“…Observational studies that relate PC and air pollution are scarce (Garcia-Perez et al, 2016a; Reynolds et al, 2003), and in most cases focus on traffic density and the proximity of high-capacity roads; no consistent results on a global scale have been reached to date. Regarding industrial pollution, several works recently published in Spain argue for the relationship between exposure to industrial pollution and leukaemia, neuroblastoma, kidney and bone tumours in children aged 0–14 (Garcia-Perez et al, 2015b, 2016a, 2016b; García-Pérez et al, 2017). The low incidence of PC, the high degree of uncertainty associated with the variables under consideration, and the formation of micro-clusters emphasise the need to carry out spatial epidemiological studies, which can then be used to analyse the incidence of cancer in small urban units (Ortega-García et al, 2016).…”