Probabilistic Ecological Risk
1,2,4-Trichlorobenzene at a Former
Industrial Contaminated Site
M A R C E L L O Z O L E Z Z I , *, †
C L A U D I A C A T T A N E O ,†A N D
J O S E Ä
V . T A R A Z O N A‡
Interuniversity Centre of Environmental Monitoring Research
(CIMA), University of Genoa, Via Cadorna, 7,
17100 Savona, Italy, and Laboratory for Ecotoxicology,
Department of the Environment, Spanish National Institute
for Agriculture and Food Research and Technology (INIA),
Ctra de La Corun ˜a km 7, 28040 Madrid, Spain
Measured concentrations of 1,2,4-trichlorobenzene
(1,2,4-TCB) in soil and groundwater detected in an industrial
contaminated site were used to test several probabilistic
ranging from comparison of single effects and exposure
values through comparison of probabilistic distributions for
exposure and effects to the use of distribution based
quotients (DBQs) obtained through Monte Carlo simulations.
The results of the deterministic approach, which suggest
that risk exceeds a level of concern for soil organisms, were
influenced mainly by the presence of hot spots reaching
concentrations able to affect acutely a large proportion of
species, while the large majority of the area presents 1,2,4-
TCB concentrations below those reported as toxic. Ground-
(pore)water concentrations were compared with aquatic
risk for aquifers and streams in the adjacent area as
well as for soil-dwelling organisms exposed via pore water.
In this case, the risk is distributed over a large proportion
of the site, while the local risk of hot spots was low,
showing that risk characterization based exclusively on
soil concentrations might be insufficient.
Risk assessment protocols are considered the best available
tool for supporting, under scientific basis, decision-making
processes on a wide range of areas, from economic develop-
ment to environmental protection (1). In the past decade
international institutions developed harmonized method-
ologies for the risk assessment of chemical pollution, and,
at present, ecological risk assessment (ERA) can cover both
the Technical Guidance Document (TGD) provides a com-
protocols for assessing certain groups such as pesticides,
biocides, or pharmaceuticals are also available (see the
Scientific Steering Committee second report on the harmo-
nization of risk assessment procedures for a comprehensive
review of EU protocols) (1). Similar documents have been
which also provides site-specific risk assessment guidance,
mostly under the Superfund activities. The estimations of
risk used in these frameworks follow the principle of the
exposure (predicted estimations or measured values) levels
with expected responses based on dose-response observa-
tions. The simplest comparison is a single-point estimate,
such as the hazard quotient (HQ) (which is the measured or
estimated environmental concentration divided by the
(PEC) and the predicted no effect concentration (PNEC) (2,
a risk refinement using higher tier approaches becomes
necessary. A high level of conservatism is required to cover
(7), but it should be made clear that this is just a screening
level approach, which can only be used to focus on the most
important contaminants and emission sources. An HQ > 1
(or RCR > 1) does not necessarily indicate real risk, but that
another more complex assessment must follow to reduce
uncertainty to an acceptable level. Moreover, an HQ < 1
be toxic, but this approach cannot quantify the likelihood
thresholds for long- and short-term effects (1, 3, 8).
Many authors and scientific institutions have suggested
the use of a tiered approach for exposure and effect
the use of probabilistic approaches to risk assessment (5, 6,
8,9). In the EU, the Scientific Steering Committee suggested
five different levels for setting exposure assessment as well
as five levels for the effect assessment, offering large
possibilities for risk refinement (1). Typical refinements in
(SSDs) combined with distributions of exposure concentra-
thresholds and thus the probability of adverse effects.
Probabilistic approaches can cover both the uncertainty in
the estimation and the true variability observed for most
can be applied with use of different methodologies and for
different purposes. The use of probabilistic approaches for
generic risk assessments is included in regulatory-based
tiered processes in several parts of the world (2, 12, 13).
Similarly, probabilistic risk assessment methods can also be
applied to site-specific risk assessments, e.g., to assess the
risk of contaminated land.
This paper presents an environmental risk assessment
for an industrial polluted site in which high levels of 1,2,4-
trichlorobenzene (1,2,4-TCB) have been observed. The risk
using information on measured levels and reported toxicity
the ecological risks in this site-specific assessment are
presented, following a tiered approach, using this contami-
nated site as a case study for investigating the kind of
information provided by each risk refinement option.
* Corresponding author phone: +39 019 23027220; fax: +39 019
862612; e-mail: email@example.com.
†University of Genoa.
Environ. Sci. Technol. 2005, 39, 2920-2926
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2005 American Chemical Society
Published on Web 03/24/2005
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Received for review May 27, 2004. Revised manuscript re-
ceived February 4, 2005. Accepted February 15, 2005.
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