Wherever there are people, there is medical waste. It is generated in small quantities in many locations. These include:
The WHO estimated 16 billion injections are done worldwide every year. This gives an idea of scope of generation sites.
Waste from different facilities may be subject to different rules. In the state of Texas, for instance, businesses that generate less than 50 pounds per month of medical waste as classified as small quantity generators (SQG) while those that generate over 50 pounds per month are large quantity generators. The two types are subject to different rules for transport of the waste and on-site treatment.
Pathogens in medical waste pose a disease risk, and if this disease is contagious (or if the waste is released over a large area), a potential public health problem of large proportion. The reason we treat medical waste before disposal is to substantially reduce (for all practical purposes eliminating it) of disease transmission. Medical waste can also include non-infectious hazardous components. These might include material that is deemed hazardous by its extreme pH, corrosiveness, reactivity, or toxicity to living organisms. Engineers often have ways of treating waste to reduce those risks, too.
The EPA website says that, in general, risks posed by medical waste are greater for health care workers than for the general public. This is because the maximum disease-causing risk is at the point of generation and over time diminishes.
Risk assessment techniques done to support permitting of a medical waste treatment facility may include a projection or prediction of waste risks at points in the handling process. The variability of medical waste coming into the facility may render this risk assessment questionable, but it is often the only thing operators and regulators have to go on.