Waste produced in the healthcare sector may in significant part be considered as the hazardous waste. The health and environmental risks caused by this waste can be well defined and conditions for its management can be clearly separated from those of the waste generated in other areas.

According to the position statement by the United Nations’ World Health Organization (WHO), in 2000 improper treatment of medical waste (primarily the use of infected hypodermic needles and syringes) caused the following infections worldwide:

• Hepatitis B: 21 million infections;
• Hepatitis C: 2 million infections; and
• HIV: 260,000 infections.

The above figures show that how relevant appropriate medical waste treatment is. According to the WHO directive, hazardous waste should be processed as near to its place of generation as is possible. The risks involved in the transportation of hazardous waste are very large and risk factor found in some materials (e.g. those that are infectious) increases daily. Suitably located and equipped waste disposal facilities can minimize the need to transport the hazardous materials.

A lot of waste from hospitals is infectious biological material or objects, which although they are considered communal waste, are in fact contaminated. These latter items include textiles, bandages, syringes, and other objects exposed to infection through contact with the patients. Very much of the waste from hospitals is made up of special surgical instruments, such as the surgical implants and other implements employed during operations. The disposal of medical waste poses numerous questions, first of which is: How can medical waste be categorized

Types Of Biomedical Waste

There are following types of biomedical waste:

1. Infectious waste:
   Infectious waste is that which is suspected of containing pathogens (bacteria, viruses, parasites, or fungi) in a sufficiently large quantity or concentration to result in disease which are in susceptible hosts.
   
   This category includes:
   Cultures and stocks of infectious agents from the laboratories;
   waste from operations and autopsies on the patients with infectious diseases (e.g. body tissues, and materials or instruments having come into contact with blood or other body fluids);
   Waste originating from the infected patients in isolation wards (e.g. feces and urine, dressings from infected or surgical wounds, clothing that is heavily soiled with blood or other body fluids);
   
   waste having come into contact with the infected haemodialysis patients (e.g. dialysis equipment such as tubing and filters, disposable towels, gloves, aprons, laboratory coats, and gowns);
   
   And infected animals from laboratories.
    
2. Pathological waste
   Infectious materials containing dead tissue may conceal especially the dangerous and/or communicable infectious agents. Such waste includes blood, body fluids, tissues, organs, body parts, human foetuses, and animal carcasses. A subcategory of pathological waste is anatomical waste, which consists of the identifiable human or animal body parts, healthy or otherwise.
    
3. Sharps
   Sharps are the objects sharp enough to cut or puncture the skin, e.g. knives, scalpels and other blades, infusion sets, needles, hypodermic needles, saws, broken glass, nails, etc. They can transmit infections directly into bloodstream. Sharps are treated as highly hazardous medical waste regardless of whether they are contaminated or not.

Regarding sharp waste, special consideration must necessarily be paid to: infusion, transfusion, and perfusion sets; butterfly needles; cannulas; disposable scalpel blades and razors; hemodialysis sets; laboratory slides; broken glass containers (bacteriological and clinical laboratories); ampoules containing solution residues, etc.

How does biomedical waste impact environment?

Improper segregation of biomedical waste and different medical waste streams from the point of origin can trigger a domino-like effect on environment that incurs dangers to people, animals, or soil and water sources.

Improper segregation and disposal of biomedical waste has the potential to contaminate groundwater sources, which in turn may infect the humans and animals alike. From a hospital’s waste and storage receptacles to the landfills, biomedical waste needs to be properly contained to keep it away from birds, rodents, and stray animals (as well as humans). This enhances packaging and labeling of the contaminants and helps prevent the spread of illness through human and animal populations – by air, land, or water.

If not properly contained, segregated, and incinerated through on-site or off-site incineration, environmental hazards associated with improper healthcare waste management can contaminate air we breathe through dangerous airborne particles. A radioactive particle produced with diagnostic technologies has the potential to reach a landfill or other areas of the environment, especially air. Air pollutants disseminated over huge areas of inhabited land have potential to trigger a number of illnesses.

Water Quality

Improper disposal of biomedical waste may cause negative impact on the water quality as different pollutants may leach out from the waste dumping sites into the ground water. Al Raisi et al. (2014) assessed and found that the heavy metals in leachate were exceeding the drinking water standards. The concentrations of the Al, V, Cr, Mn, Co, Ni, Ba, Pb, and Fe 2.050, 0.9775, 2.800, 0.503,0.128, 0.773, 0.8575, 0.130, and 39.25 mg/L, respectively. The effect of these contaminants was considered as the surface and ground water contamination.

Soil Quality

Improper and unscientific disposal of biomedical waste may change the quality of soil near the waste dumping sites. Different pollutants may get mixed with soil and may change the chemistry and biology of the soil ecosystem. Abidemi and Theresa (2015) analyzed five heavy metals (chromium, nickel, zinc, lead, and copper) for their levels in the soil. The concentration of the heavy metals in soil were zinc (1133 ± 897 mg/kg), nickel (26.3 ± 51.1 mg/kg), copper (110 ± 90 mg/kg), lead (137 ± 64 mg/kg), and chromium (3.63 ± 2.46 mg/kg). The level of heavy metals at different sampling site were higher than the soils from background with factors of 67 (zinc), 18 (copper), and 20 (lead).

Medical hazardous waste disposal and treatment technologies

Certain treatment solutions that diminish the risks of infection from medical waste and preclude scavenging may even cause other health and environmental hazards. Incineration of certain kinds of medical waste, particularly those which contain heavy metals or chlorine, may release toxic substances into the atmosphere (due to, for example, insufficiently high incineration temperatures or the inadequate control of emissions).

Disposal of waste by burial in landfill may cause the pollution of groundwater (if the site is inappropriately designed and/or managed). Because of the aforementioned hazards, when a treatment or disposal solution for medical waste is selected (especially when there is a risk of toxic emissions or other dangerous consequences), relative risks and the integration of the method into the overall framework of a comprehensive waste strategy should be carefully evaluated taking local conditions into consideration.

Various technologies for medical waste disposal are:

1. Incineration
   Incineration was formerly the most popular method of disposing of the majority of the hazardous medical waste. Although it remains a widely-used solution, alternative methods are also growing in popularity. When selecting a treatment solution, various factors must be taken into consideration and many of these depend on the local conditions, such as health and safety requirements, and the available options for the final disposal of the waste, etc.
   
   The effectiveness of incineration is beyond doubt, yet this method entails serious issues concerning air quality. Due to the fact that reagent is atmospheric oxygen, a large volume of air shall continuously pass through the system. If exhaust air does not pass through a control device, all substances that are volatile at the system’s operating temperature will be emitted with the exhaust stream.
   
   The disadvantages of incinerators are:
   
   • Investment and operating costs are high.
   • The cytotoxics are not completely destroyed.
   • The emissions of the atmospheric pollutants are significant.
   • The periodic removal of the slag and the soot is necessary.
   • Destruction of thermally-resistant chemicals and drugs such as cytotoxics is inefficient.
   • Only 99% of the microorganisms are destroyed.
      
2. Simple chemical disinfection processes
   Chemical disinfection has an extensive role in healthcare, being used to eliminate the microorganisms on medical equipment, and on walls and floors. Nowadays chemical disinfection process is also used to treat medical waste. The addition of chemicals to the waste destroys or deactivates the pathogens in it, although the result is more frequently disinfection rather than the sterilization. This solution is most appropriate for the treatment of the liquid waste including blood, liquid excreta, or hospital sewage.
   
   In spite of this fact, the solid (and even highly hazardous) medical waste materials, such as microbiological cultures, sharps, etc., can also be chemically disinfected. The aforementioned process has the following drawbacks:
   The efficiency of disinfection is dependent on the operational conditions.
   
   Chemical disinfection is typically performed on site, i.e. within the hospital itself. However there is a growing tendency for the development of commercial, self-contained, and fully automatic systems for medical waste treatment located in the industrial zones. The processed waste can be disposed of as non-risk medical waste, but if the chemical disinfectants used leak or are improperly disposed of, they may have a detrimental impact on environment.
   
   The disadvantages of chemical disinfection are:
   
   • Hazardous substances that require the comprehensive safety measures are used.
   • In cases of pharmaceutical, chemical, and some types of infectious waste, it is inadequate.
   • If chemical disinfectants are costly, the process is made expensive.
   • Ozone is an effective sterilizer in a medical waste treatment system and it does not generate any by-products to be encountered when using chlorine compounds. However, since ozone is greatly damaging to the lungs, steps must be taken to ensure that those in the vicinity of the system are not exposed to this gas.
   • Other agents utilized for chemical treatment of the medical waste are alkalis, either highly corrosive ones (sodium hydroxide or lye), or in milder forms (calcium oxide or quicklime). Among the other effects, alkalis have the tendency to hydrolyze proteins. If the expense of the reagents is disregarded, the main disadvantage of this method is the risk of contact, as alkaline solutions are injurious to the skin and the lungs.
      
3. Wet thermal treatment (steam sterilization / autoclaving)
   In wet thermal treatment, the waste is first shredded and then exposed to very high-pressure, high-temperature steam. It has some similarities to the process of autoclave sterilization. Given a suitable temperature and contact time, most varieties of the microorganism are inactivated by wet thermal disinfection (for example for sporulated bacteria, the minimum necessary temperature is 121°C).
   
   In order to increase the efficiency of the disinfection, sharps should be crushed or milled. This solution is unsuitable for the treatment of anatomical waste and animal carcasses and is inefficient when processing the chemical or pharmaceutical waste.
   
   The disadvantages of wet thermal treatment are:
   
   • Operational conditions have a pronounced influence on the efficiency of the disinfection.
   • An inadequate shredder may retard the efficiency.
   • It is unsuitable for the treatment of the anatomical, pharmaceutical, and chemical waste and also for waste materials that do not easily permit the penetration of steam.
      
4. Land disposal
   Land disposal is considered to be an acceptable solution when there is no means of treating the waste prior to its disposal. If hazardous and untreated medical waste accumulates at hospitals, for example, a far greater risk of infections being transmitted is posed than if the waste is carefully disposed of at the landfill site. Objections to this method may be religious or cultural, or they may even be based on a perceived risk of the escape of pathogens into the air, soil, and water, or on the dangers entailed by scavengers having access to the waste.

Due to the unorganized and scattered deposit of the waste at open dumps, there may be serious pollution issues, fires, a heightened risk of disease transmission, and ingress by human and animal scavengers. Medical waste must never be disposed of on or in the vicinity of the open dumps. The dangers of people or animals coming into contact with active pathogens are exacerbated by the additional risk of the subsequent transmission of infections, either directly via wounds, inhalation, or ingestion, or indirectly via the pathogenic host species or the food chain.

Sanitary landfill sites are preferable to the open dumps considering at least four points: they geologically isolate waste materials from the environment; engineering specifications for the acceptance of waste are met; operations are directed by on-site personnel; waste-deposit is organized and the wastes are covered over daily. The disposal of some of the medical waste (infectious waste and pharmaceutical waste in small amounts) is acceptable.

Medical waste disposal: the WHO's recommendation

Waste generated by the healthcare activities includes a broad range of materials, from used needles and syringes to soiled dressings, body parts, diagnostic samples, blood, chemicals, pharmaceuticals, medical devices, and radioactive materials.

Poor management of the medical waste potentially exposes healthcare workers, waste handlers, patients and the community at large to infection, toxic effects and injuries, and risks polluting the environment. It is essential that all the medical waste materials are segregated at the point of generation, appropriately treated, and disposed of safely.

Conclusion
Management of the biomedical waste is linked with risks to people who are directly and indirectly associated with this profession. Biomedical waste has caused the challenge to maintain the quality of water, air, and soil. The quantities and proportions of different constituents of the wastes, their handling, treatment, and disposal methods in different healthcare settings varies and treatment and disposal methods have been found to be inadequate in most of the studies.

Hazards associated with the poor biomedical waste management and shortcomings in the existing system have been identified by various researchers. The development of the waste management policies, plans, and protocols were recommended in most of the studies. Moreover, establishing training programs on proper waste management for all the healthcare workers was established. Research to convert the biomedical waste into energy and other useful products need to be explored. This will be helpful to prevent environmental contamination and the health risk factors.