Introduction:
Dispersion of Toxic Substances
Among
the ten policy fields,
Dispersion
of Toxic Substances
is probably the one that raises the emotion of fear most frequently: the fear
of being killed by an accident releasing toxic substances (like in Seveso or
Bhopal), or the fear of being poisoned slowly through chemicals in our food,
drinking water and in our living environment. Many people will never bite into
an apple without peeling it, in fear of pesticide residues that might be
concentrated in its skin. Others never drink tap water, in spite of evidence
that it is often "safer" than mineral water sold in bottles.
The
term "
toxic"
refers to chemical elements or substances that are harmful to biological
systems. However,
toxicity
is not the only characteristic of harmful substances. Other properties like
persistence
and
the ability to
accumulate
in a food chain should also be considered.
The
world economy produces approximately 400 million tonnes of synthetic chemicals
in a year (1995 data). We do not know much about their role in the complex
metabolisms of plants, animals and human beings. Are man-made chemicals
responsible for the decline of amphibians reported by some scientists, or for
the rising number of allergies?
Describing
this complex policy field with a handful of indicators is a close to impossible
task. Almost all the indicators suggested by our panel of toxicologists refer
to more or less heterogeneous groups of chemicals like "pesticides," "heavy
metals" or "radioactive material." Presenting them in "tonnes per capita" can
only give rough indications on the amount of key toxic substances present in
our economy. Such indices would be neither weighted by toxicity, nor can they
take account of accumulation effects. Data availability problems, and the lack
of a consensus on weighting schemes, do not yet allow indices describing the
risks caused by these groups of chemicals to human health and ecosystems to be
calculated in a way that is beyond scientific debate. We hope that through the
development of the indicators presented here, and the criticisms that will
inevitably be triggered by them, we will make progress towards better
statistical tools describing the risks of the
Dispersion
of Toxic Substances
in our environment.
