Learning to deal with offensive environmental odors

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environmental odors

What is an offensive environmental odor? How can it be defined, and how should its consequences be managed? This is what students will learn in the serious game “Les ECSPER à Smellville”, part of the Air Quality MOOC. This educational tool was developed at IMT Lille Douai, and will be available in 2018. Players will be faced with the problem of an offensive environmental odor, and will have to identify its source and the components causing the smell, before stopping the emission and making a decision on its toxicity before a media crisis breaks out.


In January 2013, near Rouen, there was an incident in a manufacturing process at the Lubrizol company factory, leading to widespread emission of mercaptans, particularly evil-smelling gaseous compounds. The smell drifted throughout the Seine Valley and up to Paris, before being noticed the following day in England! This launched a crisis. The population panicked, with many people calling local emergency services, while the media latched onto the affair. However, despite the strong odor, the doses released into the atmosphere were well below the toxicity threshold. These gaseous pollutants simply caused what we refer to as an offensive environmental odor.

“There is often no predetermined link between an offensive environmental odor and toxicity… When we smell something new, we tend to compare it to similar smells. In the Lubrizol case, people smelt “gas”, and assimilated it with a potential danger” explains Sabine Crunaire, a researcher at IMT Lille Douai. “For most odorant compounds, the thresholds for detection by the human nose are much lower than the toxicity thresholds. Only a few compounds show a direct causal link between smell and toxicity. Hence the importance of being able to manage these situations early on, to prevent a media crisis from unfolding and causing unnecessary panic among the population.”


An educational game for learning how to manage offensive environmental odors

The game, “Les ECSPER à Smellville”, was inspired by the Lubrizol incident, and is part of the serious games series, Scientific Case Studies for Expertise and Research, developed at IMT Lille Douai. It is a digital educational tool which teaches players how to manage these delicate situations. It was created as a complement to the Air Quality MOOC, a scientific Bachelor’s degree level course which is open to anyone. The game is based on a situation where an offensive environmental smell appears after an industrial incident: a strong smell of gas, which the population associates with danger, causes a crisis.

The learner has a choice between two roles: Health and Safety Manager at the company responsible for the incident, or the head of the Certified Association for Monitoring Air Quality (AASQA). “For learners, the goal is to bring on board the actors who are involved in this type of situation, like safety services, prefectural or ministerial services, and understand when to inform them, with the right information. The scenario is a very realistic one, and corresponds exactly to a real case of crisis management” explains Sabine Crunaire, who contributed to the scientific content of the game. “Playing time is limited, and the action takes place in the space of one working day. The goal is to avoid the stage which the Lubrizol incident reached, which set off an avalanche of reactions on all levels: citizens, social networks, media, State departments, associations, etc.” The idea is to put an end to the problem as quickly as possible, identify the components released and evaluate the potential consequences in the immediate and wider environment. In the second scenario, the player also has to investigate and try to find the source of the emission, with the help of witness reports from nose judges.

Nose judges are local inhabitants trained in olfactory analysis. They describe the odors they perceive using a common language, like for example, the Langage des Nez®, developed by Atmo Normandie. These “noses” are sensitive to the usual odors in their environment, and are capable of distinguishing the different types of bad smells they are confronted with and describing them in a consensual way. They liken the perceived odor to a “reference smell”. This information will assist in the analyses for identifying the substances responsible for the odor. “For instance, according to the Langage des Nez, a “sulfur” smell corresponds to references such as hydrogen sulfide (H2S) but also ethyl-mercaptan or propyl mercaptan, which are similar molecules in terms of their olfactory properties” explains Sabine Crunaire. “Three, four, even five different references can be identified by a single nose, in a single odor! If we know the olfactory properties of the industries in a given geographical area, we can identify which one has upset the normal olfactory environment.”


Defining and characterizing offensive odors

But how can a smell be defined as offensive, based on the “notes” it contains and its intensity? “By definition, an offensive environmental odor is described as an individual or collective state of intolerance to a smell” explains Sabine Crunaire. Characterizing an odor as offensive therefore depends on three criteria. Firstly, the quality of the odor and the message it sends. Does the population associate it with a toxic, dangerous compound? For instance, the smell of exhaust fumes will have a negative connotation, and will therefore be more likely to be considered as an offensive environmental odor. Secondly, the social context in which the smell appears has an impact: a farm smell in a rural area will be seen as less offensive by the population than it would in central Paris. Finally, the duration, frequency, and timing of the odor may add to the negative impact. “Even a chocolate smell can be seen as offensive! If it happens in the morning from time to time, it can be quite nice, but if it is a strong smell which lasts throughout the day, it can become a problem!” Sabine Crunaire highlights.

From a regulatory point of view, prefectural and municipal orders can prevent manufacturers from creating excessive olfactory disturbances, which bother people in the surrounding environment. The thresholds are described in terms of the concentration of the odor and are expressed in European Odor Units (uoE.m-3). The concentration of a mix of smells is conventionally defined as the dilution factor than needs to be applied to the effluent so that it is no longer perceived as a smell by 50% of a sample of the population, this is referred to as the detection threshold. “Prefectural orders generally require that factories ensure that, within a distance of several kilometers from the boundary of the factory, the concentration of the odor does not surpass 5 uoE.m-3“ Sabine Crunaire explains. “It is very difficult for them to foresee whether the odors released are going to be over the limit. The nature of the compounds released, their concentration, the sensitivity of people in the surrounding area… there are many factors to take into account! There is no regulation which precisely sets a limit for the concentration of odors in the air, unlike what we have for fine particles.”

To avoid penalties, manufacturers conduct testing of compounds at their source and dilute them using olfactometers, in order to determine the dilution factor at which the odor unit is perceived as acceptable. They use this amount and the modelling system to evaluate the impact of their odor emissions within a predetermined perimeter, but also to measure the treatment systems to be installed.

“Besides penalties, the consequences of a crisis caused by an environmental disturbance are harmful to the manufacturer’s image: the Lubrizol incident is still referred to in the media, using the name of the incriminated company” says Sabine Crunaire. “And the consequences in the media probably also lead to significant direct and indirect economic consequences for the manufacturer: a decrease in the number of orders, the cost of new safety measures imposed by the State to prevent the issue happening again, etc.”

The game “Les ECSPER à Smellville” will therefore raise awareness of these issues among students and train them in managing this type of crisis and avoiding the serious consequences. While offensive environmental odors are rarely toxic, they cause disturbance, both for citizens and manufacturers.

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