Environmental Fate and Toxicology of Chlorothalonil

The fungicide chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile; CAS 1897-45-6; Fig. 1) was introduced in 1965 by Diamond Shamrock Corp. and was first registered in 1966 for use on turfgrass within the United States. An additional registration was granted 4 years later for use on potatoes, marking it the first approved food crop for application (US EPA 1999). It is formulated as concentrates, powders, and granules, among other registered formulations. Some of the prominent products containing chlorothalonil as the active ingredient include Bravo®, Daconil® and Sweep® (US EPA 1999). These or other chlorothalonil formulations have been applied to crops such as celery, beans, peanuts, and peaches, among others. Within the USA, approximately 34% of the total chlorothalonil applied is used on peanuts, 12% on potatoes and 10% on golf courses (US EPA 1999).