“…A cross-sectional human biomonitoring survey was performed on a sample of healthy schoolchildren, aged between 5 and 11 years, living in Central Italy and attending some primary school districts. Details on the selected areas, the enrolment of children, and methods for gathering information on participants and for collecting urine samples were previously reported [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. Briefly, information on children and their parents (gender, birth date, height, weight, exposure to ETS, parents’ educational level, and the activities taken place during the sampling day) was collected through an ad hoc questionnaire filled in by parents together with the informed consent.…”