Chlorobenzilate

Chlorobenzilate was introduced in the 1950s as a selective acaricide for mite control on citrus trees — it was less acutely toxic to mammals than many organochlorine pesticides but effective against spider mites [1]. The Ciba-Geigy Corporation (now Syngenta) manufactured it under the trade name Acaraben. EPA initiated a Special Review in the 1980s after animal studies showed liver tumors in mice and rats [2]. Ciba-Geigy voluntarily cancelled U.S. registrations in 1979, though EPA continued monitoring its residues in food and environmental matrices. It is no longer registered for use in the United States but may persist in soils of former citrus groves [1]. International use continues in some countries. It is structurally related to DDT and undergoes similar environmental persistence [2].

Dietary residues on imported citrus from countries where it remains registered represent a potential food pathway [1]. Former agricultural workers in U.S. citrus groves during peak usage in the 1960s-70s are the relevant occupational exposure cohort [2]. Soil persistence in former citrus orchard sites may create exposure through soil contact and groundwater contamination [1].

Chlorobenzilate is metabolized to p-chlorobenzophenone, an intermediate that forms reactive species capable of binding to proteins and DNA [1]. Chronic feeding studies showed significant increases in liver tumors (hepatocellular carcinomas) in mice and rats — EPA classifies it as a probable (B2) human carcinogen [2]. Like other organochlorines, it shows some estrogenic activity and may act as an endocrine disruptor [1].

Former citrus farm workers with significant occupational exposure [1]. Consumers of imported citrus from countries with ongoing chlorobenzilate use [2].

1. Wash and peel citrus before eating, particularly imported citrus [1]. 2. Check import residue data from USDA Pesticide Data Program for citrus residues [2]. 3. Choose domestic or certified pesticide-free citrus where practical [1].