
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39294253
69940
10.1038/s41598-024-69940-0
Article
Economic evaluation of hazardous healthcare waste treatment systems
Sharifi Sahar 1
Yaghmaeian Kamyar 12
Golbaz Somayeh 1
Nabizadeh Ramin rnabizadeh@gmail.com
rnabizadeh@tums.ac.ir

12
Baghani Abbas Norouzian abbas.jj.norozi@gmail.com

3
1 https://ror.org/01c4pz451 grid.411705.6 0000 0001 0166 0922 Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
2 https://ror.org/01c4pz451 grid.411705.6 0000 0001 0166 0922 Center for Solid Waste Management (CSWM), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran
3 https://ror.org/035t7rn63 grid.508728.0 0000 0004 0612 1516 Environmental Health Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran
18 9 2024
18 9 2024
2024
14 2176421 3 2024
12 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
The cost estimation and assessment of healthcare waste treatment systems (HCWTSs) for preventing financial and environmental damage are essential. This work reports economic analyses of treatment of hazardous–infectious waste based on WHO approach in HCWTSS of 43 hospitals in Tehran, Iran. The waste generation rate for total hospital waste in 43 HCWTSS was 4.42 ± 2.77 kg/active-bed/day. The mean of chemical, sharps, infectious, and general wastes in 43 HCWTSS were 13.79 ± 19.71, 30.29 ± 37.46, 336.28 ± 291.31, and 539.6 ± 383.13 kg/day, respectively. Economic analyses proved that general hospitals spent 1.63 times more than specialized hospitals on treating hazardous–infectious waste per year. The annual cost of treating each kilogram of hazardous healthcare waste in studied HCWTSS was 0.3 dollars. A range of total annual costs in 43 HCWTSS was limited to 7.9–118 thousand dollars. The results of ANOVA test demonstrated that the age and performance levels of hospitals significantly affect the annual capital and operating costs, respectively. Hence, improving recycling knowledge and increasing source-separated recycling should be considered to control the costs in HCWTSS. The results of this work have implications for the hospital managers in especially developing countries to evaluate previously unknown economic analyses and policies and take action to control wasted costs in HCWTSS.

Keywords

Healthcare waste
Chemical treatment
Infectious waste
Waste management
Thermal treatment
Economic analyses
Subject terms

Health care economics
Environmental sciences
issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Healthcare waste (HCW) generation worldwide has increased rapidly throughout recent years due to the prompt population, economic growth and appropriate medical service demand1,2. Healthcare facilities (HCFS) waste is a collection of waste produced by healthcare establishments, research facilities, laboratories related to medical procedures, and home-based healthcare such as dialysis and insulin injection3,4. HCW, also called medical waste, can be categorized as nonhazardous (general) wastes and hazardous healthcare wastes (HHCW)5. Nonhazardous wastes can be originated mostly from the administrative, kitchen, and housekeeping functions at HCFS and packaging waste3,6–8. Besides, HHCW includes sharps, infectious, chemical, radioactive, and pharmaceutical waste9.

Infectious waste consists of materials containing pathogens such as bacteria, viruses, parasites, and fungi10–12. Adequate quantities of those microorganisms can cause disease in susceptible hosts11,13,14. Additionally, HHCW can create potential health and environmental risks for humans and the ecosystem3,15. Hence, it is necessary to establish safe and sustainable healthcare waste management (HCWM) to protect the environment from HHCW by the healthcare administrators16. It is important to mention that infectious waste treatment and HCWM are complicated processes with a wide variety of economic, environmental and technological factors to minimize social, environmental, and economic impacts on the environment and humans17. The management of HCW by applying those complex processes not only creates significant benefits for the environment and humans but also helps to save costs in the management system18.

To prevail over the issues of HCW, the World Health Organization (WHO) developed the HCWM strategy entitled “the safe management of waste from healthcare activities (SMWHA),” which persuades the legislators to use new incinerators or non-incineration technologies in healthcare waste treatment systems (HCWTSS)3,19,20. Besides, the effective HCWTSS can be selected on the specifications of HCW, the different types of technologies, environmental and safety aspects, and costs3. According to past works, several techniques for treating HHCW include autoclave, chemical treatment, hydroclave, and dry-heat3,21. Autoclave has applied steam at lower temperatures to destroy the pathogens, while in chemical treatment, organisms have inactivated by using disinfectants3,21–23. However, dry-heat technologies using conduction, convection, and thermal radiation apply higher temperatures and longer exposure times than steam-based technologies3,24,25.

Using these treatment technologies entails spending costs on HCWTSS3,26. According to the WHO, the cost of HCWM can be classified as capital costs, operating costs, and overhead costs3. The capital costs relate to one-time investments such as the cost of purchasing treatment sterilizers27. Those costs can be involved in the equipment costs in HCWTSs with an investment horizon for more than one year, such as plastic bins, wheeled carts, and large waste containers for disposing of waste3,26. In addition, the operating costs are recurrent costs incurred in HCWTSs3. Furthermore, the main operation and maintenance costs in HCWTSs include human resources (labour), consumable items (e.g., yellow bags), and water and electricity facilities3,26,28. Besides, overhead costs are extra costs that may be more difficult to quantify initially3. These overhead costs may include training employees and employees benefits such as health insurance and immunization of waste workers3,27. WHO reported that managers of HCFS should consider the estimation and assessment of annual costs in HCWTSs for prevention the issues of financial and environmental damage, and even human death3.

To date, few studies have focused on the effects of various factors on annual costs in the cost assessment of HCWTSs in developing countries, such as Iran, and scarce information is available regarding capital costs, operating costs, and overhead costs in HCWTSs. For example, Sepetis et al. have performed a study on recognizing and projecting the costs of HCWM in Greek public hospitals29. Accordingly, investigated variables in this study included the number of beds, hospital type, the existence of an intensive care unit, the number of internal patients, the days of stay, and the number of employees29. The result of the same study indicated that “significant differences were perceived in mean costs per bed, per patient, between the Greek health districts and mean quantities of waste generated in various types of hospitals”29.

Moreover, it is necessary for the hospital managers, officials at the governmental level, and the Ministry of Health in worldwide especially in the developing countries to be inform of the treatment costs of HHCW in hospitals to sense what requires to be changed and performed to protect the environment, reduce operating costs of hospitals, and implement the necessary policies and action plan29–31. Hereinafter, the collection of accurate data and the conduct of relevant analyses are necessary to estimate the capital costs, operating costs, and overhead costs for each HCWTS, which requires the creation of coding for organizing and explanation of the data. Based on previous studies, “coding does not constitute the totality of data analysis, but it is a method to organize the data so that underlying messages portrayed by the data may become clearer to the researcher”32–34.

Nonetheless, no studies have focused on applying the coding process of data related to cost assessment in HCWTSs. Hence, for the first time, this work has estimated the capital costs, operating costs, and overhead costs in HCWTSs and the effects of independent variables on those costs in HCWTSs by coding method. Therefore, so far, many studies have been conducted about healthcare waste management practices35,36, evaluation or prioritization of the methods for the disposal and treatment of HCW37–40, minimization of the treatment costs of HHCW41–45, and investigation of the effect of the independent variables on the production of HCW and prediction of the management costs using operating costs29, but this study attempts to regard the costs assessment in HCWTSs and the effects of independent variables (such as the age of the hospital, treatment method and etc.) on those costs in HCWTSs in developing countries such as Iran by coding method.

Hence, the present study aims to (1) fill out the questionnaires related to data collection in 43 HCWTSs of 43 hospitals in Tehran (Iran) and measure its reliability, (2) use the coding process for collecting data related to HCWTSs, (3) study the generation rate and composition of solid waste of 43 HCWTSs in Tehran, (4) compute total annualized capital costs (TACCS), total annual operating costs (TAOCS), total annual costs (TACS), overall annualized capital cost (OACC), overall annual operating cost (OAOC), and grand total annual cost (GTAC) in 43 HCWTSs in Tehran, and (5) investigate the effects of qualitative variables (such as infectious waste generation, the number of active beds and etc.) on those costs in 43 HCWTSs in Tehran.

Therefore, this study can inform the hospital managements/managers, officials at the governmental level, and the Ministry of Health in developed and developing countries how to divide the budget allocated for different parts of hospitals regarding waste management systems. Budget separation may lead to cost savings in the long term in providing services for such parts as the collection phase and treatment site in HCWTSs. Generally, the results of this work can be used by researchers and the hospital managers especially in the developing countries to evaluate previously unknown economic analyses and policies and take action to control wasted costs in HCWTSs.

Material and methods

This work included several steps: designing a questionnaire (data collection tool), selecting a study area, coding collected data, descriptive analysis, economic analyses, and statistical analysis. A diagram of the eight steps in this study is described in Fig. 1. In addition, the analyses of this work were performed by R software (version 3.3.1), Microsoft Excel® (version 2013), and the SPSS software version 22.0. It should be considered that all experimental protocols were ethically approved by the Research Ethics Committee (REC) of the Tehran University of Medical Sciences in accordance with the national and international ethical standards for biomedical research (with ethics approval ID IR.TUMS.SPH.REC.1395.1958). Informed consent was obtained from all subjects involved in the study.Figure 1 A diagram of eight steps in this study.

Designing a questionnaire and measuring its validity

Data used in this work were collected based on WHO policy (SMWHA) 3 using a face-to-face (F2F) questionnaire as shown in Supplementary Table S1 online in Supplementary Information (SI). Informed consent was obtained from all subjects involved in the study. More detailed information in terms of designing a questionnaire and measuring its validity are provided in the supporting information (Section S1).

Selecting a study area and filling out the questionnaires

The treatment costs of HHCW are usually assessed in terms of the type of treatment technology, generated waste types, and treatment equipment capacity3. The treatment costs of HHCW are often evaluated based on the treatment technology type, waste types generated, and equipment capacity for treatment. This led to the study of cost estimation in 43 HCWTSs from 43 hospitals across various areas in Tehran (Iran). More detailed information in terms of filling out the questionnaires is provided in the supporting information (Section S2).

Coding of collected variables and data

In this section, each variable in every question of questionnaire was assigned a code to facilitate future analyses (Fig. 1). More detailed information in terms of coding of collected data is provided in the supporting information (Section S3).

Descriptive statistics

Production of different types of hospital wastes

As described in “Coding of collected variables and data” section, categorized codes and subcodes related to this part of questionnaire were applied to measure the waste generation rate of various generated waste in 43 HCWTSs. More detailed information is provided in the supporting information (Section S4).

Economic analyses

The economic analyses of this work included four steps in 43 HCWTSs: (1) computing of the annualized capital costs (ACCs), TACCs, and OACC, (2) doing some calculations of the annual operating costs (AOCs), TAOCs, OAOC, and OAOCkg (overall annual operating cost per kg HHCW which became treatment), (3) doing some analyses of total and overall costs, and (4) drawing a comparison of total costs between different levels (Fig. 1). A calculation diagram of economic analyses for these four steps in this study is described in Fig. 2. Before proceeding with these four steps, all cost-related subcodes in the Excel sheet were converted from Rials to Dollars. The conversion was computed by multiplying the amounts by 9712.5, using the annual average exchange rate from the Central Bank of the Islamic Republic of Iran.Figure 2 The calculations of economic analyses for four steps in 43 HCWTSs.

ACC, TACC, and OACC

The first point is calculating annualized capital costs on the capital costs in HCWTSs 3. According to Supplementary Table S2 online, the capital costs in HCWTSs included the costs in two sections of “onsite waste-treatment technology and related accessories” and “waste-management equipment with a life span of more than a year” with some subsections such as “wheeled carts”, “onsite waste-treatment technology”, and etc. Categorized codes and subcodes related to capital cost part (dollars), according to Supplementary Table S3 online, were applied for computing ACC (dollars). In this way, a capital cost of each intended subcode (Table S3) could be multiplied into a standard annualization factor (SAF) based on Eq. (1) 3 (Fig. 2):1 ACC=CC×SAF

SAF for each CC could be computed based on the estimated lifespan of the equipment (n (year)) and discount rate (r (%)) according to a year of purchase of the equipment, as shown in Eq. (2) 3 (Fig. 2):2 SAF=r1-11+rn

According to types of equipment, “n” was obtained from the Direct Tax Law book46. More detailed information in terms of “n”, “r”, annualized capital costs, total annualized capital cost, and overall annualized capital cost for each HCWTS are provided in the supporting information (Section S5) and Fig. 2.

AOC, TAOC, OAOC, and OAOCkg

At first, the calculation of the annual operating costs (AOCs) requires operating costs and overhead costs in HCWTSs 3. According to Supplementary Table S2 online, the main operating costs in HCWTSs included four sections and subsections.

AOC (i.e., Z (dollars per year)) for each subsection of Supplementary Table S2 online can be computed by the quantity of consumption of variables related to operating and overhead costs indicated in Supplementary Table S4 online (i.e., X (the quantity of relevant variable per year)) and cost of variables related to operating and overhead costs (i.e., Y (dollars per relevant unit of variable)) as shown in Eq. (3) 3 (Fig. 2):3 Z=X×Y

More detailed information in terms of TAOC for each hospital and OAOC for all 43 hospitals are provided in the supporting information (Section S6) and Fig. 2.

In addition, according to Eq. (4), by dividing overall annual operating cost by the annual generation of HHCW for 43 HCWTSS (HHCWyear) (extracted from “Production of different types of hospital wastes” section), OAOCkg for 43 HCWTSS can be figured3 (Fig. 2). OAOCkg was known as operating treatment fees for HHCW sent to 43 HCWTSS3.4 OAOCkg=OAOCHHCWyear

where OAOCkg is OAOC per kg HHCW that became treatment in 43 HCWTSs (dollars/kg), OAOC is an overall annual operating cost in 43 HCWTSS (dollars/year), and HHCWyear is the amount of HHCW produced per year in 43 HCWTSS (kg/year).

Analyses of total and overall costs in 43 HCWTSs

At first, grand total annual cost was achieved for all 43 HCWTSs by adding OAOC and OACC (Fig. 2). Furthermore, according to Eq. (5), by dividing GTAC by HHCWyear (extracted from section “Production of different types of hospital wastes” section), the annual cost per kilogram of HHCW that becomes treatment (GTACkg) in 43 HCWTSS can be figured3 (Fig. 2). The GTACkg was known as treatment fees for HHCW sent to 43 HCWTSS3.5 GTACkg=GTACHHCWyear

where GTACkg is the grand total annual cost per kg HHCW that became treatment in 43 HCWTSS (dollars/kg), GTAC is the grand total annual cost in 43 HCWTSS (dollars/year), and HHCWyear is the amount of HHCW produced per year in 43 HCWTSS (kg/year).

Additionally, total annual cost for each HCWTS can be figured by adding TACC and TAOC from each HCWTS together (Fig. 2). The process was repeated for all 43 HCWTSs, resulting in a total annual cost for each HCWTS. Moreover, the means of TACCS, TAOCS, and total annual costs in general and specialized hospitals were individually acquired and contrasted.

Comparison of total costs between different levels in 43 HCWTSs

According to WHO, “all healthcare facilities need to establish accounting procedures to document the costs they incur in managing wastes”3. “Healthcare waste costs should be separate from budget lines in a healthcare facility’s financial accounts. This allows costs over different years to be compared”3. Hence, we tried to separate total annual cost into 3 levels in HCWTSS for more cost comparison between different levels of HCWTS to help officials understand more about the budget allocation of waste management in HCWTS (Fig. 2). More detailed information in terms of comparison of total costs between different levels in 43 HCWTSS are provided in the supporting information (Section S7).

Distribution of total annual costs in 43 HCWTSS

The distribution of TACS in 43 HCWTSS was investigated by R software (version 3.3.1) to show that 95% of those costs (thousand dollars) are which range.

Statistical analysis

Measuring the reliability of the questionnaire

To assess the reliability of the research instrument, the test–retest method and Pearson’s correlation coefficient (Pearson coefficient correlation (r)) were used. Data were analyzed using the SPSS software version 22.0 at a significance level of < 0.001. The result of the analysis is reported in the results and discussion part.

Statistical analysis of total costs in 43 HCWTSS

For investigation of the effect of different variables on total costs in 43 HCWTSS, three tests in R software (version 3.3.1) were applied, which included the Fligner-Killeen test, analysis of variance (ANOVA) test, and the Kruskal–Wallis test (Fig. 1). Before using ANOVA, the Fligner-Killeen test for homogeneity of variance was applied. If the p-value obtained from the Fligner-Killeen test exceeded 0.05, the ANOVA was performed for further analysis. But, if the p-value was less than 0.05, the Kruskal–Wallis test was applied for further analysis. More detailed information in terms of statistical analysis of total costs in 43 HCWTSS are provided in the supporting information (Section S8).

Correlation of independent variables and TACS in 43 HCWTSS

Cor.test analysis in the R software evaluated the association between independent variables and total annual costs. This association was studied in two systems: (i) healthcare waste thermal treatment systems (HCWThTSS) and (ii) healthcare waste chemical treatment systems (HCWChTSS) separately. Those various variables are described in Supplementary Table S9 online. This should be noted that all defined variables were joint parameters for both systems (HCWThTSS and HCWChTSS), except variable “the amount of disinfectant used in chemical treatment methods”, defined only for HCWChTSS. More detailed information in terms of correlation of independent variables and total annual costs in 43 HCWTSS are provided in the supporting information (Section S9).

Ethical approval

The study design was approved by the Research Ethics Committee (REC) of the Tehran University of Medical Sciences in accordance with the national and international ethical standards for biomedical research (Approval Code: (IR.TUMS.SPH.REC.1395.1958; Approval Date:13.03.2017).

Informed consent

Informed consent was obtained from all subjects involved in the study.

Results and discussion

Validity of questionnaire

The qualitative content validity of this questionnaire was reported as good based on opinions from the group of specialists.

Descriptive statistics

Generation rate and composition of hospital solid waste

The mean (± SD) of different types of generated waste in 43 HCWTSS in Tehran (Iran), including chemical, sharps, infectious, and general wastes, is shown in Table 1. Accordingly, the mean (± SD) of chemical, sharps, infectious, and general wastes were measured at 13.79 (± 19.71 kg/day), 30.29 (± 37.46 kg/day), 336.28 (± 291.31 kg/day), and 539.6 (± 383.13 kg/day), respectively. As shown in the Fig. 3 and according to the mean generation of different types of hospital waste, the total amount of generated waste by 43 HCWTSS included 58.65% general waste, 36.55% infectious waste, 3.29% sharps waste, and 1.5% chemical waste.Table 1 Mean (± SD) of different types of generated wastes in 43 HCWTSs in Tehran (Iran).

Figure 3 The composition of the medical waste in 43 HCWTSs in Tehran, Iran.

Comparison of the results of hazardous–infectious waste (infectious and sharps wastes) proportions in the current and other related studies is described in Fig. 4. According to Fig. 4, the proportions of hazardous–infectious waste (infectious and sharps wastes) in our work (39.84%) is practically consistent with other studies conducted in Iran and other developing countries47,48. For instance, in 837 hospitals in 31 provinces of Iran48, 16 hospitals in Rasht (Iran)49, 8 hospitals in Egypt50, 17 hospitals and clinics in Bangladesh51, and 5 public healthcare facilities in Adama, Ethiopia47 found that approximately 37, 38, 39, 36, and 35% of generated waste was potentially hazardous. However, hazardous–infectious waste reported in the USA52 and France53 were 15 and 15–20% of HCW, respectively (Fig. 4). The position and value of implementing source-separated waste for HCWTSs are due to the amount and proportion of hazardous–infectious waste in the entire medical waste stream54,55. Hence, this high percentage of hazardous waste in cities of developing countries like Tehran (39.84%) may be due to improper segregation or lack of segregation in HCWTSs47,50.Figure 4 The proportions of hazardous–infectious waste (infectious and sharps wastes) in 43 HCWTSs in Tehran, Iran in comparison with the other studies.

The mean (± SD) rate of different types of generated wastes in 43 HCWTSS in Tehran (Iran) is reported in Table 1. The mean total hospital waste generation rate (general, infectious, sharps, and chemical wastes) in this work was 4.42 ± 2.77 kg/active-bed/day, which is consistent with past works in different cities of Iran48,56 such as in hospitals of Qazvin in 2017 (4.2 kg/active-bed/day)48, in 15 hospitals of Fars province in 2004 (4.45 kg/active-bed/day)56, in one hospital in Tehran in 2015 (4.2 kg/active-bed/day)57, and in 5 hospitals in Tehran in 2018 (4.72 kg/active- bed/day)58. According to those results reported, it can be seen that the amount of total hospital waste generation rate in Iran has not changed noticeably56,58. It is widely accepted that, the total amount of generated waste in hospitals is related to the choice of waste management strategies, the adoption of consistent plans for the segregation of medical waste, the existence of a plan to minimize HCW in the hospitals, and the cultural status of persons (employees and patients)48,56,59. Hence, it can be said that in the last few years, the government managers in developing countries such as Iran not only have been surprisingly unable to adopt and implement a policy to achieve less hospital waste production56,58,60 but they have been affected by increases in the quantity of the generation of hospital waste61. This is probably due to a lack of knowledge and carelessness by hospital workers and patient’s companions62. Additionally, considering the very low generation rate of chemical waste (0.06 kg/active-bed/day) and total infectious and sharps wastes (1.71 kg/active-bed/day) compared to total hospital waste generation rate (4.42 kg/active-bed/day), it can be said that this difference was probably due to the improper segregation of infectious waste48. In addition, based on results of this work, the average generation of hazardous–infectious waste (infectious and sharps waste) in general hospitals (1.72 kg/act-bed/day) were higher than in specialized hospitals (1.54 kg/act-bed/day). More detailed information in terms of medical waste generation rate is provided in the supporting information (Section S10).

Analyses on costs in HCWTSS: TACCS, TAOCS, TACS, OACC, OAOC, and GTAC

Analysis of overall annualized capital cost, overall annual operating cost, and grand total annual cost in 43 HCWTSs in Tehran is shown in Table 2. As shown in Table 2, OAOC and GTAC were assessed at to be about 1.52 and 1.63 million dollars per year in 43 hospitals, respectively. It is clear that OAOC accounts for 93.2% of GTAC (1.52 million dollars per year vs. 1.63 million dollars per year). Similarly, in the study of Brayal Carry D’Souza et al. at three hospitals in India, it was found that about 80% of the expenses were spent on operating costs63.Table 2 Analyses on costs in 43 HCWTSS, in the general and specialized hospitals, and comparison of total annual costs for various phases in 43 HCWTSS in Tehran.

Furthermore, the average of total annualized capital costs, total annual operating costs, and total annual costs in general and specialized hospitals is shown in Table 2. According to Table 2, the average of total annual costs with a value of 42.68 thousand dollars per year in general hospitals was more when compared to specialized hospitals with a value of 26.20 thousand dollars per year. The average total annual costs for managing HHCW treatment is 1.63 times lower in specialized hospitals than in general hospitals. Since the existence of a significant difference in the generation of infectious waste for these two types of hospitals was confirmed by Eslami et al. in 2017, perhaps this difference in annual costs between different types of hospitals can be attributed to the difference in the generation of infectious waste in specialized hospitals compared to general hospitals48. Because probably specialized hospitals with less infectious waste generation have less need for bags and safety boxes to collect the produced waste and transfer those to the treatment site. In addition, in the treatment site, the sterilizer is used less during the day and has less depreciation. As a result, the cost spent on repairing sterilizers is less. Hence, the less generation of infectious waste in specialized hospitals can probably cause lower operating costs in HCWTSs by affecting other parameters. In addition, operating costs cover 93.2% of the total costs; hence, total annual costs can be decreased in a specialized hospital by reducing TAOCs.

As shown in Table 2, GTAC for 43 HCWTSs was 1.63 million dollars per year. Besides, according to Table 1, the amount of annual generation of HHCW (i.e., infectious (4.909 million kg per year) and sharps waste (0.42 million kg per year)) was 5.329 million kg per year in 43 HCWTSs. According to Eq. (5), by dividing GTAC by the amount of annual HHCW, the treatment fee for HHCW was sent to 43 HCWTSS was copmuted, and it was 0.3 dollars per kg HHCW. Various studies conducted during different years are presented in Supplementary Table S10 online. For comparison, GTACkg based on dollars per kg in high-temperature facilities was about 0.73 dollars per kg HHCW in England64. This quantity is approximately 2.5 times higher than the results obtained by this study (0.3 dollars per kg HHCW that became treatment). Besides, GTACkg in the incineration-microwaving treatment method was 1.72 dollars per kg HHCW for hospitals in Massachussets, USA65. A 1.7 dollars per kg HHCW is 5.7 times higher than the results obtained by this study (0.3 dollars per kg HHCW that became treatment). The treatment process in the two mentioned studies was the waste incineration64,65. In contrast, steam treatment technologies (i.e., autoclave and hydroclave), dry-heat, and chemical technologies were researched in the present work. The literature study showed that the cost of treatment per unit weight of infectious waste in incinerators is higher than alternative technologies (i.e., autoclave, hydroclave, or chemical)66,67. Hence, these differences in results are probably related to the researched treatment methods.

The GTACkg in microwave treatment method was 0.16 dollars per kg HCW for hospitals in Massachussets, USA65. A 0.16 dollars per kg HCW is about 1.87 times less than our study (0.3 dollars per kg HHCW that became treatment). For comparison, the treatment cost per unit weight of infectious waste in the microwave is lower than in autoclave and chemical technologies68,69. For example, the annual operating costs for autoclave, chemical technology, and microwave was 0.23, 0.32, and 0.13 dollars per kg HHCW68. In addition, previous work such as Soares et al. has taken a systematic approach to analyze the costs (the periodic payment, the cost of operations, and the cost of HCW transport and landfilling) for three disinfection techniques (i.e., microwave, autoclave, and lime) for HHCW treatment in hospitals69. Accordingly, the cost analyses for the waste treated with microwaves and autoclaves were 0.12 dollars per kg HCW and 1.10 dollars per kg HCW, respectively69. These differences in results are probably related to the difference in the studied treatment methods65,69.

Nevertheless, GTACkg obtained from past works in treatment sites with the shredder (0.4 dollars per kg biomedical waste)27 and from several treatment processes of special HCW in different countries such as Denmark (0.27 dollars per kg HCW)70, United Kingdom (0.35 dollars per kg HCW)70 and France (0.32 dollars per kg HCW)70 is approximately consistent with the results of present study having GTACkg 0.3 dollars per kg HHCW. The former study reported that the GTACkg for alternative treatments in England was 0.394 dollars per kg HCW, which is consistent with the results of this study (0.3 dollars per kg HHCW)64.

As shown in Table 2, overall annual operating cost for 43 hospitals was 1.52 million dollars per year. Besides, according to Table 1, the amount of annual generation of HHCW (i.e., infectious (4.909 million kg per year) and sharps waste (0.42 million kg per year)) was 5.329 million kg per year in 43 HCWTSs. According to Eq. (4), by dividing OAOC by the amount of annual HCW, OAOCkg was assessed, and it was 0.28 dollars per kg HHCW. For comparison, OAOCkg in waste-treatment facilities with 6 to 210 tonnes capacities for biomedical waste in Maine (U.S. state) was about 0.1 dollars per kg HCW27. However, the operating cost for our work is 0.28 dollars per kg HCW, which is 2.8 times more than waste-treatment facilities in Maine (U.S. state)27.

In addition, the mean, maximum and minimum total annual costs for three phases in 43 HCWTSs are described in Table 2. Accordingly, the mean of total annual costs, in 43 HCWTSs, in phase I (collection), phase II (treatment site), and phase III (sterilizer) were 25.35, 7.43, and 5.29 thousand dollars per year, respectively. Thus, the highest and the lowest total annual costs were related to phase I (collection) and phase III (sterilizer) with a percentage of 66.5% (25.35 thousand dollars per year vs. 38.07 thousand dollars per year (phase I + II + III)) and 13.9% (5.29 thousand dollars per year vs. 38.07 thousand dollars per year (phase I + II + III)), respectively. Therefore, phase I was the most effective phase in cost generation, with a share of about 70% of total annual costs in 43 HCWTSS.

It can be noted that the main route for controlling the annual costs for each of the three phases is the cost-generating variables. Therefore, the cost-generating variables in phase I (due to the higher portion) can be considered to control the cost in 43 HCWTSs. As mentioned before, Supplementary Table S7 online shows the cost-generating variables in various phases. By investigating the variables defined in different phases, it can be concluded that the variables of phases II and III were used a limited number of times or did not change in price during the year. In other words, maybe the hospital only spent money once or twice a year to buy them. In addition, despite being used monthly, maybe these variables only faced an increase in price once a year (with a certain percentage). Among these variables, it can mention the wage and benefit paid to the sterilizer’s operator, the cost of repairs, and the efficacy tests of the sterilizer.

Besides, variables of phase I were mostly purchased monthly or even weekly. It should be noted that, sometimes, the cost of purchasing variables of phase I were changed monthly due to Iran’s economic situation and the inflation rate. Among these variables, it can mention infectious plastic bags, sharps containers, and PPE for personnel. Hence, may be attributed the effectiveness of phase I in producing the annual cost to the existence of variables that must be supplied in the near time intervals. It can be stated that the only solution to control and reduce those costs in the short term is to buy bulk consumables in large quantities for several months instead of monthly purchases in smaller quantities. The main reason for this proposal is that the inflation rate and economic conditions in developing countries like Iran are constantly changing.

In addition, with bulk purchasing, the possibility of bargaining and getting more discounts from the seller increases63. Finally, there is a possibility that this action will lead to cost reduction in HCWTSs.

Distribution of total annual costs in 43 HCWTSS

The distribution of total annual costs for 43 HCWTSS in Tehran is shown in Fig. 5. Accordingly, 95% of total annual costs in 43 HCWTSS was limited to 7.9–118 thousand dollars. As shown in Fig. 5, total annual costs followed the exponential distribution. total annual costs include all the operating and capital expenses spent on treating hazardous–infectious waste in those HCWTSS so that the efforts of managers and those involved in hospital waste management can lead to safe infectious waste from the sterilizer. Hence, about total annual costs, the efforts of managers and those involved in hospital waste management can lead to safe infectious waste from the sterilizer.Figure 5 The distribution pattern of total annual costs in 43 HCWTSS in Tehran (Iran).

Statistical analysis

Reliability of the questionnaire

Pearson coefficient correlation (r) between test and re-test was 0.70 (p-value < 0.001). According to the category provided in the study of Konjengbam et al., if r (Pearson coefficient correlation) is between 0.7 and 0.8, reliability is acceptable71. Hence, based on this work’s results, our questionnaire’s reliability was acceptable.

Statistical analysis of TACCS, TAOCS, and TACS in 43 hospitals

Statistical analysis of TACCS in 43 hospitals with various age

The output of the Fligner-Killeen test was that the p-value for total annualized capital costs for different ages of hospitals (Table S8) exceeded 0.05. This shows that the difference between hospital age variances was insignificant (p > 0.05). Hence, a parametric ANOVA test was applied to study the differences between TACCS for different ages of hospitals. The results of the ANOVA test in Supplementary Table S11 online revealed that the p-value for TACCS was less than 0.05, demonstrating a significant difference in the amount of TACCS between hospitals of various ages.

In addition, the boxplot of the distribution of TACCS (thousand dollars) in 43 hospitals with different ages in Tehran (Iran) is shown in Fig. 6a. According to Fig. 3a, the distribution of TACCS in hospitals with code 4 (30–40 years old) was different from other hospitals with various codes. In addition, the mean TACCS in hospitals with code 4 (8.2 thousand dollars) was higher than the mean TACCS for other hospitals (i.e., codes 3, 6, 7, and 9 (about 1–2 thousand dollars) and hospitals with codes 1, 2, 5, and 8 (2–3 thousand dollars)). Hence, based on the results of this work and field observation, the hospitals with code 4 compared to other hospitals (i.e., codes 1, 2, 3, 5, 6, 7, 8, and 9) used no-Iranian sterilizers. Consequently, the hospitals with code 4 spent more money purchasing sterilizers because non-Iranian sterilizers were much more expensive than Iranian sterilizers. In addition, the hospitals with code 4 used to cool the air, eliminating odor and controlling the temperature. Hence, using those devices in hospitals with code 4 can be extensively affected TACCS compared with other hospitals. Generally, using no-Iranian sterilizers and many cooling appliances for eliminating odor and controlling the temperature can increase hospitals’ TACCs.Figure 6 Boxplots of TACCS distribution in 43 hospitals with different ages (a), TAOCS for 43 hospitals with different performances (b), and TACS for 43 hospitals with different performances (c) in Tehran (Iran).

Statistical analysis of TAOCS in 43 hospitals with different performances

The Fligner-Killeen test output showed that the p-value for total annual operating costs in different performance levels of 43 hospitals (general and specialized) exceeded 0.05. This indicated that the variances in different performances of 43 hospitals were insignificant (p-value > 0.05). Hence, a parametric ANOVA test was applied to study the differences between TAOCS in different performances of 43 hospitals. The results of the ANOVA test in Supplementary Table S11 online revealed that the p-value for TAOCS was less than 0.05, demonstrating a significant difference in the amount of TAOCS in different performance levels of 43 hospitals.

In addition, the boxplot of the distribution of TAOCS (thousand dollars) in 43 hospitals with different performance levels (general and specialized) in Tehran (Iran) is shown in Fig. 6b. According to Fig. 6b, the mean TAOCS for general hospitals was about 30 dollars in thousands. In contrast, TAOCS for specialized hospitals was about 12 thousand dollars. Besides, the mean TAOCS for general hospitals was 2.5 times higher than the mean TAOCS for specialized hospitals. The main reason for this difference in TAOCS in various performance levels in hospitals (general and specialized) may be attributed to a significant difference in generating infectious waste, which aligns with the findings of past work48. In addition, based on the results of this work, the average generation of hazardous–infectious waste (infectious and sharps waste) in general hospitals (1.72 kg/act-bed/day) was higher than in specialized hospitals (1.54 kg/act-bed/day). Generally, it can be concluded that more HHCW production in general hospitals led to increasing operating costs of HCWTSs for treating infectious waste. Thus, governments and hospital managers can control the operating costs of HCWTSs via HHCW generation and management in hospitals, especially in general hospitals, which aligns with the results of the former works48.

Statistical analysis of total annual costs in 43 hospitals with different performances

The Fligner-Killeen test output indicated that the p-value for total annual costs in different performances of 43 hospitals (general and specialized) exceeded 0.05. This showed that the variances in different performances of 43 hospitals were insignificant (p-value > 0.05). Hence, a parametric ANOVA test was applied to study the differences between total annual costs in different performance levels of 43 hospitals. The results of the ANOVA test in Supplementary Table S11 online revealed that the p-value for total annual costs was less than 0.05, demonstrating a significant difference in the amount of total annual costs in different performance levels of 43 hospitals.

In addition, a boxplot of the distribution of total annual costs (thousand dollars) in 43 hospitals with different performances (general and specialized) is provided in Fig. 6c. According to Fig. 6c, the mean total annual costs for general hospitals was about 32 thousand dollars. In contrast, total annual costs for specialized hospitals was about 12 thousand dollars. Besides, the mean total annual costs for general hospitals was 2.6 times higher than that for specialized hospitals to manage HHCW treatment. The main reason for this difference in total annual costs in various performances of hospitals (general and specialized) may be attributed to a significant difference in generating infectious waste, which aligns with the findings of past work48. Furthermore, the mean total annual costs for managing HHCW treatment is 2.6 times higher than in general hospitals compared with specialized hospitals. Generally, it can be concluded that more HHCW production in general hospitals led to increasing operating costs in HCWTSs for treating HHCW.

Statistical analysis of the cost of energy consumption per bed in 43 hospitals

The Fligner-Killeen test output indicated that the p-value for the annual energy consumption cost for different types of thermal technologies (i.e., autoclave, hydroclave, and dry-heat) exceeded 0.05. This showed that the difference between the variances in different the cost of annual energy consumption for different types of thermal technologies (i.e., autoclave, hydroclave, and dry-heat) were not significant (p-value > 0.05). Hence, a parametric ANOVA test was used for further analysis (Supplementary Table S11 online). The results of the ANOVA test in Supplementary Table S11 online revealed that the p-value for the cost of annual energy consumption of thermal sterilizers per active bed in different types of thermal technologies was less than 0.05, which demonstrates a significant difference in the cost of annual energy consumption for different types of thermal technologies in hospitals that use these technologies for HHCW treatment.

In addition, based on Supplementary Fig. S1 online, the annual energy consumption cost for autoclave, hydroclave, and dry-heat technologies were about 0.2, 0.6, and 2.5 dollars per active bed, respectively. As shown in Supplementary Fig. S1 online, the lowest cost of those technologies is related to autoclaves. The use of steam at lower temperatures in autoclave and hydroclave and steam recycling technology in hydroclave can decrease energy consumption per active bed compared to dry-heat technologies3,22,23. However, dry-heat technologies apply higher temperatures and longer exposure times than steam-based technologies3,24,25. Dry-heat technologies are not usually applied in large-scale facilities and generally treat only small volumes 3. Hence, dry-heat processes can increase the energy consumption cost per active bed compared with autoclave and hydroclave technologies3.

Relationships between independent variables and total annual costs in 43 HCWTSs

The relationship between total annual costs and various independent variables in healthcare waste thermal treatment systems (HCWThTSS) of hospitals in Tehran (Iran) is shown in Supplementary Table S12 online. Accordingly, cor.test analysis showed between total annual costs and the number of personnel responsible (p-value < 0.05, r = 0.7), total annual costs and the number of personnel (p-value < 0.05, r = 0.6), total annual costs and infectious waste generation (p-value < 0.05, r = 0.6), total annual costs and the number of the sterilizer’s cycles per year (p-value < 0.05, r = 0.6) in HCWThTSS. A significantly positive correlation was perceived between total annual costs and the number of personnel (p-value < 0.05, r = 0.6) and total annual costs and the infectious waste generation (p-value < 0.05, r = 0.6). It can be concluded that increasing infectious waste generation increased the number of personnel. In addition, increasing the infectious waste generation can increase the number of sterilizer cycles per year. Consequently, the increasing infectious waste generation and the number of personnel can subsequently impact total annual costs.

Besides, the relationship between total annual costs and various independent variables in (HCWChTSs) of hospitals in Tehran (Iran) is shown in Supplementary Table S12 online. Accordingly, Supplementary Table S12 online depicted that a significant correlation was acquired between total annual costs and the number of special bags (p-value < 0.05, r = 0.8968), total annual costs and the number of active beds (p-value < 0.05, r = 0.8851), total annual costs and the number of disposable sharps containers (p-value < 0.05, r = 0.8232), total annual costs and the number of the sterilizer’s cycles per year (p-value < 0.05, r = 0.8085), total annual costs and infectious waste generation (p-value < 0.05, r = 0.7834), total annual costs and the number of personnel responsible (p-value < 0.05, r = 0.7661), total annual costs and the amount of water consumed from the sterilizer and cooling appliance (p-value < 0.05, r = 0.7115), total annual costs and the number of personnel (p-value < 0.05, r = 0.6894), and total annual costs and the number of reusable hard plastic or metal bins (p-value < 0.05, r = 0.6655) in healthcare waste chemical treatment systems (HCWChTSS). According to Supplementary Table S12 online, it can be concluded that increasing the number of active beds increased the amount of HHCW. Consequently, increasing the amount of HHCW required a greater number of special bags for treatment of HHCW in the sterilizers as well as the number of personnel. Hence, the number of active beds and special bags can extensively affect the total annual costs in hospitals’ HCWChTSS in Tehran, Iran.

Conclusion

For the first time, this work reports an estimation of economic analyses of 43 HCWTSs of 43 hospitals, in Tehran, Iran, including (1) doing some calculations of ACC, TACC, and OACC, (2) the computing of AOC, TAOC, OAOC, and OAOCkg, (3) doing some analyses of total and overall costs in 43 HCWTSs, and (4) drawing a of total costs between different levels in 43 HCWTSs. The procedure of this study was performed according to WHO approach in 2022. The results indicate that the average (± SD) of chemical, sharps, infectious, and general wastes in 43 HCWTSs were 13.79 (± 19.71 kg/day), 30.29 (± 37.46 kg/day), 336.28 (± 291.31 kg/day), and 539.6 (± 383.13 kg/day), respectively. The waste generation rate for total hospital wastes in 43 hospitals was 4.42 ± 2.77 kg/active-bed/day, which includes 2.65 kg/active-bed/day for general waste and 1.71 kg/active-bed/day for hazardous–infectious waste (infectious and sharps wastes). In addition, economic analyses showed that general hospitals spent 1.63 times more than specialized hospitals on treating HHCW per year. OAOC) and GTAC were about 1.52 and 1.63 million dollars per year in 43 HCWTSs, respectively. It is clear that OAOC accounts for 93.2% of GTAC (1.52 million dollars per year vs. 1.63 million dollars per year). Furthermore, less production of HHCW in hospitals, especially specialized hospitals, may probably create lower operating costs in HCWTSs by affecting other parameters. Based on the results, operating costs spent 93.2% of the total costs of healthcare waste management; hence, total annual costs can be decreased in a specialized hospital by reducing TAOCs. The average total annual costs in collection, treatment, and sterilizer phases in 43 hospitals were 25.35, 7.43, and 5.29 thousand dollars per year, respectively. Based on the results, the collection phase was the most effective in cost generation, with a share of about 70% (66.5%) of total annual costs in 43 HCWTSs of 43 hospitals. Based on the cor-test analysis, a significant correlation was observed between total annual costs and quantitative variables such as the number of personnel responsible, number of personnel, infectious waste generation, and number of the sterilizer’s cycles per year in both HCWThTSS and HCWChTSS (p-value < 0.05). The results of the ANOVA test demonstrated that the age and performance levels of hospitals significantly affect the annual capital and operating costs, respectively. Economic analyses showed that general hospitals consume 1.63 times more than specialized hospitals for the treatment of HHCW annually. Hence, it can be concluded that more HHCW production in general hospitals led to increasing operating costs in HCWTSs of those hospitals for the treatment of HHCW. Thus, governments and hospital managers can control the operating costs of HCWTSs via HHCW generation and management in hospitals, especially in general hospitals. Finally, using local sterilizers and a low number of cooling appliances to eliminate odor and control the temperature can decrease hospitals’ TACCS.

The results of this work have implications for the hospital managers to evaluate previously unknown economic analyses and policies and take action to control wasted costs in HCWTSs of hospitals. In addition, the results of this work can motivate researchers to perform further studies in the field of various modeling to improve and reduce hospital waste management costs. This study highlights the importance of alleviating the cost of treatment in healthcare waste management.

Supplementary Information

Supplementary Information.

Abbreviations

ACC The annualized capital cost

ACCs The annualized capital costs

AOC Annual operating cost

AOCs Annual operating costs

ANOVA Analysis of variance

F2F Face-to-face

GTAC Grand total annual cost

GTACkg Grand total annual cost per kg HHCW that became treatment in 43 HCWTSS (dollars/kg)

HCFS Healthcare facilities

HCW Healthcare waste

HCWChTSS Healthcare waste chemical treatment systems

HCWM Healthcare waste management

HCWTS Healthcare waste treatment system

HCWTSS Healthcare waste treatment systems

HCWThTSS Healthcare waste thermal treatment systems

HHCWyear Amount of HHCW produced per year in 43 HCWTSS (kg/year)

HHCW Hazardous healthcare wastes

n Lifespan of the equipment (year)

OACC Overall annualized capital cost

OAOC Overall annual operating cost

OAOCkg The overall annual operating cost per kilogram of HHCW that becomes treatment in 43 HCWTSS

r Discount rate (%)

SAF Standard annualization factor

SI Supplementary information

SMWHA The safe management of waste from healthcare activities

TACC Total annualized capital cost

TACCS Total annualized capital costs

TAC Total annual cost

TAOC Total annual operating cost

WHO World Health Organization

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-69940-0.

Acknowledgements

Acknowledgments The present study was adapted from the master’s thesis of Sahar Sharifi at Tehran University of Medical Sciences. All experimental protocols were ethically approved by the Research Ethics Committee (REC) of the Tehran University of Medical Sciences in accordance with the national and international ethical standards for biomedical research (with ethics approval ID IR.TUMS.SPH.REC.1395.1958). The authors gratefully acknowledge the support given by all relevant personnel of all 43 hospitals in Tehran for dedicating time to filling out the questionnaires and authorities of the Tehran University of Medical Sciences. Informed consent was obtained from all subjects involved in the study. Data availability The data generated and/or analyzed during the current study are not publicly available for legal/ethical reasons but are available from the corresponding author on reasonable request. Ethical approval The study design was approved by the Research Ethics Committee (REC) of the Tehran University of Medical Sciences in accordance with the national and international ethical standards for biomedical research (Approval Code: (IR.TUMS.SPH.REC.1395.1958; Approval Date:13.03.2017). Informed consent Informed consent was obtained from all subjects involved in the study.

Author contributions

Conceptualization, R.N., K.Y., and S. Sh.; methodology, R.N., K.Y., and S. Sh.; Writing—Original Draft Preparation, S. Sh. A.N.B., and R.N.; Writing—Review and Editing, S. Sh., A.N.B., R.N., and S.G. Visualization, S. Sh.; Software, R.N., A.N.B., S. Sh., and S.G.; Supervision, R.N.; Project Administration, R.N.; Formal analysis R.N., S. Sh., K.Y., and S.G. All authors have read and agreed to the published version of the manuscript.

Data availability

The data generated and/or analyzed during the current study are not publicly available for legal/ethical reasons but are available from the corresponding author on reasonable request.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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