Ecoscript 50

William M. Stigliani. Chemical Time Bombs: Definition, Concepts and Examples

The environments of industrialized countries have long been
the recipients of high doses of polluting chemicals from all
kinds of societal activities. In the face of perceived threats
posed by these chemicals, policies have been enacted for safe-
guarding public health and protecting the natural environment.
While these policies have been certainly beneficial and neces-
sary, they are often implemented as a reaction to a pollution
problem that has already occurred. A preventive policy rather
than a reactive one would certainly be a better approach. How-
ever, our ability to enact preventive policies is hindered by
our limited knowledge of the complex linkages between chemical
inputs and environmental effects.

In fact, the literature abounds with references to "chemical
sinks" as the ultimate environmental depositories of pollut-
ants. The image that the word "sink" conjures up is one of a
bottomless hole into which chemicals may be washed away never
to be encountered again. In reality, is the environment a
"bottomless pit" or is it more like a sponge? This is far from
a trivial question, for if the latter analogy is true it im-
plies that, just as for a sopping-wet sponge, environmental
systems can eventually become saturated from accumulated chem-
ical inputs. At that point they may be transformed from a sink
to a source of harmful chemicals. Moreover, during the time
over which the system is capable of absorbing toxic chemicals,
overt environmental effects may not be evident or expected.
When the effects are finally manifested (after saturation oc-
curs) they are usually displaced in time from the activities
causing the problem in the first place. Because of the delayed
environmental response and because such responses may be
unanticipated, the term "chemical time bomb" has been coined
to describe the phenomenon.

This publication introduces the concept of chemical time
bombs, describes, by way of example, why we should be concer-
ned about them, and provides some guidance in how to anticipa-
te their occurrence. Subsequent publications will provide fur-
ther elaborations of the general ideas expressed in this docu-
ment. Moreover, a series of workshops focussing on potential
time bombs in specific European regions will be conducted over
the next several years.

This report, based on the deliberations among six scientists
at a three day workshop in the Netherlands in August 1990,
discusses the question of the potential long-term impacts of
the accumulation and mobilization of toxic and environmentally
harmful chemicals in the environment. It is meant to be an
introduction to an environmental problem deserving of far more
extensive research. This paper sets forth the potential prob-
lems caused by long term accumulations of chemicals in the
environment, cites examples of economic costs of such occur-
rences, and defines the means by which, under certain condit-
ions, such accumulations behave like "time bombs". Subsequent
sections of the report provide actual examples of such behav-
iour, and discuss, in a preliminary way, how chemical time
bombs may be predicted. Finally, the conclusions are cited,
based on the consensus of the participants at the workshop.


Foreword 4
Preface 5
Problem Statement 6
Examples of Economic Cost of Long-Term Chemical Pollution 6
Definition and Demarcation of the Chemical Time Bomb Concept 8
.. Definition 8
.. Mathematical formulation 10
Examples 11
.. Acidification and leaching of aluminum 11
.. Microbial induced CTBs 13
.. Biological time bombs 15
Prediction of Future Chemical Time Bombs 15
.. Lessons from the most vulnerable areas 15
.. The "bottom up" approach 16
.. Listing of system parameters 18
Conclusions 20
References 21
The International Institute for Applied Systems Analysis 22