The Association for the Advancement of Medical Instrumentation (AAMI) recently introduced ST108-2023 (Water for the processing of medical devices), a new Standard for the cleaning, disinfection, and sterilization of reusable medical devices. This Standard evolved from a previous Technical Information Report (TIR34), which focused specifically on water quality required for medical device processing.
ST108 goes beyond establishing water quality requirements and includes qualifying, monitoring, testing, and maintaining systems used to provide water for medical device processing. While not a legally binding document, regulatory and accrediting bodies are expecting facilities involved in medical device cleaning (hospitals, clinics, etc.) to adopt and maintain compliance with the Standard.
As a result, these facilities are having to re-evaluate their water purification systems to identify where they are - and where they might not be - in compliance with the Standard. This often involves going through the entire water system to make sure each component is appropriate for its intended use, is producing the required result, and has sufficient monitoring points for testing, recording, and showing compliance. Part of this is a detailed risk assessment (as required by the Standard) to identify, document, and mitigate any potential hazards affecting water quality. In the extreme, risk mitigation might involve significant upgrades - or even full replacement - of an existing water system.
An important aspect of the Standard is the establishment of a Water Management Program with a multidisciplinary team responsible for developing, implementing, and documenting the requirements of the program, as well as ongoing monitoring to ensure continued compliance. The Standard guides creating this team, including responsibilities and areas of expertise expected for team members (including but not limited to: management, facilities, water treatment, device processing, etc.). If all required disciplines are not currently on staff, it is acceptable to utilize outside vendors and contractors.
Per the Standard, a comprehensive risk assessment is required, covering both the performance of the water system and potential for failure to meet established water purity requirements, and the potential for adverse events as a result of using inadequate water quality. For a new system, this analysis should be conducted before installation. For an existing system, the analysis can still be conducted, focusing on the various existing components, potential inadequacies, and upgrades required to remediate identified risks.
Evaluation of an existing system should include:
Improvements required for compliance may not be as drastic as you think. If the existing system is capable of supplying the required water quality, it may only need additional testing/monitoring and possibly some POU filters to ensure water quality where needed.
The Standard lists quality requirements for three categories of water:
The Standard lists the requirements for each type of water (see table below).
Annex E of the Standard specifies a wide range of potential water treatment technologies that may be used to achieve the listed requirements.
Water Categories and Specifications1
|
Measurement |
Units |
Utility Water |
Critical Water |
Steam |
|
pH @ 25 oC |
pH |
6.5 - 9.5 |
5.0 - 7.5 |
5.0 - 9.2 |
|
Total Alkalinity |
mg CaCO3/L |
<400 |
<8 |
<8 |
|
Bacteria |
CFU/mL |
<500 |
<10 |
N/A |
|
Endotoxin |
EU/mL |
N/A |
<10 |
N/A |
|
Total Organic Carbon (TOC) |
mg/L (ppm) |
N/A |
<1.0 |
N/A |
|
Color and Turbidity |
Visual |
Colorless, clear without sediment |
Colorless, clear without sediment |
Colorless, clear without sediment |
|
Aluminum |
mg/L |
<0.1 |
<0.1 |
<0.1 |
|
Chloride |
mg/L |
<250 |
<1 |
<1 |
|
Conductivity |
mS/cm |
<500 |
<10 |
<10 |
|
Copper |
mg/L |
<0.1 |
<0.1 |
<0.1 |
|
Iron |
mg/L |
<0.1 |
<0.1 |
<0.1 |
|
Manganese |
mg/L |
<0.1 |
<0.1 |
<0.1 |
|
Nitrate |
mg/L |
<10 |
<1 |
<1 |
|
Phosphate |
mg/L |
<5 |
<1 |
<1 |
|
Sulfate |
mg/L |
<150 |
<1 |
<1 |
|
Silicate |
mg/L |
<50 |
<1 |
<1 |
|
Total Hardness |
mg CaCO3/L |
<150 |
<1 |
<1 |
|
Zinc |
mg/L |
<0.1 |
<0.1 |
<0.1 |
1 Values from ANSI/AAMI ST108:2023 Table 2
Existing water systems will generally consist of three segments.
If you are already producing purified water to any degree, there is a good chance you are already meeting the parameters listed in the table. If not, there may be relatively simple additions/changes to your water system that will bring it up to par.
Requirements and guidance for these activities are found in the Standard.
CPF Applications engineers can help review your system and make cost-effective suggestions to help meet compliance requirements. To start the conversation, contact customerservice@criticalprocess.com.