44 Handbook of herbs and spices
to set standards for pesticide use in food. Such new standards are intended to protect
infants and children who may be more vulnerable to pesticide exposure. To determine
pesticide safety for humans, the EPA establishes a reference dose (RfD) for each
pesticide that is approved for use. The RfD is the amount of a chemical that, if
ingested over a lifetime, is not expected to cause any adverse health effects in any
population subgroups. Using food consumption and other data, the EPA estimates
how much pesticide residue is likely to be consumed, and if the RfD is exceeded, the
agency takes steps to limit the use of the pesticide. To monitor the food supply for
pesticide residues, the FDA enforces pesticide tolerances for all foods (except for
meat, poultry and some egg products, which are monitored by the USDA). Laboratory
equipment used by these agencies usually can detect residues at one part per billion
or lower. Over the years, the FDA and other monitoring agencies have concluded that
pesticide residues in the food supply are well below established safety standards.
Many independent health experts who have examined studies on the effects of pesticides
in the diet have also concluded that the benefits of a diet rich in fruits and vegetables
far outweigh any pesticide-related risks. A 1996 report by the US National Academy
of Sciences concluded that both synthetic and naturally occurring pesticides are
consumed at such low levels that they pose little threat to human health.
Herbs and spices, in general, do not pose a high risk with regard to the presence
of pesticide residues basically because the total daily intake is very small. Further,
usage of spice and herbs at home and by food manufacturers involves such processes
as washing, peeling, cooking, canning, freezing and drying which decrease the residue
levels. Above all, usage of pesticide chemicals in agriculture and storage of most
spices are very limited. Today, most food manufacturers monitor farmers’ use of
pesticides to ensure the raw ingredients they buy meet strict quality assurance standards.
2.3 Analytical methods for detecting pesticide residues
Monitoring and measuring residue levels is a critical stage in the control of chemical
residues. Pesticides and other chemicals occur in spices and herbs only in trace levels
(generally at concentrations of parts per million). Measuring such small amounts in
the presence of enormous amounts of other chemicals that occur naturally in them is
a challenge, because these plant chemicals may interfere with measurement. A variety
of analytical methods are currently used to monitor pesticide residues, all of which
contain the following basic steps:
∑ sample preparation: by chopping, grinding, or separating herbal plant parts
∑ extraction: removal of a pesticide residue from other herbal components
∑ clean-up (isolation): removal of constituents that interfere with the analysis of
the pesticide residue of interest; this step includes partitioning and purification
∑ determination-separation: separation of components, i.e., individual pesticides,
and sample co-extractives, based on differential partitioning between a solid and
non-volatile solvent or between a liquid and gas carrier that moves through a
column (liquid and gas chromatography) or along a coated plate (thin layer
chromatography)∑ determination-detection: production of a response that measures the amount of
components moving through the column, allowing detection and quantification
of each pesticide.