Evidence of radioactive contamination of the Abai Region, Kazakhstan, from the Chinese nuclear testing program at Lop Nor

Between 1949 and 1990, tests of nuclear weapons and other explosive devices were performed by the Soviet Union at the Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan, resulting in radioactive contamination of surrounding settlements. This contamination and the associated impact on the health of the local population are a subject of ongoing radioecological, radiobiological, dosimetric, and epidemiological research. Less in known about potential additional radioactive contamination of settlements SE of SNTS, close to the border with China. This region may have been contaminated by fallout from weapons tests performed by China at Lop Nor between 1964 and 1981, during which time all tests at SNTS were underground. Here, we review available evidence of this contamination, including the results of sampling campaigns performed both at the time of the Chinese tests and in recent years, and electron paramagnetic resonance (EPR) of tooth enamel.

Soil, vegetation, and milk sampling performed in the weeks following the Lop Nor tests revealed the presence of short-lived fission products, including I-131, I-133, Sr-89, Zr-95 and Ba-140 well in excess of background levels. Contamination was greatest following the thermonuclear tests on 17/06/1967 and 27/06/1973. Contemporary soil sampling in Kazakhstan and NW China suggests radioactivity levels have returned to background levels, though with ratios of Pu-240 / Pu-239, and Pu-240+239 / Cs-137 that differ from global fallout levels. Efforts to reconstruct exposure levels are ongoing, including collection of fortuitous dosimeters (e.g. bricks from settlement buildings) and teeth of exposed residents.