Search strategy

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist was followed; the protocol was not pre-registered. A library professional assisted in designing the search and protocol for article inclusion. The research was exempt from institutional ethics review as it only assessed previously published studies and did not involve human or animal subjects or field research. The MEDLINE, Science Citation Index-Expanded, Emerging Sources Citation Index, and Embase databases were searched for the following terms from January 1, 1948, to March 26, 2025:

1. 1) exp water/ or exp water purification/ or wastewater/ or (wastewater or water)
2. 2) Operating rooms/ or exp surgical equipment/ or ((operating or surgical) adj3 (room* or theat* or suite* or equipment))
3. 3) exp waste management/ or exp environment, controlled/ or greenhouse effect/ or exp conservation of natural resources/ or exp sterilization/ or (conserv* or recycl* or green or environ* or consum* or sustainab* or waste or sterilize* or disinfect* or ventilat* or heating or climate or resource*).ti,ab. or (air adj3 condition*)

Final search combined 1 and 2 and 3.

Inclusion/exclusion criteria

Peer-reviewed and gray literature articles were reviewed; gray literature and multiple databases were included to attempt to capture all possible studies meeting inclusion criteria. Inclusion criteria included: 1) reports of original data, 2) quantification of water use and/or interventions conserving water in the hospital setting, 3) studies modeling hospital water use. Exclusion criteria included articles lacking original data, opinion pieces, non-medical reports, dental studies, lay press reporting. Outcomes included quantification of water use and quantification of water conserved through interventions.

Screening, extraction, and synthesis

Title/abstract review was conducted independently by NK/DAM. Four independent reviewers (NK, MH, JZ, DAM) completed full text review, data abstraction, and analysis, with extracted data documented in a spreadsheet. Variables extracted included study design, topic, methods, key findings/outcomes, and quality rating. Inter-rater reliability was ensured via strict adherence to inclusion/exclusion criteria, independent review of all articles followed by discussion to clarify details and confirm a shared mental model, and a requirement for unanimous consensus on all decisions for inclusion/exclusion and rating. Disagreements were resolved with live group discussion of all articles and ratings, with unanimous consensus reached in all cases.

Rating system

The quality of the articles was initially assessed using a standard framework for medical research publications, and overall quality was found to be low; only two small-scale handwashing studies [12,13] could be categorized as well-designed controlled trials without randomization, and the remainder were of lower quality. However, many articles using high-quality methods appropriate for environmental impact studies (e.g., life cycle assessment) did not fall into traditional quality rating categories for medical research studies, leading to a lower rating. This was felt to not accurately represent the quality of the studies. To address this issue, the evaluation framework established by Rizan and colleagues [14] in their investigation of carbon emissions within the operating room was adapted to assess water use literature. The modified system assesses the articles based on four key domains: completeness, consistency, transparency, and accuracy, with additional subcategories in the domains of transparency and accuracy. Each category or subcategory is scored between 0 and 2, reflecting an increasing alignment with each respective category. Ultimately, each article is assigned a percentile score out of a maximum score of 20, or a maximum score of 18 for noncomparative studies (a study was categorized as noncomparative if it did not perform a measured comparison of outcomes between two alternatives or compare measurements before and after intervention).

An example of modification to adapt this system to our study is as follows: The Consistency subdomain 3b in the Rizan system reads “To what extent are the greenhouse gases included clearly stated? Number of GHGs included clearly stated (2) Number of GHGs deducible (1) Number of GHGs not deducible (0)”. This subdomain was modified in our system to “To what extent is the quantity of water measured clearly stated? Quantity of water included clearly stated (2) Quantity of water deducible (1) Quantity of water not deducible (0)”. For this subdomain, an article which reported exact quantities of water would receive a score of 2; an article in which the quantity was deducible from graphic data or could be calculated from reported results would receive a 1, and an article in which the exact quantity could not be determined would receive a zero.

All included articles were reviewed and rated independently by NK, JZ, and DAM and disagreement was resolved with discussion and consensus. Studies were divided into three quality tiers: low (score ≤50%), moderate (51–75%), and high quality (76–100%). See S2 Table in the Supporting Information for full detail of all rating system categories as well as rating system results.

Surgical scrubbing

Thirteen articles examined water use related to surgical scrubbing. These were divided into three sub-categories: 1) baseline water use, 2) “on demand” vs. constant-flow water taps, and 3) alcohol-based waterless scrubs compared to water-based techniques.

Textiles

Three articles evaluated water use related to OR textiles, using life cycle assessment (LCA). LCA comprehensively quantifies environmental impacts and costs across all life cycle stages of a process, product, or system, and is well established for application in medical systems [26].

Vozzola et al. compared synthetic reusable to synthetic disposable surgical gowns for their consumption of fresh water. The study found that for every 1,000 uses, reusable gowns consumed 185L versus 1,097L for disposable gowns [27]. Cohen et al. compared the water usage of synthetic reusable to synthetic disposable OR head covers over the course of one year at a single tertiary care hospital. The authors found that reusable polyester (PE) head covers consumed 80% less water than disposable viscose and 50% less than disposable polyethylene options (32,000L for disposable viscose head covers, 13,000L for disposable polypropylene, and 6,000L for reusable) [28]. Burguburu et al. found that reusable scrub suits composed of 35% cotton and 65% PE consumed 95% more water than disposable suits made of 100% PE (6070L per four years of use by one staff member, compared to 300L for disposable), largely attributed to the substantial water required to produce the cotton for the reusable suits [29].

Sterilization

Four articles evaluated water use related to sterilization and washing of instruments. McGain et al. evaluated bacterial contamination of anesthesia breathing circuits by rinsing the circuits after use and plating the resulting fluid on bacterial growth plates to quantify colony-forming units. Various time intervals between cleaning of the circuits were evaluated for their impact on bacterial contamination. The authors found no difference in bacterial colony-forming units if the time interval of circuit cleaning was increased from every 24 hours to every 7 days. Annual water savings were projected at 47,900L per year in a 300-bed hospital with use of the longer interval [30]. Two additional studies by McGain et al. examined the water consumption of equipment sterilizers and found that sterilizers consume 81/L water/hour during idling/standby mode, including a warm-up cycle whenever a sterilizer is idle for 2 or more hours. Overall, a fifth of sterilizer water was consumed during idling/standby mode, and heavier sterilizer loads were found to be more water-efficient. Strategies to selectively turn off a single hospital’s sterilizers could reduce annual water use by 450,000–1 million L [31,32]. Adler et al. tabulated water used in washing instruments used for laparoscopic cholecystectomy, and projected water used for this purpose at nearly 375,000L over five years [33].

Equipment

Six articles evaluated water use related to equipment used in surgical procedures. Four studies used LCA methodology: Rouviere and colleagues found that reusable laryngoscope blades save 10L water per intubation compared to single-use disposable blades, or 221,600L/year at their institution based on 17,200 intubations/year [34]. Eckelman and colleagues compared water consumption between reusable and disposable laryngeal mask airways (LMA) and determined that reusable LMAs use 60% less water than disposable LMAs [35]. McGain et al. reported fully reusable anesthetic drug trays consume 3.1L water per use, compared to 10.3L for a disposable tray, and 26.7L for a disposable tray with cotton gauze pads and a paper towel added. The authors project savings of 70,000–100,000L water annually with use of reusable tray [36]. A second study led by McGain evaluated water consumption of reusable versus disposable anesthesia equipment, including breathing circuits, face masks, LMAs, and laryngoscopes. Several scenarios were evaluated; overall the authors found increased annual water consumption with increasing the proportion of reusable equipment, ranging from 30,900L/year (almost all disposable equipment) to 82,200L/year (all reusable equipment) [37].

Two studies which did not employ LCA focused on cystoscopes and compared water consumed for a single cystoscopy procedure using reusable equipment vs. disposable equipment. Both reported identical findings of 60L of water per procedure consumed by reusable cystoscopes and 0L water for the disposable cystoscope [38,39].

Surgical hand scrubbing

Methodology varied across the evaluated surgical hand scrubbing studies, and time spent scrubbing and measured amounts of water used during scrub sessions varied significantly. All studies making direct, measured comparisons between handwashing techniques were limited by short duration, small numbers of study participants and non-blinding, and lack of rigorous technique for measuring water used. Most studies also failed to repeat measurements across multiple sinks and OR settings; these limitations may over- or underestimate water use.

Crucially, no published studies used LCA to comprehensively evaluate the water consumption from manufacture of waterless scrub products, however there is one LCA-based study currently in the data analysis stage, which compared chlorhexidine gluconate water-based scrub to a chlorhexidine gluconate/ethyl alcohol-based waterless scrub. Preliminary findings from this work confirm that water use is significantly higher in water-based scrub compared to waterless scrub, even when accounting for production and transport, including each product’s packaging (A. Artsen, personal communication).

Despite the variability of study design and other limitations noted above, all studies in this review found waterless scrub techniques superior for water conservation, and “on-demand” taps superior when water-based scrub technique is used. Importantly, these methods are equivalent in antisepsis efficacy for surgical procedures after an initial water-based scrub [40,41]. For future studies, LCA methodology is recommended to compare water-based to waterless scrub technique (including tabulating water consumed in manufacture of product containers, packaging, and disposable sponges/brushes), use of sink flow meters for direct measurement rather than estimation, that studies include increased numbers of observations and study participants, and expansion to more scrub settings. There also is a need for further quality improvement studies, with specific outcome measures, on interventions to promote water-friendly scrub techniques.

Textiles

Whether reusable or disposable textiles are favored depends upon the textile composition; plastic polymer-based reusable textiles are water-saving compared to disposable textiles [27,28] while cotton materials were found to consume significantly more water due to agricultural water requirements [29]. Though more water-intensive, reusable cotton textiles are superior in seven out of ten overall environmental impact categories, including greenhouse gas release and particulate pollution [29]. A growing literature also emphasizes the health risks of plastic products, including but not limited to harms from tissue accumulation of micro- and nano-plastics [42,43] and adverse effects on a broad spectrum of human organ systems [44]. It is possible that reusable organic-based textiles may ultimately be preferred from a public health standpoint despite their higher water footprint. Future studies should incorporate LCA or similar comprehensive methodology to quantify the evaluate the various health implications of textile options.

Sterilization

Optimizing sterilization efficiency is a promising target for reducing water consumption. Reducing equipment idle time has previously been shown to have potential in improving efficiency and cost savings [45–47] and moderate- to high-quality research by McGain et al. in this review confirms water savings as well [31,32]. A third study by the same group addressed decreasing the frequency of anesthesia circuit cleaning, with resulting projected water and cost savings [30]. In this study bacterial counts only and not actual infections were reported, however the authors point out that the rate of ventilator-associated infection in outpatient surgery is so low as to make this a less meaningful indicator, and that prior studies also support the safety of decreased cleaning frequency [48–50]. Future research in this area should focus on repeating these findings in other countries and settings and comparing the water consumption of high-level disinfection and waterless sterilization/disinfection techniques.

Equipment

Studies addressing use of disposable versus reusable equipment options were mixed. Studies by Boucheron and Bertolo found disposable cystoscopes significantly superior to reusable, however neither addresses the water required for manufacture of the disposable instruments. The production of raw plastic alone consumes a significant amount of water, ranging from ~15-66L/kg plastic [51,52], in addition to the previously noted adverse health effects of plastics. Manufacturing processes for a complex surgical instrument such as a cystoscope, requiring multiple plastic and non-plastic materials, are expected to consume still more, multiplied by the number of procedures performed. Indeed, three studies that accounted for the water consumed by disposable equipment manufacture found that the reusable option was clearly superior for water consumption [34–36]. Finally, McGain and colleagues found that water use was significantly increased with reusable anesthesia equipment compared to disposable, however their scenario involved a hospital in Australia with an electrical power mix relying heavily on polluting, non-renewable energy generation, including coal [37]. Coal-based electricity generation consumes large quantities of water compared to renewable energy sources such as photovoltaic or wind [53]; it is expected that a cleaner energy mix powering hospital disinfection and sterilization would reduce the water consumption of the reusable options. Overall, reusable options for surgical and anesthesia equipment appear to be favored for water use in studies employing rigorous methodology; however, this effect is likely variable and may be setting dependent. Future studies should account for all life cycle stages for both reusable and disposable equipment options.