ABSTRACT Lung cancer is the leading cause of cancer mortality, yet the disease remains highly preventable by eliminating exposure to tobacco smoke and radon. As rural communities lead the nation in lung cancer incidence and mortality, there is urgency to lower radon exposure in rural areas. Radon on the RADAR (Residents Acting to Detect and Alleviate Radon) 1.0 uncovered disparities in access to and affordability of radon mitigation, and low testing and mitigation rates despite access to radon detectors in public libraries, and geologic impacts on home radon exposure that warrant further investigation to reduce exposure to the deadly gas in rural areas. RADAR 2.0 will strengthen partnerships with citizen scientists, public libraries, and local radon coalitions to increase access to affordable radon mitigation, develop effective radon risk communication messaging, automate report-back using a novel website platform, and translate geologic and residential data to builders and policymakers to educate and inform radon resistant new construction policy. Aim 1 will evaluate the reach, effectiveness, adoption, implementation, and maintenance of a radon measurement and mitigation curriculum developed and implemented by Kentucky Community and Technical College System Construction Technology faculty and students. Aim 2 will develop and test the effects of radon risk messages with rural homeowners who have never tested for radon and those with high radon who have not mitigated. Aim 3 will design and test the effects of My Radon Report, a novel automated, personalized radon report-back tool, on intention to test and mitigate for radon, environmental health literacy, and efficacy for radon testing and mitigation among rural homeowners, and track usage and website metrics for scalability. Aim 4 will examine the association among geologic, soil, and residential characteristics and indoor radon values to guide education and better inform radon resistant new construction policy. RADAR 2.0 is innovative in several ways: 1) partnering with the community college system to build capacity for certified radon mitigators in rural Kentucky by offering and evaluating a radon measurement and mitigation certification and training curriculum; 2) evaluating radon testing and mitigation messages with key target groups; 3) developing and testing a user-initiated, personalized report-back website platform to accompany the radon detector library loan program; and 4) performing in-depth analyses of soil processes and characteristics that relate to elevated indoor radon levels, closing a critical gap in our understanding of the role of geologic factors on radon risk potential. RADAR 2.0 will address gaps in radon risk reduction in rural communities by designing and evaluating a novel approach to increasing access to certified radon professionals, expanding our understanding of radon risk messaging and report-back, and conducting in-depth geo-assessment to guide education and infor...