Aims:Type 1 Diabetes is an autoimmune disease affecting ~400,000 people across the UK. Environmental factors likely trigger the disease processin genetically susceptible individuals. We assessed the associations between a wide range of environmental factors and childhood type 1 diabetesincidence in England, using an agnostic, ecological Environment Wide Association Study (EnWAS) approach, to generate hypotheses about environmental triggers. Methods:We undertook analyses at the Local Authority District (LAD) level using a national Hospital Episode Statistics (HES) based incident type 1 diabetesdataset, comprising 13,948 cases aged 0-9 years over the period April 2000-March 2011. We compiled LAD-level estimates for a range of potential demographic and environmental risk factors including meteorological, land use and environmental pollution variables. The associations between type 1 diabetesincidence and risk factors were assessed via Poisson regression, disease mapping and ecological regression. 8Results:Case counts by LAD varied from 1 to 236(median 33;inter quartile range: 24-46). Overall type 1 diabetesincidence was 21.2 (95% CI 20.9-21.6) per 100,000individuals. The EnWASand disease mapping indicated that 15out of 53 demographic and environmental risk factors were significantly associated with diabetes incidence after adjusting for multiple testing.These included air pollutants (particulate matter, nitrogen dioxide, nitrogen oxides, carbon monoxide, all inversely associated), as well as lead in soil, radon, outdoor light at night, overcrowding, population density and ethnicity. Disease mapping revealed spatial heterogeneity in type 1 diabetesrisk. The ecological regression found anassociationbetween type 1 diabetesand thelivingenvironmentdomainof the Index of Multiple Deprivation(RR 0.995 (95%Credible Interval (CrI)0.991-0.998))and radon potential class (RR 1.044 95%CrI 1.015-1.074). Conclusions:Our analysis identifiesa range of demographic and environmental factors associated with type 1 diabetesin children in England.