WHO Guidance on Cross-Contamination

1. Definition:
   Cross-contamination is the unintended presence of one product (or its residues, microbes, cleaning agents, etc.) in another product.

2. Prevention Measures (as per WHO TRS, GMP guidelines):

   • Dedicated facilities or equipment should be used for highly sensitizing or potent drugs (e.g., penicillins, hormones, cytotoxic drugs, biological preparations).

   • Technical measures: Closed systems, airlocks, pressure differentials, efficient dust extraction, and HVAC controls to prevent mix-ups.

   • Organizational measures: Effective cleaning procedures, validated cleaning processes, clear SOPs, restricted movement of personnel and materials, and well-defined workflows.

   • Personnel hygiene & training: Proper gowning, training on risks of contamination, and adherence to gowning procedures.

   • Quality control & monitoring: Regular environmental monitoring, line clearance checks, and validation of cleaning effectiveness.

   • Risk assessment: Conducting toxicological risk assessments to establish acceptable carryover limits (e.g., PDE – Permitted Daily Exposure).

3. WHO Emphasis:
   WHO stresses that prevention must be based on both technical and procedural controls, not just end-product testing, since testing cannot reliably detect all cross-contamination.

✅ In short:
WHO states that cross-contamination must be prevented through dedicated facilities (when necessary), validated cleaning, robust technical controls, staff training, and risk assessment, since it poses a serious patient safety risk and regulatory non-compliance issue.