Objective  To understand the selenium levels in the internal and external environments in endemic and non-endemic areas of Keshan disease in Zhangjiakou, Hebei province, and provide the basis for the identification of the prevention and control priorities and development of sustainable prevention and control measures to eliminate Keshan disease.

  Methods  According to the National Survey Program on Selenium Levels and Related Factors in Internal and External Environments in endemic and non-endemic areas of Keshan Disease, the Keshan Disease Selenium Survey was carried out in September 2018 in 3 counties (district) where Keshan disease has been controlled and 4 counties (district) where Keshan disease has been eliminated and 2 counties (district) without Keshan disease in Zhangjiakou. Ten families, including 3, 4 and 3 families with poor, moderate and good living conditions, in one village of one township of these areas were surveyed. A total of 270 hair samples were collected from children, childbearing aged women and adult males and a total of 270 samples of 3 kinds of staple foods were collected. Meanwhile, a total of 90 soil samples were collected from the survey sites. The selenium content was detected by hydride atomic fluorescence spectrometry, and the t-test and variance analysis were performed by using software EpiData 3.5.1 and SPSS 22.0.

  Results  The soil selenium content in Keshan disease endemic area was higher than that in non-endemic area, but the difference was not significant (P＞0.05). The average hair selenium content in residents in 9 counties of Zhangjiakou was (0.3507±0.1014) mg/kg, and the overall nutrient level of selenium was moderate. The selenium content in children in the disease endemic area was lower than that in those in non-disease endemic area, and there was no significant difference (P＞0.05), and the difference in hair selenium content between the adults in the disease endemic area and those in the non-disease endemic area had no significance. The food selenium content in the disease endemic area was lower than that in the non-disease endemic area, and there was no significant difference (P＞0.05). The differences in food selenium content among the different stable foods, including wheat flour, rice and broomcorn millet flour, in the families with different living conditions were not significant.

  Conclusion  The selenium level in the external environment in Keshan disease endemic area in Zhangjiakou were basically stable, while the selenium content in the internal environment in the Keshan disease endemic area significantly increased, which might be related to the improvement of living standard and the change of dietary structure, so continuous surveillance should be carried out to consolidate the achievement in the elimination of Keshan disease.