Odour Annoyance Research Articles

Self‐Ratings of Olfactory Function Reflect Odor Annoyance Rather than Olfactory Acuity

Self-ratings of olfactory function often correlates poorly with results of objective smell tests. We explored these ratings relative to self-rating of odor annoyance, to odor identification ability, and to mean perceived intensity of odors, and estimated relative genetic and environmental contributions to these traits. A total of 1,311 individual twins from the general population (62% females and 38% males, aged 10-83 years, mean age 29 years) including 191 monozygous and 343 dizygous complete twin pairs from Australia, Denmark, Finland, and the United Kingdom rated their sense of smell and annoyance caused by ambient smells (e.g., smells of foods) using seven categories, and performed odor identification and evaluation task for six scratch-and-sniff odor stimuli. The self-rating of olfactory function correlated with the self-rating of odor annoyance (r = 0.30) but neither correlated with the odor identification score. Quantitative genetic modeling revealed no unambiguously significant genetic contribution to variation in any of the studied traits. The results suggest that environmental rather than genetic factors modify the self-rating of olfactory function and support earlier findings of discrepancy between subjective and objective measures of olfactory function. In addition, the results imply that the self-rating of olfactory function arises from experienced odor annoyance rather than from actual olfactory acuity.

Hydrogen sulfide (H 2S) in urban ambient air

Despite indications of high hydrogen sulfide levels in some urban environments, only sparse measurements have been reported in the literature. Here we present one full year of hydrogen sulfide measurements in an urban traffic site in the city of Thessaloniki, Greece. In this 1-million-population city the H 2S concentrations were surprisingly high, with a mean annual concentration of 8 μg m −3 and wintertime mean monthly concentrations up to 20 μg m −3 (12.9 ppb). Daily mean concentrations in the winter were up to 30 μg m −3 (19.3 ppb), while hourly concentrations were up to 54 μg m −3 (34.8 ppb). During calm (wind velocity < 0.5 m s −1) conditions, mainly encountered during night-time hours, hourly values of H 2S were highly correlated with those of CO ( r 2 = 0.75) and SO 2 ( r 2 = 0.70), pointing to a common traffic source from catalytic converters. Annual mean concentrations are above the WHO recommendation for odor annoyance; hence, H 2S might play a role to the malodorous episodes that the city occasionally experiences. The high ambient H 2S levels might also be relevant to the implementation of preservation efforts for outdoor marble and limestone historical monuments that have been targeting SO 2 emissions as an atmospheric acidity source, since the measurements presented here suggest that about 19% of the annual sulfur (SO 2 + H 2S) emissions in Thessaloniki are in the form of H 2S.

Development and validating procedure of a formula to calculate a minimum separation distance from piggeries and poultry facilities to sensitive receptors

A specific formula to calculate separation distance from piggeries and poultry facilities to sensitive receptor is developed for Walloon Region, in Belgium. The paper briefly presents the main principles of the formula and discusses more deeply the compatibility of the distance approach with odour units, odour rate and percentiles usually applied to assess the odour annoyance zones. A method of validation is presented and tested to adjust the different parameters of the formula to Belgian field reality. A total of 43 farms of which 21 piggeries and 22 poultry facilities are visited and, for each case, the distance calculated by the formula is compared to the one deduced from odour annoyance criterion (10 ou m −3 at 98th percentile). Validation work results in discussing the sensibility of different factors of the formula and especially in adjusting a fitting factor to match the absolute distances to real field annoyance impression. Conclusions show that both approaches – separation distance formula and percentile evaluation – are coherent. The validation method allows parameter adjustment but should need further refinements to examine separately piggeries and poultry facilities.

Odor Annoyance of Environmental Chemicals: Sensory and Cognitive Influences

In low concentrations, environment pollutants like volatile organic compounds (VOCs) may be perceived via olfaction. Modulators of odor-mediated health effects include age, gender, or personality traits related to chemical sensitivity. Severe multi-organ symptoms in response to odors also characterize a syndrome referred to as idiopathic environmental intolerance (IEI). One prominent feature of IEI is self-reported odor hypersensitivity that is usually not accompanied by enhanced olfactory functioning. The impact of interindividual differences in olfactory functioning on chemosensory perceptions is sparsely investigated, and therefore this study addressed the influences of different types of modulators, including olfactory functioning. In a psychophysical scaling experiment, an age-stratified sample of 44 males and females was examined. After controlled application of nine concentrations of six chemicals by flow-olfactometry, the participants rated four olfactory and nine trigeminal perceptions. Weak effects were found for gender and age, as well as some modulating effects of self-reported chemical sensitivity and odor discrimination ability. For chemical sensitivity, the results were as expected: Subjects with higher sensitivity reported stronger perceptions. The individual odor threshold (n-butanol) exerted no influence on the subjects' ratings of olfactory and trigeminal perceptions. Surprisingly, above-average odor discrimination ability was associated with lower ratings of odor intensity and nausea. This particular aspect of olfactory functioning might be a reflection of a more objective odor evaluation model buffering emotional responses to environmental odors.

Effectiveness of Field Olfactometry and Neighbor Control to Reduce Odor Annoyance from Biosolids and Municipal Solid Waste Composting

An odor monitoring study was carried out with fifteen voluntary residents living in the vicinity of an source-separated municipal solid waste (MSW) composting plant (10 4 T/y) and an aerated channel biosolids composting facility (10 4 T/y). In the period June 2005-October 2007 residents recorded odor annoyance of up to fourteen different odors three times a day (on a 1 to 5 scale). All residents were nose-calibrated three times with the Odor Sensitivity Test (St. Croix Sensory, Inc.).Additionally, five residents were trained to use a field olfactometer (Nasal Ranger™) to measure ambient odor dilutions to threshold (D/T) at home. They participated in several field intercomparisons at the two odor sources obtaining excellent coefficients of variation (< 40%) against a certified odor inspector. Unannounced field D/T inspections and resident measurements with the Nasal Ranger™ showed very good agreement in both ambient odor strength and time of day. For biosolids odor the highest value recorded at the site was 30 D/T (475 m from the source) while for source-separated MSW odor was 7 D/T (700 m from the source). Good correlations were found between the monthly-averaged Odor Annoyance Index (OAI) and the monthlyaveraged global D/T measured around each odor source by a certified odor inspector. Random field D/T inspections at the site agreed also quite well with the daily OAI for each odor source. By the end of 2006 new management practices were implemented in both facilities and major structural changes were undertaken in 2007. The effectiveness of field olfactometry and neighbour control in providing meaningful and objective indicators of odor annoyance reduction following those corrective actions has kept neighbours patient and supportive of the communication program established in June 2005. Odor annoyance in the neighbourhood is expected to reach acceptable levels in the first semester of 2008.

Complementary approaches to measure environmental odours emitted by landfill areas

This paper presents different methods to assess the odour emission and the odour annoyance in the surroundings. It is shown, on the example of landfill areas and composting facilities, that chemical analyses are helpful to identify key compounds of the odour release, and to set up the specification of a monitoring instrument. Sensitive methods, like dynamic olfactometry or sniffing team investigation, are mainly applicable to provide a global odour plume or an average annoyance zone. And the electronic nose can supply a warning signal to the plant manager or a real time estimation of the annoyance zone.

Odor frequency and odor annoyance. Part I: assessment of frequency, intensity and hedonic tone of environmental odors in the field

Odors can be evaluated as being pleasant or unpleasant (hedonic tone), but this differentiation was not incorporated into environmental odor regulation. In order to study the hedonic-induced modification of dose-response associations for community odor annoyance a pertinent field study was conducted. This paper covers the first step, namely the development and validation of a standardized human observation strategy for the direct quantification of the frequency, intensity, and hedonic tone of environmental odors in the field. Grids with equidistant observation points were located around six industrial odor sources, two with pleasant (sweets, rusk bakery), two with neutral (textile production, seed oil production), and two with unpleasant odor emissions (fat refinery, cast iron production). These points were visited by trained observers, screened for normal olfaction and reliable performance, in a systematic fashion for an observation time of 10 min duration. Exposure-related information from the observers in terms of frequency, intensity (six-point scale) and hedonic tone (nine-point scale) were compared to that of 1,456 residents using the same rating scales. Residents evaluated the industrial odors more intense and more unpleasant than the panelists. Furthermore, for the residents only negative relations between odor intensity and hedonic tone were found while for the observer pleasant odor became more pleasant with increasing intensity. Instead of three classes of industrial odors, namely pleasant, neutral and unpleasant, the responses allowed only for two odor classes, namely pleasant and not pleasant, the latter also covering the neutral category. The developed methodology has been shown to yield valid information about odor exposure in the field. With regard to different application settings the discrepancies between external observers and affected residents are discussed in terms of different information processing strategies, namely stimulus-based (bottom-up) for the panel and memory-based and, thus, subject to cognitive bias for the residents (top-down).

Odor frequency and odor annoyance Part II: dose–response associations and their modification by hedonic tone

Risk-assessment for environmental odors and the development of an appropriate guideline for protection against undue odor annoyance have long been hampered by the difficulties of assessing odor exposure and community annoyance responses. In recent years, however, dose-response associations between frequency of odor events and odor annoyance level in the affected population were established. However, the influence of hedonic tone (pleasantness-unpleasantness) and perceived odor strength (intensity) on the degree of odor annoyance have long been neglected in such studies and accompanying guidelines. In order to close this gap a pertinent field study was conducted in the vicinity of six odor emitting plants, two with pleasant (sweets production, rusk bakery), with neutral (textile production, seed oil production), and with presumably unpleasant odor emissions (fat refinery, cast iron production). A standardized sensory method was developed (described in Part I in the accompanying paper) to quantify intensity and hedonic tone within the assessment of odor exposure by systematic field inspection with trained observers. Additionally, exposure-information, the degree of annoyance, and the frequency of general health complaints and irritation symptoms were collected from the exposed residents through direct interviews. Multiple logistic regression analysis was used to establish dose-response associations between odor frequency, intensity and hedonic tone as independent variables and annoyance or symptom reporting as the dependent variable. It is shown that exposure-annoyance as well as exposure-symptom associations are strongly influenced by odor hedonic. Whereas pleasant odors induced little to no annoyance, both neutral and unpleasant ones did. Additional inclusion of odor intensity did not improve the prediction of odor annoyance. Frequency of reported symptoms was found to be exclusively mediated by annoyance. The results are discussed in terms of environmental stress emphasizing the WHO-definition of health. Based on these findings the existing German guideline against undue odor annoyance was modified.

Environmental Exposure to Confined Animal Feeding Operations and Respiratory Health of Neighboring Residents

Despite public concern about potential adverse health effects of concentrated animal feeding operations, objectively assessed data on environmental exposure to concentrated animal feeding operations and respiratory health are sparse. We aimed to assess respiratory health in neighbors of confined animal feeding operations. A survey was done in 2002-2004 among all adults (18-45 years old) living in 4 rural German towns with a high density of confined animal feeding operations. Questionnaire data were available for 6937 (68%) eligible subjects. In a random sample we measured the following outcomes: specific IgE to common and farm-specific allergens, lung function, and bronchial hyperresponsiveness to methacholine. Exposure was measured by collecting data on odor annoyance and geo-coded data on the number of animal houses within 500 m of the home. Locally optimal estimating and smoothing scatter plots were used to model the association between exposure and outcome. Analyses were restricted to subjects without private or professional contact with farming environments. The prevalence of self-reported asthma symptoms and nasal allergies increased with self-reported odor annoyance. The number of animal houses was a predictor of self-reported wheeze and decreased forced expiratory volume in 1 second, but not allergic rhinitis or specific sensitization. Self-reported exposure and results of clinical measurements were poorly correlated. Confined animal feeding operations may contribute to the burden of respiratory disease among their neighbors. Our findings underline the importance of objective assessment of exposure and outcome in environmental epidemiology.

Practice and Outcomes of Multidisciplinary Research for Environmental Sustainability

Since about 1990, when sustainability became a key concept for a wide range of scientific disciplines, the need for multidisciplinary collaboration has increased. We present five illustrative cases from the long‐standing environmental research work at the University of Groningen. The projects described are about hazardous materials risk, odor annoyance, energy scenario evaluation, climate decision analysis, and household consumption, respectively. The various case discussions emphasize experiences in research conceptualization, project design and execution, main findings, policy advice and surplus value, and difficulties met. Conclusions and recommendations are presented about the practice of multidisciplinary research. Finally, some challenges for research and development about environmental sustainability are discussed.

Systematisch erhöhte elterliche Nennung von Symptomen im Sinne einer Neurodermitis (“overreporting”) in Abhängigkeit zur Nähe zu Tierställen als einem vermuteten umweltbezogenen Risikofaktor

In Lower Saxony there has been ongoing discussion on potential health effects caused by emissions (bioaerosols) of livestock production facilities. We investigated the relationship between intensive livestock facilities in the neighborhood and respiratory, cutaneous or allergic diseases in 5- to 6-year-old children. Within a cross-sectional epidemiological study in 2001 a standardized questionnaire about respiratory and allergic symptoms and corresponding risk factors was used (n = 7,943). In addition, we examined flexural eczema. Individual exposition to bioaerosols coming from livestock facilities, for example endotoxin, was estimated on the basis of a Lagrangian simulation model of aerosol transport. For the investigation on overreporting with respect to dermatitis symptoms 3,374 observations were used. A probable overreporting was identified for the group of parents who did not live near livestock production facilities, but complained about agricultural odor annoyance. They reported twice as much skin symptoms (itchy skin condition during the last year 50.7% vs. 21.5 - 26.1% for the other groups), whereas the prevalence rate for visible signs of dermatitis hardly varies between the different strata of exposition (overall 5.8%). The homogeneity of odds ratios between.reported itchy skin condition and examined flexural eczema for the different strata is not fulfilled (p value < 0.05). Taking into account the odor annoyance, we have a strong hint for an overreporting of skin symptoms by a small study population group (3.2% of all), so that a general overreporting of allergic symptoms in this group can be assumed. Complementary objective medical examinations seem to be necessary to identify potential sources of bias even in case standardized questionnaires are used, particularly when issues of environmental health are dealt with.

Environmental odor annoyance from air pollution from steel industry and bio-fuel processing

Calibration with the master-scale procedure provides a defined unit of measurement for direct comparison between subjective reports from different individuals, obtained at different occasions, and in different contextual settings. A standard set of reference stimuli and the environmental target stimulus are rated on the same scale. The applicability of this procedure was demonstrated by applying it to odor annoyance from environmental pollution at three sites in communities with steel industry (Study 1) and bio-fuel processing (Study 2). Series of pyridine concentrations were used as reference stimuli that, together with the environmental target stimuli, were judged with magnitude estimation by participants with normal olfactory function. The results provide annoyance estimates for each of the six sites expressed in master-scale units and in pyridine equivalents that are directly comparable with each other and with those from other environmental studies using this procedure.

Estimation of odor emission rate from landfill areas using the sniffing team method

The monitoring of the odor annoyance generated by a landfill area is difficult, since it is a multi-area-sources problem, with a discontinuous odor emission. This paper proposes an adaptation of the method of sniffing team campaigns to the particular case of fresh waste odors. The method is based on the field determination of odor perception points, followed by data processing with a bi-Gaussian-type model, adapted to handle the odors. In a first step, field observers delineate the region in which odor impact is experienced and then the emission rate is manipulated in a dispersion model until the predicted size of the impact zone matches that observed in the field. In a second step the adjusted emission rate is entered into the model to calculate the percentiles corresponding to the average annoyance zone. The originality of the proposed method is the introduction of all observation points and of all recorded meteorological data into the model. The paper discusses the method limitations and the errors induced on the results, i.e. the odor emission rate and the percentile lines (or iso-concentration lines) which are used to describe the odor concentrations on a map of the surroundings of the plant. The proposed method proves to be reliable for diffuse sources, such as landfill areas. The obtained results are coherent with other results found in the literature with other techniques.

Organic compounds in office environments - sensory irritation, odor, measurements and the role of reactive chemistry

Abstract Sensory irritation and odor effects of organic compounds in indoor environments are reviewed. It is proposed to subdivide volatile organic compounds (VOCs) into four categories: (i) chemically non-reactive, (ii) chemically 'reactive', (iii) biologically reactive (i.e. form chemical bonds to receptor sites in mucous membranes) and (iv) toxic compounds. Chemically non-reactive VOCs are considered non-irritants at typical indoor air levels. However, compounds with low odor thresholds contribute to the overall perception of the indoor air quality. Reported sensory irritation may be the result of odor annoyance. It appears that odor thresholds for many VOCs probably are considerably lower than previously reported. This explains why many building materials persistently are perceived as odorous, although the concentrations of the detected organic compounds are close to or below their reported odor thresholds. Ozone reacts with certain alkenes to form a gas and aerosol phase of oxidation products, some of which are sensory irritants. However, all of the sensory irritating species have not yet been identified and whether the secondary aerosols (ultrafine and fine particles) contribute to sensory irritation requires investigation. Low relative humidity may exacerbate the sensory irritation impact. Practical Implications Certain odors, in addition to odor annoyance, may result in psychological effects and distraction from work. Some building materials continually cause perceivable odors, because the odor thresholds of the emitted compounds are low. Some oxidation products of alkenes (e.g. terpenes) may contribute to eye and airway symptoms under certain conditions and low relative humidity.

A dispersion modelling approach to determine the odour impact of intensive poultry production units in Ireland

The use of atmospheric dispersion modelling has become more common for the determination of odour impacts from existing poultry production facilities and the assessment of setback distances for new facilities. Setback distances for broiler, layer and turkey units were determined using the atmospheric dispersion model ISCST3 and the Environmental Protection Agency (EPA, Ireland) recommended criterion ( C 98,1-h ⩽ 6.0 ou E m −3) and a new odour annoyance criterion ( C 98,1-h ⩽ 9.7 ou E m −3) developed in this study. For a typical size unit in Ireland, maximum setback distances of 660, 665 and 1035 m were calculated for 40,000 broilers, 40,000 layers and 10,000 turkeys respectively at the current limit ( C 98,1-h ⩽ 6.0 ou E m −3). However, if the suggested odour impact criterion ( C 98,1-h ⩽ 9.7 ou E m −3) is implemented, the maximum setback distances decrease to 460, 500 and 785 m for broilers, layers and turkeys, respectively.

SIGNIFICANCE OF STANDARDIZED ASSESSMENT OF ENVIRONMENTAL WORRY IN STUDIES OF HEALTH EFFECTS ASSOCIATED WITH EXPOSURE TO ENVIRONMENTAL ODOURS

ISEE-172 Introduction: Evaluating public health relevance of an industrial source is complicated if the source in question leads to annoyance due to environmental odours. As worry is expected to arise with perception of environmental odours, higher rates of reported health complaints are expected in those exposed. Aim: In the process of evaluating an industrial source it would be favourable to consider effects of annoyance due to environmental factors, as well as environmental worry on reported health, separately from those attributed to actual organic impairment. Methods: Reported bodily complaints (47 single bodily complaints for which the subject’s house physicians had found no explanation, SOMS 2 questionnaire acc. to Rief et al. 1997) and environmental worry (scale acc. to Hodapp et al. 1996) were assessed in questionnaire based interviews in residents living near large scale composting sites. These sites were causing considerable odour annoyance. Microbiological measurements were performed in residential air, assuring that health relevant bioaerosol pollution (determination of viable microorganisms in residential air) did not occur in the neighborhood. With logistic regression (SPSS version 11.5) adjusted (age, gender, education) odds ratios (OR) were calculated for single bodily complaints, sum of bodily complaints (complaints index) being >4 in a basic model for residents near composting sites in association to their reported odour annoyance. In a second step, environmental worry was included in the model. Results: 130 subjects were included in the study, 67% reported being annoyed by residential odour. In odur annoyed residents, odds ratios were elevated for reporting single complaints: nausea [OR 4.07, 95% Confidence interval (CI) 1.11, 14.97], headache [OR 3.21, 95% CI 1.25, 8.25], intolerance of food [4.10, 95% CI 0.87, 19.34], dryness of mouth [OR 8.62, 95% CI 0.98, 75.92], hot or cold sweating [4.32, 95% CI 0.82, 22.86] as well as complaints index of >4: [OR 2.56, 95% CI 1,07, 6.12] in the basic model. When further adjustment was performed for individual environmental worry, OR for complaints associated with odour annoyance decreased and were considerably weaker for general unspecific complaints: headache [OR 2.38, 95% CI 0.89, 6.38], dryness of mouth [OR 5.77, 95% CI 0.61, 54.69], sweating [OR 4.32, 95% CI 0.82, 22.86] as well as complaint index being >4 [OR 2.18, 95% CI 0.87, 5.43], while OR for nausea increased, OR [4.39, 95% CI 1.10, 17.59]. Conclusion: This study was able to discriminate between environmental odour annoyance and worry, in association with reported health status in residents near an odorous industrial source. Association between individual odour annoyance and complaint rates decreased clearly once individual worry was considered. Possible health effects of microbial pollution from the composting sites did not need to be considered, on the basis of prior measurements showing no relevant bioaerosols pollution. From this it can be deduced that in situations where environmental annoyance (e.g. due to an industrial source) is inevitable, risk communication and public information leading to a decrease in environmental worry may improve individual perception (and reports) of health status in affected subjects. This in turn may lead to better acceptance of the environmental source in question.

Health effects associated with exposure to residential organic dust.

This study aimed at relating self-reported health complaints to bioaerosol pollution in the residential outdoor air and to duration of storing organic waste indoors. In a cross-sectional study, double blinded to ongoing environmental microbial measurements, physicians collected questionnaires in a neighborhood with a composting site and in unexposed controls. Self-reported prevalence of health complaints, physician diagnoses as well as residential odor annoyance and home hygiene were assessed. An elevation of reports of irritative airway complaints was associated with residency in an area with highest bioaerosol exposure but not with odor annoyance. Longer indoor storage of organic waste was associated with skin related symptoms. Atopic subjects were at higher risk. Airway-related health problems were not associated with longer storage of organic wastes in homes. Exposure to organic dust in residential air affects airways of residents while exposure in homes due to organic wastes affects the skin.

Odour intensity and hedonic tone - important parameters to describe odour annoyance to residents?

The Guideline on Odour in Ambient Air has been in use for many years for odour regulation in Germany. The main parameter that the odour regulation authority has to take into account is the odour frequency expressed as odour hours per year. In the guideline, limit values are given for the maximum odour frequency per year. These limit values are based on field investigations in which significant relationships between odour impact and odour annoyance was found. In these investigations, odour intensity did not yield a better description of the degree of annoyance caused to the residents. The hedonic tone was not mentioned. In a new research project finished in 2003, the influence of odour intensity and hedonic tone, in addition to odour frequency, has been assessed. Two installations emitting pleasant odours, two emitting neutral and two emitting unpleasant odours, have been selected. In each case grid field measurements by a panel were carried out, and the annoyance of the residents was assessed using a special questionnaire. The results of this project are: (1) A new method to measure odour intensity and hedonic tone in the field with data record forms was developed and validated. With this method, reliable and reproducible results are obtained. (2) The parameter odour frequency based on the system of "odour hours" is suitable and sufficient to predict the odour annoyance caused by unpleasant/neutral odours. (3) In the case of pleasant odours, hedonic tone has an abundantly clear effect on the dose-response relationship between odour frequency and annoyance. Pleasant odours have a significant lower annoyance potential than unpleasant/neutral odours. (4) The odour intensity has no additional influence on this relationship. If odours are recognisable then they can cause annoyance.

Integrated odour modelling for sewage treatment works

Odours from sewage treatment works are a significant source of environmental annoyance. There is a need for tools to assess the degree of annoyance caused, and to assess strategies for mitigation of the problem. This is the role of odour modelling. Four main stages are important in the development of an odour problem. Firstly, the odorous molecules must be formed in the liquid phase. They must then transfer from the liquid to the gaseous phase. They are then transported through the atmosphere to the population surrounding the odour source, and are then perceived and assessed by that population. Odour modelling as currently practised tends to concentrate on the transportation of odorants through the atmosphere, with the other areas receiving less attention. Instead, odour modelling should consider each stage in an integrated manner. This paper describes the development of integrated odour models for annoyance prediction. The models describe the liquid-phase transformations and emission of hydrogen sulphide from sewage treatment processes. Model output is in a form suitable for integration with dispersion models, the predictions of which can in turn be used to indicate the probability of annoyance. The models have been applied to both hypothetical and real sewage treatment works cases. Simulation results have highlighted the potential variability of emission rates from sewage treatment works, resulting from flow, quality and meteorological variations. Emission rate variations can have significant effects on annoyance predictions, which is an important finding, as they are usually considered to be fixed and only meteorological variations are considered in predicting the odour footprint. Areas for further development of integrated odour modelling are discussed, in particular the search for improved links between analytical and sensory measurements, and a better understanding of dose/response relationships for odour annoyance.

Odour emission inventory of German wastewater treatment plants - odour flow rates and odour emission capacity

Wastewater Treatment plants can cause odour emissions that may lead to significant odour annoyance in their vicinity. Thus, over the past 20 years, several measurements were taken of the odour emissions that occur at WWTPs of different sizes, treatment technology, plant design and under different operating conditions. The specific aspects of odour sampling and measurement have to be considered. I presented some of the results of my odour emission measurements 11 years ago. However, it is now necessary to update the figures by evaluating newer measurement results obtained from measurements taken from 1994 to 2003. These are presented in this paper. Also, the paper highlights the odour emission capacity (OEC) measurement technique which characterises liquids and can be used to assess the results achieved by different types of treatment in the liquid phase, e.g. in a sewerage system. In addition, the OEC is a suitable parameter to set standards for the odorant content of industrial wastewaters that are discharged into the publicly owned sewerage system.