Infectious waste management in Japan: assessment of current trends in waste measurement and reporting in general and psychiatric hospitals

Infectious waste (IW) may include waste contaminated with blood and other bodily fluids, cultures of infectious agents from laboratory work, or waste from patients with infections. Accurate and standardized measurement is an important aspect of waste management. In Japan, data on infectious waste generated by hospitals are limited. Therefore, we aimed to identify the current status of infectious waste management and disposal in hospitals. To this end, data on the amount of IW generated and IW disposal costs from 54 public hospitals—25 general hospitals and 29 psychiatric hospitals—between April 2015 and March 2016 were analyzed. The results revealed the absence of a standardized unit of IW measurement, with 33 hospitals reporting IW in kilograms and 21 hospitals reporting it in liters. As expected, the amount of IW generated at psychiatric hospitals was significantly lower than that generated at general hospitals. The amount of IW produced correlated positively with the number of in-patients. Disposal costs varied not only by hospital type and prefecture but also across hospitals of the same type within the same prefecture. A system that consolidates IW data management using standardized units is necessary.


Introduction
Infectious waste (IW) may include waste contaminated with blood and other bodily fluids, cultures of infectious agents from laboratory work such as waste from autopsies and infected animals from laboratory, or waste from patients with infections such as swabs, bandages, and disposable medical devices [1]. To differentiate between IW and noninfectious materials, hospitals in Japan may refer to documents such as the Infectious Waste Management Manual in accordance with the Waste Disposal and Public Cleansing Law (WDPCL) [2].
In Japan, there is unfortunately no act within the current legislation that applies specifically to IW management; there are, however, stipulations pertaining to the disposal of waste in general in an act related to the cleaning and disposal of waste. The WDPCL [2] was enacted in 1970 as a special law under the Basic Environmental Law of the jurisdiction of the Ministry of the Environment. The term "infectious" is not used as a category in the WDPCL but is included under the broader categories of "industrial waste requiring special management" and "general waste requiring special management". Nevertheless, despite the existence of these classifications, hospitals in Japan are not required to describe in detail the contents of their waste and often use their own internal classifications.
The Waste Management Act was amended in 1991 with the addition of the terms "specially controlled industrial waste" and "specially controlled general waste," which include the term "infectious waste". Accordingly, the Enforcement Order and Enforcement Regulations of the Act were established, and the phrases "infectious waste," "infectious industrial waste," and "infectious general waste" appeared for the first time in the Enforcement Order (1971) [3].
In many instances, the current WDPCL is vague and lacks specificity; it broadly categorizes waste into only two 1 3 categories-"industrial waste" and "general waste" and defines the parties responsible for each type of disposal. The wording "industrial waste" seems to include all waste from business operators; however, the law only stipulates 20 types of industrial waste, and thus all other non-specified types of waste fall under the "general waste" category. As a result, in some cases, waste from businesses are legally classified as general waste, and confusion may consequently arise as to who is responsible for ensuring proper disposal thereof and covering of costs.
The primary purpose of the legislation pertaining to the management of IW disposal is the prevention of the spread of infection and the preservation of public health safety and sanitation. We, therefore, believe that a uniform national standard should be developed to achieve this goal, and we hope that this study will aid in the development and implementation of such standardization.
Globally, the management of waste generated by healthcare centers is still a major problem [4]. The risks associated with medical waste management, particularly IW, have gained international attention and continue to be a primary topic of discussion [5]. The management of patients suffering from infectious diseases generates IW that puts waste collectors, other hospital patients, and healthcare workers at great risk [6] and may lead to the spread of infection, either through direct contact or indirectly through environmental exposure [7]. To limit such risks, countries around the world are implementing strategies to improve their IW management health policies. This includes the adoption of new laws, the revision of old laws, and the establishment of more efficient management systems. It should be noted, however, that although IW can be segregated according to the IW management manual, IW materials are not recyclable [7,8].
In Japan, the data available on IW management are limited. Proper and efficient waste management begins with the segregation and measurement of waste generated in hospitals and ends with appropriate treatment methods. While there is sufficient data on appropriate IW treatment methods in Japan, very few studies have examined waste measurement parameters and the disposal costs of IW generated in Japanese hospitals, and even less have compared this phenomenon between hospitals of different type (e.g., hospitals with low vs. high levels of IW). The current study is based on the premise that to improve the management of IW in Japan, reliable and accurate data on waste production, with particular attention to measurement parameters such as disposal volume and disposal cost, are required. This study aimed to identify the current status and related issues of infectious waste management disposal in hospitals with different levels of production of IW and to provide recommendations for proper disposal. To this end, we investigated the current situation regarding the disposal volume and disposal cost of IW generated by psychiatric and general hospitals in Japan.
The data from the current study can serve as an inventory to guide proposals for strategies to improve the measurement of IW in hospitals.

Sampling
Data were collected from 54 public hospitals (25 public general hospitals and 29 public psychiatric hospitals). In Japan, public hospitals are run by prefectural governments and National Hospital Organizations; prefectural governments rank immediately below the national government and comprise the first level of Japanese jurisdiction. General hospitals engage in multiple fields of medicine, and are equipped to perform surgical procedures. In psychiatric hospitals, diagnoses and treatment departments are mainly related to the field of psychiatry, with over 90% of all beds reserved for patients in need of psychiatric care. Such hospitals do not have operating theaters and do not conduct surgical procedures. This study included data from 16% of all hospitals governed by the prefectural government and National Hospital Organizations (n = 339). The hospitals included in this study were selected at random based on the availability of data (see Section Collection of data) and covered 55% (n = 26) of the 47 prefectures of Japan.

Collection of data
The Medical Research Ethics Committee of our university deemed that, due to the nature of the study, no ethical approval was required. A request for freedom of information was submitted to obtain access to data on IW generated by public hospitals. Data on the amount of IW produced and the costs of IW disposal for each hospital, the number of surgical procedures carried out within the stipulated 12-month period, and the number of hospital beds per facility were requested. Data were collected over 12 months, from April 2015 to March 2016, and data collection depended on the availability of the relevant data. Data were sourced retroactively via the Japanese Act on Access to Information Held by Administrative Organizations. Only public hospitals fall under this act; hence the inclusion of only public hospital data in this study.

Data analysis
Data analysis was carried out using the statistical computing language R (Version 3.5.1; R Core Team 2018, R Foundation for Statistical Computing, Vienna, Austria). In Japan, the amount of IW produced can be reported in kilograms (kg), liters (L), or tons. For analysis, hospitals were divided into kg hospitals and L hospitals according to the unit of measurement used. A linear regression model was used to evaluate the relationship between the amount of IW generated and other factors. A Mann-Whitney U test was used to compare data from general and psychiatric hospitals. Multivariate analysis (alpha level of 0.05) was performed to evaluate the relationship between multiple factors associated with the amount of IW generated.

Infectious waste
In Japan, the measurement of IW is not standardized, as it is measured in either kilograms, liters, or tons. Data were collected from 33 (19 general and 14 psychiatric) hospitals that reported IW in kg ( Fig. 1) and 21 (6 general and 15 psychiatric) hospitals that provided this information in L (Fig. 2).
All hospitals disclosed information on the amounts of IW generated, but not all disclosed the disposal costs; 19/19 and 5/6 general hospitals reporting in kg and L, respectively, disclosed disposal costs, but only 7/14 and 8/15 of psychiatric hospitals reporting in kg and L, respectively, disclosed disposal costs. Thus, the sample sizes of hospitals were different in terms of waste generated and disposal costs.  Figures 1, 2, 3, and 4 clearly indicate the distribution of data and variation in the IW amounts. These data show that in general and psychiatric hospitals that report IW in kilograms, there were very large variations in the amount of IW generated per month (intra-hospital monthly variation) and also among hospitals over a 12-month period (annual, inter-hospital variation). A large variation in IW amounts was also observed within (intra-hospital monthly variation) and among (annual, inter-hospital variation) general hospitals that reported in liters (Fig. 3); interestingly however, less variation in the amount of IW was observed within and among L psychiatric hospitals (Fig. 4).
Multivariate analysis (Supplementary Tables S1-S5) of the differences in disposal amount between general and psychiatric hospitals showed that the kg hospitals showed a regression coefficient of − 1880.09 (95% confidence interval − 2266.58, − 1493.61) with a p value of 1.840E-19, and the L hospitals showed a regression coefficient of − 2417.66 (95% confidence interval − 3176.43, − 1658.90) with a p value of 2.30E-09. The amount of IW generated at psychiatric hospitals was significantly lower than that at general hospitals.  In the psychiatric kg hospitals, there was no significant difference between individual hospitals within the group, except for one hospital, which differed significantly from all other psychiatric hospitals in terms of the amount of waste generated.
Furthermore, as expected, the number of surgical procedures was positively correlated with the amount of IW produced and with disposal costs.

Correlation between in-patients per 100 beds and amount of IW generated
Multivariate analysis (Supplementary Tables S1-S5) revealed an association between the amount of disposed IW and the number of in-patients per 100 beds. In the kg hospitals, the regression coefficient and p value observed were 0.19 (95% confidence interval 0.03, 0.35) and 2.49E-02, respectively. This suggests that when the number of inpatients per 100 beds increases by 1, there is a significant increase of ~ 0.189 kg/100 beds in the amount of waste generated. We could not analyze this in L hospitals because of insufficient data. Figure 5 shows the IW disposal costs in US$/kg or US$/L for general and psychiatric hospitals reporting IW in kg or L, respectively. The analysis revealed a large variation in cost per kg or cost per L and the cost per L was overall lower than the cost per kg. Furthermore, a large variance was observed in the disposal costs for individual hospitals belonging to the same category (kg or L) and between general and psychiatric hospitals. Figure 6 shows the average disposal cost per hospital over the 12-month study period and the prefecture in which the hospital is located. Disposal costs correlated positively with the amount of IW generated.

Discussion
The objective of this study was to assess the current situation in Japan regarding the measurement of IW, reporting thereof, and the management of IW disposal, using real-world data. We found that various factors, made it very challenging to collect real-world data, and this current trend hinders the effective management of IW disposal in Japan.
First, we found that due to the lack of a national datagathering system, even a retrospective one, individual hospitals are left solely responsible for the management of data on the amount of IW generated and associated disposal costs. This negatively impacts waste management and record keeping.
Second, we found that there is no unified consensus regarding the unit of measurement used for reporting the amount of IW generated. Out of the 54 hospitals included in this study, 33 measured IW disposal amounts in kilograms, while 21 hospitals measured it in liters. Due to the heterogeneous nature of IW, it is not possible to accurately convert liters of waste into kilograms of waste, and therefore data from liter hospitals cannot be compared with that of kilogram hospitals; the former dataset is included here to illustrate the lack of measurement uniformity, and henceforth we will focus on data from kilogram hospitals only, unless otherwise specified.
In this study, the average monthly IW disposal amounts reported in kilograms by general hospitals equates to approximately 0.8 kg/bed/day. In comparison with European countries, this amount is relatively low, with top IWproducing European countries like Luxemburg and Ireland, producing 5.07 and 5.03 kg/bed/day, respectively, and bottom-end IW-producing countries like Poland and Sweden producing 0.76 and 0.63 kg/bed/day, respectively [9]. Large variations in the amount of IW produced were observed within and among individual hospitals, except among L psychiatric hospitals. Minoglou et al. [10] found positive correlations of hospital waste generation with health expenditure and carbon dioxide emissions, among other variables. Various factors, such as the type of hospital (i.e., the services they provide), number of hospital beds, socioeconomic and cultural status of the patients, and the waste management processes employed, could also affect the amount of IW produced [4,11]. Although, identifying the factors that could cause the observed variations in IW produced is outside the scope of the present study, speculations may be made based on the existing literature on the topic.
The positive correlation between number of in-patients and IW produced was logically expected and is consistent with previous reports of positive correlations between the amount of waste generated by hospitals and the number of patients treated (R 2 = 1) [12], which have found that insurance reimbursement values and the number of hospital beds are significant predictors of infectious and general medical waste volumes [13]. In the hospital that consistently reported the most IW over the 12-month period, the largest amount of IW was generated during the winter months (December-March), in which infectious diseases are more prevalent. Furthermore, people tend to postpone elective surgeries to winter months, to avoid such procedures during the summer months, when they usually take their annual holiday. Furthermore, variation in the amount of IW produced by hospitals of the same type could be attributable to differences in the demographics of the prefectures/areas in which the hospitals are located (whether they are urban or more Average costs of infectious waste disposal by general and psychiatric hospitals (reporting in kg or L) over a 12-month period (from April 2015 to March 2016)-box and whisker plot is depicted, where maximum and minimum values are restricted to 1.5 times the interquartile range, and potential outliers that fall outside these ranges are indicated as dots outside the area of the box. The maximum and mini-mum IW disposal cost in general and psychiatric hospitals that report in kg was 261 US$/kg and 38 US$/kg, and 230 US$/kg and 21 US$/ kg, respectively, while in general and psychiatric hospitals that report in L, the costs were 97 US$/L and 11 US$/L, and 119 US$/L and 15 US$/L, respectively rural), and the expertise of the resident medical staff and specific services they may offer on a routine basis.
As expected, the amount of IW generated was significantly lower in psychiatric hospitals than in general hospitals. This is due to the difference in the nature of the healthcare provided within these types of hospitals. We observed substantial variations in the disposal costs (US$/kg or US$/L) between hospitals of the same type using the same reporting unit and between different types of hospitals and hospitals using different reporting units. Disposal costs are covered by individual hospitals that receive some government funding, which may be used for waste disposal; however, data collection on exactly how IW disposal is budgeted by individual hospitals did not fall within the scope of this study. As expected, disposal costs correlated positively with the amount of IW generated. The difference in cost between general and psychiatric hospitals, in which the latter had overall higher disposal costs, could simply be due to economy of scale. No obvious relationship between the gross domestic profit of the prefectures and the average IW disposal cost was observed, although it is interesting to note that Chiba, which showed the highest gross domestic profit out of the 15 prefectures, ranked third in IW disposal cost.
Furthermore, recent studies have shown that segregation of non-hazardous waste from hazardous waste at the source can significantly influence the costs associated with the disposal of healthcare-generated waste. This is an important economic factor with respect to healthcare facilities [14,15]. According to Hadipour et al. [16], accurate separation of infectious and pseudo-household waste at the source could be an essential step toward mitigating environmental and health risks while minimizing the cost of hospital waste management procedures. In Japan, all business operators, including hospitals and vendors, are required to dispose IW in accordance with a management manual that is based on the Waste Management and Public Cleansing Law published by the Environmental Remediation and Resources Recycling Bureau, Ministry of the Environment [17]. We, therefore, assumed the uniformity in the disposal methods used by the hospitals, and thus the disposal method was not a contributing factor for the observed variations in disposal costs. We should nevertheless consider the level of segregation prior to disposal as a possible factor-affecting costs.
Although an analysis of a detailed breakdown of the disposal cost of individual hospitals did not fall within the scope of this study, this could represent a valuable follow-up investigation, which together with the current study, could help establish a specific and effective system for the measurement and management of IW in Japan. Further, despite the available information on the composition of IW [7], given that hospitals are not required to determine the composition of their IW, current data on the subject do not allow to analyze this subject with sufficient depth.

Limitations
This study was based on limited data on the amount of waste generated and disposal costs. It would be interesting to analyze specific data on waste treatment procedures and factors that could influence disposal costs. The sample size in this study was also relatively small. This study did not evaluate data on the composition of IW and waste sorting carried out in each hospital. In addition, the obtained values are not directly comparable with those of other countries or even across Japan due to the unknown differences in the composition of IW, which is in fact one of the main points of this article. These shortcomings constitute prospects for further research into the management of IW in Japan and globally.

Conclusion
A major and a fundamental shortcoming in the management of IW in Japan is the absence of a single institution overseeing IW management and the lack of a unified reporting and record-keeping system. The results from this study emphasize the necessity for such a system in Japan, overseen and governed by a specific institution and legislation that consolidate the management of data on IW using a standardized unit of measurement.
Although the data from this study were limited, the results were in line with previously published studies. It was interesting to note that some hospitals generated substantially more IW than others, and that disposal costs varied across hospitals of the same kind and within the same prefecture. More extensive studies investigating which factors could be attributable to such variations would be valuable in generating a knowledge base that could be corroborated using data from studies in other countries and that could be specifically applied to the development of better IW management legislation and guidelines in Japan. Furthermore, it should be noted that proper management of IW disposal is imperative in the prevention of environmental contamination and spreading of infectious agents, and therefore further investigation is warranted to determine the suitability and value of the current system, where IW management is governed by a non-binding manual rather than by explicit and unambiguous legislation.