Pest Management Science Pest Manag Sci 56:947±949 (2000)

The realities of pesticide use †

Professor Sir Colin Berry*Department of Morbid Anatomy, Queen Mary and Westfield College, London E1, UK

(Rec

* CoUKE-ma† BaSCI14/15

# 2

Abstract: The objectives of Integrated Crop Management will be readily endorsed by all those working

in agriculture and by those with concerns about the human or environmental effects of pesticides. The

absence of demonstrable effects in man means that systems that identify bene®t to human beings from

this new approach will be dif®cult to devise; environmental and yield objectives are more likely to

deliver measurable outcomes. If we fail to produce and apply a consensus-based set of measurement

objectives to ICM this management system will generate objections similar to those that apply to

current schemes of risk evaluation.

# 2000 Society of Chemical Industry

Keywords: risk; pesticides; integrated crop management; measurement

1 INTRODUCTIONIntegrated Crop Management (ICM) has all of the

appeal of `Motherhood and Apple Pie.' The principles

of the system, as set out in 1997 in a British Crop

Protection Council document1 describe an approach

to crop management characterised by:

. Optimum economy and precision of chemical and

energy inputs

. Use of bene®cial interactions between inputs

. Encouragement of natural pest predators and

establishment of soil or crop conditions that

suppress pest, disease and weed development

. Enhancement of soil fertility, through the most

appropriate crop rotation and cultivation methods

. Maintenance or increases in pro®t margins, empha-

sis on gross margin rather than absolute level of crop

yield

. Minimising the risk of adverse effects in the

environment

. Delaying or avoiding the build-up of strains of pests,

pathogens or weeds resistant to chemical or bio-

logical agents.

It is impossible to be against any of this, since what is

described is coherent and rational. What will be

necessary is to decide how we are to determine

whether this approach works and what we are to

measure to see if it does. These points are critical,

because the non-rational factors that affect decisions

about pesticides make it is necessary to seek agreement

not only about objectives but also about how

objectives are realised. If this is not done, a new

agenda of dissent will replace the old.

eived 4 April 2000; accepted 14 June 2000)

rrespondence to: Professor Sir Colin Berry, Department of Morbid An

il: C.L.Berry@mds.qmw.ac.uksed on a paper presented at the symposium, ‘The Economic and ComCrop Protection Group in collaboration with the Volcani Centre, Israe

Belgrave Square, London SW1X 8PS, UK

000 Society of Chemical Industry. Pest Manag Sci 1526±498X/2

2 CURRENT CONCERNSIn most discussions about pesticide use, hazards to

consumers or environmental concerns are usually the

drivers. Despite many scares, the persistent absence of

data has tended to remove some of the emphasis on

consumers (operators, the highest `at risk' human

group, are always low on the lists of public concernÐ

perhaps because many of them are farmers) and

environmental hazards have come to the fore. Here

the general problem of demonstration of an absence of

harm is more dif®cult than in what are generally well-

de®ned concerns about particular outcomes in terms

of disease; it is possible to determine whether someone

has a disease or not or whether death rates in a

particular group exceed those expected. Outcome

measures may be harder to arrive at in the environ-

mental ®eld; it is not always easy to arrive at a clear

consensus about what is the aspect of the environment

that is to be conserved.

This type of failure is important. If we do not agree

what is to be measured and what constitutes a bene®t

we will always disagree about the outcomes of any

intervention. If the intervention is resisted by a group

with a particular interest there will often be an effective

misrepresentation. By de®nition, there is no attempt at

balance in the consideration of data by pressure

groups; they generally ignore data non-supportive of

their argument. Thus the papers of Casey et al,2,3

which provide information of real clinical signi®cance,

are disregarded by those who emphasise potential

harm to children and postulate links between soft

tissue sarcoma and herbicides as if they still had

credibility despite later and/or better studies which

atomy, The Royal London Hospital, Whitechapel, London E1 1BB,

mercial Impact of Integrated Crop Management’, organised by thel and the Fresh Produce Consortium and held on 3–4 April 2000 at

000/$30.00 947

C Berry

have devalued them.4 Alar is the best example of this

type of nonsenseÐbut `Pesticide Which' repeated

damaging and unwarranted assertions about risk long

after an effective scienti®c riposte.5

So the simple production of scienti®c data of good

quality will not affect particular issues once they are

established as problems in the mind of the public (a

problem not con®ned to pesticides). The techniques

by which a methodology should be evaluated should

thus bear in mind not only what are the scienti®c issues

at stake but also the questions that some may want

answered. These will often be discussed in terms of

risk.

3 RISKIt is interesting to note how readily the term `risk' is

used in discussions about pesticide use. In fact, risks to

consumers from pesticides, if properly de®ned as `the

probability that a particular adverse event occurs

during a stated period of time, or results from a

particular challenge', are so low that their measure-

ment is extremely dif®cult. The standard technique of

looking for changes in rates of those events which have

been documented as practice changes (an intervention

study) is thus rarely successful. Further, the use of

conservative models in risk extrapolation means that

changes in use designed to minimise exposure, say, do

not generally produce measurable effects in any

calculationÐthere is so much slack in the system.

Vague statements about possible harm (hazard)

should be avoided and should certainly not be used

as a basis for regulationÐinterventions in this ®eld

which depend on clinical data should obey the dicta of

Lord Rothschild in his Dimbleby lecture on risk.6

These dif®culties mean that man will not be a good

target if you wish to look for changes produced by

ICM; anything that happens is not likely to be

measurable.

4 WHAT TO MEASUREHowever, we must look for measurable effects; the

idea that because you ®nd something dif®cult to

measure you substitute for data a model, or even a

prejudice, is absurd. This type of thinking underlies

the demand for safetyÐto demonstrate an absence of

harm from any process is impossible (see Reference 7).

This general conceptual problem about risks has been

further confounded by the proposed use of the

precautionary principle (PP; see below). The idea of

using prejudices is not a remote one; it is inherent in

the use of the PP. I believe this to be very damaging,

since it eschews the scienti®c method in the way that it

deals with data. Holm and Harris8 have de®ned the PP

(in a paper objecting to it) in this way:-

`When an activity raises threats of serious or

irreversible harm to human health or the environ-

ment, precautionary measures that prevent the

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possibility of harm shall be taken even if the causal

link between the activity and the possible harm has

not been proven or the causal link is weak and the

harm is unlikely to occur'.

This principle should never be used in evaluating

toxicity data; it arbitrarily changes the weight that is

given to evidence from different investigations on an

uncertain basis, and represents the antithesis of

science. Simply to say that what is proposed in ICM

is sensible is not a basis for regulation; after all, a desire

to use less solvent and to minimise energy inputs

played a big part in generating the BSE problem and a

change in cultivation practice for carrots greatly

reduced the safety margins for some organophos-

phates.

I assume that those who advocate ICM wish to

demonstrate that it is an effective management system.

So what can be done? The organisations that will

investigate the potential bene®t of ICM include Less

Intensive Farming and the Environment (LIFE),

LINK: Integrated Farming Systems (IFS), Focus On

Farming Practice (FOFP) and the Rhone-Poulenc

Farm Management Study (RPMS), and useful in-

formation will come from SCARAB (seeking con-

®rmation about results at Boxworth) and TALISMAN

(Towards a Lower Input System Minimising Agro-

chemicals and Nitrogen). The proliferation of

acronyms is ominous; if there is a common purpose

where is the co-ordinating body?

So far the collective appears to have found that there

is evidence of a fall in yields, but not in margins. Weed

control was adversely affected, however and there are

problems with crop rotationsÐsome crops require

insecticide inputs which do not `®t' the aspirations of

the scheme.

The profusion of investigating bodies illustrates an

important potential failing, in my view. What is needed

is less a particular approach or study from a given

viewpoint than an agreed set of outcome measures for

the objectives of the schemes to be used. There will, of

course, be a need for a number of approaches to

measuring these objectives and a bene®t to be had

from these different approaches. It may be dif®cult to

devise an agreed outcome for insect biodiversity, say,

but are the attempts to produce them directed toward

common objectives?

5 PRECISIONThere have been many attempts to quantify adverse

effects of pesticides by the use of a number of risk

indices, well reviewed in a recent MAFF document.9

The document noted the very different data used by

different indices and the poor correlation between

ranking of pesticides when using different indices.

This problem may be seen as inevitable (the indices

may well have been devised for different purposes).

These indices should generally, as the document

suggests, exclude possible human effects; they are best

Pest Manag Sci 56:947±949 (2000)

The realities of pesticide use

dealt with separately. The F-PURE system (Florida

Pesticide Use Risk Evaluation) ignores potential

human impacts, but in other schemes in which they

are included, their variability and imprecision makes

comparisons dif®cult. For example, a decision to miss

work because of a health effect may depend on a

number of unrelated variables including ®nance and

the availability of childcare. Volume of pesticide

applied is probably the best indicator of risk, but it

will not satisfy those who look for more precise

outcomes in seeking to make predictions. In ICM it

will show an improvement, by de®nition. Other

approaches include weighting of particular factors in

an index, but this will depend on the views of those

who select the weightings. A viewpoint in favour of a

particular species or group (birds vs insects vs

invertebrates vs soil macrobiota) further confuses

matters. Concerns about man, together with the

bizarre views of some about the costs of preventing

rare events in that favoured speciesÐit is interesting

that these are far in excess of what would be considered

reasonable in the cost/effectiveness calculation of

therapy in medical practiceÐwill further complicate

matters.

6 ASPIRATIONSIt is not suf®cient to state that ICM is obviously

desirable and then to suppose that opposition to this

scheme is irrational. Believers are essential to any faith

but zealots can be dangerous.

Thus, as an example from the medical ®eld, there

are a number of failed trials of the effects of adding

anti-oxidants,10±13 and even soy proteins, to the diet.

Such practices appeared to be as good an approach as

ICM is to agriculture but some worrying data14,15 have

suggested that these latter materials can be associated

with malformation in man.16 Nevertheless, if the

outcomes to be measured in ICM can be agreed, and

the methods of measurement standardised to some

extent, this thoughtful approach may lead to a more

critical appraisal of the problems associated with, and

the bene®ts conferred by, pesticides.

Pest Manag Sci 56:947±949 (2000)

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pesticide poisoning in the UK. 1 ± Home Accident

Surveillance System. Hum Exp Toxicol 13:529±523 (1994).

3 Casey P and Vale JA, Deaths from pesticide poisoning in England

and Wales 1945±1989. Hum Exp Toxicol 13:95±101 (1994).

4 Gough M, Dioxin, Agent Orange. The Facts, Plenum, New York,

USA (1986).

5 Marshall E, A is for Apple, Alar and Alarmist? Science

(Washington) 54:20±22 (1991).

6 Lord Rothschild, Risk. The Listener, 715±718 (1978).

7 Guillen M, Bridges to In®nity, Rider, London, Melbourne,

Sidney, Auckland, Johannesburg (1983).

8 Holm S and Harris J, Precautionary principle sti¯es discovery.

Nature (London) 400:398 (1999).

9 College SA, Pesticide use optimisation, Ministry of Agriculture

Fisheries and Food, London, UK (1999).

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MR, Glass A, Keogh JP, Meyskens FL, Valanis B, Williams

JH, Barnhart S and Hammar S, Effects of a combination of

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(1996).

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estrogens coumestrol and genistin induce structural chromo-

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Exposure of infants to phyto-oestrogens from soy-based infant

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