Odour nuisance is an ignored environmental problem, an invisible face of air quality analysis and monitoring in Portugal. Local and governmental authorities have been receiving odour complaints, but only in recent years this issue is seen as a growing concern and not just a matter of licensing and inspection. This fact and the lack of specific ambient air odour regulation in Portugal originated a bottom up approach focused on citizens and their contribution to a more comprehensive analysis.
Despite the existence of odour measuring instruments, the human nose is a universal sensor with higher sensitivity that allows to assess the impact of discomfort on sensitive receptors. From this point of view, a sensorial method has been conducted with community neighbours of an odour emission source as an integrative approach to the problem and a complementary vector to a quantitative analysis. The human nose used as a “tool”, allows to address the issue instantly and at a local level, which is not always possible with other methodologies, even in situations where the detection limit is reduced and therefore not measurable with certain equipment. It should be noted that this olfactory evaluations are the ones responsible for triggering formal complaints to the authorities whether it is the National Guard, the municipality or the environmental regulators. But the lack of a unified form to register the complaints is a mandatory issue to help addressing the correct odour sources and better understand the problem. So, this sensorial approach also aims to develop a tool to aggregate the needed elements to a valid form, to ensure that the complaints can be verified and validated. This would help to make a comparison and create a record history database, at the odour emitter level or at local and national scale.
The results obtained with this approach have led to the application of several actions such as the real knowledge of the problem from an industrial operator perspective, inclusion of public stakeholders, and the design and implementation of an odour management plan with the purpose of the establishment of mitigation measures.