danger of radioactive contamination from radon gas - concept with warning of radioactivity on road sign against a building

activity air alert area atom atomic attention building cancer caution concepts conservation contaminant contamination damage danger dangerous energy environment environmental estate gas hazard indoor intoxication ionizing issues land lot lung nuclear parcel plot poisonous polluted pollution precaution property quality radiation radioactive radioactivity radon real risk road safe safety security sign signal substance symbol symbols test uranium vacant warning water