Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal disease of unknown cause that selectively targets brain and spinal cord motor neurons (MNs). The lifetime risk is 1 in 2000, and most cases are sporadic although up to 10% of patients are predisposed by familial mutations in MN protection or repair genes (Bruijn et al., 2004). Risk factors include agrochemical exposure and trauma (Walters et al., 2019), although why they target MN is perplexing. Farmers are at a greater risk than non-farming rural residents (Kang et al, 2014), and ALS clusters occur in abrasion prone activities conducted on agrochemical treated fields such as baseball and soccer (Chio et al., 2005). These observations suggest that one mechanism for targeted loss of MNs may be the retrograde transport of neurotoxins subsequent to peripheral nerve injury, a process termed ‘retrotoxicity’.