Holistic health and environmental risk assessment of PM and bioaerosol emissions in hospital waste and wastewater departments using FMEA and DMRA methods

Abstract

Bioaerosol and particulate matter (PM) from hospital waste and wastewater pose significant pathogen transmission and workplace safety risks to healthcare workers and surrounding communities, requiring thorough risk assessments. This study pioneers a comprehensive risk assessment of PM and bioaerosol emissions in waste disposal and wastewater treatment departments across four Iranian hospitals, employing cutting-edge methodologies like Failure Mode and Effective Analysis (FMEA) and Decision Matrix Risk Assessment (DMRA) to enhance the precision and efficacy of risk evaluation in these high-stakes environments. The study systematically identified 15 primary risk sources, with Risk Priority Numbers (RPN) ranging from 168 to 900. The investigation involved experts, focusing on evaluating health hazards faced by hospital staff through detailed analysis of emission risks, transmission pathways, and potential health implications of bioaerosols and PM. The research confirmed the reliability of the FMEA checklist for analyzing PM and bioaerosols in waste disposal and wastewater treatment departments, with intra-class correlation coefficients (ICC) and Cronbach's Alpha values of 0.913 and 0.619, respectively. The study revealed that most risks in hospital wards originated from two primary sources: technical device malfunctions and personnel skill deficiencies. Critical high-risk activities were identified, including direct dermal exposure to wastewater and wastes, leachate dispersal during waste transportation, and inadequate segregation of sharp and infectious wastes. The research advocates for comprehensive interventions, including staff training and systematic waste handling, to ensure a safer healthcare environment through One Health strategy integrating technical and educational measures. Thus, DMRA and FMEA are complementary methods that provide an effective risk assessment.

Graphical abstract

1. Introduction

In various processes and operations conducted at wastewater treatment plants and waste disposal sites, pollutants such as bioaerosols and suspended particles (PM) can be released into the surrounding environment [1,2]. Wastewater contains pathogenic and non-pathogenic microorganisms that are released into the environment as bioaerosols during various processes in the treatment plant [3]. Bioaerosols present in the air can enter the human body through inhalation, skin contact, or ingestion, leading to health effects on the personnel working at the wastewater treatment plants [4,5]. Studies have shown that exposure to bioaerosols containing pathogenic microorganisms can result in respiratory infections, gastrointestinal symptoms, hypersensitivity, and allergies among treatment plant staff [6,7]. Furthermore, research has indicated that staff at the wastewater treatment plant are exposed to high levels of endotoxin [8], and there is a notable correlation between airborne bacteria exposure and the development of respiratory and flu-like symptoms in these workers [9].

Apart from wastewater treatment plants, waste disposal sites also face challenges in identifying sources of odor emissions and gases from waste. Bioaerosols and PM emitted at these sites pose a significant health risk to employees, which is often overlooked. The health impact of these particles and bioaerosols at waste disposal sites is influenced by factors such as the quantity and characteristics of the waste collected, the type, shape, and age of the landfill, technologies employed, and prevailing weather conditions [10].

Hospitals are significant sources of solid waste production, particularly infectious waste, and wastewater contaminated with infectious agents [11,12]. As the production of infectious waste increases, so does the potential for spreading bioaerosols to the surrounding environment, putting employees at higher health risk.

Overall, Bioaerosols and PM emissions from hospital waste and wastewater are critical pathways for pathogen transmission, impacting the health of healthcare workers and the surrounding community ecosystem [13]. These bioaerosols, which contain pathogenic microorganisms, pose risks of respiratory infections, allergic reactions, and other health issues not only through inhalation but also via skin contact and ingestion [1]. Furthermore, environmental factors such as poor ventilation and aging hospital infrastructure exacerbate these risks by increasing indoor concentrations of PM and bioaerosols [14]. For instance, Bauer et al. (2002) identified bioaerosols smaller than 2 μm in WWTPs, highlighting potential health risks due to their respirable size [15]. Valdez-Castillo et al. (2019) explored biological waste management and advanced nanotechnologies to mitigate these emissions [16]. Additionally, recent hospital-based studies have characterized correlations between PM concentrations and bioaerosol levels, indicating the complex interplay influencing indoor air quality [17]. Addressing these interconnected human and environmental health challenges requires comprehensive risk assessments and integrated management strategies to protect both occupational and public health [18]. However, comprehensive risk assessments specific to hospital waste disposal and wastewater treatment units employing combined operational risk management methodologies remain limited, underscoring the novelty of the present research. Therefore, by utilizing existing risk assessment methods, potential risks can be identified and mitigated to reduce their impacts. These methods encompass predictive models that analyze the consequences of human and natural activities, errors, and provide valuable insights to decision-makers regarding the associated risks. Over 60 risk assessment methods have been developed recently to evaluate and manage risks [19]. Among these, commonly used methods include Preliminary Risk Analysis (PHA), Failure Mode and Effect Analysis (FMEA), and Hazard and Operability Study (HAZOP) [20].

FMEA stands out as a crucial risk assessment method for enhancing systems and processes, pinpointing potential risks, and recommending corrective actions [21]. This method identifies potential risk scenarios within processes and assesses their impact on system performance [22]. It is recognized for its structured and dependable approach, ease of learning and implementation compared to other methods, and its ability to evaluate complex systems effectively [[23], [24], [25]]. The FMEA technique provides a systematic way to identify and prioritize health, safety, and environmental risks in hospital solid waste management, enabling proactive prevention and resource optimization [18,26]. While effective for complex healthcare waste processes, its limitations include subjective scoring and the need for expert involvement, making it time-consuming [26,27]. Despite these challenges, FMEA proves valuable for targeted risk control and continuous improvement in hospital waste management [26,27].

The study used qualitative risk assessment to model the analysis of FMEA to identify the sources and risks of these pollutants and the appropriate control methods for them in the wastewater treatment plant and the waste disposal sites of hospitals. In addition, Decision Matrix Risk Assessment (DMRA) will be conducted to control and reduce these pollutants or eliminate their emission sources to prevent employees from contracting various infections and diseases, and provide a more suitable working environment for employees. Thus, the primary objective of this study is to comprehensively evaluate the effectiveness of the FMEA and DMRA techniques in identifying critical risk points within the management and governance of hazardous materials and wastewater treatment processes in hospital settings.

2. Materials and methods

2.1. Study area

Following the feasibility assessments conducted in the present study, two cities, Bushehr and Tehran, were selected for evaluating PM and bioaerosol risk assessment. Bushehr, located in southwestern Iran, was chosen due to its prolonged warm seasons, geographical location, presence of various industries, seasonal dust storms, and the lack of prior studies on assessing the health risk of PM and bioaerosols in the surrounding air of hospital wards in this city [28,29]. Additionally, Tehran, the most populous city and the capital of Iran, which experiences longer cold seasons, was also selected for this study [30].

In this descriptive-analytical-cross-sectional study, the risks of the release of PM and bioaerosols (bacteria and fungi) in the air around the waste disposal and wastewater treatment departments were examined by four selected hospitals in Iran (a total of two specialized hospitals and two general hospitals), among the staff of these departments. The selection of hospitals was based on factors such as the existence of waste disposal sites and wastewater treatment plants in each hospital, the population of hospital patients, and the availability of highly qualified individuals with expertise in the management of PM and bioaerosols within these facilities (Table S1).

2.2. Risk level assessment by failure mode and effective analysis (FMEA)

One of the most effective tools for hazard prevention is the FMEA model, which aims to identify and prioritize potential risks and their causes and effects within a risk assessment. This model helps determine risks before they occur, reducing the cost and time needed for corrective actions when risks materialize [31]. The FMEA model involves several stages. Initially, it was used to evaluate health risks related to the tasks of healthcare workers, focusing on activities that release PM and bioaerosols in hospital waste disposal and wastewater treatment areas. Scenarios were analyzed to assess risks, considering the environmental and health impacts of these activities for risk prioritization. Identified risks included environmental pollution and health consequences, with suggested measures to control PM and bioaerosol emissions to prevent associated risks (see Fig. 1).

Fig. 1.

Different stages of the FMEA risk assessment model.

In this study, data on risk assessment were organized and summarized using the standard FMEA checklist. The analysis incorporated the perspectives of team members as documented in this checklist (Table S2) [32]. The study engaged experienced professionals involved in managing the pollutants under investigation from selected hospitals, as outlined in Table S2. The team included members from the Environmental Health Committee of four selected Iranian hospitals, comprising experts in environmental health, occupational health, infection control, and quality and safety improvement. These members utilized scores from Tables S3, S4, and S5 to calculate the Risk Priority Number (RPN) and prioritize risks associated with PM and bioaerosol emissions in various hospital wards [33,34].

The equation for RPN is given by:

$$\mathrm{RPN}=\text{Severity}\times \text{Occurrence}\times \text{Detection}$$ (1)

The severity of risk indicates the potential extent of losses to environmental and human health due to PM and bioaerosol emissions. Detection capability reflects the ability to recognize emission scenarios before they occur, aiding in effective management. The occurrence aspect defines how frequently these environmental and health impacts are likely to happen within a specified timeframe. The RPN serves as an indicator of the likelihood that these risks will result in adverse health effects. Tables S3, S4, and S5 outline the severity levels for impact, occurrence, and detection risk probability. The RPN can range from 1 to 1000, with risks categorized into three levels based on assessor opinions: high (500–1000), medium (250–500), and low (1–250) [34,35].

The process of accountability and completion of checklists by various experts from the Environmental Health Committee at the selected hospitals in this study progressed until a consensus was reached among the experts. Consequently, 15 members of the Environmental Health Committee participated in the study, providing their expertise to suggest necessary control measures for the identified risks. A comprehensive summary of the identified risks and proposed control measures provided by the members was documented in this study.

2.3. Decision matrix risk assessment (DMRA)

The risk matrix method, also known as the “decision matrix risk assessment (DMRA) technique,” is a systematic approach used in the risk assessment process to evaluate and prioritize different levels of risk. This technique allows for the comparison of various risks to determine which threats should be addressed first to minimize potential hazards. It is easy to use and visually clear, making it applicable even with limited data and without the need for specialized knowledge [[36], [37], [38]]. Consequently, the risk matrix has become a popular decision-support tool in both public and private sectors, including healthcare organizations, due to its capacity to standardize the risk grading process. Furthermore, it helps risk managers, boards, and stakeholders in establishing priority levels for necessary corrective actions or controls within departments or facilities based on their scores [39,40]. Additionaly, the risk matrix enables the evaluation and documentation of changes in risk before and after implementing control measures [41].

Using the DMRA method, the identified risks related to PM and bioaerosol emissions in the surrounding air of hospital wards were classified into three categories based on the calculated Risk Priority Number (RPN): high, medium, and low risk, represented by red, yellow, and green colors in the diagrams. The study analyzed three distinct scenarios focusing on severity as the primary factor in risk assessment along with other parameters used in RPN calculations, including matrices for Severity-Occurrence, Severity-Detection, and Severity-Probability (Detection × Occurrence). The resulting scenarios were illustrated as graphs in this study.

2.4. Statistical analysis

This risk assessment method has been widely utilized by researchers across various health fields, which supports its established validity [42,43]. To assess the reliability and correlation among the components of the questionnaire—Severity, Occurrence, and Detection—and the responses from each assessor to the checklist questions aligned with the study objectives, the Cronbach Alpha coefficient was employed. This coefficient is a commonly used statistical measure for evaluating the internal consistency of questionnaires and scales. The Alpha values were categorized as follows: excellent (0.93–0.94), strong (0.91–0.93), reliable (0.84–0.90), robust (0.81), fairly high (0.76–0.95), high (0.73–0.95), good (0.71–0.91), relatively high (0.70–0.77), slightly low (0.68), reasonable (0.67–0.87), adequate (0.64–0.85), moderate (0.61–0.65), satisfactory (0.58–0.97), acceptable (0.45–0.98), sufficient (0.45–0.96), not satisfactory (0.4–0.55), and low (0.11) [44]. In this study, the recovery method, recognized as a standard reliability calculation technique [45]—was applied to each identified risk for determining the final RPN. This method involved two rounds of tests with a single group of participants, spaced 2 to 4 weeks apart, followed by comparing the scores. The intra-class correlation coefficient (ICC) was then calculated to assess test reliability, with ICC values ranging from 0 to 1; scores below 0.5 indicate poor reliability, scores between 0.5 and 0.75 suggest moderate reliability, scores from 0.75 to 0.9 reflect good reliability, and scores above 0.9 denote excellent reliability [46]. If any risks proposed by experts were mentioned multiple times in the checklists, outlier data related to Severity, Occurrence, and Detection coefficients were excluded using the Q-Dixon test, and their mean values were reported in the risk assessment table. Statistical analyses were conducted for this study using SPSS 26 and Minitab 21 software.

3. Results and discussion

The FMEA risk assessment results for PM and bioaerosol emissions in the air around waste disposal departments and wastewater treatment plants of hospitals are presented in Table 1. The study aimed to identify factors influencing the emission of pollutants, such as PMs and bioaerosols, in hospital wards and their association with the onset of various diseases among staff. The Cronbach Alpha coefficient and ICC were 0.619 and 0.913, respectively, confirming the validity and applicability of the checklists for analyzing PM and bioaerosols in the air. The ICC coefficient's proximity to 1 and the Cronbach Alpha's mediocrity supported this validation. Based on the checklists completed by the research team in hospitals, 15 main risks were identified as causing PM and bioaerosol emissions in the air around hospital wards. The RPN range was also calculated between 900 and 168, with higher risks for PM and bioaerosol emission, including direct skin contact with wastewater, effluent, and waste, distribution of leachate during waste transfer, and failure to comply with the proper separation of sharp and non-sharpened waste. According to the results, 8 risks were identified as high risks of PM and bioaerosol emissions in hospital wards. The study revealed that many of these risks stem from device failures, inadequate process performance, or a lack of employee skills in hospital departments. Direct skin contact with wastewater and waste posed the highest RPN, potentially leading to the transmission of fungal diseases, primarily skin-related, to employees. Activities like distributing leachate during waste transfer and improper separation of sharp and non-sharpened waste were also identified as high-risk factors, necessitating skilled staff to prevent the transmission of infectious and respiratory diseases. While low-RPN risks should not be overlooked, they can lead to additional risks if waste is not handled correctly or ventilation and disinfection systems malfunction. The study by Nashira et al. (2024) focused on wastewater treatment plant risks in a Class B Hospital in Indonesia using the FMEA model, identifying one unacceptable risk and 23 undesirable but acceptable risks [47]. This study specifically addresses the risks of suspended particles and bioaerosols around wastewater treatment plants and waste disposal departments in hospitals, potentially resulting in fewer identified risks compared to other studies. In a study by Bhirich et al. (2023), the risk assessment of personnel exposure in the pharmacy of the National Institute of Oncology was investigated using the FMEA method. The study identified three major risks related to the particulate environment, direct contact, and daily passive inhalation among 12 identified failure modes [48]. Similarly, Godini et al. used the FMEA method to assess the risk of hospital waste management in the Children's Medical Center of Tehran, identifying 33 risks with varying levels of risk [31]. Another study focused on the risks of hospital waste production in disease spread, identifying 23 risks, with 9 of them posing significant risks (RPN more than 100) [42]. Additionally, a study evaluated the risks of exposure to PM in ambient air, identifying 17 risks that resulted from lung disease (524) with the highest number of RPNs, and traffic symptom distortion (50) with the lowest risk [43].

Table 1.

Identified risks in the surrounding air of waste disposal departments and wastewater treatment plants in hospitals using the FMEA method.

No.	Failure mode	Frequency	Potential Failure Effect	Average RPN (Sa×Ob×Dc) (Before recommended control measures)	Risk level	Suggested control measures
1	Transmission of infection by direct contact with sewage and waste	3	Transmission of bacterial and fungal respiratory and skin diseases	10 × 9 × 10 = 900	High	-Employing a skilled and trained operator -Daily checking of the cleaning mechanisms of the House -Observing the use of personal protective equipment
2	Distribution of leachate during the transfer of waste to the machine	3	Transmission of bacterial and fungal respiratory and skin diseases	10 × 9 × 10 = 900	High	-Use of personal protective equipment -The exodus of the garbage nylons after three-quarters of them have been filled. -Ensure the tightness of the waste nylons. -No sharp, winning waste in the nylons. -No trash bags thrown into trash cans. -Buy quality and durable garbage bags.
3	Failure to properly comply with the separation of sharp and non-sharpened waste	3	Damage to employees and the development of various bacterial and fungal infections	9 × 10 × 9 = 810	High	-Continuous training of hospital employees for proper separation -Use of personal protective equipment by the device operator
4	The breakdown of the disposal device and the accumulation of infectious waste in the hospital	4	Leachate production and contamination of surfaces with bacterial and fungal contaminants	10 × 8 × 9 = 720	High	-Hiring a skilled operator -Daily checking of the disposal mechanism -Daily mechanical, chemical, and microbial monitoring of devices
5	Needle-sticking waste employee	4	Damage to employees and the development of various bacterial infections through the blood	9 × 9 × 8 = 648	High	-Disposal of sharp objects in the Safety box -Continuous monitoring of environmental health experts on sharp-tipped waste disposal -Use of personal protective equipment by waste disposal employees -Continuous operator training and proper use of personal protective equipment
6	Excessive steam pressure in the autoclave	1	Increasing environmental humidity and creating a suitable environment for the release of bioaerosols, especially fungi	10 × 8 × 7 = 560	High	-Annual certification of hydrostatic testing and thickness of the autoclave -Daily autoclave checks -Employing a skilled and trained operator -Continuous operator training and proper use of personal protective equipment -Constant monitoring of the environmental health expert on waste disposal
7	The autoclave is not working properly	2	No loss of bacterial and fungal contaminants from hospital waste Contact with bioaerosols while transporting bags	10 × 8 × 7 = 560	High	-Annual certification of hydrostatic testing and thickness of the autoclave -Daily autoclave checks -Employing a skilled and trained operator -Continuous operator training and proper use of personal protective equipment -Constant monitoring of the environmental health expert on waste disposal
8	Failure to properly treat wastewater according to existing standards	1	The release of fungal and bacterial bioaerosols into the surrounding environment	9 × 7 × 8 = 504	High	-Performing various physical, chemical, and microbial analyses continuously -Continuous training of operators -Use of skilled and expert operators
9	Failure to properly close the door of the autoclave and cause an accident	1	The release of fungal and bacterial bioaerosols into the surrounding environment	9 × 7 × 8 = 504	Medium	-Use of a skilled operator -Use of devices with warning systems -Final check of the system's performance in each waste disposal series -Use of personal protective equipment
10	Lack of adequate ventilation in waste disposal sites	1	High pollution load associated with PMs and bioaerosols in indoor air	7 × 7 × 8 = 392	Medium	-Use of strong fans and ventilation systems to replace the indoor air in the site
11	Use of natural ventilation in the disposal site	1	PM entering the indoor air of the disposal site	7 × 8 × 7 = 392	Medium	-Use of strong fans and ventilation systems to replace the indoor air in the site
12	Failure to properly remove the steam from the autoclave in the waste disposal room	1	High spread of microbial pollution in the indoor air	9 × 7 × 6 = 378	Medium	-Daily autoclave visits -Employing a skilled and trained operator -Continuous operator training and proper use of personal protective equipment -Constant monitoring of the environmental health expert on waste disposal
13	Transportation of waste at the site of the waste disposal and the waste transportation machine	2	Emissions of particles and bioaerosols during transmission	7 × 8 × 6 = 336	Medium	-Use the stairs to make it easier to access the autoclave basket -The transfer of waste from the waste site to the trash truck by the car lift -Teaching the basics of freight safety -Continuous face-to-face training on the basics of freight transportation -Periodic inspections of the autoclave -Separation of the garbage outlet from the hospital environment or use of emerging systems, including shooting -The proximity of the waste disposal department to the main hospital building
14	Lack of proper operation of wastewater ventilation systems	1	High emissions of bioaerosols into the surrounding air	9 × 6 × 6 = 324	Medium	-Permanent control of the aeration system. -Use of the alarm system if the ventilation system is not working properly -Continuous service of the air conditioning system -Operator training -Use of a skilled and expert operator
15	Incorrect or inadequate sewage disinfection	2	The presence of bacterial and fungal contamination in the drainage	7 × 6 × 4 = 168	Low	-Continuous testing of the sewage outlet -Permanent control of the decomposition process -Skilled and expert operator

^aSeverity.

^bOccurrence.

^cDetection.

These findings showed the critical importance of thoroughly assessing and managing the health risks posed by PM and bioaerosol emissions in hospital settings to protect workers and nearby populations from infectious and respiratory diseases. Exposure to bioaerosols and PM emitted from hospital waste and wastewater environments presents a significant route for the transmission of various pathogens, including bacteria, fungi, and viruses, to humans [1]. These microorganisms can become aerosolized during waste handling and wastewater treatment processes, facilitating their dispersal in the air and increasing the risk of inhalation by healthcare workers and nearby individuals [1,3]. Inhalation of contaminated bioaerosols can lead to a range of respiratory infections and hypersensitivity reactions, while direct skin contact with contaminated waste or wastewater can cause dermal infections and serve as another pathway for pathogen entry [6,7]. Additionally, environmental contamination via deposition of bioaerosols on surfaces can propagate indirect transmission, further exacerbating infection risks in hospital settings [4]. Viruses, such as noroviruses or other hospital-associated viral agents, have also been detected in airborne particles within these environments, underscoring the necessity of comprehensive airborne infection control measures [3,49]. Collectively, these transmission routes highlight the complex interplay between airborne and contact exposure pathways, emphasizing the need for integrated risk management approaches to protect healthcare workers and surrounding communities from infectious hazards associated with hospital waste and wastewater emissions.

To the best of our knowledge, no study has determined the control measurements for identified risks by the FMEA risk assessment until now, while the suitable measurements in the present study for each risk were defined. In this study, control solutions were proposed by the evaluation team for each identified risk. Implementation of these control measures could help reduce the risks in healthcare settings and prevent the spread of diseases among staff due to exposure to PM and bioaerosols in the air. Controlling emissions in hospital waste and wastewater management is critical not only for protecting healthcare workers from direct exposure to harmful PM and bioaerosols but also for significantly reducing the environmental pathogen load [50]. By mitigating the release of infectious agents into the surrounding air, these control measures help prevent the dissemination of pathogens beyond hospital settings, thereby reducing the risk of community-level disease transmission. This dual benefit underscores the importance of comprehensive risk management strategies, including proper waste segregation, effective wastewater treatment, maintenance of equipment such as autoclaves, and continuous staff training. As identified in this study, high-risk exposures can lead to respiratory and skin infections among staff, which if uncontrolled, pose broader public health risks through environmental contamination [18]. Therefore, investment in emission control measures not only improves occupational safety but also serves as a preventive public health intervention to curb infectious diseases in the wider community. Key proposed control measures in the present study include ongoing staff training and regular monitoring of the autoclave and wastewater treatment system. Moreover, other suggested measures are detailed in Table 1, providing guidance for governments and decision-makers to mitigate potential risks associated with PM and bioaerosols, ultimately safeguarding the health of healthcare workers.

Thus, the results of this study clearly demonstrate that the risk assessments are directly linked to the potential spread of infectious agents. High-risk activities such as direct skin contact with sewage and waste, leachate dispersion during waste transfer, and improper segregation of sharp and infectious waste serve as key transmission pathways for bacteria, fungi, and viruses. This alignment between the identified risks and pathogen transmission dynamics underscores the critical need for targeted control measures to prevent the spread of infections in hospital waste and wastewater environments. Based on the study, bioaerosol emissions from hospital waste disposal and wastewater treatment departments not only pose health risks to workers but can also adversely affect local air quality and microbial ecology [50]. These airborne microorganisms may disperse into the broader environment, potentially altering microbial communities and facilitating zoonotic or environmental transmission pathways of infectious agents [50].

Finally, based on the identified risks and existing studies, three types of decision matrices (DMRA) were created and evaluated, with the results displayed in Fig. 2, Fig. 3, Fig. 4. These matrices indicated a higher likelihood of occurrence and lower detection rates for most of the risks identified in the waste disposal and wastewater treatment plant departments of hospitals.

Fig. 2.

Matrix (Severity×Occurance) risk assessment in this study using the FMEA method.

Fig. 3.

Matrix (Severity×Detection) risk assessment in this study using the FMEA method.

Fig. 4.

Matrix (Severity×Probability) risk assessment in this study using the FMEA method.

Based on the Severity-(Occurrence×Detection) Matrix (Fig. 4) revealed that more identified risks fell within the orange zone compared to the other two decision matrices (Fig. 2, Fig. 3), suggesting that factors such as occurrence and detection had a significant impact on the calculated RPN using this method. The other two matrices also highlighted that many identified risks had high detection rates and a high probability of occurrence, necessitating the implementation of pre-existing control measures. Based on the Severity-Detection Matrix (Fig. 3) indicated that certain risks, such as leachate distribution or improper device operation, were challenging to detect, emphasizing the need for precise risk identification methods in hospitals to prevent their occurrence. Some risks, like insufficient wastewater disinfection, fell within the low to moderate risk range across all three types of matrices in this study, posing minor risks of PM or bioaerosol release in these environments. These risks are easily detectable and preventable. However, no studies have yet examined the risk of PM and bioaerosol release into the air around waste disposal and sewage treatment plants in hospitals using the DMRA technique. According to the results of the DMRA method in this study, the majority of identified risks were classified as high risks (60 %), underscoring the importance of implementing control measures.

Finally, in this study, FMEA systematically identified 15 primary failure modes, with RPN ranging from 168 to 900, emphasizing critical high-risk activities such as direct contact with sewage, leachate dispersion during waste transportation, and improper segregation of waste. Complementarily, the DMRA method classified these risks into high, medium, and low categories using severity-based matrices, thereby visually reinforcing the prioritization derived from the FMEA analysis. The strong correlation observed between elevated RPN values and the red-coded high-risk categories in the DMRA validates the reliability and robustness of this integrated dual-method approach. Collectively, these methodologies established a comprehensive framework that not only quantitatively assessed and categorized risks but also informed the development of customized control measures—including personnel training and technical interventions—to effectively mitigate the identified hazards and improve occupational safety as well as environmental health within hospital environments. Therefore, given the identification of the risks involved in this study and the control measures mentioned, guidelines can be developed to reduce the emissions of PM and bioaerosols in the safe environments of waste disposal sites and wastewater treatment plants of hospitals and inform the relevant managers to avoid the possible risks associated with these pollutants in the surrounding air of hospitals for employees.

The findings of this study underscore the critical need for adopting One Health strategies that integrate environmental controls, occupational safety, and public health to effectively manage the risks associated with PM and bioaerosol emissions in hospital waste disposal and wastewater treatment departments. By identifying key high-risk activities linked to device malfunctions and personnel skill gaps, the research highlights the importance of a holistic approach that combines technical interventions, such as improved waste handling systems and ventilation, with continuous staff training and protective measures. This integrated framework not only safeguards healthcare workers from occupational exposures but also mitigates environmental contamination, thereby reducing pathogen transmission risks to surrounding communities. Implementing such One Health-based strategies will enhance healthcare facility safety, promote environmental sustainability, and contribute to broader public health protection.

4. Limitations and ideas for future research

It is important to acknowledge that while this risk assessment method offers several advantages, it also has certain limitations. These limitations are reflected in the descriptive statements found in Tables S3, S4 and S5, which may not completely capture or convey the criteria for an identified risk. Additionally, expert opinions on ranking the decimal indicators for a specific risk can vary among different specialists; thus, selecting experienced experts and considering the average of their assessments is essential. In instances where opinions showed little difference or were repeated, the average RPN was used as the final risk ranking. Moreover, the average alpha coefficient observed in this study (0.619) may indicate the influence of varying expert opinions on the components or a limited number of skilled professionals available within the Environmental Health Committee of hospitals. Therefore, future studies should involve more qualified FMEA risk assessment experts. The study suggested several control measures for the identified risks, which will necessitate further research to implement these measures and evaluate the extent of risk reduction achieved. It is crucial that checklists are completed and RPNs recalculated after implementing these control measures. If these measures prove effective in mitigating risks, their implementation should continue; otherwise, new strategies will be required to prevent the release of pollutants and bioaerosols into the environment. Lastly, this study represents the application of FMEA risk assessment to pollutants in the hospital's surrounding air of waste disposal and wastewater treatment sites, highlighting the need for additional research on other indoor and outdoor air pollutants in hospital wards.

5. Conclusion

This study employed the Failure Mode and Effects Analysis (FMEA) and Decision Matrix Risk Assessment (DMRA) techniques to comprehensively evaluate risks associated with particulate matter (PM) and bioaerosol transmission in the hospital's surrounding air of waste disposal departments and wastewater treatment plants for employees. The research identified 15 critical risks with Risk Priority Numbers (RPN) ranging from 168 to 900, revealing significant insights into potential health hazards. The study revealed critical insights into occupational health risks, highlighting that the majority of identified risks were from device failures, inadequate process performance, and insufficient employee skills. The high-risk activities included direct skin contact with wastewater and waste, leachate distribution during waste transfer, and improper separation of sharp and infectious waste. The research underscores the significant potential for disease transmission, including fungal and respiratory infections, and emphasizes the urgent need for enhanced staff training, improved waste handling protocols, and comprehensive protective measures to mitigate health risks in hospital waste management settings. Thus, this study thorough evaluation of PM and bioaerosol emissions significantly advances the understanding and mitigation of pathogen transmission pathways within a One Health framework, addressing microbial risks and infectious agents to enhance environmental health and protect both human and ecological well-being. Our findings indicate that while DMRA provides a straightforward framework for risk communication, the FMEA method offers a more detailed, systematic, and reliable risk identification and prioritization process, particularly suited to the complex nature of hospital waste management and wastewater treatment. Therefore, FMEA is the superior model in this context, as it enables targeted control measures and continuous improvement to effectively mitigate critical risks in healthcare environments.

CRediT authorship contribution statement

Ahmad Jonidi Jafari: Writing – review & editing, Supervision, Project administration, Investigation, Conceptualization. Mahbubeh Tangestani: Writing – original draft, Software, Methodology, Formal analysis, Conceptualization. Majid Kermani: Writing – review & editing, Methodology, Investigation, Conceptualization. Roshanak Rezaei Kalantary: Writing – review & editing, Methodology, Investigation, Conceptualization.

Declaration of generative AI and AI-assisted technologies in the writing process

During the preparation of this work the author(s) used Perplexity AI, GPT-4 language model in order to improve readability and language. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the published article.

Declaration of competing interest

The author has no competing interests to declare.

Appendix A. Supplementary data

Supplementary material

Data availability

No data was used for the research described in the article.