Database: toxicology
Question: What percentage of carcinogenic-type molecules does not contain fluorine?
SQL: SELECT CAST(COUNT(DISTINCT CASE WHEN T1.element <> 'f' THEN T2.molecule_id ELSE NULL END) AS REAL) * 100 / COUNT(DISTINCT T2.molecule_id) FROM atom AS T1 INNER JOIN molecule AS T2 ON T1.molecule_id = T2.molecule_id WHERE T2.label = '+'