Environmental Odour Impacts
By: Vincenzo Naddeo
Tags: Sustainability, Odour, Pollution, Environment, Air Quality

Environmental Odour Impacts

Odours have become a priority concern for facility operators, engineers and urban planners who deal with waste and industrial treatment plants. The subjectivity of smell perception, its variability due to frequency and weather conditions, and the complex nature of the substances involved, has long hampered the regulation of odour emissions.

These work summarize and introduce the main issues and contents fully described in the Edited Book “Odour Impact Assessment Handbook” published by John Wiley & Sons, Ltd. The book provides a comprehensive framework for the assessment, measurement and monitoring of odour emissions, and covers:

• monitoring compliance withre source consent conditions;

• investigating odour complaints to determine if an offensive or objectionable odour is present;

• odour characterization and exposure effects;

• instruments and methods for sampling and measurement;

• strategies for odour control;

• dispersion modelling for odour exposure assessment

• odour regulations and policies

• procedures for odour impact assessment

• case studies: Wastewater treatment, composting, industrial and CAFO plants, and landfill

Intended for researchers in environmental chemistry, environmental engineering, and civil engineering, the handbook is also an invaluable guide for industry professionals working in wastewater treatment, environmental and air analysis, and waste management.

1. Odour: origin and definition

Odour is the property of a substance, or better; a mixture of substances that depending on their concentration, are capable of stimulating the olfaction sense sufficiently to trigger a sensation of odour (Brennan, 1993; Devos et al., 1990; Bertoni et al., 1993). Even better, odour is a sensory response to the inhalation of air containing chemicals substances. When the sensory receptors in the nose come into contact with odorous chemicals, they send a signal to the brain, which interprets the signal as an odour. The olfactory nerve cells in humans are highly sensitive instruments, capable of detecting extremely low concentrations of a wide range of odorous chemicals. The type and amount (or intensity) of odour are both important in processing the signal sent to the brain. Most odours are a complex mixture of many odorous compounds.

Fresh or clean air is usually perceived as not containing any contaminants that could cause harm and it smells clean. Clean air may contain some chemical substances with an associated odour, but these odours will usually be perceived as pleasant, such as the smell of grass or flowers. However, not everyone likes the smell of wet grass or hay. Due to our sense of odour and our emotional response to it being synthesized by our brain, different life experiences and natural variation in the population can result in people having different sensations and emotional responses to the same odorous compounds.

Odour is a parameter that cannot be physically measured, unlike wavelength for sight or pressure oscillation frequency for hearing, nor can it be chemically determined as it is not an intrinsic characteristic of themolecule. It represents, in fact, the sensation that the substance provokes after it has been interpreted by the human olfactic system. The impossibility of physically and chemically measuring odour, the complexity of the odorants, the vast range of potentially odorous substances, the physical and psychic subjectivity of odour perception and environmental factors, together with the complexity of the olfactic system, represent a series of obstacles that render the characterization of odours and the control of olfactive pollution particularly complex (Zarra et al., 2007a; Dalton, 2002).

Public opinion plays a decisive role in evaluating the extent of annoyance caused by bad odours, often leading to associating unpleasant or malodorous emissions with any industrial or sanitary installation (Bertoni et al., 1993; Stuetz et al., 2001). In fact, even though nuisance odours are not generally associable to harmful effects on human health, they do represent a cause of undoubted and persistent annoyance for the resident population, thus becoming an element of contention both in the case of existing plants as well as in the selection of new sites (Shusterman et al., 1991; Zarra, 2007b). In this light, the impacts caused by the aesthetics of the plants and their inclusion in the landscape, the noise produced, the traffic generated and, above all, the emissions of unpleasant odours are becoming increasingly important (Zarra et al., 2008b).

Over the last few years, there has been more and more technical and scientific interest in these matters thanks to the greater attention being paid to protecting the environment and human health and, above all, due to the growing number of plants located in urbanized zones (Zarra, 2007b). As a result, for some time now, attention has been drawn to the need to monitor air quality in relation to environmental odour levels. However, the particular and complex nature of the substances responsible for odour impact, their variability both over time and with respect to meteoclimatic conditions and the subjective nature of olfactic perception are factors delaying any such regulation (Park and Shin, 2001; Zarra, 2007b).

As described in the following chapters, the components that can be evaluated in order to identify an olfactic type annoyance are concentration, intensity, hedonic tone (i.e. the pleasant or unpleasant sensation obtained from an odour) and quality (association of an odour with a known natural compound). As detailed later, of these components, only the first can be determined in an objective manner, while the others are highly subjective (see Part 3).

2. Quantifying Odour

Dynamic olfactometry, electronic noses (e-nose) and specific chemicals can be used (with varying success) to indicate the relative amount of odorous chemicals present in the air. This and other techniques for odour sampling and measurement are described in detail in Part 3.8.

Briefly, we could distinguish between sensorial, analytical and mixed methods. Sensory analysis, carried out prevalently using dynamic olfactometry, provides precise data on odour concentration, but it does not allow to evaluate the magnitude of the disturbance to which a population is exposed, nor can it determine the effective contribution of different sources to the level of environmental odour (Jiang, 1996; Sneath, 2001). The principal causes of the uncertainty of the olfactometric method are the significant biological variability in olfactic sensitivity and its inability to detect low odour concentration. Even though the introduction of criteria for the selection and behaviour coding of the panel has notably increased the repeatability and reproducibility of the measurements, the variability associated with the use of human subjects as detectors constitutes one of the principal limitations (Koster, 1985; Zarra et al., 2008b).

Analytical methods (GC-MS, colorimetric methods) allow the substances present to be screened and their concentrations identified, but they do not provide information on the odorous sensation produced by the mixture as a whole (Davoli, 2004; Zarra et al., 2007b; Zarra et al. 2008c). The analysis methods are also heavily influenced by the sampling techniques (Gostelow et al., 2001) which differ according to the type of source (areal or point, active or passive type) and the actual sampling methods (see Part 5). In order to reduce problems linked to sampling, a number of recent literary works propose the use of portable GC-MS analysers (Zarra et al., 2008b; Zarra et al., 2008c).

3. Effects of Odour

Odour exposure could cause annoyance and nuisance. A more serious effect, it may lead to feelings of nausea and headache, and other symptoms that appear to be related to stress. It has been postulated that the mechanism of ‘environmental worry’ helps to explain the occur- rence of physiological effects in people exposed to odorous substances at concentrations much lower than might be expected to lead to actual toxic effects (see Section 2.5).

Many odorous compounds are indeed toxic at high concentrations, and in extreme cases of acute exposure toxic effects such as skin, eye or nose irritation can occur. However, such effects are most likely to occur as the result of industrial accidents, such as the rupture of tanks containing toxic compounds or severe upset conditions in chemical or combustion processes.

Repeated exposure to odour can lead to a high level of annoyance, with the receiver becoming particularly sensitive to the odour. Complaints are most likely to come from individuals who are either physiologically or psychologically sensitive to the odour, and certainly a combination of both types of sensitivity will increase the likelihood of complaint. The individual components of an odour necessary to cause an adverse reaction from people are usually present in very low concentrations; far less than will cause adverse effects on physical health or impacts on any other part of the environment.

The odour threshold values for many chemicals are several orders of magnitude less than the relative threshold limit values (TLV). This means that the chemicals can be smelled at much lower concentrations than those causing adverse effects on health. Therefore, if present in sufficient quantities, these compounds would create an odour problem at much lower concentrations than would be needed to create a public health problem.

Despite these examples, it should not be assumed that odour thresholds will always be much lower than toxicological thresholds. The potential for significant adverse effects on public health from chemicals in odorous discharges should be considered on a case-by- case basis.

There is very little information available about the physiological effects of odour nui- sance on humans. However, it is known that prolonged exposure to environmental odours can generate undesirable reactions in people such as unease, irritation, discomfort, anger, depression, nausea, headaches or vomiting. In our experience, other effects reported by people subjected to environmental odours can include:

• difficulty breathing;

• frustration, stress and tear fulness;

• being woken during the night by the odour;

• odour invading the house and washing;

• reduced appetite and pleasure in eating,and difficulty preparing food;

• reduced comfort at night;

• reduce damenity due to the need;

• embarrassment when visitors experience the odours;

• reduced business due to prospective customers being affected by the odour.

All these aspects are related to odour attribute and the relative response of people, discussed in Part 2.

4. Odour Impact Assessment Approaches

Odour impact is defined as the alteration of air quality in terms of odours that cause nuisances. An assessment of odour impacts in the environment may need to be carried out for a variety of reasons, including:

preparing or evaluating resource consent applications, or impact assessments, for three separate categories:

1. renewing an existing activity,

2. proposed modifications to an existing activity (mitigation or process change),

3. proposed new activity.

1. renewing an existing activity, 2. proposed modifications to an existing activity (mitigation or process change), 3. proposed new activity. monitoring compliance withre source consent conditions;

investigating odour complaints to determine if an offensive or objectionable odour is present.

The methods used to assess the odours will depend on the type of situation. A number of different techniques for odour assessment are available and discussed in Part 7. The choices of the best tools to use for an odour assessment partly depend on whether the assessment is an evaluation or a compliance issue.

Evaluation involves assessing the actual and potential effects of an activity to determine whether significant adverse environmental effects will occur. If the consent is granted, the consent holder is then required to comply with (and be able to demonstrate compliance with) any conditions imposed as part of that consent. These two processes for evaluation and compliance are quite separate, and often the evaluation criteria are different to the criteria imposed as conditions of consent. Assessment tools can also be classified in two categories, methods with direct measure- ment of odour exposures or their assessment by dispersion modelling, and respectively:

1. Odour impact assessment from exposures measurement;

2. Odour impact assessment from sources.

All these tools with their strengths and weaknesses are discussed in Part 7, where the criteria for choosing the best one according to the specific situation are also presented.

Main References

Bertoni, D., Mazzali, P., and e Vignali A. (1993) Analisi e controllo degli odori. Quaderni di Tecniche di Protezione Ambientale n.28. Pitagora Editrice, Bologna.

Brennan, B. (1993) Odour nuisance. Water and Waste Treatment, 36, 30–33.

Dalton, P. (2002) Olfaction in Yantis, in Handbook of Experimental Psychology. S. Stevens (ed.), Vol. 1, Sensation and Perception, 3rd edn. John Wiley & Sons, Inc., New York, pp. 691–746.

Davoli, E. (2004) I recenti sviluppi nella caratterizzazione dell’inquinamento olfattivo. Tutto sugli odori, Rapporti GSISR.

Devos, M., Patte, F., Rouault, S., et al. (1990) Standardized Human Olfactory Thresholds, p. 165. Oxford University Press, New York.

Gostelow, P., Parsons, S.A. and Stuetz, R.M. (2001). Odour measurements for sewage treatment works. Water Research, 35 (3), 579–597.

Jiang, J.K. (1996) Concentration measurement by dynamic olfactometer. Water Environ. Technol., 8, 55–58.

Koster, E.P. (1985) Limitations Imposed on Olfactometry Measurement by the Human Factor. Elsevier Applied Science.

Park, J.W. and Shin, H.C. (2001) Surface Emission of Landfill Gas from Solid Waste Landfill. Atmospheric Environment, 35 (20), 3445–3451.

Reiser, M., Zarra, T. and Belgiorno, V. (2007) Geruchsmessung mit allen Mitteln — wieaufwendig muss die Analytik von Geruchsemissionen sein? VDI

Berichte 1995, ‘Geru ̈che in der Umwelt’, 13–14 Novembre 2007, Bad Kissingen (D), ISBN: 978- 3–18–091995–9.

Shusterman D., Lipscomb, J., Neutra, R., and Kenneth, S. (1991). Symptom prevalence and odour-worry interaction near hazardous waste sites. Environmental Health Per- spectives, 94, 25–30.

Sneath, R.W. (2001) Olfactometry and the CEN Standard prEN13725, in Odours in Wastew- ater Treatment: Measurement, Modelling and Control. R. Stuetz and B.F. Frechen (eds), pp. 130–154, IWA Publishing.

Stuetz, R. and Frechen, F.B. (2001) Odours in Wastewater Treatment: Measurement, Mod- elling and Control. IWA Publishing, ISBN 1–900222–46–9.

Zarra, T. (2007b) Procedures for detection and modelling of odours impact from sanitary environmental engineering plants. PhD Thesis, University of Salerno, Salerno, Italy.

Zarra, T., Naddeo, V. and Belgiorno, V. (2007a) Gestione e controllo delle emissioni odorigene da impianti di compostaggio con tecniche analitiche. ECOMONDO 2007, pp. 73–78, Maggioli Editore, ISBN: 978–88–387–3979-X.

Zarra, T., Naddeo, V. and Belgiorno, V. (2008a) Tecniche analitiche per la caratterizzazione delle emissioni di odori da impianti di compostaggio di rifiuti solidi urbani. Emissioni odorigene e Impatto olfattivo. Geva Edizioni.

Zarra, T., Naddeo, V. and Belgiorno, V. (2008c) A novel tool for estimating odour emis- sions of composting plants in air pollution management, in stampa su. Global Nest International Journal, 11 (I.4), 477–486.

Zarra, T., Naddeo, V., Belgiorno, V., et al. (2008b) New developments in monitoring and characterization of odour emissions — at the example of a biological waste water treatment plant. Zeitgema ̈ße Deponietechnik, 2008. Oldenburg GmbH, Vol. 88, ISBN 3–486–63102–0.