Social & Preventive Medicine Environment and health d82959c3 Percentage of para-para isomer in DDT is - A 20-30% B 40-50% C 60-70% D 70-80% High-Yield Explanation park's textbook of preventive and social medicine 23rd edition. *The 'technical' DDT contains 70-80% of para-para isomer,which is the most active fraction of DDT.