Supplementary Material for: Environmental Factors and the Risk of Brain Tumours in Young People: A Systematic Review

Background: Brain tumours (BT) are one of the most frequent tumour types in young people, although little is known about their risk factors. Objective: The objective of the current work was to review and summarize the scientific literature concerning exposure to environmental factors and BT risk in young people (<25 years old). Methods: PUBMED, Embase, Cochrane Library, Scopus, IME-Biomedina (bibliographic database of Consejo Superior de Investigaciones Científicas) and Web of science databases were searched. A score to assess the quality of the methodological information was created. Results: Some possible associations between BT risk in young people were reported for cadmium, consumption of well water, presence of nitrate or nitrate-nitrogen in tap water, mother’s passive smoking, air pollution, parental handling of pesticides at home and/or professional pesticide treatment within houses, living on a farm and/or with farm animals, some parental occupations and high amount of meat consumption. Conclusions: Although many of the studies reviewed suggest associations between the environmental exposures and BT in children and young adults, at present no reliable conclusion can be drawn as most results are based on small number of cases and exposure assessment is limited. Large-scale studies with better exposure assessment are needed to shed light on these possible associations, especially on exposure to heavy metals, tab water consumption, pesticides and parental smoking.