Problem
You are conducting a study to understand if landscape workers who use leaf blowers experience higher rates of chronic obstructive pulmonary disease (COPD) than workers who use rakes. You know from previous studies that use of leaf blowers leads to inhalation of particulate matter and that inhalation of particulates leads to COPD. Based on this information, how are the researchers conceptualizing inhalation of particulate matter in their causal theory and should they adjust for it?