Outdoor environmental effects on cleanrooms - A study from a Swedish hospital pharmacy compounding unit

In this study we examined how outdoor climate affects indoor conditions of a cleanroom used for the preparation of radiopharmaceuticals in the Uppsala university hospital pharmacy, Sweden. Further objectives were to identify associated risk factors to ensure a consistent extemporaneous manufacturing process. Data for two years from the facility monitoring system (with one minute resolution for temperature, relative humidity (%RH), differential pressure) were compared with meteorological outdoor data from Uppsala (Swedish Meteorological and Hydrological Institute, 60-minute mean data for temperature, relative humidity, wind speed and air pressure). The findings of this study indicate a linear relationship between indoor and outdoor temperature for the autumn, winter and spring seasons. The typical summer outdoor diurnal pattern is also seen for indoor temperature. During the study period, the minimum outdoor temperature was -17.5 °C and the maximum 31.4 °C. This wide temperature range also entails a wide range of air humidity from 10 %RH to 100 %RH indoors. Cleanroom temperature and %RH are factors that may affect the quality of medications, especially the risk of microbiological growth in aseptic processes, stability of medications during storage but also may affect handling of for example uncoated tablets or weighing of powder, especially at high %RH for hygroscopic drugs or at low %RH due to static electricity. Further the risk of damage on electrical equipment from electrostatic discharge at low %RH is discussed with a focus on the need for humidity control of cleanrooms and/or systems for mitigation of electrostatic discharge in climates with outdoor temperature in the wintertime below freezing point.