Objective To survey and analyze the environmental gamma radiation level and the status of birth defects among perinatal infants in Huizhou within 50 km away from the Guangdong Daya Bay Nuclear Power Station(GNPS).

Methods Unit 1 of GNPS was taken as the center of the circle and divided into four circular investigation areas with radii of 0–20 km, 20–30 km, 30–40 km, and 40 –50 km(each interval excluded the lower boundary). Data on the accumulated doses of environmental gamma radiation and the status of birth defects among perinatal infants in each investigation area from 2015 to 2017 were collected, and the birth defect rate of perinatal infants and the top five birth defects in Huizhou among different years and within different ranges around GNPS were analyzed. Analysis of variance was used to compare the differences in accumulated dose of the environmental gamma radiation among various distances, and Chi-square test was used to compare the differences in birth defect rate among various years and various distances.

Results The annual accumulated dose of environmental gamma radiation was(2.00±0.20) mSv from 2015 to 2017 and did not vary among different investigation areas. Out of the 58,999 perinatal infants, 691 were born with birth defects. The total incidence of birth defects was 11712 per million. The incidence of birth defects varied from year to year. Specifically, the lowest rate was found in 2015(7486 per million), whereas the highest rate was observed in 2017(13992 per million). Significant difference in birth defect rate was observed among different years(χ²=35.807, P=0.000). The incidence of birth defects was different among various investigation areas within the distance from the nuclear power plant. In particular, the highest birth defect rate was found at 40 –50 km(15881 per million), whereas the lowest birth defect rate was observed at 30 –40 km(8056 per million). Significant differences in birth defect rate was also observed among the investigation areas(χ²=63.622, P=0.000). The top five detected birth defects were polydactyly(114 cases), congenital heart defects(102 cases), glucose-6-phosphate dehydrogenase deficiency(75 cases), talipes equinovarus(31 cases), and hydrops fetalis syndrome(23 cases).

Conclusions Within 50 km around GNPS, the environmental gamma radiation level and the birth defect rate were stable and consistent with the average level in Guangdong. Moreover, the changes in birth defect rate and sequence were spontaneous.