t_Articles
July 5, 2005
Introduction
Fruits, vegetables and
cereal crops treated with pesticides are perceived by some as a health risk, and
this belief along with affordability, and time pressures may all play a role in
limiting consumption of plant foods, such as cereal grains, fruit and vegetable
consumption of consumers in Asia. The World Health Organisation (WHO), the World
Cancer Research Fund (WCRF) and many other national and inter-governmental
agencies recommend that adults consume at least 400g of fruit and vegetables per
day and 25-30 grammes of dietary fibre per day, but analysis of current dietary
patterns around the world indicate that many consumer are not achieving these
dietary goals, particularly those who are less affluent. AFIC’s Short Briefing
on Pesticides, Food Safety and Health is intended to provide a science-based
factual overview of the issue, to enable consumers to make better informed
choice about their diet, in particular fruit, vegetables and grains consumption,
and allay unwarranted anxieties and concerns.
Consumer Concerns
AFIC consumer survey
conducted in 2002 and 2003 which included questions on consumer perceptions of
food safety, found pesticides to be one of the most common food safety concerns.
Similarly, in 2000 a survey
of over 2000 people, commissioned by the Hong Kong Food and Environmental
Hygiene Department found 2/3 of respondents indicated they were concerned about
the safety of pesticide residues.
Definition of Pesticide
The Food and Agriculture
Organisation (FAO) defines a pesticide as ‘any substance or mixture of
substances intended for preventing, destroying, attracting, repelling, or
controlling any pest including unwanted species of plants or animals during the
production, storage, transport, distribution, and processing of food,
agricultural commodities, or animal feeds or which may be administered to
animals for the control of ectoparasites’.
Why are Pesticides Used?
Agricultural chemicals
including pesticides have made significant contributions to the efficiency and
productivity of Asian agriculture, making sure that the rise in Asia's food
production has kept ahead of its growing population. Responsible pesticide use,
delivers important benefits to agriculture and in turn society, such as year
round availability of agricultural produce; improved quality and variety;
reduced production costs which in turn results in lower prices for consumers.
Pesticide Limits and
Regulation
Approval for use of any
pesticide in a country is subject to its safety evaluation. Safety levels for
any pesticide are calculated over a number of formal assessments. The Codex
Alimentarius Commission is an international body which sets international
guidelines on many elements of food safety, including pesticides residues on
food. These guidelines are not mandatory, but many countries in Asia use these
guidelines, sometimes with additional scientific data determined by their
national regulatory agencies to establish limits on use and also acceptable
residue levels at point of sale.
Acceptable Daily Intake
One of the most important
tools in the safety evaluation of pesticide use on food crops is the calculation
of what is an Acceptable Daily Intake (ADI). The ADI for any given pesticide is
a measure of the quantity of a particular chemical in food that can be consumed
daily over a lifetime without any known risk to health. It is expressed in
relation to bodyweight.
ADI is derived by first
conducting diet trials on laboratory animals and observing the maximum level of
pesticide that can be consumed by the animal with no observable adverse effect
on health. This level expressed as percentage of body weight is known as the No
Observable Adverse Effect Level (NOAEL or NOEL), The investigations include
checks for birth defects, cancer, reproductive changes, damage to the nervous
system, harm to organs such as the kidney or liver, and many other measurable
health indicators.
A safe level for human
consumption is estimated by dividing the NOAEL on humans by an uncertainty
factor (usually 100) to allow for the possibility that humans may more sensitive
than the animals used for testing and also to account for possible variation in
sensitivity to the pesticide between human individuals, for example adults and
children. This results in an ADI for humans which is 100 times lower than the
NOAEL consumption rate established from trials on laboratory animals.
Acute Reference Dose
Safety evaluation of all
pesticides also requires an estimate of the acute refrence dose (ARfD). The ARfD
is an estimate of the amount of a substance in food or drinking water expressed
as percentage of body weight, that can be consumed over a short period of time,
usually one meal or one day, without any known effect on health. This figure is
also expressed as a percentage of body weight.
Maximum Residue Levels
A maximum reside levels (MRL)
is the maximum permissible quantity of pesticide that may still be present on
the crop at point of sale. It is derived from an assessment of the residues
found when the crop is treated according to good agricultural practices. The MRL
is the maximum concentration of a pesticide residue that is legally permitted
in, or on, a food commodity, and is set by national governments if the approval
is given for the use of the pesticide on specified crops. MRLs are set to
determine legal trading limit, and are not an indicator of risk to health. MRLs
are set at levels which would result in consumption of any residue at a level
substantially lower than the ADI or the ARfD for the pesticide, and any
pesticide whose MRL could result in dietary intake which might exceed the ADI or
ARfD would not receive approval.,
Total Diet Studies
To assess potential health
problems from contaminants, both natural and man-made in the food supply, the
WHO recommends total diet studies (TDS) as the one of the most cost-effective
means for assuring that people are not exposed to unsafe levels of toxic
chemicals through food. TDS provides an additional tool to assess whether or not
any pesticides may be present in the diet at levels which might pose a risk to
health.
A TDS is conducted by
purchasing through standard retail outlets a typical selection of foods commonly
consumed in the country or region. The ‘basket’ of foods is processed and
prepared as if for normal consumption and then analysed in the laboratory to
measure total levels of the substances of interest, for example pesticides.
Drinking water and water used in cooking are also included in the assessments.
The TDS provides a measure of the average amount of the pesticide consumed by
different age/sex groups living in a country. See box for an example of an
actual TDS and results for estimate of pesticide consumption
Tips for Consumers Who Wish
to Minimise Possible Consumption of Pesticide Residues
For those consumers who wish
to take additional measures to reduce any possible pesticide residues on their
foods, here are some tips from AFIC.
Ø
Raw foods
should be washed thoroughly before cooking and/or consumption. Washing in dilute
vinegar solution, or solution of sodium bicarbonate, then rinsing with clean
water will help to remove any chemical residues and also any soil or other
foreign matter on the produce.
Ø
Many chemicals
applied to crops to protect from insects and disease are sprayed onto external
surfaces, so peeling outer layer or skin when preparing fresh fruit and
vegetables will remove any surface residues.
Ø
Look out for
the many of the quality assurance schemes, which guarantee chemical treatment of
produce has strictly followed manufacturers recommendations and residues levels
at point of harvest are either zero or very low. There are also an increasing
number of retailers and growers offering ‘organic’ produce, however, be aware
that ‘organic’ farming often uses some pest control substances, approved by the
various associations established to promote this form of cultivation.
Ø
Do not
consumer berries, leaves or other edible plant material picked from roadsides or
other public areas, as these plants as it is not possible to know if these
plants have been sprayed intentionally or unintentionally contaminated with
pesticides or other substances and will not be subject to safety restrictions of
designated food crops.
Conclusion
The positive effects of
eating fresh fruit and vegetables and cereal grains as part of a balanced,
healthy diet are well proven and far outweigh any concern about pesticide
residues.
Here is an example of a
total diet study conducted in Thailand, by the Thai Ministry of Public Health (Vongbuddhapitak
ET AL.: Journal of AOAC International Vol. 85, No. 1, 2002). Table 1 illustrates
the food consumption patterns of the Thai population.
Table 1: Food Consumption
Data for Thais (Vongbudohapitak et al, 2001)
