capacity, originally proposed by Cairns
(1977), is based on the definition of the
assimilative capacity, which is defined as
the "ability of receiving system or ecosystem
to cope with certain concentrations or levels
of waste discharges without suffering any
significant deleterious effects" (see also
Cairns 1989). The environmental capacity
approach works well as an interactive
environmentalmanagement strategy. Other
traaitionally used complex strategies, based
on environmental quality objectives or
simple but readily enforceable strategies,
such as those based on uniform emission
standards, maximum allowable
concentrations in effluent, the blacWgrey/
white lists (Hellawelll986) or the application
of principles of best practicable means
available, are considered as simple
components of this adaptive, interactive
strategy (GESAMP 1986, 1991).
This scientific approach requires
technical and socioeconomic inputs as
parallel, interactive and complementary
activities in decisionmaking in integrated,
environmentally compatible, development
planning. It emphasizes the objectivity and
independence of technical inputs and their
influences on decisions related to
socioeconomic feasibility. It also emphasizes
that the acceptability of environmental
impact rests on much more than political
considerations. Such acceptability can be
determined scientifically, assuming that the
enviro~mental capacity can be quantified.
Once the environmental capacity of a given
substance is determined, it can be
apportioned for various resource uses and
needs. It is also important to recognize that
many ecosystems do have the potential to
recover from pollution, provided that
corrective or remedial measures are
implemented.
The methodology for the assessment
of the environmental capacity, which is
site- and contaminant-specific, uses criti-
cal pathway analysis for both conserva-
tive and nonconservative contaminants
and establishment of environmental qual-
ity objectives, criteria and standards. Faced
with the inevitability of several sources of
uncertainties in real situations, a
probabilistic approach is used as an alter-
native to deterministic analysis. The
methodology recommended (GESAMP
1986) consists of three decision stages.
Socioeconomic goals (priorities and objec-
tives) are assessed in the planning stage,
considering present and future use of
resources. In the preliminary scientific
assessment stage, the environmental
capacity is derived and quantified, result-
ing in the setup of allowable inputs. Fi-
nally, monitoring provides a continuous
test of whether the environmental capac-
ity is balanced, exceeded or underutilized.
Consequently, adaptation measures may
be required.
Within the environmental capacity
approach, hazard assessment is a key
scientific tool for predicting possible ad-
verse effects of the discharge ofpollutants.
It is based on the relationship of the
expected environmental concentration of
a chemical substance (to which target
organisms are potentially exposed) and
the toxicological properties of the sub-
stance, ie., the predicted concentrations
with potential/possible adverse biological
effect (Cairns et al. 1978). The prediction
of the environmental concentration starts
with the determination of exposure-re-
lated data (Landner 1988), which refer to
the rate of chemical substance input, the
properties of the substance and the envi-
ronment. The persistence and the distri-
bution of the substance is evaluated from
data on physicochemical characteristics,
biogeochemical behavior, biodegradabil-
ity, bioaccumulation potential and
bioavailability. Biological effects are pre-
dicted on the basis of acute and chronic
toxicity studies or are calculated on the
basis of quantitative stucture activity
relationships (QSARs) (Konemann 1981;
Boudou and Ribeyre 1989; Halfon 1989).