Evaluating the dispersion of toxic odour emissions from complex sources.

This article describes an original approach for evaluating exposure to toxic odour emissions, based on methods commonly used for assessing the impact of odour, adopted in this specific case to examine the non-carcinogenic health effects of odours in the city of Terni, Italy. First the hazardous volatile organic compounds emitted from the main odour sources were identified and quantified by chemical analysis. The Hazard Index (HI) was used to assess the toxicity associated with the emissions. The HI is the sum of the concentrations of the hazardous compounds weighted with their Reference Concentration (RfC). A RfC is the estimated continuous inhalation concentration at which people are unlikely to risk any deleterious effects during their lifetime. Atmospheric dispersion modelling was based on the Toxicity Emission Rate (TER) which, like the Odour Emission Rate (OER) conventionally used to quantify odour emissions, relates the HI with the air flow of an emission source; it is as a simple but effective method for the general characterization of toxic odour emissions in complex scenarios. The results indicated that citizens' exposure to the non-carcinogenic toxic compounds involved in odour emissions was below the level expected to have adverse effects on human health. Classical risk assessment techniques should now be employed to define the pollutants and their effects better and to validate this approach.