A reliable and highly scalable Internet of Things (IoT) end-to-end data infrastructure has been developed for environmental radiation monitoring at CERN based on a Low-Power Wide-Area Network (LPWAN). The proposed system,called W-MON (Waste radiation MONitoring), consists of an interconnected network of thousands of highly sensitive and ultra-low power gamma radiation sensors acting as LoRa transceivers. The aim of the system is to improve and automatize the radiological controls of conventional waste containers. The end-devices measure the radiation levels in the waste containers on a continuous basis and send the data periodically to the LoRaWAN network server. The network has been deployed in an outdoor environment covering hundreds of hectares. A set of web-based user applications for real-time monitoring, data visualization and status control of the devices have been designed based on open source tools. The data pipeline infrastructure has been designed to allow an easy integration into REMUS, the overall CERN Radiation and Environment Monitoring Unified Supervision service.