342 Introduction to Human Nutrition
ent uncertainties in extrapolating animal toxicity data
to potential effects in humans and for variation within
the human species. JECFA traditionally uses a safety
factor of 100 (10 × 10) in setting ADI values based on
long-term animal studies. It is intended to provide an
adequate margin of safety for the consumer by assum-
ing that the human being is 10 times more sensitive
than the test animal and that the difference in sensi-
tivity within the human population is in a 10-fold
range. However, different safety factors apply depend-
ing on the substance and test species in question.
Maximum levels for food commodities
These levels are calculated taking the above-
mentioned levels into consideration. Depending on
the substance, different principles apply. Residues
such as pesticides and residues of veterinary drugs in
foodstuffs are limited by setting a maximum residue
limit (MRL). Additives are regulated by setting
maximum limits or by applying the “quantum satis”
principle (the least amount required to exert the
desired technological function).
For contaminants, maximum levels/limits are
established for those foods that provide a signifi cant
contribution to the total dietary exposure. However,
as a general principle the levels in all foods should
always be kept as low as reasonably achievable (the
ALARA principle).
In Europe, additives, pesticides, veterinary residues,
and a wide range of contaminants are regulated by
EU legislation in the form of directives or regulations
that are transposed into national legislation by each
member state.
Pesticide residues
Pesticides are chemicals or biological products used
to control harmful or undesired organisms and plants,
or to regulate the growth of plants as crop protection
agents. They are classifi ed into the groups shown in
Box 14.3.
Most pesticides are toxic substances that are highly
selective, especially those developed since the early
1980s, and only have an effect on those pests or plants
to which they are applied. Unlike other environ-
mental contaminants, pesticides are applied under
controlled conditions that should conform to “good
agricultural practice” (GAP). This defi nes the effec-
tive use of pesticides, up to the maximum allowable
dose, applied in a manner that ensures the smallest
amount of residue in the foodstuff.
Pesticides can also be toxic to humans since certain
biochemical pathways are relatively conserved across
species, as are some enzymes and hormones. In the
context of food safety, exposure to pesticides is clas-
sifi ed as acute or chronic. An acute intoxication
usually has an immediate effect on the body, whereas
a chronic effect may reveal itself over the lifespan. The
severity depends on the dose and the toxicity of the
pesticide compound or breakdown product. Toxic
effects that have been identifi ed include enzyme inhi-
bition, endocrine disruption, and carcinogenic action,
depending on the compound in question.
In Europe the control of pesticides is based on
Council Directive 91/414/EEC. Under this legislation,
pesticides must be evaluated for safety based on dos-
siers prepared by their manufacturers. If a pesticide is
accepted it is placed on a positive list with an MRL
assigned to it.
In the case of a limited number of highly toxic
pesticides, for which the ADI is necessarily based on
acute toxicity rather than chronic toxicity, the level of
exposure is considered in relation to the acute refer-
ence dose (ARfD). ARfD values are measures of the
maximum level of intake at one meal, or consump-Box 14.3 Classifi cation of pesticidesPesticidesInsecticides Herbicides Fungicides Rodenticides Molluscides Plant growthregulators