separately from the costs which must be paid to
ensure the correct use of pesticides.
0008 It has been estimated that if pesticides were not
used, the potential loss of food production would be
45% (30% attributed to pests, including weeds and
diseases before harvest, and 15% as a postharvest
loss). In addition, in over 100 countries, more than
4 10
8
clinical cases of vectorborne diseases cur-
rently exist. For some of these diseases, control of
vectors remains the main control measure, and for
others, pesticides are considered to be an essential
part of disease control. The use of pesticides in the
control of household pests should not be neglected,
regardless of whether they are used in the control
of vectors of diseases or to control nuisance pests.
This aspect of pesticide use is of great importance,
as pesticides intended for this kind of application are
available to the general population.
0009 Although the exact figures for the global use of
pesticides, either according to intended use (agricul-
ture, public health, household) or according to re-
gional or country use, are not available, it is certain
that the quantities of pesticides used are steadily
growing, albeit less in the developed countries than
in developing countries, and this trend may continue
for some years. A few highly developed countries
show a decline in the quantities used as more efficient
compounds are applied, and the trend to organic
farming increases. (See Organically Farmed Food.)
0010 In western Europe and North America, herbicides
are the most represented groups of pesticides,
whereas in the tropics, insecticides are used more
than other groups of pesticides. This fact gives rise
to ever-growing concern, mainly attributable to
the indiscriminate use and frequently to the misuse
of pesticides. This concern is supported by the fact
that, although only about 20% of pesticides are used
in developing countries, they account for the majority
of total deaths caused by pesticide poisonings.
Evaluation of the Risk and Testing
Procedure
0011 In general pesticides, in common with drugs, are
among the most carefully studied chemicals, and
this makes the toxicological evaluation of active
material possible and meaningful.
0012 According to the widely accepted International
Code of Conduct on the Distribution and Use of
Pesticides, pesticide manufacturers are expected to
ensure that each pesticide is adequately and effectively
tested in accordance with sound scientific procedures
and good laboratory practice. Generated toxico-
logical data and use patterns are then meticulously
evaluated by competent international or national in-
stitutions, and results made available to the relevant
national authorities in order to allow them to intro-
duce the necessary legislation for their regulation,
including registration. (See Legislation: Contamin-
ants and Adulterants.)
0013In many countries, registration procedures are
elaborated upon in great detail, offering possibilities,
for preparing precise precautionary measures for
their production, transport, storage, and use. Unfor-
tunately, in many areas, the implementation of
carefully prescribed safety measures is lacking, and
pesticides are greatly misused.
0014The activities of the WHOin thesafety assessment of
pesticideswereinitiatedsoonafteritsfoundation,anda
number of expert committees have been devoted to the
toxic hazards arising from pesticides used in public
health programs. Subsequently, the experts also
became concerned with the safety aspects of pesticides
usedin agriculture.The evaluation ofpesticide residues
in food started in 1963 in collaboration with the Food
and Agriculture Organization (FAO). Since then, the
JointMeeting of PesticideResidues in Food (JMPR)has
evaluated a large number of pesticides. The main ob-
jectives of the WHO Expert Group on Pesticide Resi-
dues (the WHO component of JMPR) are consistent
with those of the International Programme on Chem-
ical Safety and include the formulation of guiding prin-
ciples for exposure limits such as acceptable daily
intake (ADI) for pesticide residues in food. Tolerances
for these substances in air, water, soil, and the working
environment are recommended by other WHO expert
groups. (See World Health Organization.)
0015Although the requirements for toxicological data
needed for health-risk assessment vary considerably
from country to country, they comprise short- and
long-term toxicity studies in several species of experi-
mental animals, data on absorption, distribution, me-
tabolism and excretion of a pesticide, carcinogenicity,
reproduction, and genotoxicity, and other special
studies for particular classes of compounds.
0016Evaluation of data is an extremely complicated
process, and results are not always equivocal. This is
particularly so because extrapolation of animal data
to humans is mainly based on the introduction of a
safety factor and, when possible, on pharmacokinetic
extrapolation. Whenever applicable, observations on
humans following occupational and/or accidental
exposure are incorporated within the health-risk
evaluation process.
Biological Activity of Pesticides
0017The inherent toxicity of a pesticide to humans is the
same regardless of its use, either in agriculture or
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