Lactofen

Lactofen was registered in the 1980s as a protox (protoporphyrinogen oxidase, PPO) inhibitor herbicide — a mechanism distinct from glyphosate and the phenoxy herbicides, acting on porphyrin biosynthesis in plants [1]. It is applied post-emergently to soybeans, dried beans, and peanuts to control broadleaf weeds like common ragweed, velvetleaf, and morningglory [2]. In the United States, soybean field use represents the dominant application, with millions of acres treated annually in the Corn Belt [1]. EPA conducted a special review based on cancer bioassay results showing thyroid tumors in both sexes of rats and liver tumors in male rats [2].

Agricultural workers applying lactofen to soybean fields face inhalation and dermal exposure during mixing, loading, and application [1]. Dietary residues on soybeans and soybean products represent the primary consumer exposure [2]. Environmental contamination from agricultural runoff reaches surface water in soybean-growing regions [1].

Lactofen inhibits protoporphyrinogen oxidase, causing porphyrin accumulation and porphyrin-sensitized photooxidative injury [1]. In animal studies, thyroid hyperplasia, thyroid tumors, and hepatic effects were observed — EPA classifies it as a Group C possible carcinogen [2]. The thyroid effects may be secondary to liver enzyme induction and altered thyroid hormone metabolism [1].

Soybean and legume farmworkers during application and early post-application field entry [1]. Communities near large-scale soybean agriculture with irrigation runoff [2].

1. Agricultural workers must wear PPE (gloves, chemical-resistant apron, eye protection) during lactofen application [1]. 2. Follow restricted-entry intervals posted on the product label [2]. 3. Check USDA PDP for lactofen residue data in soy products [1].