Classifying evidence of causality between a risk factor and its potential health effect is challenging, in particular in an already emotional situation. Even the assessment of health risks by designated bodies may still depend on their composition of individuals with their background, bias, and, in worst case, their interests. This may explain opposing conclusions from the same pool of data which, consequently, may undermine credibility if not communicated properly. To overcome existing weakness in classifying and communicating evidence of health risks such as from electromagnetic fields, a new rule-based approach is presented. Developed by the German Commission on Radiological Protection (SSK), it discloses step-by-step the criteria for weighing scientific data and pools partial evidences of different scientific approaches to conclude on the overall evidence of causality between risk factor and effects. The validity of the approach is demonstrated by analyzing evidence of carcinogenicity of ionizing radiation, mobile phone use, and nocturnal exposure to visible light.