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5.8.2 APPLICATION OF FRAMEWORK TO IPA OF WASTE
INCINERATOR EMISSIONS ON A LOCAL SCALE

Following the same procedure used for the LCI results, the framework for uncertainty
assessment in IPA was also applied to the case study of local human health impacts
due to the emissions of the MSWI in Tarragona. As in the approach used previously,
some goals were proposed:

• Assigning probability distributions to the parameters considered in the
study
• Assessing the uncertainties and the variation in application
• Determining the most relevant parameters in such an IPA by sensitivity
analysis

5.8.2.1 Assigning Probability Distributions to Considered
Parameters
As explained by Rabl and Spadaro (1999), the probability distributions mainly used
in environmental damage estimations are the normal distribution and the log-normal
probability distribution. As mentioned earlier, all normal distributions are symmetric
and have bell-shaped density curves with a single peak. The log-normal distribution,
in turn, is calculated assuming that the logarithm of the variable has a normal distri-
bution. As in the previous case of uncertainty assessment in LCI, the proper determi-
nation of the probability distribution is only possible if measured data are extensively
available, as in the case of atmospheric emissions, electricity production, working
hours and flow gas volume. If the parameters are based on little proper information,
literature values must be applied to determine the probability distribution. That is the
case of PCDD/Fs emissions, dispersion modeling results, dose–response and expo-
sure–response functions, population data and monetary valuation.
The necessary information for determining the probability distributions from
measured data was taken from the LCA study of the Servei de Tecnologìa Química,
STQ (1998), and from information given by the director of Tarragona’s MSWI
(Nadal, 1999). Probability distributions published in the literature were available
from the ExternE project (EC, 1995; EC, 2000) and in particular from the publication
about uncertainty analysis of environmental damages and costs by Rabl and Spadaro
(1999). The estimation of the uncertainty for the dispersion model was taken from
McKone and Ryan (1989). Further local information was obtained from the Public
Health Plan of the Tarragona region (GenCat, 1997) and from a diagnosis on the
socioeconomic development of the Tarragona province by Soler (1999).
The probability distributions used in the study are summarized from Table 5.11
to Table 5.13. “Variable mean” stands for an enormous number of values that are
not constant but differ depending on the grid and pollutant considered.
In Table 5.11 the technology and modeling parameters are presented together
with their respective probability distributions and characteristics. The technology
parameters in Table 5.11 consist respectively of electricity production, working hours
and specific characteristics of the incinerator (stack dimensions, geographical situ-

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