UCLA

Exposures to environmental odors often result in complaints that local air inspectors must address. Current practices vary around the world, so interviews were conducted with experts to gather the latest approaches. Several trends were apparent: odor limits based on number of dilutions are ineffective, working directly with the complainant to verify that an odor is present and then tracing it to the source is the first line of inquiry, and lengthy lists or scales of odor descriptors (e.g., type of odor, hedonic tone, intensity) are unnecessary for initial investigations. When further investigation is required, due to overlapping odor sources or ongoing complaints, the steps of traditional risk assessment apply (hazard identification, dose-response assessment, exposure assessment and risk characterization). Unlike the exposure and risk assessment of conventional air pollutants, the human sense of smell can be used as a detector by the air inspector or a trained panel. Analytical instruments then confirm or further explore the exposure to individual odorant compounds. The hazards from odor exposure, including both irritation and smell, are usually headache or nausea but also can include stress and emotional responses. Dose- response relationships pass through several thresholds, the most commonly used being the odor- detection threshold for 50% of a sensory panel (ODTC50). In addition, acute and chronic health hazard thresholds for odorants and odorless co-pollutants can be applied to air monitoring results, as demonstrated by several case studies.

For complex or unresolved odor exposures, sensory methods such as the Odor Profile Method have identified culprit odorants using an odor wheel, panel assessment of the intensity of the odor, and location information to identify the odor source. Confirmation is provided by analytical techniques, such as gas chromatography with a sensory port and parallel mass spectrometry. The promise of electronic noses that mimic the human sense of smell remains allusive, often failing to perform as well in the field as in the laboratory. The current path forward for environmental odor exposure assessment includes population-based metrics of odor, such as odor diaries and plume monitoring by panels, confirmed by modern analytical techniques.