What Environmental Monitoring Requires Under USP 797
USP <797> requires compounding pharmacies to maintain an ongoing environmental monitoring program that includes: viable (microbial) air sampling, viable surface sampling, and non-viable particulate monitoring. The 2023 revision added more prescriptive guidance on sampling locations, frequencies, and corrective action thresholds.
Viable Air Sampling
Active air sampling using volumetric impactors (e.g., RCS or Merck MAS systems) is required in the PEC, buffer room, and ante-room. Passive settling plates may supplement but not replace active sampling. Sample volumes and incubation conditions (TSA plates, 30–35°C for 48–72 hours; MEA plates, 20–25°C for 5–7 days for mold) are specified in USP 1116.
Surface Sampling
Contact plates (RODAC) or swabs are used on work surfaces, equipment, and interior walls. ISO 5 PEC surfaces should be sampled at the end of each compounding session and after cleaning/disinfection procedures.
Alert and Action Limits
| Classification | Alert Limit (CFU) | Action Limit (CFU) |
|---|---|---|
| ISO 5 (air) | >1 CFU/m³ | >3 CFU/m³ |
| ISO 7 (air) | >10 CFU/m³ | >100 CFU/m³ |
| ISO 8 (air) | >100 CFU/m³ | >200 CFU/m³ |
Trending and Corrective Action
USP 797 requires that EM data be trended over time. A single exceedance triggers an investigation; repeated exceedances at or above action limits require documented corrective action, re-testing, and potentially suspension of compounding in the affected zone pending remediation.
Documentation Requirements
All EM records must be retained for at least 3 years and made available to state board inspectors on request. Records should include: sample date/time, location, personnel, media lot numbers, incubation conditions, organism identification (if colonies are recovered), and corrective actions taken.