PURPOSE: To safely and efficiently decompose a relatively large amount of polyhalogenated aliphatic hydrocarbon at low temp. by adding a chain transfer agent low in a chain transfer constant value to a superoxide generating system.

CONSTITUTION: Polyhalogenated aliphatic hydrocarbon is decomposed at low temp. while a superoxide ion is generated in a polyhalogenated aliphatic hydrocarbon-containing solution to which a chain transfer agent low in a chain transfer constant is added. As a method generating superoxide, from an aspect generating strong superoxide, a method generating superoxide from hydrogen peroxide and periodate is most pref. Since superoxide forming reaction due to hydrogen peroxide and periodate is performed in an aqueous system, a hydrophilic solvent is used as a reaction medium. As the hydrophilic solvent, methanol is pref. because of a high decomposition rate. As the chain transfer agent, pyridine is pref. because of the highest decomposition rate.