Final answer:
Waste disposal containers must be kept clean and free from contaminants to maintain hygiene standards and prevent the spread of infections.
Step-by-step explanation:
All outer surfaces of waste disposal containers must be kept clean and free from contaminants. It is crucial to maintain hygiene standards to prevent the spread of infections and ensure the safety of both the people who come into contact with these containers, such as sanitation workers, and the general public.
Regular cleaning and disinfection is important as it minimizes potential health risks that might arise from the accumulation of waste and harmful bacteria or substances.