pesticides and health myth vs realities

8/12/2019 Pesticides and Health Myth vs Realities

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PESTICIDES

A Posi tion Paper of the

AMERICAN COUNCIL

ON SCIENCE AND HE ALTH

Professor Allan S. Felsot

Washington State University

&HealthM y t h s v s . R e a l i t i e s


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Pest ic ides & Heal th: Myths vs . Real i t ies

John Berlau

Compeiive Enerprise Insiue

Christine Bruhn, Ph.D.Universiy o Caliornia, Davis

Janice E. Chambers, Ph.D., D.A.B..,A..S.Mississippi Sae Universiy

Jay Lehr, Ph.D.Te Hearland Insiue

Bob Krieger, Ph.D.Universiy o Caliornia, iverside

Manfred Kroger, Ph.D.Te Pennsylvania Sae Universiy

Angela Logomasini, Ph.D.Compeiive Enerprise Insiue

Alan McHughen, D.Phil.Universiy o Caliornia, iverside

AcknowledgementsTe American Council on Science and Healh (ACSH) appreciaes

he conribuions o he reviewers named below:

ACSH acceps unresriced grans on he condiion ha i is solely responsible orhe conduc o is research and he disseminaion o is work o he public. Teorganizaion does no perorm proprieary research, nor does i accep supporrom individual corporaions or specific research projecs. All conribuions o

ACSHa publicly unded organizaion under Secion 501(c)(3) o he Inernalevenue Codeare ax deducible.

Individual copies o his repor are available a a cos o $5.00. educed prices or10 or more copies are available upon reques.

Published by he American Council on Science and Healh, Inc.May 2011. Tisbook may no be reproduced in whole or in par, by mimeograph or any ohermeans, wihou permission o ACSH.


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Table of ContentsAcknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

A Rationale for Confronting Myths

about Pesticide Technology . . . . . . . . . . . . . . . . . . . . . . . . . 3

Pesticides with Benefits for All:

An Agricultural Perspective . . . . . . . . . . . . . . . . . . . . . . . . . 5

Agricultural Reality: The Economic Perspective . . . . . . . . . . . . . . . . . . . 5

Agricultural Reality: Practical & Environmental Advantages

of Crop Protection Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Pesticides with Benefits for All:

A Public Health Perspective . . . . . . . . . . . . . . . . . . . . . . . . 11

The Public Health Reality: Historical and Modern . . . . . . . . . . . . . . 11

Synthetic Chemistry for Crop Protection: Humans Imitate

Plants and Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Technological Reality: Weve Always Copied

the Good Ideas of Plants and Bacteria . . . . . . . . . . . . . . . . . . . . . . . 14

Youve Come a Long Way, Baby . . . . . . . . . . . . . . . . . . . . . . 16

The Reality of Modern Pesticide Technology:

Dynamics & Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Its Still About the Dose(and Timing) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

The Reality of A Modern Biochemical Perspective

on Toxicity, Hazard, and Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22


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Endocrine Disruption: Is It Just Hormonal? . . . . . . . . . . . . 25

The Reality: Confusion Between a Changing Paradigm and a Shift

in Focus, Away from Cancer, to a Different Physiological System . . 25

Vetting and Regulating Pesticides . . . . . . . . . . . . . . . . . . . 28

The Reality of Pesticide Regulation in the U.S.: An Example

of Moving the Precautionary Principle from Idealistic Philosophyto Real World Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

The Reality of Pesticide Regulation: Truckloads of Data on Every

Conceivable Effect from Studies with Overlapping and Redundant

Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Whose Data Are They? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

How EPA Determines Safety Under the Mandates of the Law . . . . . 33

Some Case Studies: Reports

of Hazards Do Not Reflect Risks . . . . . . . . . . . . . . . . . . . . 35

Atrazine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Chlorpyrifos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Pyrethroid Insecticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Glyphosate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54


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Executive Summary

Will we aver a crisis o ood supply shorage? Tis quesion coninues oloom large alhough populaion growh rae has empered considerably,compared o projecions 30 years ago. Bu several years ago, as ood prices

seemed o be on he verge o skyrockeing, owing o

rapid increases in grain prices, we arguably go a aseo he uure. When you consider uncerainy abou cli-

mae variabiliy and land use changes as well, we seem

always on a precipice o doing wih less raher han

more. Forunaely, agriculural echnology has hus ar

kep pace wih a growing populaion. A crucial com-

ponen o his oolbox has hisorically been a dynamic

chemical echnology, led by he availabiliy o synheic

erilizers and innovaions in chemical pes conrol.

Tis repor analyzes he myhs surrounding pesicide

science and correcs each wih a realisic perspecive o

he echnology: how i is possible o kill pess wihou

harming oher organisms, how he science is regulaed

wih a precauionary perspecive, and, finally, wih an

analysis o claims made abou hazards and he probabil-

iy ha hese pose credible risks o healh. Tis repor

makes he case or he benefis o pesicides, ranging

rom he proecion o crop yields o he proecion o

public healh. Indeed, he benefis are abundan enough

ha one can simply sae ha he availabiliy o pesi-cides has significanly improved human healh.

Conroversy surrounding pesicide use a firs

glance would seem o dae back o he 1962 publicaion

o achel Carsons Silen Spring. However, his superfi-

cial analysis ignores he long hisory o pesicide conrol

saues such as he Federal Food, Drug, and Cosmeic

Ac (FFDCA 1938) and he Federal Insecicide, Fungi-

cide, odenicide Ac (FIFR 1947). One migh argue

abou he effeciveness o hese laws, bu hey have beenamended many imes, beore and afer Silen Spring,

o address heir weaknesses. Indeed, perhaps he mos

ar-reaching modificaion was he Food Qualiy Proec-

ion Ac o 1996 which, or he firs ime, oriened he

main law, FIFR, o consider risk o consumer healh

as he only basis or re-regisering older chemicals and

regisering new producs. Veneraion o Silen Springby

advocacy groups has overlooked he reams o daa al-

ready in he public secor ha Carson had been reading

o inorm her lierary endeavor.

And so, curren pesicide laws have evolved and

are arguably he mos precauionary o all congressio-

nal mandaes involving echnology. Indeed, we asser

ha modern pesicide laws epiomize in acion an oh-

erwise vacuous precauionary principle ha eschews

risk assessmen as a basis or risk managemen. isk

assessmen righully recognizes he oo ofen ignored

principles ha all chemicals (wheher plan-derived

or cooked up by humans) are subjec o he samephysical laws o hermodynamics and he principles

o kineics. Such recogniion explains how we humans

can ea a myriad mixure o plan chemicals, many

o which are recognized as oxins hemselves, arising

rom an evoluion o plan meabolism ha aids heir

survival agains voracious predaors and he vagaries

o weaher.


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Execut ive Summary

disposiion wihin he body, his repor specifically

examines he claims abou our ypes o conempo-

rary pesicidesarazine, chlorpyrios, pyrehroids,

and glyphosae. In each case sudy, he published

scholarly lieraure is used o show ha he percep-ion o adverse effecs has arisen as a resul o misak-

ingeiher hrough ignorance or ideologylabora-

ory sudies o oxicological mechanisms or analysis

o risk based on consideraion o how he chemicals

are acually used.

One imporan poin o consider in any analysis

o pesicide echnology is he evoluion o a dynamic

sysem o managemen. Ta is, any repors o adverse

effecs are deal wih by developmen and implemen-

aion o new esing requiremens or by changes in

permissible uses o a produc. Te sysem provides

eedback o boh regulaory agencies and manuacur-

ers hemselves. Te later have hisorically responded

by a ocus on discovery o new producs ha mee he

goals o a saer chemical echnology. Unorunaely,

public atiudesed by atenion-seeking media

scare sories seem ocused on he pas and ail o see

a comparaively rapid change in chemical echnology

and how i has been deployed. Similarly, public aten-ion is drawn o misinerpreaions and hal-analysis o

sories o hazards. However, scruiny o he published

lieraure has ailed o find evidence o a credible prob-

abiliy o adverse human healh effecs derived rom

he use o modern pesicides as occurs in he real world,

no in he laboraory-generaed environmen. Despie

he headlines o hazard, modern chemical echnology

provides hope or coninued improvemen o human

healh, wheher helping o make vegeables and ruis

o high qualiy more abundan and cheaper, or o pre-

serve (or indeed, enhance) he healh o individuals

and sociey a large.

In his background o survival, he principle o

reasonable cerainy o no harm guides decisions

abou releasing man-made pesicides o help in he

batle o proec crop yields and ood qualiy. Eco-

nomic analyses prove how ood supply would becomeprecarious wihou he use o chemical echnology.

Epidemiological analyses prove how eliminaing an

effecive surace-sprayed insecicide like DD has os-

ered large oubreaks o malaria, he mosquio-borne

scourge o 300 million humans a year. Ye despie

he proven benefis o pesicides, years o research

have shown ha hese valuable ools canno be used

wihou proper managemen, and ha, moreover,

hey should exhibi seleciviy o pess over nonarge

organisms so ha hey become complemenary o

naural biological conrol processes exising wihin all

agriculural ecosysems.

Indusry has responded o he goals and needs

o a compaible pesicide echnology wih develop-

men o ever more selecively oxic chemicals ha

are used a comparaively low raes compared o he

chemicals hey are replacing in he markeplace. Te

recen generaions o EPA-designaed reduced-risk

pesicides are in many cases ens o hundreds o imesless oxic o fish, birds, and nonarge predaors and

parasioids han chemicals ha were inroduced o

armers beween he 1950s and 1970s. However, he

biochemical heory o ligand-recepor and enzyme-

subsrae kineics, in combinaion wih consideraions

o pharmacokineics, is applied herein o show ha

some o he older chemicals acually presen litle risk

o adverse effecs in associaion wih realisic environ-

menal raes o use.

Following explicaions o oxicological mecha-

nisms o seleciviy and he imporance o consider-

ing pharmacokineic acors influencing pesicide

Despite the headlines of hazard, modern chemical technology

provides hope for continued improvement of human health.


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ing risk. While consumers are reacing by expressing

heir eelings abou a generic echnology, he scienific

exper is mos likely ocusing on he idiosyncrasies o

an individual compound. Neverheless, general prin-

ciples o biochemisry and physiology are imporan

or assessing pesicide echnology. Applicaion o

hese principles is crucial o properly regulaing as well

as using he echnology. Furhermore, he benefis o

he echnology mus be considered in ligh o he pos-sible and likely adverse consequences o notusing i.

Te lieraure on he percepion and communica-

ion o risk suggess ha perhaps consumers are no

he real audience in need o inormaion abou he

inricacies o pesicide echnology. For example, 84%

o surveyed residens in Washingon Sae did no

hink pesicide use and conrol was an environmenal

problem (LaFlamme and VanDerslice 2004). I seems

ha inormaion may be beter direced o legislaive

members and heir saff (Cohen 1997). When hesecohors were surveyed, he mos desired inormaion

was explanaions o how risk assessmens are con-

duced, wih applicaion o paricular chemicals as an

example. I legislaors and heir saffs are recepive o a

beter undersanding o chemical echnology hrough

risk assessmen, hen dispelling misconcepions abou

pesicides as a precursor o raional risk manage-

A Rationale for Confronting Mythsabout Pesticide Technology

O

ver he las decade, ood preerence surveys as well as sales saisics show anincreasing percenage o consumer preerence or buying organic, raw, and

processed ood producs (Saba and Messina 2003; Hughner e al. 2007).Alhough he absolue numbers o individuals pur-

chasing hese ood iems compared o convenional

iems is sill quie small (Hughner e al. 2007), he daa

seem o validae he percepion ha consumers gener-

ally have a negaive opinion o pesicide use (Chipman

e al. 1995; Makaouni 2002; Magnusson e al. 2003;

Yiridoe e al. 2005). Tis negaive opinion is relaed o

several concerns, ranging rom worry abou he healh

effecs o pesicide residue exposure o a misrus oindusries synhesizing and markeing pesicides

(Chipman e al. 1995; Slovic 1999). Various surveys

also sugges ha consumers do no perceive any bene-

fis rom he use o pesicide echnology (Hansen e al.

2003). Consumers may undersand he need o man-

age crop and livesock pess, bu hey may also hink

ha pesicides are no necessary o achieve his goal,

or, alernaively, ha hey are overused in agriculure

(Chipman e al. 1995). isk percepion surveys gen-

erally agree ha consumers view pesicides as a highhazard echnology ha is unconrollable, unknowable,

and o litle benefi o hemselves (Chipman e al.

1995; Slovic 1987).

Given ha pesicide echnology encompasses

a vas array o individual chemicals and ormulaed

producs, changing consumer percepions seems o

presen an insurmounable obsacle in communica-


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A Rat iona le for Confro nt ing Myths about Pest ic ide Te chnology

icide echnology, his repor will firs sae miscon-

cepions or myhs abou pesicides ha can be gleaned

rom a combinaion o risk percepion lieraure, as

well as examining pesicide sories in he media (Fel-

so 2010). Afer saing a myh, he realiy based onbiochemical principles will be explained. Similarly,

misconcepions relaed o he real benefis o pesicide

use will be answered wih examples o how pesicides

acually conribue o proecion o human healh and

a general improvemen in wellbeing. Finally, o illus-

rae how misundersandings o he naure o oxicol-

ogy and epidemiology sudies conribue o a skewed

conflaion o hazard and risk, he repor will review

some commonly used biodegradable pesicides and

atemp o alleviae issues o specific concern. By dis-

cussing misconcepions and realiies abou pesicide

echnology, and highlighing paricular pesicides,

his repor can provide risk communicaors wihin he

business communiy and governmen wih a sronger

echnical basis or discussing pesicide issues.

One cavea needs emphasis up ron. Argumens

promoing global benefis rom pesicide echnologies

as heyve evolved over he pas 40 years are no argu-

mens agains ensuring ha hese compounds havelitle risk as hey are used. aher, our regulaory sys-

em or pesicides has acually been quie precauion-

ary. Ironically, as calls or adopion o a precauionary

principle in place o a risk assessmen process have

begun o permeae governmenal regulaory aciviy,

pesicides are arguably he one echnology where so-

called enes o his principle are acively praciced.

Tus, anoher objecive o his repor is o clariy

muliple aspecs o pesicide echnology ha mus

be known i we wish o move pas he myh ha we

have no properly considered hazards in he mids o

overwhelming benefis.

men may no be an insurmounable ask. Afer all,

legislaures mandae regulaion o he echnology.

egulaors hemselves, hereore, mus undersand

undamenal biochemical principles, as hey regulae

many kinds o chemicals.Ye simply educaing regulaors may no be an e-

ecive way o dispel misconcepions. Comparisons o

lay and exper opinion abou chemical hazards in gen-

eral revealed unpredicable disagreemens abou he

hazard and risk o chemical echnology among expers

(or example, regulaors and academic or indusry re-

searchers engaged in some aspec o oxicology) ha

were no oo differen rom hose expeced beween

consumers and expers (raus e al. 1992; Merz e

al. 1998). I here is as wide a divergence o opinion

among expers hemselves as ha which occurs be-

ween expers and consumers, one canno expec o

be very successul a risk communicaion unless some

o hese percepions are addressed direcly. Perhaps

wihin he echnical communiy isel insufficien a-

enion has been paid o common wisdom in order

o deermine operaional misconcepions abou pesi-

cide echnology in general.

Tis repor is a response o a need expressed oracual inormaion among legislaive auhoriies, bu

i also addresses expers hemselves by considering

enuous he assumpion o agreemen abou he risks

o chemical echnologies. Our analysis subsiues ac-

ual inormaion (some undamenal principles o ox-

icology based on biochemical conceps, an overview

o properies o modern reduced risk pesicides, and

a delineaion o pesicide benefis o human wellbe-

ing) or misconcepions specifically abou pesicide

echnology.

o communicae he undamenal principles o

oxicology necessary or appropriaely regulaing pes-


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Pesicide and erilizer use has been recorded since

ancien imes, suggesing ha ecosysem managemen

is no a recen culural atribue. In he conex o mod-

ern agriculure, he objecives o pesicide use are o

increase producion efficiency and yields; reduce he

cos o ood and, especially, o increase he availabiliy

o grains, ruis, and vegeables; improve ood qualiyand losses during ranspor and sorage; improve soil

conservaion; and ensure a sable and predicable ood

supply (NRC 2000).

Pesicide use is widespread on arms, bu more

imporanly, differen classes o pesicides are differen-

ially used (NRC 2000; Padgit e al. 2000), suggesing

ha growers make decisions based on need raher

han solely on prophylaxis. For example, in he U.S.

during 2002 approximaely 303 million acres o crops

were harvesed, and 95% were reaed wih some ype

o pesicide. However, 64% o he acreage was reaed

o conrol weeds (i.e., herbicide use), 22% o conrol

insecs (insecicide use), 6% o conrol diseases and

nemaodes (ungicide and nemaicide use). Anoher

4% o he crop acreage was reaed wih a plan growh

regulaor or rui hinning, growh conrol, or deolia-

ion (Felso and acke 2007).

Pesticides with Benets for All:An Agricultural Perspective

Myth: Farmers use pesicides or heir own economic gain wihou regard or needor a social responsibiliy o proec he environmen. Pesicides are no needed or

arming, as has been proven by he increasing adopion o organic arming.

Agricultural Reality: The Economic Perspective

Te proporional use o differen kinds o pesicides

(i.e., herbicides, insecicides, ungicides, ec.) shows ha

armers do no monolihically use he chemicals on ev-

ery acre. aher, he daa show ha use is ied o specific

need. Furhermore, he inensiy o specific pesicide

classes also varies significanly by crop. Grains end o

be disproporionaely reaed wih herbicides, bu ruiand vegeables mosly receive insecicide and ungicide

applicaions (able I). Farmers use he echnology

ha conrols he pes a hand bu, imporanly, use

is driven by need as influenced by weaher condiions,

anicipaed and acual pes inesaions, and he balanc-

ing o coss and reurns.

Te benefis o crop proecion chemicals or im-

proving and proecing crop produciviy is difficul

o separae rom he effecs o hybrid seed echnol-

ogy and oher plan breeding advances. Neverheless,

an examinaion o crop yields relaive o land under

producion shows ha boh ypes o echnologies

have had major conribuions. For example, he grea-

es proporion o U.S. armland is devoed o corn

producion. A hisorical examinaion o area o land,

yields, and he inroducion o differen echnologies

over ime suggess ha insec conrol (mainly o he


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Pest ic ides wi th Benef i ts for Al l : An Agricul tural Perspect ive

and umigans, in crop producion efficiency is sug-

gesed by poao producion saisics. In 1900, nearly

3 million acres o poaoes were harvesed, yielding an

average o 52 cw/acre (USDA2005). In 1950, aver-

age yields were 153 cw/acre. In crop year 2004, 1.2million acres o harvesed poaoes yielded an average

752 cw/acre. Surely, advances in plan breeding play

an imporan role in producion increases, bu by he

1950s, umigans or conrol o nemaodes became

widely available nearly coincidenally wih he

corn rooworm complex) has grealy enhanced he

effeciveness o hybrid seed echnology (Figure 1).

Furhermore, he inroducion o modern synheic

herbicides aciliaed widespread adopion o conser-

vaion illage in he Corn Bel, which in urn grealy re-duced he major cause o environmenal degradaion

in Norh Americasoil erosion and sedimenaion in

rivers (Pimenel e al. 1995).

Perhaps an even more compelling case or he role

o crop proecion chemicals, especially ungicides

Crop Herbicide Insecticide Fungicide

Corn 95 29


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o decreased pesicide use or no use seem large, he

acual decrease in yields (and consequen effecs on

consumer prices) would depend on he availabiliy o

oher alernaive crop proecion echnologies or prac-

ices (NC 2000). For example, field crops like corncan be grown wih minimal herbicide use i illage is

used more requenly. Addiionally, hand weeding, as

is ofen praciced in cerified organic crop producion,

along wih illage, can subsiue or herbicide use.

However, aggregae analysis o grain, vegeable, and

rui crop managemen, assuming only hand weeding

and illage wihou herbicide use, showed an average

yield reducion o 20 percen (Gianessi and eigner

2007). Furhermore, subsiuion o increased illage

or weed conrol would couner he benefis o re-

duced illage or soil conservaion.

Vegeable and rui producion would likely be

he mos adversely affeced by wholesale loss o use o

insecicides and ungicides, owing o heir dispropor-

ional problems wih insec pess and plan pahogens.

Loss o pesicide availabiliy would also adversely a-

ec consumer prices, and poenially mean a loss o

domesic sources o supply as producion is relocaed

o oher regions (Zilberman e al. 1991).Is imporan o realize ha he economic reurn-

cos raio or pesicide use is generally avorable. Te

raio depends on he specific crop because he annual

commodiy price mus be acored in, as well as he

sie-specific yield and expenses due o chemical pur-

chases. Neverheless, older esimaes or reurn ranged

rom $4-$29 or every $1 spen (Mecal and Luckman

1975), and more recen esimaes sugges a $3-$6 rae

o reurn per $1 spen (Zilberman e al. 1991; Pimenel

e al. 1992). Significan or he grower is he compara-

ively low incremenal cos o pesicide use relaive o

all producion expenses. Te mos recen esimae

(crop year 2002) is ha purchase o pesicides repre-

sens 4.4% o oal expenses, compared o he 12.7%

o expenses or hired and conrac arm labor (USDA

2004). Pesicides hemselves help lower coss by sub-

siuing or labor. For example, rui hinning required

widespread adopion o mineralized erilizers. Bu he

producion rends srongly sugges an environmenal

benefi because presenly seven imes more poaoes

are produced per acre han were produced in 1900. I

one hus exrapolaes or oher crops ha yields haveincreased owing o adopion o modern echnolo-

gies like improved breeding using bioechnology and

chemical pesicides, hen a large benefi is a reurn o

arm land o oher uses, such as oress and/or prairies

and conservaion o naural areas, as well as residences

or a burgeoning populaion.

Wha is more, he aggregae economic benefis

associaed wih pesicide use have been subjeced o

various empirical modeling exercises and expressed

as he loss o producion i pesicides were no used

(NC 2000). Producion losses during he mid-1980s

were esimaed o be as high as 37% o oal oupu

(Pimenel e al. 1992). Tis esimaed loss occurred

despie pesicide use, bu he esimae seems raher

high when assessed agains specific crop analyses. For

example, one o he mos desrucive pess o poaoes,

lae bligh disease, broke ou in he Columbia Basin o

Washingon Sae and Oregon during 1995. Fungicide

use rose rom ypically wo applicaions per season oas many as 12 (Johnsoneal. 1997). However, yield

differences beween he pre- and pos-bligh oubreak

were only 4-6 percen. On he oher hand, wihou any

managemen, he bligh epidemic could have reduced

yields 30-100 percen.

Oher economic analyses have projeced he e-

ec on resh and processed vegeable and rui yields

i pesicide use were reduced 50 percen or simply

no used a all (nuson e al. 1993). educions

in resh rui yields were 40 percen and 75 percen,

respecively. Subsanial reducions were projeced in

grain producion under condiions o no herbicide

use (Fernandez-Cornejo e al. 1998). Anoher sudy

esimaed ha a oal pesicide use ban would require

an addiional 2.5 million acres o vegeable and rui

producion o make up or he yield loss (aylor

1995). Alhough modeling esimaes o he impacs


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8


by cerified organic growers. For example, spinosad

insecicide, a complex macrocyclic lacone saccharide

derived rom a bacerial ermenaion culure, is used

by odays cherry growers regardless o heir produc-

ion philosophy. Even hough NOSB policy ends oavoid subsances ha are oxic, spinosad has a bio-

chemical mode o acion ha would classiy i as a ype

o neurooxin (Sparks e al. 2001; Orr e al. 2009).

Te puriy o organic ood is urher dispelled

by analyical surveys o organic commodiies o reveal

ha some conain synheic pesicide residues boh

banned and currenly regisered, albei much less re-

quenly han so-called convenional oods (Baker e

al. 2002). esidues in organic commodiies are likely

inadveren, due o airborne ranspor and deposiion,

as well as soil residues rom pas use. ecognizing

he ubiquiy and mobiliy o environmenal residues,

NOP rules allow inadveren pesicide residues up

o 5 percen o he esablished ederal olerance level

wihou a loss o organic cerificaion. Wheher one

likes or dislikes pesicide use, pas pracices influence

residues in ood. However, curren residue sudies

indicae ha he vas majoriy o convenional oods

have no detectable pesticide residues (FDA 2009;USDA AMS 2009).

In summary, various economic analyses are in

agreemen ha pesicide use has been definiely as-

sociaed wih profiable reurns o armers (and hus

o sociey), and i is no rue ha pesicides are used

on every crop indiscriminaely. Te realiy is ha

some crops require disproporionaely more herbicide

use and some crops require more insecicide and/or

ungicide use. Tus, effors o globally limi pesicide

use ail o ake ino accoun specific and local needs

or crop proecion. Furhermore, cerified organic

producers have an array o pesicides hey can use un-

der he rules o he NOSB. Pas land pracices have led

o deecions o pesicide residues in organic ood, bu

curren analyical surveys show ha so-called conven-

ionally produced ood mos ofen has no deecable

pesicide residues.

in he pome rui indusry is mosly done by chemical

hinners bu sill requires some hand hinning i loads

are deemed excessive.

Perhaps he mos popular misconcepion among

consumers o organic oods is ha such producs lackpesicide residues and oher addiives. Te basis or

his belie is he ofen-repeaed argumen ha organic

agriculure disinguishes isel rom convenional

producion mehods because no synheic pesicides

are used. Prolonged pronouncemens o no synheic

pesicide use easily evolve ino a consumer percepion

o no pesicide use. Conracion o no synheic use

o he equivalency o no use a all may be aciliaed

by he myh ha somehow synheic subsances are

generically differen in heir adherence o hermody-

namic laws and reaciviy han naural subsances.

Te realiy is ha U.S. rules or cerificaion o

organic producion allow or he willul use o ap-

proved crop proecion producs. Under he Federal

Insecicide, Fungicide, and odenicide Ac (FIFR)

many o heses producs are legally pesicides and

mus be regisered wih EPA (Felso and acke

2007). However, organic growers by rule canno use

synheic maerials unless approved by he NaionalOrganic Sandards Board (NOSB). Bu no pesicide

(NOSB-approved or oherwise) can be used in any

ype o arming pracice unless veted by EPA firs.

EPA does a comprehensive risk assessmen on all

chemicals submited or regisraion, using he raw

daa submited by a prospecive pesicide regisran.

Similarly, NOSB conracs wih he Organic Maerials

esearch Insiue (OMI) o do a comprehensive

hazard assessmen o maerials proposed or cerified

organic producion. In ha case, similar quesions

are asked, excep ha he OMI speculaes wheher

a candidae produc is really needed and hereore a

credible subsiue. One crierion would be ha i is

less hazardous. Alhough a perspecive o hazard di-

ers rom one ha uses hazard along wih exposure o

characerize risk, some o he acive ingrediens used

by nonorganic growers are he same as hose used


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9


Te inorganic pesicides used during he firs hal o

he 20h

cenury and he firs wave o synhesized pesi-cides afer 1950 were generally broad specrum bu no

necessarily adequae or all cropping sysems (Sern e

al. 1959). Over he las hiry years new chemisries

have been inroduced o narrow he specrum o ac-

iviy. Along wih new ormulaions and applicaion

mehods, modern pesicides can be beter ailored o

specific crops pes problems. Similarly, insecicides

inroduced over he las 15 years are also much less

oxic o he naural bioconrol organisms han he

broad-specrum synheics inroduced during he1950s. Furhermore, modern pesicides rapidly de-

grade in he environmen and do no bioaccumulae

in lipid issues as did he chlorinaed hydrocarbon and

cyclodiene pesicides ha were heavily used prior o

heir ban in he early 1970s.

A ourh benefi sems rom herbicide use in grain

producion hroughou he Corn Bel. Beore he ad-

ven o synheic chemical herbicides like arazine, ero-

sion was severe on even genly sloping lands becausearmers relied on he moldboard plow and urher

culivaion o he soil during crop growh o conrol

weeds. Many environmenal scieniss agree ha eu-

rophicaion and sedimenaion o aquaic resources

due o runoff and erosion rom agriculural land is he

mos imporan cause o waer qualiy impairmen,

no o menion being reponsible or ransporaion

problems as rivers backfill wih sedimen. By he

1960s, a ew herbicides were commercially available

In addiion o heir economic benefis accruing

rom he objecives or which hey are used, pesicideshave cerain advanages over oher pracices or crop

proecion (as well as producion) ha make hem very

convenien, efficien, and cos-effecive (Mecal and

Luckman 1975). Firs, or mos cropping sysems, pes-

icides are he only pracical available echnology be-

cause oher echnologies are no available, unproved,

or do no work efficienly. For insance, hybrids o cer-

ain crops may lack a pes-resisan culivar. In oher

cases, a nonchemical pes conrol pracice ails o work

over ime. An example o he later siuaion is he ap-paren adapaion o wesern corn rooworms o he

pracice o annual corn-soybean roaions ha were

very successul in reducing he need or soil inseci-

cides (Sammons e al. 1997; ondon and Gray 2004).

Second, pesicides have rapid curaive acion in

prevening loss o crop yield or proecing human and

animal healh. Tus, hey can be used when a pes

populaion becomes inolerable. One o he enes

o inegraed pes managemen (IPM) is eschewingprophylacic sprays in avor o as needed reamens.

Tus, here may be a very shor window o ime during

which he pes needs o be conrolled, and nonchemi-

cal mehods may lack a rapid enough acion.

Tird, he diversiy o locaions where crops are

grown means differen pes complexes hrive under

a wide range o climaic condiions. Pesicides have

a wide range o properies, uses, and mehods o ap-

plicaion ha can cover many problems as hey arise.

Agricultural Reality: Practical & EnvironmentalAdvantages of Crop Protect ion Chemicals

The diversity of locations where crops are grown means different

pest complexes thrive under a wide range of climatic conditions.

Pesticides have a wide range of properties, uses, and methods

of application that can cover many problems as they arise.


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10


lands available or wildlie conservaion (Cooper and

Dobson 2007). Direc conrol o human and livesock

pess (as discussed in he ollowing secions) creae

similar secondary benefis or economic produciviy,

public healh, and longeviy.An analysis o hisorical and conemporary man-

agemen o coton pess provides anoher affirmaion

o he benefi o pesicide echnology and also sug-

gess indirec benefis beyond a specific crop (Naranjo

and Ellsworh 2009). Coton has hisorically been a

crop requiring arguably he highes per acre inensiy

o pesicide use. Coton pes managemen in Arizona

has evolved ino a highly sraegic sysem ha employs

boh naural biological conrol organisms (i.e., preda-

ors and parasioids) bu also relies on highly selecive

insecicides or conrolling he mos imporan pess,

which include he pink bollworm and whieflies.

Pink bollworms have been managed by use o coton

culivars bred o conain he highly selecive bace-

rial oxin proein derived rom he naurally occurring

insec pahogen Bacillus huringiensis. Deploymen

o such culivars can conserve predaor populaions.

Te whiefly, on he oher hand has, been successully

managed by judicious inegraion o highly seleciveinsecicides ha affec insec developmen. Te avail-

abiliy o such insecicides has no only increased pro-

is by reducing he overall need or pesicides, i has

also indirecly benefied oher regional crops atacked

by whieflies: Tese now show an overall reducion in

heir populaions. Tus, innovaive pesicide echnol-

ogy has resuled in an unprecedened sabiliy o eco-

sysem services and major economic and environmen-

al gains in Arizona coton ha has exended o benefi

he enire agroecosysem o he region (Naranjo and

Ellsworh 2009).

and allowed armers o consider subsiuing chemical

conrol o weeds or urning he soil over and hereby

making i highly suscepible o he erosion caused by

wind and spring rains on bare soil. No-ill agriculure

bloomed, especially in corn producion, because arm-ers were able o rely on herbicides. Aggregae soil ero-

sion rom illed soil in our Corn Bel saes (Illinois,

Indiana, Iowa, Nebraska) was esimaed a 14.9 ons/

acre/year bu only 2.8 ons/acre/year rom unilled

grain fields (Gianessi and eigner 2006).

Furhermore, by eliminaing he need o ill soil,

herbicides also allow or he conservaion o uel. Over

111 million gallons o uel may be saved by using her-

bicides insead o illage in he aoremenioned our

Corn Bel Saes (Gianessi and eigner 2006). Low-

ered emissions o greenhouse gases are also associaed

wih a reducion in uel use (oberson e al. 2000).

In addiion o uel reducions, an increased yield

or every dollar invesed in agriculural producion

significanly reduces per acre increases in carbon emis-

sions; his is by virue o avoiding he land clearing

oherwise necessary o mainain sufficien producion

or an increasing populaion (Burney e al. 2010).

Tus, curren analyses suppor he idea ha pesicideechnology also conribues o environmenal qualiy

by virue o enhancing yield.

wo oher recen analyses also suppor he con-

clusion ha here are boh direc and indirec benefis

o pesicide echnology. Alhough he direc benefis

o suppression o pes densiy, and hus suppression

o damage, are obvious, indirec benefis can also be

considerable. Some examples o he later include

increased financial resources or a communiy, due

o greaer producer profis; increased consumer ac-

cess o resh ruis and vegeables; and an increase in


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11

on a coninen like Arica, where publicly financed

programs are inrequen, and poor when hey exis.

Anophelesmosquioes oday sill ransmi per annum

over 500 million cases o malaria (WHO 2010), a

disease caused byPlasmodium falciparum, a prois re-

quiring boh he mosquio and human body in which

o complee is lie cycle. Malaria causes paroxysms

o ever, ofen several imes each day. Wih so many

ineced, economies become inefficien as workers are

sruck ill. And because inan and child nuriion is

so deficien in hese counries, a nearly unimaginable

800,000 children die rom mosquio-ransmited ma-

laria each year.

Bu many counries have malaria under conrol.

Tey adoped he use o DD, he chemical echnol-

ogy used by he miliary during WWII and by he

European Command afer he war o conrol mos-

quio populaions. Daa on malaria incidence beore

and afer he adven o DD proved ha he pesicidecould be effecive wihou causing acue harm (Hayes

1991). Te evidence or lack o acue harm became

apparen when millions o Europeans were direcly

dused o conrol lice ha ransmited a orm o yphus

caused by he bacerium Ricketsia.

However, DD was essenially banned in he U.S.

in 1972 when he recenly-creaed EPA decided o

Daily lie in he developed counries o he Wes

is no likely plagued by insec-ransmited inecious

diseases. While i is rue ha he yellow ever vecor

mosquio Aedes aegypi once hauned he srees o

New Orleans, a program o publicly financed mosqui-

o conrol arose in he 1960s and spread hroughou

he U.S. o dampen he disease-ransmission poenial

o insecs. Even so, over he las decade, Wes Nile

virus, ransmited by he bie o he Culex mosquio,

has spread rom New York o Caliornia, becoming

endemic in every sae (Arsob e al. 2009). Lyme dis-

ease, a spriochee bacerium ransmited by he bie o

he iny deer ick, disables nearly 20,000 people each

year (Bacon e al. 2008); i is in many places now in

he U.S., alhough he epicener is in New England.

Insec bies are mosly a nuisance o ciizens in highly

developed counries, bu he las decade o Wes Nile

virus epidemiology shows he need or vigilance abou

inecious disease conrol even as megaciies and ex-urbs pave over widening expanses o naural lands.

Furhermore, he widespread oubreak and spread o

Wes Nile virus has had observably negaive impacs

on bird populaions (LaDeau e al. 2007).

ecen experience indicaes he need or vigilance

agains arhropod-vecored diseases even in devel-

oped counriesbu he siuaion is surely more dire

Pesticides with Benets for All:A Public Health Perspective

Myth: Pesicides offer no benefi o public healh and, arguably, derac rom i.

The Public Health Reality: Historical and Modern


18/76

12

Pest ic ides wi th Benef i ts for Al l : A Publ ic Heal th Perspect ive

Mosquio larval, egg-laying, and breeding habia

mus be moniored and managed. Wesern counries

now use insecicides based on microbial oxins, name-

ly Bacillus huringiensis israeliensis (Bi) and Bacillus

sphaericus.BiandB. sphaericusare incredibly specific,naurally occurring baceria ha are oxic only when

ingesed by mosquio larvae. Tese organisms are sill

deemed pesicides, specially regulaed under EPAs

biopesicides program (EPA 2010).

In addiion o habia managemen or mosquio

conrol, individuals are encouraged o proec hem-

selves wih mosquio neting around heir beds a

nigh. Emphasis has been placed on using insecicide-

impregnaed bed neting, which can be effecive when

whole communiies are included in conrol programs.

However, even such relaively passive conrol mea-

sures are very much influenced by he ype o insec-

icide deployed (e.g., irrian vs. non-irrian effecs)

(Curis and Mnzava 2000), urher illusraing ha he

benefis o pesicides depend on he appropriae use o

specific chemicals.

One aspec o proecing public healh ha is

no ofen menioned is he poenial o pesicides o

reduce microbial conaminaion and he associaedproducion o ungal oxins. Overlooked is he use o

chlorine and oher disinecans, all o which are reg-

isered pesicides, in waer reamen. U.S. consumers

appreciae waer devoid o bacerial conaminans and

know implicily ha bacerial inecion rom drinking

waer is very rare here. However, inadequaely reaed

public supplies do occur, as evidenced by he oubreak

o cryposporidium in a Wisconsin waer supply dur-

ing 1993 (Macenzie e al. 1994). A waer-borne ou-

break o pahogenicE. coli in Walkeron, ON during

2000 was also definiively conneced o inadequae

chlorinaion (Hrudey e al. 2003).

Ani-pesicide aciviss may ry o asser ha pes-

icide use is all abou blemish-ree rui and vegeables.

rue, use o crop proecion echnologies reduces

marking and scarring, hereby filling o overflowing

produce couners wih picure-book ood. Bu insec

suspend is regisraion or any agriculural use. (In

ac, he decision was enirely he work o EPAs firs

adminisraor, William uckelshaus.) Unorunaely,

he hisory o agriculural use o DD and is demise

as an effecive pes conrol echnology on crops hasbeen conflaed wih is coninued success wih mos-

quio conrol in lesser developed counries o Arica,

pars o Lain America, and pars o Asia. Alhough

DD was memorialized ino inamy by achel Car-

sons Silen Spring, i was he agriculural use o he

chemical ha go i ino rouble, no he public healh

use. Even so, since Carsons ime, how DD is used in

public healh has been he key o is successul conrol

o mosquioes where hey mater, in he house. During

and shorly afer WWII, spraying o DD was wide-

spread in he environmen. However, by he 1950s i

was well known ha mosquioes resed on walls and

ceilings o buildings. Tus, by he lae 1950s research-

ers had already esablished he efficacy o a space

spray, wherein only resing areas on walls would be

reaed (Barlow and Hadaway 1956).

o his day, he public likely does no undersand

how DD is acually used, and hus visions o Silen

Springdominae he conversaion. So prevalen is hemisundersanding ha a number o counries decided

o eschew is use wih devasaing consequences

or malarial incidence. e-adopion o he limied

spraying o house walls was associaed wih a rapid

decline in malarial incidence (obers e al. 1997).

However, aerial spraying or mosquioes is sill viewed

as effecive under cerain circumsances or some

insec vecored diseases. Te benefis o using aduli-

cides o conrol Wes Nile virus mosquio vecors have

been shown o subsanially exceed coss as well as e-

ecively proec human healh wihou adverse healh

effecs or ecological problems rom pesicide exposure

(Peerson e al. 2006; Davis e al. 2007; Carney e al.

2008; Barber e al. 2010).

Perinenly, public healh proecion specialiss

have long known ha DD alone is no enough o

conrol he scourge o malaria-inesed mosquioes.


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13


are sarling or jus our major Bel Saes alone (i.e.,

Illinois, Indiana, Iowa, Nebraska). Economic analysis

o labor requiremens in he absence o herbicide use

has esimaed he need or a oal o 338 million hours

o work by over wo million workers (Gianessi andeigner 2006). Considering ha less han 2% o he

enire US populaion (approximaely 6 million peo-

ple) works on arms, replacing chemicals wih people

is no pracical.

Perhaps jus as imporan is o quesion how peo-

ple would are doing srenuous physical labor in he

sun or a ypical 8-hour work day. Sun exposure may

explain elevaed lip cancer risks, as well as he slighly

elevaed skin cancer risk, among armers (Aquavella

e al. 1998). Musculoskeleal healh would likely be

seriously impaired, given he physical naure o hand-

pulling and hoeing weeds. As evidence o such physi-

cally adverse impacs, Caliornia insiued an admin-

israive policy prohibiing he use o shor-handled

hoes. Organic letuce growers rely on hand weeding

o atain profiable producion and have peiioned

he Sae o Caliornia agains sricer labor rules,

osensibly because sufficienly effecive approved her-

bicides are unavailable ( James 2005). Tus he lacko appropriae available pesicides adds o labor coss

as i simulaneously raises he issue o hand-weeding

labors impac on worker healh.

Te oregoing sory o public healh benefis now

comes ull circle, back o he hisorical roos o using

pesicides direcly o affec insecs afflicing our bodies.

Te flowers o chrysanhemums (specifically Chysan-

hemum cinerariaefolium) were used in he early 1800s

by Souheasern Europeans and Persians o produce an

exrac called pyrehrum ha alleviaed a lice sufferers

scourge. Tus, over a span o less han 200 years, we

have aken and improved upon Moher Naures chem-

isry o improve our own public healh. W hich leads o

he nex myh abou chemical pesicides.

eeding causes harm ha makes a ood more suscep-

ible o ungal invasion. Cerain ungi commonly

associaed wih crops produce mycooxins ha have

well-documened physiological effecs in mammals,

including humans and livesock (Marasas 2001). Al-lowing insec or plan disease injury o progress wih-

ou proecing a crop only increases he likelihood o

mycooxin residues. Indeed, he problems graviy is

evidenced by an inernaional sandard or maximum

allowable residues o mycooxins. Furhermore, he

value o proecing crops agains direc insec eeding

has been proven wih he adopion o corn geneically

bred wih a gene romBacillus huringiensis(called B

corn) o produce a very insec-specific proein ha

kills he European corn borer. Tis insec damages

corn and is arguably he major cause o ungal myco-

oxin conaminaion, as damaged seed is pushed ino

sorage. Mycooxins are considered boh human and

livesock hazards wih carcinogenic, neurooxic, and

eraogenic effecs. However, B corn has subsanially

lower levels o mycooxin conaminaion han corn no

proeced agains corn borers (Bakan e al. 2002; Wu

2006). Tus B corn, which is regulaed as a pesicide,

helps keep grain qualiy wihin esablished regulaorysandards ha proec agains mycooxin exposure.

One pracical benefi o pesicide use ha is ofen

overlooked is ied boh o public healh proecion o

workers as well as economics o producion. Herbi-

cides, which are used more requenly and in greaer

quaniies han any oher pesicide class, are quickly

applied o all kinds o crops and hus eliminae he

need or hand labor o hoe ou weeds (Gianessi and

eigner 2007). Hand labor is expensive, and is avail-

abiliy is diminished by a shorage o people willing o

become par o a migran worker culure ha moves

rom arm o arm. One applicaion o herbicides or

weed conrol in a single field is worh he hand labor o

ens o hundreds o workers. Te aggregae numbers


20/76

14

ecion agains predaceous proiss or oher baceria.

A perinen example o humans using such hazardous

bacerial meabolies is he subcuaneous injecion or

opical epidermal applicaion o he highly oxic bou-

linim neurooxin, which is derived rom he anaerobic

ood spoilage organism Colsridium boulinin; i is

commonly used or cosmeic or correcive purposes

(Collins and Nasir 2010).

Te examples o aceic acid and boulinin, as well

as oher insances o naural oxins in ood, are bu

some examples o he many incidenal chemicals pro-

duced by plans and/or baceria ha are quie oxic in

high doses. Cerain ungi o he genusAspergillusgrowon cereals and produce chemicals called aflaoxins ha

are hundreds o imes more poen han any synheic

pesicide synhesized by humans. Ye our perspecive

abou he risks o pesicides does no apply oAspergil-

lus, as our concerns are ocused on he imely applica-

ion o a ungicide on sored grainshe righ hing o

do in order o proec ood and aver healh problems.

Many organisms, especially plans, produce chem-

icals incidenal o heir normal energy-producing bio-

chemisry ha uncion o ward off predaors, proec

seeds, or atrac insecs or pollinaion (Ames e al.

1990a, 1990b; Ames and Gold 1997). Someimes,

hese chemicals are jus by-producs o meabolism

ha may serve oher purposes, or hey are perhaps

excreory producs ha would be oxic i allowed o

accumulae in he cells. Someimes we can only specu-

lae abou he evoluionary role o hese chemicals.

For example, apples conain aceic acid. Alhough is

a naural componen o apples, he acid is neverheless

lised as a hazardous subsance, and he MSDS sheeliss horrific adverse effecs rom exposure, including

vomiing, diarrhea, ulceraion, bleeding rom ines-

ines and circulaory collapse. Perhaps he evoluion-

ary benefi o such a meabolic pahway and sorage

in rui accrued rom he known anisepic qualiies o

aceic acid (Levine 1940). Similarly, baceria produce

well-known oxins ha osensibly provide some pro-

Synthetic Chemistry for CropProtection: Humans Imitate

Plants and Bacteria

Myth: Synheic chemical pesicides are unnaural and canno be degraded. Tus,hey are paricularly dangerous in comparison wih naural producs derived romplans.

Technological Reality: Weve A lways C opie dthe Good Ideas of Pl ants and Bacter ia


21/76

15


Humans have always used chemical echnology.

Wheher he chemicals are made by plans, baceria,

or by our own hands is irrelevan. Some have main-

ained here is a difference beween chemicals rom

he ropical rain oress and chemicals rom he gianchemical indusries. Bu principles o environmenal

chemisry would dicae ha behavior o a chemical

is governed primarily by hermodynamics, no how

i was made.

Some would say ha our coevoluion wih plans

over many generaions has allowed us o deoxiy many

o he naural dieary chemicals. Consider, however,

ha many o our oods are recen invenions o selec-

ive breeding ha sill possess he same poenially

oxic chemicals as heir wild ancesors.

In considering synheic pesicides, a credible

argumen can be made or he human use o ools o

synhesize oher useul ools, e.g., pesicides, as an

evoluionary adapaion. Tis adapaion is analo-

gous o he evoluion o secondary meabolic pah-

ways in plans ha resul in biochemicals proecive

o heir survival.

Because chemicals produced by plans are unc-

ional, evoluion has arguably resuled in a orm o

chemical echnology. Trough our own chemical

echnology, aren we jus imiaing our boanical

and bacerial counerpars? For example, Swiss cheeseresuls rom bacerial species ha produce subsanial

amouns o propionic acid when growing on milk

producs. Te propionic acid is a by-produc, along

wih he carbon dioxide ormaion ha creaes he a-

miliar holes, bu i also suppresses prolific ungal (i.e.,

mold) growh (Suomalainen and Mayra-Makinen

1999). oday, humans add synhesized propionaes o

baked goods o obain he same proecion.

Members o indigenous culures have long used

plans as heir medicines. Te knowledge o which

plans o use, how o prepare hem, and he amouns

o adminiser has been passed rom generaion o

generaion. Isn he use o flora or our benefi, our

survival, a orm o chemical echnology? Perhaps we

should consider generaions o rial and error in dis-

covering beneficial and harmul plans as analogous o

a risk assessmen process.


22/76

16

and is one environmenal oxidaion produc, DDE,

drove i o move readily ino he amosphere. Such a

mechanism, commonly called phase pariioning in

he field o environmenal chemisry, was arguably he

mos influenial process in widespread environmenal

disribuion o DD. Unorunaely, is properies o

persisence, along wih broad-specrum biological ac-

iviy agains pess and beneficial insecs (e.g., preda-

ors and parasioids eeding on he pess) alike made

i a poor choice or use in agriculure afer WWII. Add

he rapid developmen o insecs resisan o is effecs,

and he sage was se or enomologisslong beore

he publicaion o Silen Springo recommend ha i

no be used on field and orchard crops.

Evidence o he dynamic naure o indusrys re-

sponse o changing pes-conrol needs, and hus is

abiliy o synhesize and es new chemical designs, is

a new group o chemicals called organophosphorus(OP) insecicides ha were inroduced ino commer-

cial agriculure in he lae 1960s. Soon hereafer, a sec-

ond group, called mehyl carbamae (CB) insecicides,

was inroduced. OP and CB insecicides had shor

persisence in he environmen, and a leas some

were no quie as oxic o predaors and parasioids.

A he very leas, hey gave growers more opions or

Te argumens se orh in his repor by no means

deend he properies o DD as ideal. aher, he

aoremenioned discussion ocused on DDs effecive-

ness in conrolling resing adul mosquioes when he

compound is used in a very specific and locally confined

manner inside o a dwelling. Furhermore, i is used

no solely bu as an adjunc o pyrehroid insecicide-

impregnaed mosquio neting. Ideally, governmen-

unded programs o habia managemen would accom-

pany individuals atemps a mosquio conrol.

All chemicals have disinc physicochemical prop-

eries ha make hem behave differenly rom each

oher. Chemicals wih similar srucural elemens, i.e.,

arrangemen o he same aoms, will behave similarly

ye sill possess idiosyncraic properies. Chemicals

having divergen srucural elemens will be even more

unlike one anoher. Tus, o conclude ha all pesicides,

because hey can kill pess, are jus like DD is o seri-ously lack an undersanding o basic chemisry, no o

menion he complexiy o biochemical ineracions.

Te specific physicochemical properies o DD

ha made i unique were very low waer solubiliy (i is

pracically insoluble in waer) and resisance o exen-

sive degradaion in organisms or on plan suraces. On

he oher hand, he very low waer solubiliy o DD

Youve Come a Long Way, Baby

Myth: Pesicides used oday are all jus like DD, and hus jus as dangerous. Allpesicides are alike and have no changed since DD. All synheic chemicals areequally hazardous.

The Reality of Modern Pesticide Technology:Dynamics & Evolution


23/76

17


o he naural pyrehrins. By he lae 1970s, new insec

growh regulaors were synhesized based on naural

hormones or plan meabolies ha exhibied eiher

juvenile hormone agonisic or anagonisic aciviy

(Menn and Henrick 1981). Te later endeavors wereenhanced by basic research on specific biochemical

and physiological sysems o pess. Te second orm

o bioraional design was he combinaion o more

radiional synhesis mehods wih he opimizaion

o srucure-aciviy relaionships, which occasionally

resuled in compounds ha could affec specific physi-

ological mechanisms o insec pess. For example, an

array o compounds have been synhesized based on

he model compound diflubenzuron, serendipiously

ound o inhibi he synhesis o chiin in he insec

exoskeleon (Menn 1980). Tese ypes o compounds

are sill being used oday, and more recen discover-

ies o heir effecive use as ermiicides have won EPA

Presidenial Green Chemisry Awards. Many o hese

compounds wih effecs on specific insec physiologi-

cal sysems could be used a low raes per acre, owing

o heir poen effecs on he pess even beter, heir

impacs on predaors were low, because hey have o

be direcly eaen or maximal biological effec.Te idea o a silver bulle, as exemplified by

DDs deploymen and overuse in agriculure, had

disappeared rom he mindse o indusrial research

by he mid 1980s; his was because new discoveries o

chemicals wih compleely differen modes o acion

coninued unabaed. Te new bevy o chemicals since

he lae 1980s evenually were recognized by EPA as

meeing heir crieria or reduced risk (EPA 1993).

Tese chemicals were ulimaely used a lower use

raes han many oher chemicals previously markeed,

and hey were even less oxic o mammals, birds, fish,

inegraing chemical use wih biological conrol (Sern

e al. 1959).

As DD and relaed compounds ell ino disavor

in agriculure, and pressure rom regulaory decisions

mouned, growers became heavily relian on OP andCB insecicides. Overreliance on one echnology ofen

leads o pes resisance, bu again he dynamic naure

o he echnology shone: Te Briish had sared work-

ing on modiying he naural insecicidal componens

o pyrehrum exracs, i.e., he pyrehrins, o produce

ligh-sable compounds, and hus longeviy in he field

beyond a ew hours. Forunaely, such compounds

were ar less oxic han he OPs o mammals, which

is always o concern or worker healh, as well as or

birds. Unorunaely, fish were quie suscepible o he

new synheic derivaive o he naural pyrehrins

jus as hey were o he naural producs. However, he

amouns used dropped rom wo or more pounds ap-

plied per acre o ranges o 0.1-0.2 pounds per acre. Ap-

propriae iming o applicaion, combined wih good

soil managemen pracices o proec agains erosion,

could resolve he likelihood o runoff ino aquaic hab-

ias in sufficien quaniies or fish kills. Tus anoher

chemical wih a differen mode o biochemical acionwas added o he growers oolbox. Unorunaely,

overreliance on a paricular chemical again resuled in

developmen o resisan insecs.

By he ime o pyrehroid developmen, inseci-

cide manuacurers had begun o ocus on he concep

o bioraional design o chemicals wih insecicidal

aciviy (Menn and Henrick 1981). Tis concep ook

wo orms. Firs, naural producs wih biological ac-

iviy could be inkered wih, alering heir srucure

o more precisely arge heir aciviy. Developmen o

synheic pyrehroids were iniially based on srucures

The idea of a silver bullet, as exemplied by DDTs deployment

and overuse in agriculture, had disappeared from the mindset of

industrial research by the mid 1980s.


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18

Youve Come a Long Way, Baby

could be applied o a bluegrass lawn or a field o whea

wihou damaging i. Ineresingly, dichlorophenol, a

puaive meabolie o 2,4-D, is synhesized naurally

by a soil ungus and is isomeric analog is used by some

icks as a sex pheromone, as well as an an repellen bya grasshopper species (Gribble 1998). Te discovery

o he specific biological aciviy o 2,4-D reieraes an

imporan concep in biochemisry alluded o beore

seleciviy. Tus, as maniesed by he aoremenioned

evoluion o insecicide chemisry, synheic organic

chemical herbicides invened circa WWII allowed or

biological seleciviy beween animals and plans bu

also wihin he Plan ingdom isel.

By he lae 1950s, he mos inensely used pes-

icide o all ime, arazine, was synhesized and dis-

covered o have only one biochemical effec a field

applicaion raesnamely, inhibiion o a paricular

elecron accepor in Phoosysem II o plans. Ara-

zines poency is selecively limied o broadlea weeds

bu has no aciviy agains grasses like corn. o curail

a long sory, herbicide synhesis coninued o produce

compounds wih oher modes o acion specific o

and aquaic inverebraes (able 2, Figures 2-5). Wih

some excepions, hese chemicals ended o be more

selecive or killing pess raher han predaors. Tus,

even more opporuniy arose or compaibly inegra-

ing hese new chemisries ino programs ha wouldry o deploy ecologically-based, inegraed pes man-

agemen sraegies.

Te hisorical use o herbicides and he evoluion

o chemical classes parallel ha o he insecicides

wih a major excepion. Prior o WWII, abou he only

herbicides available ha could be pracically used on

fields were dinirophenolic compounds like dinoseb

and DNOC. Tese uncouplers o oxidaive phosphory-

laion had a general mechanism o oxiciy ha made

hem nonselecive or weeds, insecs, and ungi. How-

ever, by he 1940s 2,4-D was discovered and ound o

mimic he naural plan hormone auxin (indole-3-aceic

acid), ushering in he discovery o a very specific plan

mechanism o oxic acion. Tus, biological aciviy

a field applicaion raes was only applicable o plans

and no animals. Surprisingly, 2,4-D was only oxic o

cerain dicoyledon (broadlea) plans. Tus, 2,4-D

Table 2. Comparative mammalian toxicity of insecticides registered over the last

decade and designated as reduced risk by EPA.

Active

Ingredient

Commercial

Formulation

Oral LD50

(mg/kg)

Dermal LD50

(mg/kg)

NOAEL

(mg/kg/d)

Azinphos-methyl Guthion 4.4 155 0.149

Chlorpyrifos Lorsban 223 222 0.03

Acetamiprid Assail 1064 >2000 7.1

Indoxacarb Advion 1277 >5000 2

Pyriproxyfen Esteem 4253 >2000 35Methoxyfenozide Intrepid >5000 >2000 10.2

Novaluron Rimon >5000 >2000 1.1

Pymetrozine Fulfil >5000 >2000 0.377

Spinosad Success >5000 >2000 2.7

Rynaxypyr Altacor >5000 >5000 158

o place he concep o reduced risk in perspecive, parameers or azinphos-mehyl and chlorpyrios are shown because hese were

developed prior o EPAs iniiaive, saed in P Noice 93-2 (EPA 1993).


25/76


26/76


27/76

21

recepor or any ineracion o occur. In addiion o

srucure, molecular ineracions are also influenced

by physicochemical properies relaed o molecular

charges and hydrophobiciy. Such ineracions oc-

cur very readily i he srucures o a oxican and is

recepor are highly complemenary. In such cases, he

subsance is considered highly poen. Ineracionswould occur wih srucures no as complemenary

only under condiions o inordinaely high oxican

concenraions, ypically hose no likely o be ound

in he environmen bu cerainly possible o creae

in he lab when animals are esed. A oxican requir-

ing exremely high concenraions in order o have

an ineracion wih an enzyme or recepor, and hus

cause an adverse physiological reacion, would be

considered o have low poency. In summary, hen,

oxiciy is a propery inheren o any molecule, allow-ing i o elici an adverse physiological response when

an organism has specific enzymes, recepors, or oher

macromolecules whose hree-dimensional srucures

are complemenary.

Te naure o undamenal hermodynamic and ki-

neic laws governing chemical ineracions prescribes

ha any molecule could, hypoheically, inerac wih

Ulimaely, consumers wan o know wheher any

echnology is sae. Te concep o chemical saey

among regulaory oxicologiss is undersood no as a

quaniaive uniary concep bu raher as a descripion

o a probabiliy o a reasonable cerainy o no harm.

Te validiy o he concep o reasonable cerainy o

no harm, which is acually more science policy hanscience, depends on a disincion among he erms

oxiciy, hazard, and risk. Disinguishing hese

erms and, moreover, defining hem rom a biochemi-

cal perspecive, is crucial or a raional argumen abou

he naure o pesicide use in modern sociey.

oxiciy is an inheren propery o boh a paricu-

lar molecule (called he subsrae or ligand) and any

organismal enzymes or recepors (issue cell macro-

molecules) ha i can reac or inerac wih. Such in-

eracion resuls in a physiological reacion ha couldbe inimical o he survival o an organism, and hus

he subsrae or ligand would be called a oxican. By

definiion, pesicides are inimical o he lives o pess,

hus pesicides are oxicans. Te concep o inheren

propery reers o he ac ha he hree-dimensional

srucure o any oxican mus be complemenary

o he hree dimensional srucure o an enzyme or

Its Still About the Dose(and Timing)

Myths: Exposure o pesicides resuls in adverse healh effecs. Hazards o pesicidesare equivalen o he risk o adverse effecs.

The Reality of A Modern Biochemical Perspectiveon Toxic ity, Hazard, and Ri sk


28/76

22

I t s St i l l About the Dose (and Timin g)

reacion o do somehing abou i? We are cauious by

naure and hus wan o be careul when we have knowl-

edge o poenial harm. Te problem is knowing he

appropriae amoun o resources (financial, inellecual,

ec.) o expend on managing wha may be only poen-ial harm, sincebecause hazard is conexuali may

never be maniesed, or i may be maniesed only under

he mos exreme condiions o chemical use.

o judge jus how worried we should be abou a

oxican in he environmen, and hereore allocae

he appropriae atenion o is hazardousness, we

have o undersand he risk o adverse effec. isk is

also conexual, bu a simple definiion is he prob-

abiliy (likelihood) ha adverse effecs would occur

under a specific siuaion or se o condiions. Ofen,

regulaory oxicologiss will express risk as a uncion

o oxiciy and exposure. Tus, risk is he probabil-

iy or likelihood ha he array o known hazards o a

subsance will acually occur i or when an organism

is exposed. I exposure is nonexisen, hen he likeli-

hood o an effec is nil. I exposure does occur, hen

he likelihood o he subsance being a hazard is con-

diioned no only on he dose bu also on he age, gen-

der, and healh o ha organism as well as he specificroue o exposure. Te imporan poin is ha he risk

o adverse effecs afer exposure o a subsance may be

low or high, depending on all he acors affecing he

hazards o ha subsance.

Thresholds

Low levels o exposure, even o a highly poen

oxican, may have a low probabiliy o causing an ad-verse effec. In any case o exposure, wheher hrough

skin conac, inhalaion, or oral ingesion, a number o

physiological processes occur o modulae he dose or

concenraion o oxican arriving a he cellular level,

and hus he probabiliy o ineracion wih enzymes

or recepors. All o hese physiological processes ha

deermine wha amoun o oxican arrives a he sie

o he cell enzymes or recepors is described by phar-

any oher molecule. However, he concenraion o he

wo molecules mus be sufficienly high or he iner-

acion o have any reasonable probabiliy o occurring.

Tis later concep leads o he definiion o hazard.

Hazard describes he poenial o a chemical o causeharm under a paricular se o condiions. In oher

words, oxicans are no inherenly hazardous unless

he conex is conducive o he sufficien ineracion o

he oxican wih he paricular enzymes or recepors

o which i is complemenary. o sudy how chemicals

inerac wih organisms, scieniss in he laboraory

always creae condiions in which he subjec chemical

will be hazardous. Ofen he condiions are concen-

raions (or doses) o chemical sufficien o cause an

observable response in a es populaion o organisms.

I he condiions o he exposure change (or example,

using a very low dose) hen he hazard may change or

simply disappear alogeher.

Experimens repeaedly show ha naural and

synheic subsances a one dose may have no adverse

effecs on an organism, bu a anoher higher dose can

cause harm. Tis concep, requenly called he dose

makes he poison, is he undamenal principle guid-

ing oxicological sudies, and i is discussed in all basicoxicology exbooks. O course, ha popular oxico-

logical aphorism belies more complex ineracions

beween a subsance and is effecs on an organism.

Te dose required o cause deleerious effecs wihin

a populaion o organisms can vary depending on he

roue o exposure (oral, dermal, or inhalaional), he

lengh o ime over which i is adminisered (acue

versus chronic), and he age, sex, and healh o an or-

ganism. Neverheless, he appearance or magniude o

an effec o any subsance is ied o is dose. Hazard,

hereore, can be hough o as a subsances dose-rela-

ed array o possible deleerious effecs on an organism

o a specific age, gender, and healh saus exposed via

oral, dermal, and/or inhalaional pahways.

Should he knowledge ha a subsance is hazard-

ous, i.e., poenially harmul under a specific se o cir-

cumsances, precipiae a corresponding (and urgen)


29/76

23


esearchers sudying he ineracion o oxicans

wih whole animals (in vivosudies) or wih animal

issues, cells, and macromolecules (in viro sudies)

atemp o esablish a hreshold or a physiological or

biochemical reacion. Tey use a wide range o doses(exposures) and concenraions. Te hreshold is

ofen repored as an empirical dose level in which no

observable adverse effec (i.e., he NOAEL) occurs.

o deermine he NOAEL, however, he researcher

mus expose an animal o sufficienly high concenra-

ions o see wha a ypical response looks like. Te

dose jus causing a reacion is called he LOAEL

(lowes observable adverse effecs level). For any

one specific response, he proporion o animals re-

sponding orms a monoonic uncional relaionship

wih he dose ha is mahemaically depiced as an

S-shaped curve (Figure 6). For any effec, hereore,

he researcher can esimae he proporion o he

populaion responding o a paricular dose. Similarly,

he researcher can esimae when no responses in a

populaion will occur.

macokineics. Pharmacokineic sudies examine rae

and exen o chemical upake processes ollowing

dermal, oral, and inhalaional exposures. Te amoun

o oxican enering ino he sysemic circulaion

(bloodsream) is sudied and hen ollowed o issubsequen disribuion among all body regions down

o he cellular level. Te oxican amoun changes as i

is degraded by enzyme sysems and excreed (some-

imes unalered) rom he body. Whaever oxican

is lef over rom all hese pharmacokineic processes

arrives a he sie o he poenial enzymes or recep-

ors complemenary enough in srucure o have any

probabiliy o ineracion. Te specific ineracions are

called pharmacodynamics.

Te combinaion o pharmacokineic processes

and he kineics o pharmacodynamic ineracions

may resul in adverse physiological effecs. Generally

speaking, he physiological sysems mos ofen sud-

ied are he nervous and endocrine sysem, alhough

he immune sysem is necessarily included because

hese hree sysems communicae wih one anoher.

Te relaionship can be expressed as he numbers responding o any given dose meric. I he numbers are ransormed o he cumulaive

proporion (i.e., percen) o he populaion responding, hen an S-shaped curve resuls, which can be described by a logisic mahemaical

uncion. A some dose, no measurable response is observed, and his dose is designaed he no observable adverse effec level (NOAEL)

or concenraion (NOAEC). Te LOAEL represens he dose a which an adverse effec is saisically significanly differen rom he

response in he conrol. Te LD50 and ED50 represen he median response in he populaion (i.e., 50% response) or eiher lehaliy

(L) or any oher measured response (E).

Dose (mg/kg)or Concentration (mg/L)

NumbersResponding

50% Response (median)

PopulationResponse

(Cumulative%)

Dose (mg/kg)or Concentration (mg/L)

100%

50%

0%

Slope

LOAEL

NOAEL

LD50

; LC50

ED50

; EC50

Figure 6. Typical monotonic relationship between increasing dose

(or concentration) and population response.


30/76

24

I t s St i l l About the Dose (and Timin g)

cal exposure in he environmen (i.e., ouside o he

laboraory).

In summary, hen, he oxiciy o a chemical is an

inheren propery relaed o is srucural abiliy o in-

erac wih some complemenary enzyme or receporin a cell. I he srucures are highly complemenary,

such ha he probabiliy o ineracion is high, hen he

oxican is considered highly poen; bu i srucural

complemenariy is low, he oxican has low poency.

egardless o poency, pharmacokineic processes

modiy he probabiliy o pharmacodynamic inerac-

ions, and hus all oxicans have hresholds or an

effec. Perinenly, hese ineracions and hresholds

apply o all chemicals, naural and synheic, because

all are under conrol o he undamenal laws o her-

modynamics and kineics.

Te ype o experimen ha allows consrucion

o he aoremenioned dose-response curves and de-

erminaion o a no-effecs hreshold alls under he

rubric o regulaory oxicology. Tese experimens

are mos useul or assessing risk o an adverse effecollowing exposure under environmenal condiions.

Furhermore, experimens ha atemp o define a

hreshold or an effec are quie differen in objecive

han experimens ha are designed o undersand

he mechanism o an effec. Tese later experimens

dominae he published oxicology lieraure oday.

However, hose experimens necessarily use high

enough doses so ha an effec is always maniesed

and can hereore be sudied. Alhough inormaive

rom he perspecive o a basic biochemical under-

sanding, mechanisic experimens are no very useul

or characerizing he risk o effecs ollowing chemi-


31/76

25

consrained by undamenal laws o hermodynamics

and kineics. More specifically, over he las several

decades, oxicological ocus has shifed rom carci-

nogenic responses o endocrine sysem responses.

Whereas he 1950s hrough he 1980s ocused on car-cinogenic mechanisms largely ied o ineracions wih

he genome, during he ime beween he lae1980s

and now, ocus has shifed o chemicals (synheic and

naural) and heir ineracions wih recepors o he

endocrine sysem. A firs, he esrogen recepor, ow-

ing o inense ineres in reproducive biology, was he

objec o mos scruiny, bu now he esoserone (i.e.,

androgen) and hyroid recepors have been hrown

ino he mix.A handul o sudies puaively indicaing ha

chemicals a very low levels o exposure could resul in

endocrine-mediaed aleraions in issues o neonaal

rodens, especially male prosae gland srucure, sug-

gesed ha a new perspecive on oxicans was needed

(vom Saal e al. 1997). O course, ones percepion

o wha consiues a low dose requires empering

by how he dose is adminisered and a query as o

In he hisory o biology, hose remembered by

poseriy are individuals who have creaed a paradigm

shif in hinking abou undamenal lie processes.

Perhaps a he pinnacle o paradigm shifers is Charles

Darwin. Indeed, an ofen-quoed paraphrase is noh-ing in biology makes sense excep in he ligh o evolu-

ion (Dobzhansky 1964), and o course we have Dar-

win o hank or generaing a line o inquiry leading o

he modern heory o biological evoluion. Cracking

he geneic code, ollowing he discovery o he sruc-

ure o DNA, resuled in a plehora o new mehods o

sudy how lie works a he molecular level. O course,

as we sudy differen levels o organizaion, rom cells

o issues o organs o whole organisms, new proper-ies emerge ha are increasingly difficul o describe in

simple molecular erms.

In he conex o biological hisory, perhaps we

shouldn be surprised ha some researchers would

enjoy being called paradigm shifers. However, chang-

ing he ocus o sudy rom one physiological sysem

o anoher is no a paradigm shif, because all possible

ineracions o oxicans in he new sysem are sill

Endocrine Disruption:Is It Just Hormonal?

Myth: Consideraion o endocrine disrupion changes he paradigm o wha weknow abou pesicide effecs. Dose makes he poison is no longer relevan because

pesicides affec he endocrine sysem a levels equivalen o environmenal exposures.

The Reality:Confusion Between a Changing Paradigmand a Shift in Focus, Away from Cancer, to a DifferentPhysiological System


32/76

26

Endocrine Disrupt ion: Is I t Jus t Hormonal?

are incredibly low i he ligand concenraion is low.

Similarly, ligand-recepor ineracions are reduced

and slowed down as a chemicals poency decreases

(Figure 9). Tereore, no paradigm has really shifed.

ecall he premise ha mechanisic sudies are no de-

signed o show he hreshold level o plausible effecs.

Ye reexaminaion o Figure 7 does show a definiive

hreshold (i.e., a 0.002 g/kg), even or he drug DES,

arguably o similar or greaer poency o esrogen in

binding o he esrogen recepor (Okluicz and Leavit

1988; Hendry e al. 1999, 2004).

wheher he specified dose was chosen, because any

dose lower would no resul in he measured effec a

all. In addiion o observaions o a sligh difference in

male prosae gland weigh beween dosed and conrol

animals (vom Saal e al. 1997), as one example o anendocrine sysem paradigm-changing effec, he dose-

response relaionship accompanying he observaion

was nonmonoonic. In oher words, he observed e-

ecs on gland weigh did no vary in a locksep linear

ashion wih increasing doses (Figure 7). Te high-

es dose caused loss o gland weigh and mid-doses

caused increase in gland weigh. Te validiy o he

conclusions o hese early repors has been quesioned

on grounds o saisical inadequacies (Haseman e al.

2001) or have been judged inconclusive, imprecise,

and o uncerain biological relevance (Melnick e

al. 2002). Neverheless, he problem in inerpreing

nonmonoonic responses arises when wo differen

physiological phenomena are acually being measured

by he same endpoin, such as gland weigh changes.

For example, no pahology oher han gland weigh

changes may occur a low doses, bu a high doses

oxiciy may se in and gland weigh changes are ac-

ually due o a differen phenomenon, such as grealyincreased cell deah.

egardless o he cause o a nonmonoonic re-

sponse (assuming he same physiological response is

acually being measured on each side o he dosage

range), recepor (e.g., esrogen recepor) ineracions

wih ligands (e.g., esrogen or a oxican) are governed

by he principles o biochemical kineics. Tus, he

paradigm has no shifed; concenraion o he ligand

sill influences recepor-ligand complexaion. ineic

analyses o molecule-molecule ineracions can show

he probabiliy o hose ineracions as a uncion o

dose (or concenraion). An illusraion o his con-

cep can help dispel he myh ha low doses rom

environmenal exposures o hormonally acive agens

are inordinaely hazardous. Tus, Figure 8 shows ha

ligand-recepor complexes, he kineic mechanism ini-

iaing a hormonally induced physiological response,

140

120

100

80

60

40

20

00 0.002 0.02 0.2 2 20 200

ProstateGlandChange

RelativetoControl(%)

Diethylstilbestrol Dose (g/kg body weight)

A A

B

B

B AB

C

DES, a drug given o reduce miscarriages during he 1960s, and

also used as a simulaory hormone in catle eed, has a poency

similar in magniude o ha o esradiol. Tis graph is based

on he one presened in vom Saal e al. (1997) ha arguably

iniiaed concerns abou nonmonoonic effecs o hormonally

acive agens. Te daa are shown as percenage change in gland

weigh relaive o he conrol (100%), and he graph has been

rescaled o sar rom zero change. Bars wih he same leters

are no significanly differen rom one anoher (probably

pesticides and health myth vs realities

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