Urinary perchlorate level in primary school students and its correlation with traffic pollutants exposure in Changping district, Beijing, China

Objective To investigate the level of urinary perchlorate in primary school students and its correlation with traffic pollutants exposure in Beijing, so as to provide an important basis for larger regional exposure studies in children in the future.

Methods A fixed cohort study was performed to select 20 students from each of two primary schools, where the schools located < 150 m and ≥150 m away from the main traffic road, respectively, from May to October 2018.Urine samples of the students were collected 3 times a day (8:00, 11:00, and 16:00)for 7 consecutive days (Monday to Sunday) to determine the level of perchlorate in urine. Besides, the pupils' basic information and daily activities were collected through questionnaires.

Results The detection rate of perchlorate in 741 urine samples was 88.53% (LOD: 1.00 μg/L). The median level (P₂₅, P₇₅) and geometric mean level of urinary perchlorate in primary school students were 8.45(4.86, 14.39)μg/g creatinine and 7.22 μg/g creatinine, respectively. Perchlorate levels were 10.71(6.17, 16.34)μg/g creatinine for students whose school is less than 150 m from main traffic roads and 6.95(3.63, 11.18)μg/g creatinine for students whose school is more than or equal to 150 m from main traffic roads. The distance between the schools and the main traffic roads was significantly correlated with the urinary perchlorate level in primary school students (P=0.002).

Conclusion There is a clear perchlorate exposure in primary school students in Beijing and the level of perchlorate in urine is high. Traffic pollutants exposure may be correlated with the level of urinary perchlorate in children.