A methodological approach for assessing indoor occupational risk from odor perception

This paper combines risk assessment principles with odor measurement concepts to develop a risk management tool that assists water reclamation plants' administrators to identify, predict, and interpret the magnitude of risk associated with occupational odor perception. Analogous to the noncarcinogenic hazard index, an Odor Hazard Index (OHI) was formulated based on an Odor Reference Concentration (ORfC), which is a new concept similar to the widely used Reference Concentration (RfC) for inhalation exposures to chemicals. The OHI equals to the ratio of observed odor concentration over the ORfC, and sets a new acceptable level of odor perception, which specifies that 80% of building occupants do not perceive the odor. As the OHI approaches unity, concern about negative responses to odor perception increases. The OHI was estimated using a database generated in the dewatering building of a large water reclamation plant and was applied to evaluate odor levels and their perception at conditions with and without an odor control strategy. The control strategy was assessed using AERMOD model estimations of H 2 S outdoor concentrations to assure that it did not impact surrounding residential areas. The OHI responds to research limitations of odor risk assessment and management, and helps determine if a particular control strategy reduces indoor odors to acceptable levels. The risk management component of this study verified that outdoor acute and long-term ambient H 2 S standards are not violated as a result of the control strategy implemented by this work.