Participate is etymologically related to Capable. Participate is etymologically related to Part. Part is related to Shoulder. Shoulder is related to Arm. 
Pollution is related to Environmental. 
Capable <--EtymologicallyRelatedTo-- Participate --EtymologicallyRelatedTo--> Part <--RelatedTo--> Shoulder <--RelatedTo--> Arm 
Pollution <--RelatedTo--> Environmental 