Experts on safety of pesticide residue in foods
Safe food campaigner Alison White has compiled a list of commonly consumed foods that contain pesticide residue and
claims there are "various serious long term effects associated with particular pesticides found in our food".
The list, which found celery to be the most likely food to contain pesticide residue, ranked foods based on "the
percentage of samples with pesticide residues and the number of pesticides detected in the total samples," and was based
on data from the New Zealand Food Safety Authority.
Alison White will present her study in Wellington tonight.
The SMC asked experts on pesticide residue and toxicology to comment on the methodology of the research and the safety
of pesticide residue in food.
Ian Shaw, Professor of Toxicology, Department of Chemistry, University of Canterbury comments:
"It is not the percentage of a particular crop found to contain pesticide residues that matters, but the levels of the
pesticides. As analytic techniques get more and more sensitive there is no doubt that the percentage of analytical
samples that are positive is going to increase.
"In order to assess the risk to the consumer we need to assess the health impacts of the residues; this is done by
comparing the intake to the Acceptable Daily Intake (ADI) for a particular pesticide. The ADI is calculated based on the
toxicology of the pesticide and relates to the maximum amount that can be ingested daily for an entire lifetime without
no ill effects. I would be very surprised indeed if any of the celery pesticide residues exceeded the ADI.
"There is a little naughtiness around the references given in support of some of the statements - the writer quotes a
paper (ref 2) about chlorothalonil and dieldrin being associated with an increased risk of cancer. This paper is about
sprayer occupational exposure which is a very much greater level of exposure.
"Clearly the writer does not fully understand the distinction between hazard (the intrinsic danger of a chemical) and
risk (the chance of it causing harm). Risk = Hazard x Exposure. If exposure is low (as in the case of pesticide residues
in food) the risk will be concomitantly low. This is perhaps best illustrated by potassium cyanide. If I took a gram of
KCN I would die, but if I drank a few milliliters of a 0.000001% KCN solution I would suffer no ill effect whatsoever.
The risk is low because the dose is low, even though the hazard of KCN is high!
"If the use of pesticides had been considered on environmental rather than human health ground I would be concerned. I
do not think that the amount of pesticides necessary to grow some crops (e.g. celery) is warranted because of their
environmental impact It would be far better to concentrate on this argument rather than the human health argument if
ones raison d'etre is reducing pesticide use."
Dr John Reeve, toxicologist at the New Zealand Food Safety Authority comments:
"There are at least 500,000 identified natural chemicals that are present in all foods, including natural pesticides
that work to protect the plant or animal from attack or from loss of nutrients. Very few of those chemicals have been
tested. There are about 500 agricultural compounds used as pesticides. They have been extensively tested and
internationally accepted, including by the World Health Organization, as safe when used as they are meant to be.
"We are three-quarters of the way through a total diet survey and have found nothing that would suggest any possible
health risk. We detect residues at extremely low levels as a result of improved detection limits and so it is not
surprising that we find them. The bottom line is that none are at levels that could even remotely be considered to be a
"The claimed effect of pesticide combinations has been studied and what is clear is that only when residues are at
levels that are close to those which could have an individual effect do we see an effect of the combination, and the
levels we have found are so low that this is not a possibility.
"The only worry people should have about fresh fruit and vegetables is that they are eating enough. The 2007
comprehensive 500-page World Cancer Research Fund report notes that 'there is no epidemiological evidence that current
exposures are causes of cancers in humans' and is clear that 'most diets that are protective against cancer are mainly
made up of foods of plant origin.
"Our testing does show that while some foods such as celery do contain residues this is largely because of the shape of
the plant, but again, the levels found do not pose any likely health risk.
"The use of pesticides, herbicides, fertilisers, and veterinary medicines in all food is strictly regulated in New
Zealand. Any residues due to the use of these agricultural compounds are at levels that present notional zero risk to
consumers. The term 'notional zero risk' describes the risk associated with consuming levels of substances below the
acceptable daily intake (ADI). This is the level at which a substance can be consumed every day for a whole lifetime
without noticeable effect. In all respects, agricultural compounds allowed for use in certified organic systems are
subject to the same risk management requirements as those used in conventional systems.
"As the use of agricultural compounds in both organic and conventional produce are regulated and monitored so that
residues pose notional zero risk, the inevitable conclusion is that there is no measurable difference in health risk
posed by eating produce from either method of production.
"Just because organic production uses 'natural' as opposed to synthetic agricultural compounds does not make it
Peter Beaven, Chief Executive, Pipfruit New Zealand comments:
"The Apple Futures programme is an orchard production system introduced over a three year period for apple and pear
growers. It is just entering its third year.
It was introduced in response to supermarket demand in Europe in particular where our suppliers were facing requirements
for residue levels that were as low as 30% of currently allowable country MRLs.
"Although the time to measure residues from a consumer perspective is when the fruit is export boxes, we wanted to
understand what impacted on residues around harvest time, and as a result of water dumps and packing processes. In
consequence the residue testing programme to underpin the Apple Futures research has examined residue levels 10 days
before harvest, at harvest and after packing to develop profiles to use as predictors.
"In the 2009 season, more than 900 residue tests were conducted, and this year we will carry our more than 1000 tests -
a robust sampling regime!
"If we look just at residues after packing from the 2009 season, we find that the vast majority of residues measured are
at the limits of detection - we are measuring at a few parts per billion. At these levels, we are getting a few false
readings related to the residue extraction methodologies. We can only account for these by assuming some of the residues
are naturally occurring in the fruit itself. The highest (worst) residue we found in this year's testing was a mere 13%
of allowable MRL for Europe.
"Hence the Pipfruit industry has high levels of confidence in the results attainable from Apple Futures. Already 65% of
the land area is under the programme.
"This programme is sufficiently well regarded that it has been entered in the innovation category competition as a new
product at Fruit Logistica in Berlin next February. This is the world's largest fresh produce conference.