Development of an Environmental Quality Index ...

RECENT ADVANCES in ENVIRONMENT, ECOSYSTEMS and DEVELOPMENT

Development of an Environmental Quality Index Related to Polluting Agents Quartieri* J., Troisi° A., Guarnaccia* C., D’Agostino+ P., D’Ambrosio° S., Iannone* G. * Department of Physics, Faculty of Engineering ° Department of Mechanical Engineering, Faculty of Engineering + Department of Civil Engineering, Faculty of Engineering University of Salerno Via Ponte don Melillo, I-84084 Fisciano (SA) - ITALY [email protected] , [email protected]

Abstract: - Nowadays attention to environmental pollution induced a very hard debate in the scientific community in order to face issues related with this problem. In particular the need for a significant level of health care both in working areas and in civil settings suggested to develop several methods capable to evaluate the quality of ambient. Up to now, all approaches are conceived considering well defined ambits of application. In this paper we will discuss the possibility of developing a general index of environmental quality which deals with different kind of polluting agents. The effective result is represented by a quantity which measures a weighted combination of sub-indexes related to each polluting agent and described by means of a normalized opportune mathematical function. Our idea is to furnish a healthy parameter which describes in a synthetic matter the state of ambient under investigation, suggesting what are areas where it is necessary to intervene in order to ameliorate environmental conditions. Key-Words: - Environment, Healthness, Physical Polluting Agents, Quality Index.

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method one is adopting. The aim is to translate multiple variables descending by each polluting agent into a single suitable criterion and to take into account health care standards. Typically, such kind of approach takes origin from socio-economical methods which evaluate quality of life [1]. The basic idea is to work out a method for integrating complex data of different origin and generating a score that describes environment quality status and it is capable to evaluate environment quality trends. Approaches in this sense have been defined considering a EU recommendation protocol called DPSIR [2] which takes into account human being activities with respect to their impact on environment and the answer of ambient to these external effects. In other words, the DPSIR method is a casual framework which allows to describe in a synthetic way interactions between society and the environment by means of parametric indexes. The method has been developed by European Environment Agency considering five fundamental components: Driving forces, Pressures, States, Impacts, Responses and is based on an original pressure-state-response model developed by Organization for Economic Co-operation and Development. Actually, many environmental

Introduction

The growing of a significant attention with respect to problems related to environmental pollution induced in the last years enormous efforts in order to develop studies capable to face such a relevant problem. A very important task, in this sense, is represented by the development of suitable techniques in order to analyze problems related to polluting agents. Among these, the definition of an environmental index can represent a very useful tool in order to describe the quality of ambient. This approach can represent not only a qualitative method of analysis but, relying on experimental measurements, can furnish even a significant approach to quantitatively characterize the health state of human environments. Environment quality indicators can represent an ideal approach to check, physical, chemical and biological conditions and in addition to monitor changes incoming on the areas of particular interest. The methodological approach conceived to develop an environmental quality description has to be referred to a branch of multi-criteria decision analysis. In fact, in order to construct a well defined quality index, it is necessary a systematic procedure for analyzing the decision process underlying the

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relation to different behaviour with respect to different regimes. As a matter of fact, we will not consider these quantities among sub-indexes we will deal with. Such choice is based even on the consideration that infrasound, ultrasound and high atmospheric pressures are typical of a very small set of working frameworks. On the other side one could consider microclimate effects by separately taking into account temperature, humidity and in certain contexts velocity of wind. Therefore, in our idea, a viable quality index defined on polluting agents can be represented by a quantity which collects issues coming from five basic ingredients: acoustical radiation, electromagnetic radiation (both low and high frequency), atmospheric pollution, temperature and humidity. This choice can be further generalized adding some other quantities which turns out to be suitable in relation to the environment which is investigated. It has to be remarked that, at this level, the formulation of a quality index of environment represents only a work proposal. We are not intended to furnish a rigorous analysis of the problem. In this paper we want, above all, to suggest a strategy which can be pursued in order to check the health of a whatever physical environment. The first step necessary to determine a quality index is to individuate the relevant variables characterizing environment quality. Once such variables have been considered it is possible to characterize each quantity with a certain parameter and then transform each parameter as well defined relative sub-index. This approach implies to force the different quantities to be described within a common scale so that to make our sub-indexes comparable. Such a rescaling is necessary since different variables are defined in term of different physical units and that makes impossible a coherent relation among them. The third phase is the definition of a weight value to each sub-index in order to establish its relative importance with respect to the overall environment quality. From a practical point of view, the simplest way to overcome the commensurability problem in the combination phase is to consider ratios of the environmental descriptors Qi

indexes have been developed in different contests in relation to the DPSIR protocol. However, despite a very huge amount of quality parameters have been developed referring to specific areas of interest [2,3,4,5,6], only a small number of models is based on a more complex combination of some of these (see for example [7]) considered as basic sub-indexes. In our work we pursue a slightly different approach. In order to manage with a more versatile quantity, we develop a complex index based on specific sub-indexes which are related to different polluting agents. In particular we consider quantities which can be measurable and can give back an analytical description of each phenomenon under consideration. Our idea is to define a parameter which can be able to phenomenologically describe the healthness of a certain environment, taking into account a rigorous analysis of data coming by some relevant subquantities. Fundamental sub-indexes are identified taking into account prescriptions of Italian agency on environment and considering a law norm of Italian government (D.L. 81/2008) [8] regarding polluting agents in working areas. In such a way, we can have a parameter suitably useful both in working environments and civil ambits which can be easily adapted at different contexts. Of course, it has to be considered that civil frameworks need more careful analyses since there is not any reference of a list of effective polluting agents and, in addition, annoying effect can be the result of multiple components. In fact, in such a case, one should take into account several variables (in particular anthropic activity) which does not allow to simply characterize the issue of pollution in a schematic manner just associating the effect to a well defined source.

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The model

In order to develop our model we consider as basic reference the ex art. 28, art. 180 and art. 181 of DLgs. 81/2008 of Italian government [8]. This norm indicates that in the ambit of working settings the following effects are recognized as polluting agents: acoustic noise, ultrasound, infrasound, vibrations, electromagnetic fields, optical radiations produced by artificial sources, microclimate, high atmospheric pressures. Actually there are some explicit regulations on ultrasound, infrasound, microclimate and high atmospheric pressures which are in some way based only on phenomenological considerations. In fact it is quite hard to define well determined prescriptions on these quantities in

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qi =

Qi Qref

(1)

referring each quantity to a particular reference value Qref which is suitably fixed (i.e. taking into account upper limits admissible for human health

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evaluated on daytime or night time interval. The correspondent sub-index can be obtained by dividing over a reference value Lrefeq(A). Actually the choice of the reference value depends on the particular ambit one wants to analyze. Of course there are different limit values in relation to the fact that the exposition to the acoustic field is experienced in a civil or in an industrial framework. For example, in the case of residential ambits during daytime, law [9] suggests as a quality level (to be hopefully obtained) the value of 52 dBA, while it fixes a warning level of 55 dBA. On the other hand, in working areas, the safety level is fixed to 80 dBA, according to the art. 181 of DLgs. 81/2008 of Italian government [8]. Even the experimental approach and whatever related to the phase of measurement is regulated by the same law prescriptions. As already said, the simplest way to define the sub-index related to the acoustic field emission is to take into account the ratio of the measured level over the reference value, thus, we define:

as suggested by law). In such a way, the physical indicator Qi can be transformed into a dimensionless characteristic index qi which furnishes a measure of the phenomenon with respect to a certain reference value. An important remark regards the choice of the reference value Qref. In fact, depending on its value, we can have positive or negative values and greater than 1 or lower than 1 indexes. This behaviour requires a careful analysis, since, in order to make the clearest and the most effective the definition of our general index, we need to have a well defined set of sub-indexes. For example, considering reference values Qref which are either upper values or less stringent values in relation to law prescriptions, can lead astray and make the overall quantity not clear to be interpreted. The solution to such an issue is to consider coherent definition of sub-quantities. In other words is preferable to consider all positive or negative sub-indexes and all upper limits or lower limits quantities as reference parameters in the sub-indexes definition. In such a way one can have a well defined overall quantity which can be easily interpreted.

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q Ac =

Lref eq ( A)

(2)

An important remark regards the possibility to interpolate data coming from acoustical measurements. If one wants to perform an analysis on a continuous area starting from a discrete collection of datapoints, considering data measured in dBA can be misleading. In fact, such a measure unit is based on a log rescaling of the pressure level of the acoustic signal, thus if an interpolation of data is performed, using a dB evaluation of acoustic signal will make inconsistent the interpolation process. The correct way to proceed is to consider the data expressed in term of pressure level and to perform the interpolation on this data and then, eventually, transform back the whole set of data in dBA for sake of simplicity.

Sub-indexes definition

As discussed before, the choice of the physical quantities which are relevant in order to characterize the healthness level of a certain environment represents a fundamental task. According with indications coming from official government prescriptions, among the phenomena referred as polluting agents we select: acoustic noise, electromagnetic noise (both electric and magnetic at low and high frequency), atmospheric pollution and microclimatic effects, expressed by means of temperature and humidity. Other physical effects as: vibrations, high pressure effects, etc., although described by law as polluting agents, will be not considered here. In the following we will discuss singularly each quantity with respect to its redefinition in term of sub-index necessary to the definition of an overall more general quantity.

3.2 Electromagnetic noise As for acoustic pollution, electromagnetic noise represents a very fundamental physical phenomenon which has to be severely monitored in order to protect human health. Both electric and magnetic field are responsible for damages to biological systems. In particular the electric field can interact with the cardiac frequency of human being, while the magnetic field can generate eventually currents. Nevertheless at this level we will skip any discussion on the biological effects of polluting agents since this matter turns out to be

3.1 Acoustic Noise Acoustical emissions represent a rather annoying problem both in civil and working environments. This phenomenon represents one of the fundamental issue which has to be taken into account once one wants to define an overall quality index. The physical relevant quantity which can be taken into account is the A weighted equivalent acoustic level Leq(A) measured in dBA,

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Leq ( A)

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very complex and requires a rather careful analysis well beyond the aim of this paper. An important remark, which on the contrary has to be done, regards the different action of low frequency electromagnetic fields (power lines, engines..), and of high frequency electromagnetic fields (i.e. antennas). Thus, effects of the so called non-ionizing radiation have to be carefully investigated in relation to its frequency as well as ionizing radiation must to be carefully taken into account since can represent a straightforward source of danger for human health. As first step we will define a sub-index by only considering non ionizing radiation which are currently experienced in all day life; however, in principle, it is easy to extend the health quality index also to ionizing phenomena. Even in this case, the easiest way to obtain a sub-index is to start from the definition of the physical quantity which measures this effect [10], i.e. the intensity of the electric field, measured in Volt/meter (low and high frequency), and the intensity of the magnetic field, measured in Ampere/meter (high frequency) or Tesla (low frequency)1. The subsequent step to define the relative sub-index is dividing by reference quantities determined by law. In relation with this choice one can assume as reference values a set of intensities of electric field and magnetic field which correspond to full safety thresholds [10]. In particular, we refer to the long time exposition threshold which means to consider the averaged value on 24 hours monitoring. In this case we adopt EHighref = 6V/m (high frequency), ELowref = 5kV/m (Low frequency) for the electric field and Href = 0.016 A/m (High frequency) and Bref = 3µT (Low frequency) for the magnetic field. The relative sub-indexes will be: Low q El =

E Low ; Low Eref

B , Bref

(3a)

High q El =

E High H High ; qMagn = , High Eref H ref

(3b)

Low qMagn =

the instantaneous value of the Electromagnetic field, we have only to take into account different estimates for the reference values of the electric field and of the magnetic field. Of course, the definition of the sub-index will remain the same.

3.3 Atmospheric pollution Issues related to atmospheric pollution represent by themselves a very complex problem in order to characterize the quality of a whatever setting. Actually there are several factors which concur to define the healthness of air and, in this sense, there are several index describing air quality. In particular, these parameters are generally based on a collection of the most important physical quantities which measure the amount of polluting agents present in a certain environment. As in the previous cases, we should discriminate between civil frameworks and industrial contexts. Nevertheless, in this paper we will only discuss the general prescriptions without specifying particularities related to working areas since, in such a case, the discussion becomes very complex and depends on the particular industrial settlement which is considered. The general scheme to approach air pollution is based on considering among the most important physical quantities: PM10 measuring the concentration of fine dust (i.e. air born solid particles due to human activity), CO measuring Carbonic Monoxide, NO2, (Nitrogen dioxide) O3 (Ozone), and other quantities measuring different concentration of nano-particles and oxides or anhydrides in air, like SO2, NOx, , Pb [11,12]. All these parameters can be recast into relative indexes by dividing over a reference value according to law regulation. The combination of such quantities or their weighted combination can furnish an atmospheric pollution sub-index which has to be combined with the other sub-indexes of our model. In particular, Italian agencies for pollution are custom to take into account PM10, NO2, and O3, neglecting CO and SO2 which nowadays turn out to be typically below their limit values. Nevertheless some more quantities can be inserted in the effective atmospheric pollution index in relation to the specification of the environment under investigation. Characteristic values of threshold for PM10, NO2, and O3 are respectively: 50 µg/m3 (per day), 200 µg/m3 (per hour) and 180 µg/m3 (per hour) [11,12]. In principle, the effective sub-index describing air health should require a process of analysis of the previous physical parameters in order to establish their relative importance. However, it is quite hard

It is evident that if we prefer to consider the effective value of the field in place of the averaged quantities, that is if we are interested in

1

For the high frequency range, the considered physical

r

quantity is the intensity of the magnetic field H , while, in the low frequency range, it is the intensity of the

r

magnetic induction field B [10].

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close to the comfort level, according to the definition of the other sub-indexes. This choice allows to have a penalizing subindex when measured temperatures are far from the reference value. In particular, we adopt a square root function to make shallow corrections obtained when measured temperature takes values far from the reference quantity. Such a choice is made in order to have a rate comparable with the other subindexes. Thus we have:

to define the relative weight of one quantity with respect to the others within the overall index. Therefore, two different approaches are mainly used. In the first approach one can identify the overall atmospheric pollution index with its worst sub-index. The second approach, often pursued by Italian agency for polluting agents [12], is to consider an average between the sub-index relative to PM10 and the worst indicator between NO2, and O3. Both methods can be suitably used. In order to make the definition of the overall health quality index the most efficient, we prefer to exploit the second approach, which allows us to define our air pollution sub-index as:

qatm

A 1 = ∑ refi 2 i Ai

qTemp =

Tref

(5)

A particular choice of Tref can be: Tref = 18°C. We recognize this value as an opportune quantity in order to give a reference range where feasible condition are achieved. In our opinion, it is reasonable to consider that temperatures comprised between 8°C and 28°C can represent a quite favourable climate for human living even in working areas. One could object that a person has different reactions when is obliged to stay at temperatures which are below to a certain value or at temperatures which are upper to a certain limit. However, since typically we discuss of temperatures ranging from -20°C and +45°C, thus excluding very extreme conditions which man meets only in the polar circles and very close to equator, our approximation can be considered quite reasonable. Of course, this discussion represents at the status only a working proposal and it is feasible of improvements and further developments. Above all, phenomenological considerations could be ameliorate by means of more formal analyses of the problem. In particular it is possible to encounter evidences from epidemiological studies or to perform complex microclimate analyses in order to have a more analytic formulation of (5). A similar phenomenological discussion can be drawn with regard to humidity. It is possible to postulate a reference value with some suggestion coming by law regulation and construct a sub-index which is again the ratio between the measured value and the reference quantity. As a matter of fact, we have again a sub-index of the form:

(4)

where with Ai we have indicated the measured amount relative to PM10 and the worst indicator between NO2, and O3. The time of monitoring of these observables suggested by law [11] is 24 hours and the measurement protocol needed in this sense is as well provided by the same law.

3.4 Temperature and Humidity (Microclimate sub-index) The last issue which represents a very important aspect to be monitored in order to have a significant environmental index, is represented by microclimate parameters. In particular, we consider temperature and humidity, even if, in principle, it could be also taken into account wind velocity. Developing a sub-index which describes temperature effects is not straightforward. In fact, up to now, we have considered only ratios of our physical quantity with respect to a suitable reference value. In the case of temperature this approach cannot be used since disturbing effects on human health can be obtained both at low and high temperature, while there is a middle range (e.g. from 10°C to 25°C adopting a Celsius scale) which guarantees comfortable conditions. In other words, it is necessary to obtain a parameter which can penalize both lower and higher temperatures once an averaged value is fixed, with the same amount of penalty with respect to both negative and positive deviations from the chosen value. In order to overcome this problem the choice of the subindex function has been more elaborated. Therefore, differently from the previous cases, one is forced to choose a reference value which corresponds to a satisfactory comfort level. Then the subsequent sub-index is a quantity which is near to zero when the measured temperature is

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Temp − Tref

q Hum =

Humidity Humref

(6)

Of course, in order to specialize our proposal, a careful analysis is needed thus to accept suggestions coming by specific literature. Actually,

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one can adopt in our toy model a reference value Humref = 85%. For sake of completeness, one should remark that even wind velocity could represent a significant parameter. In fact, in some working contexts, its impact on human activities can represent a relevant variable. A sub-index referred to such parameter can be introduced with the same methodology of the Humidity parameter, by defining a ratio between the measured value and a certain reference value coming from phenomenological considerations or taking into account limits on such quantity deriving from micro-environment analysis results.

one), thus we have developed our index in such a way to take into account this difference. In other words, higher risk phenomena will be weighted with a higher impact factor, while lower risk phenomena with a lower specific coefficient. A possible method which can be followed in order to give an estimation of such coefficients will be briefly sketched in the following section and it will be object of a dedicated forthcoming paper.

5 The weighting coefficients As previously said, constructing a environment healthness index which is based on the scientific relevance of polluting agents requires a phase of evaluation regarding the health risk of whatever casual combination of physical phenomena can occur. However, nowadays knowledge about epidemiological effects due to polluting agents is quite far from this objective. In fact, at this stage, there are still huge difficulties at statistical and toxicological levels in order to collect the significant amount of data needed to establish the relative effect of each component on human health. Such an analysis is still more complicated when one wants to describe the effect by means of a collective index, summing up the effect of several polluting agents. It is evident that the purpose of an assignment of weights to variables which concur to define the HQI of a certain environment is to denote each variable importance. A larger weight value implies greater impact of the sub-index. In order to overcome the epidemiological problems hinted above, one can recur to expert suggestions. In assigning the weight of each variable, the most challenging factor is that different people may have different opinions. Thus, our parameter can be obtained assigning sub-indexes weights by combining the opinion of such experts. Since each expert evaluates the importance of every variable based on his opinion, in order to validate this phenomenological approach, it can be adopted a rigorous statistical method which finally provides the effective weight of each polluting agents on the overall index. Typical useful statistical approaches, when one is dealing with a decision theory, are multi-criteria analysis, fuzzy logic or the Analytic Hierarchy Process. All these methods are widely used in the realm of environmental decisional schemes which contemplate indexing of effective quantities capable of influencing the environmental status [13, 14].

4 The overall Health Quality Index Once sub-indexes have been defined and for each of them a process of homogenizing of the physical data has been performed providing opportune functions, the overall Health Quality Index (HQI) can be built. The most immediate scheme for such definition is a linear combination of sub-indexes by means of suitably weight coefficients:  Leq ( A) E Low E Hig Π s =  a ⋅ ref +eLow ⋅ Low +eHigh ⋅ High +  Leq ( A) Eref Eref  Ai B H 1 + mLow ⋅ + mHigh ⋅ +d⋅ + (7a) 2 i Airef Bref H ref

∑

+t ⋅

Temp − Tref Tref

+u ⋅

Humidi ty  Humref 

which can be written in a more compact form as:

Πs =

∑pq

i i

(7b)

i

where pi = a, eLow, eHigh, mLow, mHigh,, d, t, u, are the weights related to each sub-index. We prefer to do not normalize our sum since a wider admissible range of values favours a better graphical representations of the parameter. Weights pi represent a very important issue of our approach. In fact, in order to make the Health Quality Index (HQI) a significant parameter, we need to take in the right count effects on biological systems deriving from different physical phenomena. Of course, each polluting agent influences in a different manner human health (e.g. low frequency electromagnetic field affects biological systems differently than high frequency

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Classes

6 The evaluation method After the analysis of how to determine weights related to each sub-index, a second fundamental stage of the construction of our approach is to establish the right evaluation method of the parameter we are developing. As previously said, we cannot develop a method based on scientific considerations, thus we have to recur again to phenomenological suggestions. In fact, we have no clear way to establish a quantitative influence of polluting agents on health and neither we can discriminate among what is the true respective incidence of each physical effect, with respect to a certain pathology. As a matter of fact, one can only follow a heuristic method. In particular, in order to make our method practical and easily interpretable, it is possible to develop a criticalities scale which is based on the assignment of a health risk proportional to the polluting level determined by the overall index. Of course, such an approach cannot assign to any level a clear scientific significance but it has to be considered only on a phenomenological basis. In relation to our definition of the overall index HQI (7), one can define 6 classes of health safety level. We assign a class of health safety to a particular environment, if the respective HQI falls into a certain range of values. The ranges are obtained defining the limits for each class assuming the same suitable constant value for all the subindexes. From a practical point of view, each class can be formulated as follow:

∑pq

i i, A

i

≤ Πs