Lillian Myers

Project title: Assessing Occupational Ozone Exposure at a Marine Mammal Hospital

Degree: MS (Thesis) | Program: Occupational Hygiene (OH) | Project type: Thesis/Dissertation
Completed in: 2022 | Faculty advisor: Peter Rabinowitz


Background: Ozone is a popular water sterilization agent utilized in marine mammal husbandry to maintain the pool water in the animal enclosures. The health hazards posed by ozone are well understood, but its role as an occupational hazard, especially in marine mammal husbandry, is understudied and not well characterized. The purpose of this study was to assess occupational exposure to ozone off-gassed from a water treatment system at a marine mammal hospital and to understand how environmental conditions (temperature, relative humidity, wind speed, and wind direction) might modulate the ozone concentrations being off-gassed from the water treatment system.

Methods: We conducted area monitoring of ozone in three zones within the marine mammal hospital facility for five, 8-hour days per zone. Environmental data was collected using a weather station that was mounted in one location for the duration of the data collection. The difference in ozone concentrations in the study zones were evaluated. Correlations between ozone and temperature and ozone and relative humidity were assessed. The effect of wind behavior on ozone was characterized using Conditional Bivariate Function Plots. The effect of all of the environmental conditions on predicted ozone concentrations were further characterized using a predictive Quasi-Poisson model.

Results: Ozone concentrations were highest closest to the water treatment system. Correlations between ozone and temperature and ozone and relative humidity were stronger further away from the source. Wind speed and direction had a stronger influence on ozone concentrations at the site than temperature and relative humidity. The environmental conditions were unable to explain all the variability in ozone concentrations at the study site.

Conclusions: Ozone concentrations were greatest closest to the source and environmental conditions had varying impacts on the exposures. The results of this study found that there were exposures over the Ceiling limit set by WA L&I and the recommended exposure limit set by NIOSH. This data can inform decisions and recommendations in the workplace to reduce over-exposure to ozone. This data also demonstrates that ozone can pose a significant occupational hazard in a marine mammal hospital setting. More research on employee personal exposure to ozone is needed to better understand the impact of ozone exposure in this understudied industry.