Is hand-to-mouth contact the main pathway of children's soil and dust intake?

Children (n = 240) between the ages of 2 and 17 years were randomly selected from three cities in China. The total amount of soil and dust (SD) on their hands was measured and ranged from 3.50-187.39 mg (median = 19.49 mg). We screened for seven elements (Ce, V, Y, Al, Ba, Sc, and Mn), and Ce levels were used to calculate hand SD by variability and soil elements. The main factors affecting SD amount were location and age group, as identified using a conditional inference tree. Hand SD and the hand SD intake rate were highest in Gansu Province, followed by Guangdong and Hubei provinces, respectively. Hand SD and the hand SD intake rate were highest among children in primary school, followed by kindergarten and secondary school, respectively. The hand SD intake rate of the three typical areas was 11.9 mg/d, which was about 26.6% of the children's soil intake rate (44.8 mg/d), indicating that hand-to-mouth contact is not the main route for children's soil intake in the three areas of China.