Medical and health care waste is generated by activities and procedures conducted in hospitals, healthcare facilities, emergency field hospitals, medical laboratories, diagnostic centres and other medical institutions. According to the World Health Organization (WHO), 75%- 90% of this waste includes materials similar to domestic solid waste. These wastes are mainly generated by administrative activities, regular housekeeping and food provision for staff, patients and visitors. Categorised as ’general waste’ or ’non-hazardous waste’, this waste can be handled and disposed of in the same way as domestic solid waste. The remaining much smaller fraction of medical waste originates from medical procedures. Classified as hazardous waste W.2 it poses significant health risks, especially for care staff, staff involved in medical waste handling as well as patients and their families. Hazardous medical waste can be further classified into sub-categories characterised by the nature of different hazards - such as cut and puncture injuries, the spreading of infectious diseases or other properties which can cause health problems or even death. The types, amounts and items included in these sub-categories vary between medical institutions and depend on the size and sophistication of a facility and the procedures it provides. 

WHO classifies hazardous medical waste into the following subcategories:

• Sharps waste: such as used or unused needles, syringes, scalpels, blades, broken glass.
• Infectious waste: potentially pathogen-containing and disease-transmitting items such as waste contaminated with blood or other body fluids, laboratory cultures, microbiological stocks, human excreta and materials from isolation wards.
• Pathological waste: human tissues, organs, body parts, foetuses.
• Pharmaceutical waste and cytotoxic waste: pharmaceutical waste includes pharmaceuticals that have expired, or no longer needed, and materials which contain or are contaminated by pharmaceuticals. Cytotoxic waste includes substances with genotoxic properties, used, for instance, in cancer therapy.
• Chemical waste: chemical substances including laboratory reagents, disinfectants, materials and substances containing heavy metals, solvents.
• Radioactive waste: including liquids from radiotherapy, urine and excreta from patients undergoing unsealed radiation therapy, radioactively contaminated materials.

Some medical institutions classify pressurised canisters as an additional hazardous waste category. The canisters contain different types of gases, some highly flammable; they may explode or release their contents if punctured.

The Need for Strict Source-Segregation of Medical Waste 

Because of the severe risk to health from hazardous medical waste, its segregation at source and safe containment is essential in Medical Waste Management (MWM). Without strict segregation, a relatively small amount of hazardous waste can contaminate the general waste and enter the waste management stream for regular domestic solid waste, threatening public health and the environment. If strictly segregated at source and safely contained, hazardous medical waste can be transferred to a safe treatment and disposal site where its hazards are eliminated. Strict source segregation also keeps the amount of hazardous medical waste small, minimising the effort and high costs of its safe containment and disposal.

Source segregation of hazardous medical waste must be systematic and the waste contained in appropriate colour-coded vessels marked with labels and hazard pictograms. 

In the absence of national guidance on medical waste segregation, the following WHO-recommended segregation scheme is recommended:

• Highly infectious waste: strong, leak-proof and autoclavable plastic bags or containers in yellow, labelled with ’Highly Infectious’
• ther infectious waste, pathological and anatomical waste: leak-proof plastic bag or container in yellow, marked with a biohazard symbol
• Sharps waste: yellow puncture-proof containers labelled with ’Sharps’
• Chemical and pharmaceutical waste: brown plastic bags or rigid containers labelled with the appropriate hazard symbol
• Radioactive waste: lead box marked with the radiation symbol
• General (non-hazardous) medical waste: black plastic bag

To limit the volume of hazardous waste, medical facilities should reduce their waste generation in the first place and reuse equipment (after adequate cleaning and sterilisation).

Training of all health staff is required to ensure that hazardous medical waste is completely and correctly segregated and disposed of. The entire MWM system in a facility can be compromised by incomplete or faulty segregation or later remixing of general waste with hazardous waste. 

The safe containment of source-segregated and safely stored hazardous waste must be maintained until the final disposal. This includes during internal transport for each facility, subsequent storage on the premises of medical institutions, external transport and handling and disposal at disposal sites. 

Treatment and Safe Disposal of Hazardous Medical Waste

General and non-hazardous waste from medical institutions can be disposed of along with domestic solid waste. It is, however, essential that no hazardous waste materials are deliberately or unintentionally disposed of with it.

The treatment and disposal of hazardous medical waste must address its specific hazardous characteristics to ensure the complete elimination of public health and environmental risks. Disposal procedures therefore differentiate between the different hazardous waste subcategories and use specialised equipment and personnel. The procedures also vary according to the sophistication of the disposal infrastructure and the availability of specialised personnel. Humanitarian crises may reduce the availability and quality of the infrastructure and capacity of actors. A risk analysis should determine whether the existing infrastructure and specialist capacity of external waste facilities can still manage the treatment and disposal of medical waste, or whether treatment and disposal must be undertaken on the medical facility’s premises. A hybrid approach may also be viable, where the medical facility carries out some pre-treatment (such as sterilisation of waste) to facilitate external transport for off-site processing. Medical waste (such as pharmaceutical or radioactive waste) may be returned to suppliers for safe disposal. 

Hazardous waste treatment and disposal includes:

• Thermal low-heat processes, such as autoclaving, eliminate microorganisms and sterilise waste at temperatures of between 100°C and 180°C. Low-heat treatment can be done with wet or dry heat but as it does not lead to thermal degradation, the pathogen-free waste still requires safe disposal.
• Thermal high-heat processes, such as incineration or pyrolysis, completely disintegrate organic and combustible materials, reducing them to ash which contains inorganic and incombustible matter. High-heat processes produce combustion by-products which may require flue gas cleaning and the safe disposal of ash.
• Chemical treatment can be used to disinfect and destroy microorganisms.
• Landfilling untreated medical waste in sanitary landfills is not advised by WHO. If it is the only option, waste must be at least robustly encapsulated.
• Radioactive waste storage depends on its radiation level and decay rate. Radioactive waste is usually under the authority of the national nuclear regulatory agency. The handling and disposal of radioactive waste must adhere to its guidance.

In all cases, the handling, treatment and disposal of medical waste requires adequately trained staff and the use of special personal protective equipment. WHO (2014) provides detailed guidance on safe management.

MWM in Upper-Middle and High-Income Countries

Upper-middle and high-income countries usually establish specialised infrastructure and personnel for the treatment and disposal of medical waste. Some fractions of hazardous medical waste may be incinerated in municipal waste incineration (MWI) plants, depending on their availability, functionality and official authorisation. If MWIs are used, hazardous medical waste is transported by specialist organisations and fed directly into the combustion system. Unlike regular domestic waste, it is not deposited in the waste storage pit of the MWI plant. In the absence of MWI, hazardous medical waste may be incinerated in specific hazardous waste incineration plants. Pathological waste can also be incinerated in crematoria but typically requires sterilisation or disinfection before transportation.

MWM in Middle and Low-Income Countries

Specialised infrastructure and actors with the capacity to safely treat and dispose of medical waste may not exist in middle and low-income countries (or in high-income countries affected by conflict and disaster). In these cases, the responsibility for treatment and disposal rests with the medical facility, usually on its premises. 

If space is available and a safe distance from the population, medical waste might be disposed of in separate lined waste burial pits (e.g. sharp pits, anatomical waste pits or burial pits). However, this approach has significant disadvantages, including that the waste remains hazardous. If space permits, small-scale and low-tech incinerators made from locally available materials, such as the De Montfort incinerator, can combust high-risk fractions of medical waste. Such incinerators have very low combustion capacities and lack flue gas cleaning but still enable combustion at high temperatures of ca. 800°C. Small-scale incinerators can also be imported and assembled on the premises of medical facilities. 

Regulatory Frameworks and Guiding Principles

The implementation of MWM in humanitarian settings must adhere to the relevant national regulatory framework and international conventions X.1. National regulatory frameworks may define how hazardous medical waste must be segregated, stored, treated and disposed of. International conventions relevant to hazardous medical waste include:

• The Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal regulates the transboundary movement of hazardous wastes, including hazardous medical wastes.
• The Bamako Convention prohibits the importation of hazardous wastes into Africa. The Bamako Convention was established due to the failure of the Basel Convention to prevent the export of hazardous wastes from developed to less-developed countries.
• The Stockholm Convention on Persistent Organic Pollutants (POP). POPs can be produced during the incineration of hazardous medical waste.

Social, Ethical and Cultural Implications

MWM must respect social, ethical and cultural norms and traditions. These considerations particularly apply to the management of pathological waste, including body parts, foetuses and placentas.