Editorial Feature

How Olfactometry Can Measure Odor For Environmental Assessment

Learn about how olfactometry can be used to analyze odor emissions and contribute to accurate, fully-rounded environmental assessments.

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What is Olfactometry?

Olfactometry refers to the scientific method of measuring and analyzing environmental odors. This method provides a quantitative and qualitative analysis of odor emissions and plays an important role in environmental assessments as a result. Assessing odor emissions enables the development of effective mitigation strategies in the environment surrounding sources of odors, including industrial factories, sewage treatment plans, or other facilities.

Measuring odors is also relevant in the context of environmental regulations as they provide comprehensive data related to compliance with odor-related standards and regulations. Olfactometry can help determine the potential impact of odor emissions on public health and well-being, addressing public concerns and ensuring a livable environment for communities.

One such example was reported by Kulig et al. (2019) in a study comparing odors pre and post-modernization of a Polish wastewater treatment plant. Researchers compared odor intensity and odor concentration measurements and found a significant decrease in the concentration of odor emitted from the sludge dewatering building and sludge containers post-modernization. The study indicated that olfactometry methods allowed a quantification and identification of odor sources, which can then allow regulators to minimize the nuisance.

Technical Depth

A commonly used technique in olfactometry is dynamic dilution, which relies on diluting odor samples to measurable levels to ensure an appropriate concentration range for analysis. The detection threshold, the lowest concentration at which an odor can be detected, can then inform the sensitivity of the human panelists involved in the considered odor assessments. Detecting odor thresholds is further complicated with the layering of different odors, with one odor covering another, as was found in a 2023 study by Zhou et al.  

Olfactometers range from dynamic forced-choice olfactometers to static olfactometers. Dynamic forced-choice models involve a continuous flow of diluted odor samples presented to panelists who must detect and identify the target odor.

Contrastingly, static olfactometers, involve the presentation of discrete samples in closed containers for evaluation, allowing for the assessment of odor concentration and intensity. Both olfactometers play a crucial role in quantifying and characterizing odors in various environmental and industrial applications.

Typically, olfactometers are used to quantify odor intensity (OI), odor concentration (OC), odor nature (ON) and hedonic tone (HT). In a review of existing techniques, Hawko et al. (2021) presented and compared the different assessment techniques. Overall, the study indicated that using a reference scale for OI assessment offers less subjectivity than other techniques but is harder to use.

For OC assessment, the use of dynamic olfactometry was shown to be the least biased. For odor qualification, the ON description was less subjective when a reference-based lexicon was used but at the expense of simplicity, cost, and lesser panel-training requirements.

The sampling technique involved in olfactometry is key to avoiding contamination and preserving odor integrity. Sample timing is carefully determined to ensure representative data, often requiring multiple samples taken over extended periods.

Volatile compounds require careful consideration, including the use of sorbent materials, minimizing exposure to air, and proper storage conditions to prevent the loss or alteration of volatile odorous compounds during sample collection and transport.

Commercial Relevance

Environmental regulations require the measurement of odor emissions worldwide to mitigate the impact of odors on human health and the environment. Regulations can vary in specifications across regions, as detailed by the European Union's Industrial Emissions Directive (IED) or the United States' Clean Air Act.

These regulations set standards for odor emissions, requiring industries and facilities to measure and control odorous pollutants in compliance with regulations to maintain a safe and livable environment for local communities.

For industries, odor measurements ensure a pleasant and healthy environment for workers and surrounding communities. As a result, many industries have adopted best practices to manage and reduce odors, including implementing effective odor control technologies, regular monitoring and maintenance programs, and proactive engagement with stakeholders to address concerns.

Prioritizing odor management enables industries to improve their environmental impacts, maintain regulatory compliance, and foster positive relationships with the communities they operate in.

However, if industries fail to comply with regulations, they may face economic repercussions, including fines, legal penalties, and reputational damage. Addressing odor issues, on the other hand, is beneficial since it improves community relations, enhances public perception, and increases operational efficiency.

By investing in odor control measures and addressing concerns promptly, industries can protect their economic outlook, maintain a positive reputation, and foster sustainable long-term growth.

Challenges & Innovations

Olfactometry faces various challenges. When measuring, the inherent variability in human perception of odors can lead to subjective results or be confounded by multiple chemical compounds that can interact and create unique sensory experiences. Moreover, environmental factors, such as temperature, humidity, and air movement, influence odor dispersion and perception.

In a 2022 study by Spinazza et al., the human health aspect of olfactometry was also discussed. The study presented how human panelists are often exposed to non-negligible carcinogenic risks when examining chemical samples.

To minimize risks, the researchers offer a new methodology of risk assessment for workers involved in dynamic olfactometry based on further diluting the samples to healthy concentrations.

The field of olfactometry has also undergone new advances, including the use of sensor arrays and pattern recognition algorithms assembled to function as an ‘electronic nose’, offering rapid and objective odor analysis.

Additionally, odor mapping techniques using molecular data also enable the visualization and characterization of odor sources in complex environments. Integrating artificial intelligence applications, including machine learning and data analysis algorithms, enhances the accuracy and efficiency of odor detection, classification, and source identification in olfactometry.

Conclusion

Environmental assessments of nuisance and sources of odor rely on olfactometry for quantitative and qualitative data on odor emissions. Olfactometry contributes towards regulatory compliance and enables the development of effective mitigation strategies.

Continued advancement in olfactometry, including the integration of innovative technologies and methodologies, is central to enhancing its accuracy and reliability, ultimately leading to both regulatory compliance and public satisfaction in odor management and environmental protection efforts.

References and Further Reading

Hawko, C., et al. (2021). A review of environmental odor quantification and qualification methods: The question of objectivity in sensory analysis. Science of the Total Environment, 795, p. 148862. doi.org/10.1016/j.scitotenv.2021.148862

Kulig, A. & Szyłak-Szydłowski, M. (2019). Assessment of the effects of wastewater treatment plant modernization by means of the field olfactometry method. Water, 11(11), p. 2367. doi.org/10.3390/w11112367

Spinazzè, A., et al. (2022). Dynamic Olfactometry and oil refinery odour samples: Application of a new method for occupational risk assessment. Toxics, 10(5), p. 202. doi.org/10.3390/toxics10050202

Zhou, Y., et al. (2023). A new method for evaluating nuisance of odorants by chemical and sensory analyses and the assessing of masked odors by olfactometry. Science of the Total Environment, 862, p. 160905. doi.org/10.1016/j.scitotenv.2022.160905

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James Ducker

Written by

James Ducker

James completed his bachelor in Science studying Zoology at the University of Manchester, with his undergraduate work culminating in the study of the physiological impacts of ocean warming and hypoxia on catsharks. He then pursued a Masters in Research (MRes) in Marine Biology at the University of Plymouth focusing on the urbanization of coastlines and its consequences for biodiversity.  

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