A dinitrile that is benzene-1,3-dicarbonitrile substituted by four chloro groups. A non-systemic fungicide first introduced in the 1960s, it is used to control a range of diseases in a wide variety of crops. California Office of Environmental Health Hazard Assessment (OEHHA): Chlorothalonil can cause cancer according to an independent committee of scientific and health experts.ChEBI: Chlorothalonil is a dinitrile that is benzene-1,3-dicarbonitrile substituted by four chloro groups. A non-systemic fungicide first introduced in the 1960s, it is used to control a range of diseases in a wide variety of crops. It has a role as an antifungal agrochemical. It is a dinitrile, a tetrachlorobenzene and an aromatic fungicide. It is functionally related to an isophthalonitrile.