Isolated case reports have circumstantially linked the use of the herbicide 
2,4-dichlorophenoxyacetic acid (2,4-D) to polyneuropathy. However, a critical 
review of the literature reveals numerous reasons for doubting a relationship of 
2,4-D to polyneuropathy: (1) too few cases given the wide use of the chemical; 
(2) no valid toxicologic or epidemiologic evidence; (3) the diversity of 
antecedent illness; (4) an unlikely time sequence of antecedent illness to 
exposure (pharmacokinetics); (5) the lack of polyneuropathy in medical patients 
given repetitive doses of 2,4-D; (6) the lack of polyneuropathy in heavily 
exposed military personnel involved in operation Ranch Hand; (7) the biological 
properties of 2,4-D which minimize penetration of 2,4-D into the nervous system 
under normal exposure conditions; and (8) the lack of polyneuropathy in a 
variety of experimental animal species given 2,4-D by several routes of exposure 
and at dose levels and durations of exposure many times greater than human 
applicator exposure. Thus, the weight of evidence indicates that 2,4-D is an 
unlikely cause of polyneuropathy.