II might be getting more explosive with time, research has found.

Because of their unique chemical makeup, bombs and other explosives remaining in the ground after the wars are becoming more volatile and therefore have an increased chance of exploding if disturbed, a new paper in the online journal Royal Society Open Science says.

The discovery came after researchers from the University of Stavanger’s Department of Safety, Economics and Planning in Norway and the Norwegian Defense Research Establishment tested several bombs. They found that the “high explosives in the examined specimens were generally much more sensitive to impact than previously assumed,” according to the paper.

Huge numbers of explosives were fired by both sides during both world wars, many of which never exploded and were embedded in the ground for over a century. Many of the explosives used in these wars contained chemicals known as amatols, which were mixtures of ammonium nitrate and TNT.

These amatols were used increasingly in World War I because of the limited supply of TNT at the time and because amatols were easy to make and ammonium nitrate was readily available and much cheaper than TNT. They continued to be used in World War II until TNT was produced in much greater quantities toward the end of that conflict.

“Although they are now mostly obsolescent, Amatols were universally used for several decades by all nations in all types of ammunition as a substitute for TNT,” the paper’s authors wrote. “Consequently, the only time Amatols are normally encountered in explosive ordnance today is in legacy munitions, at ammunition dumping sites and in explosive remnants of war.”

However, the researchers found that these amatols become more and more volatile with time because they slowly react with substances in the soil. This means that if they are disturbed, these old explosives are more likely to detonate and could endanger people.

“As the explosives deteriorate over time, often resulting from inferior storage conditions or the presence of undesired factors such as moisture and certain metals, the munitions may become increasingly sensitive to external stimuli and susceptible to accidental detonation,” the authors wrote.

They discovered this by dropping heavy materials onto small samples of amatol collected from across Europe. They found that amatol bombs are more likely to explode from disturbances over time.

This could pose a major risk for people who stumble across unexploded bombs when building or digging, the authors said. Explosives are found in backyards on occasion, such as earlier this year, when a 1,100-pound bomb was discovered in a yard in Plymouth, England. It was safely removed and detonated at sea. But in 2008 17 people were injured after a bomb was detonated by an excavator working in Hattingen, Germany.

In addition, Amatol slowly leaches into the soil, poisoning the groundwater.

“The munitions are continuously deteriorating, resulting in the release of hazardous materials into the environment, potentially posing environmental and societal risks,” the authors wrote.

The authors said these findings are crucial to consider when construction is done in places once involved in battles, as this could lead to explosions and risks to human life.

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