How many atoms belong to the molecule that element is hydrogen and labeled with carcinogenic compound?
label = '+' mean molecules are carcinogenic; hydrogen refers to element = h'
SELECT COUNT(T1.atom_id) AS atomnums_h FROM atom AS T1 INNER JOIN molecule AS T2 ON T1.molecule_id = T2.molecule_id WHERE T2.label = '+' AND T1.element = 'h'