There are associations between ALS and dozens of occupations, and exposure to thousands of substances. There is a difference between the prodomal (causative) e

There are associations between ALS and dozens of occupations, and exposure to thousands of substances. There is a difference between the prodomal (causative) event and the consequence: The disease. ALS and probably many other neurodegenerative disease could be caused by many events. The scientists tell of multi-step diseases.