No. 25: Port Harcourt, Nigeria See all 25 photos Mercer Health and Sanitation Index Score: 46.8 Problems with waste disposal continue to contaminate the rivers of Nigeria, especially affecting residents in Port Harcourt. The area lacks strategies for preventing oil spills and contamination, and the clean-up methods after disasters require significant improvement. No. 24: New Delhi, India Mercer Health and Sanitation Index Score: 46.6 You'll find just about everything except marine life in New Delhi's Yamuna River. Garbage and sewage flow freely, creating a rich environment for the growth of water-borne diseases contributing to extremely high rates of infant morbidity. No. 23: Maputo, Mozambique Mercer Health and Sanitation Index Score: 46.3 Located on the Indian Ocean, the Eastern African country of Mozambique suffers from lack of sanitation processes--specific ally the...