In 1966, four hydrogen bombs were dropped near the Spanish city of Palomares, when a U.S. B-52 bomber crashed into another plane in mid-air. The non-nuclear explosives of two of the bombs detonated, spreading radioactive plutonium across a vast area. Forty years later, contaminated soil still continues to be found near the crash site.

History

On January 17, 1966, a U.S. B-52 bomber collided with a tanker plane in mid-air during refueling. The crash occurred about 9,500 m above the small Spanish fishing community of Palomares. At that time, the B-52 bomber was carrying four Mark 28 thermonuclear bombs, which plummeted to the ground together with the plane. The parachutes on two bombs failed to deploy. They went down on the eastern and western edges of the town, causing the chemical explosives to detonate upon impact. By a stroke of luck, the nuclear warheads did not detonate, but the explosion spread radioactive material, including uranium and plutonium, across the fields of Palomares. Clouds of plutonium dust were blown over the fields, contaminating large stretches of land. The third hydrogen bomb was recovered relatively intact, while the fourth bomb was only recovered from the ocean floor 80 days later. After this accident, flights with nuclear weapons were prohibited over Spanish territory. Regular patrol flights with nuclear warheads were gradually reduced, and after a second crash involving a nuclear armed plane in Thule, Greenland in 1968, this dangerous practice was finally abandoned.

Health and environmental effects

As toxic heavy metals and radioactive alpha-emitters, plutonium and uranium and their short-lived decay products cause severe health problems when ingested, inhaled, or absorbed through cuts in the skin. Scientists from Princeton University developed a model to calculate the expected health effects of the accident. As most of the plutonium was turned into an aerosol by the explosions, it could be transported over large distances by the wind. It is important to note that the ensuing dispersion effect did not decrease the total mortality for the population. While each individual’s risk is reduced through dispersion, the total number of cancer deaths remains approximately the same, since more people come in contact with the dangerous substance and their individual risks add up. The scientists calculated that about 2.85 cancer deaths would result from each mg of inhaled plutonium. The National Academy of Sciences Advisory Committee on the Biological Effects of Ionizing Radiation issued an even higher estimate: 6 to 12 cancer deaths per mg.

In the aftermath of the accident, the U.S. undertook a massive clean-up operation for around $80 million and shipped about 10,000 cubic meters of contaminated soil to a U.S. nuclear waste facility. 1,600 people were involved in this mission, 20 % of whom were later found to be contaminated with plutonium. The rushed clean-up effort further aggravated the situation by burning contaminated tomato, bean and cabbage crops, spreading radioactive contamination even further. It was never publicly admitted how much plutonium was left in the ground after the end of clean-up operations.

Vast quantities of plutonium have also contaminated the western Mediterranean, where scientists found increased concentrations of radioactive plankton as late as 2003. In 2006, high levels of radiation were detected in snails from this region. U.S. and Spanish research institutions have been conducting annual health check-ups of the 1,500 residents of Palomares. Financed by the U.S. government, these check-ups have found no medical consequences related to the accident. Critics argue, however, that no independent epidemiological studies have been perfomed.

Outlook

With a half-life of 24,000 years, plutonium remains in the environment for thousands of generations to come. Despite the clean-up efforts, radioactive material continues to be found near the crash site, including two trenches filled with radioactively contaminated soil, which were discovered in 2008. The main concern is that plutonium decays into other radioactive components like americium, a gamma-emitter, which can harm people over large distances. In 2010, the U.S. government ceased the annual payments to Spain. It is unclear whether the annual health check-ups will continue. Additional long term environmental effects may yet be identified.

In October 2015, Spain and the United States agreed that about 50,000 cubic meters of contaminated earth removed during the cleaning work should be shipped to and disposed of in the United States. In November 2018, the daily newspaper El Pais reported, however, that the Trump administration did not feel bound by the deal made under the Obama administration.

The true extent of the effects caused by the accident will most likely never be known. The people of Palomares are also Hibakusha – they are also living with the radioactive legacy of nuclear weapons.

References

• “Palomares Nuclear Weapons Accident – Revised Dose Evaluation Report.” Office of the Surgeon General USAF, April 2001
• Place et al. “Palomares Summary Report.” Field Command, Defense Nuclear Agency, January 15, 1975. www.dod.mil/pubs/foi/International_security_affairs/spain/844.pdf
• Mian et al. “Plutonium dispersal and health hazards from nuclear weapon accidents.” Current Science, Vol 80, No 10, May 25, 2001. www.iisc.ernet.in/currsci/may252001/1275.pdf
• Minder R. “Spain and U.S. accord on atomic cleanup.” NY Times. April 5, 2011. www.nytimes.com/2011/04/06/world/europe/06iht-spain06.html?pagewanted=all&_r=0
• Sanchez-Cabeza et al. “Concentrations of plutonium and americium in plankton from the western Mediterranean Sea.” Science of the Total Environment. 2003; 311(1-3): 233-245. www.ncbi.nlm.nih.gov/pubmed/12826395
• Aragón et al. “Study on the contamination by transuranides of pulmonata gastropod collected in Palomares.” Czech. Journal of Physics. 2006; 56(1). www.ingentaconnect.com/content/klu/cjop/2006/00000056/a00100s4/00000497
• Schlosser E: “Command and Control,” 2013
• “Palomares nuclear crash: US agrees Spanish coast clean-up”; www.bbc.com/news/world-europe-34569614
• Miguel González: “Trump no quiere llevarse la tierra radiactiva de Palomares.” In: El País. November 7, 2018, elpais.com/politica/2018/11/07/actualidad/1541616530_406692.html