Environmental Engineering Reference
istics) through which it is possible to describe a certain phenomenon. The
indicators must be representative of the current as well as the final envi-
ronmental status, so that a simple comparison operation makes it possible
to identify the variation. Both indicators and environmental components
are selected via a scoping phase, depending on the issue under examina-
tion. In this phase, consultative activities with the local communities,
aimed at integrating the knowledge of the evaluating experts become
Returning to the atmosphere-air quality component, about 3,000 air-
contaminating substances have been classified, mostly deriving from
human activities. The principal pollutants include carbon monoxide, sulfur
and nitrogen oxides, benzene, ozone, and particulate matter.
Within the frame of the core environmental indicators for urban air
quality description, the Organisation for Economic Co-operation and
Development (OECD) uses air pollutant concentrations as a status indica-
tor in relation to population exposure to such pollutants. The OECD uses
the so-called pressure-status-response (PSR) model to describe a country's
advance as to its environment. A frequent model for the elaboration of the
VAS environmental reports is the Driving forces-Pressures-States-Impacts-
Responses (DPSIR) model, an evolution of the PSR. It allows one to corre-
late the information describing the status and the modifications of a certain
environmental context, by following a logical scheme. The DPSIR model is
not “rigid,” i.e., a component may have different roles (determinant,
impact, and so on) depending on logical scheme construction.
A further concept to introduce for the definition of an environmental
quality evaluation method is that of the threshold limit value. In the previ-
ously mentioned example regarding the atmosphere-air quality component,
the threshold limit value is a limit value for the concentration of the pollu-
tant in the atmosphere. The threshold limit values are typically identified
by international research institutes. Then, each country adopts them
through the legislative process.
The use of the DPSIR model therefore consists of:
Analyzing a “determinant” (e.g., car traffic).
Evaluating “pressures” throughout the assessment/direct measuring of
the consequent emissions (e.g., NO2).
Analyzing the “status” through the direct measurement of the pollutant
concentration, and subsequently evaluate current air quality.
Evaluating the “impact” of a potential car traffic variation through an
assessment of the “status” variation (i.e., variation in the pollutant con-
centration), comparing it with the threshold limit values identified by
scientific research and by the legislative process.
Hypothesizing any “responses” (mitigation and oriented measures), if