the toxic truth - Greenpeace

214 Amnesty internAtionAl And greenpeAce netherlAnds
ANNEX I
chemical oxygen
demand
COD is Chemical Oxygen Demand.
This is essentially a measure of the
maximum amount of oxygen that
would be consumed in aqueous solution
if all the oxidizable chemical (and
biochemical) materials in a sample
were completely oxidized. It involves a
very aggressive process of chemical
oxidation (ie using strong oxidizing
agents) and therefore should always
be taken as a maximum rather than a
direct indication of how much oxygen
would be consumed from water in contact
with the waste. In practice, it is
likely that only a proportion of the material
would be oxidized (though what
proportion depends on too many different
factors to be able to estimate).
Nonetheless, COD is used as a sound
measure of the relative potential for
a waste to deplete or even remove oxygen
from water, and a very high COD
is a major cause for concern (given
that each liter of well aerated fresh
water contains only around 8-10mg
of oxygen), even if the maximum
potential is never realized in practice.
What a COD figure of 720,000mg/l
indicates is essentially that, if all the
material in just 1kg of the waste were
to be completely oxidized, it could
consume all the oxygen from around
80-100m 3 (80-100,000 litres) of well
aerated water. Even a small fraction
of that could clearly have substantial
and long-lasting impacts on aquatic
life downstream from the waste, as
few aquatic species can survive under
very low oxygen conditions. It is this
potential for depletion of oxygen and
its knock-on effects that explain the
concern about very high COD.
Remarkably high CoD level reason
for environmental concern
The waste dumped in Abidjan had a very high COD (Chemical
Oxygen Demand). NFI measured it at 720,000mg/l, while BMA
reported a measure of almost 500,000 to Falcon Navigation. 54
This value, even for spent caustic, does seem extremely, even
unusually high – such wastes are commonly reported to have
CODs of around 30-50,000mg/l, and only very occasionally up
to 400,000mg/l or 500,000mg/l. Compounds like sulphur,
phenols and hydrocarbon residues are generally responsible for
the high COD in this type of waste.
Impact of the waste on health
UNDAC (United Nations Disaster Assessment and
Coordination), which carried out a mission to Abidjan between
11 and 19 September, reported that “evaporation of volatile
substances would likely have occurred in the direct aftermath
of the dumping, resulting in serious or even life-threatening
concentrations”, and that “it is believed that three weeks after
the dumping the concentrations of the concerned compounds
in the air are low and no further adverse health effects are to be
expected”. UNDAC further noted that “the chemicals, especially
mercaptans, have strong smells at low concentrations. The
smell is already detectable by the human nose at concentration
far below danger levels and that this may give a false impression
of toxicity”. Nonetheless, mercaptans, having strong smells
even at low concentrations, can cause anxiety and/or feelings
of nausea. UNDAC also noted that the technical experts made
a contribution to “reducing the tension caused by the lack of
objective and comprehensible information”. 55
There is, however, a general underlying lack of data on the
variables prevailing at the time of the dumping, including the
rates of release of hazardous chemicals in the many different
dumping sites. It was certainly the case that there was a
lack of information and that this inevitably would increase
anxieties. While anxiety can exacerbate suffering, any
suggestion that the physical symptoms experienced by tens of
thousands of people were due to anxiety rather than the effect
of chemicals is not credible.
A toxicologist consulted by Amnesty International and
Greenpeace 56 confirmed that many factors might have altered
exposure to chemicals and their impact on people living or
working near the site. These factors include: