Pesticide Exposure and Human Health (Part 3)DONNA L. HOUGHTON, Ph.D., SYNGENTA CROP PROTECTION CAN. INC.

his final article of a three-part se-ries will address allegations thatpesticide exposure causes asthma,disruption of endocrine (hormone)systems, and neurological effects

in children. Suggestions regarding expo-sure mitigation will be provided, as wellas conclusions pertaining to the entirethree-part series. References are footnotedin the text and are available on requestfrom the Sports Turf Association. Parts Iand II of the series were published in theprevious two issues of the Sports TurfManager and can be viewed online atwww.sportsturfassociation.com.

Pesticide Exposure and AsthmaMany articles in the press have stated

that pesticide exposure is responsible foran increase in the incidence of asthma inchildren. While the rate of occurrence ofasthma, particularly among children, hasbeen rising over the past decade, there isno definitive evidence that pesticide ex-posure contributes to the frequency of thisdisease'? 11. The increase itself is some-what confusing because physicians havelong debated which symptoms warrant adiagnosis of asthma. In addition, aware-ness of the disease has grown which couldaccount for a portion of the reported in-crease.

Research indicates that factors knownto cause or exacerbate asthma are as fol-lows: a family history of the disease, gen-der (males are more prone), and exposureto tobacco smoke, household dust, dustmites, cockroach integuments and feces,and damp environments 10, 12. Diet may alsoplaya role. The fact that we have tightlysealed homes is an issue.

Recent research is suggesting that it isan underdeveloped immune system thatis responsible for the development ofasthma in children. Current thinking sug-gests that we are actually keeping our en-vironments too clean. Challenges to theimmune system early in life (exposuresto viruses, bacteria, animal dander, dog

hair, dust, etc.) are required for properdevelopment of the immune system 13.

Through the frequent use of antibiotics,and keeping our homes extremely clean,we may have prevented the immune sys-tems of many children from developingappropriately.

Children from rural areas, where pesti-cides are commonly used, have a muchlower incidence of asthma than childrenfrom urban environments 14,15. Farm chil-dren are exposed to dander from pets andfarm animals, as well as pollens, dust anddirt from an early age. There is no defini-tive evidence to indicate that pesticidesincrease the incidence of asthma in chil-dren. The use of pesticides may actuallyhelp to alleviate allergic reactions amongindividuals whose condition is made moreserious by exposure to weed pollen.

Endocrine Disrupting Chemicals(Hormone mimics)

For the past decade, the news has beenflooded with articles on endocrine disrupt-ing substances and the havoc they are cre-ating in the environment and potentiallyin our children; however, the scientific lit-erature does not support effects in humans.Pesticides have been implicated in themedia as endocrine disrupting substances.Almost everything, including the food weeat, contains natural chemicals that act likehormones.

The endocrine system is extremely sen-sitive and can even be affected by theamount of daylight received by the livingorganism. It will be extremely difficult tosort out what affects, and what doesn'taffect, hormone systems because manythings (natural and man-made) influencethe endocrine system.

W.J. Waddell, an MD, professor, andChair of the Dept. of Pharmacology andToxicology at the University of LouisvilleSchool of Medicine, published a reviewof epidemiology studies and the effects ofenvironmental estrogens and concluded"the data available at present do not lead

to the conclusion that endocrine-modulat-ing substances account for worldwidetrends in these epidemiological studies'?'.

While some researchers have hypoth-esized that pesticides act as hormones inthe environment, a direct association atenvironmentally relevant concentrationshas not been established; In addition, ex-posure to pesticides is extremely low incomparison with exposure to endogenoushormones such as 17- B estradiol andestrone, naturally occurring hormonessuch as estrogen (e.g. phytoestrogens infood such as cabbage), and therapeutichormone supplementation (e.g. hormonereplacement therapy and contraceptives);therefore, this hypothesis is unlikely.Wood and paper products also containestrogenic substances of natural origin.

Dr. Stephen Safe, of Texas A&M, hasauthored many papers indicating that theendocrine modulating hypothesis isflawed'"". His publications also point outflaws in the hypothesis that endocrine-dis-rupting industrial chemicals have causeda reduction in sperm counts among men.

The National Research Council (NRC)Report on "l'Hormonally active agents(HAAs) in the environment" concludedthat prenatal exposure to HAAs may af-

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feet development and nervous system de-velopment but more research is required'".The report stated that data available areinadequate to assess whether exposure af-fects immune systems in humans and con-cluded that post-natal exposure to HAAshas been shown not to increase the risk ofcancer in endocrine organs.

While more research is certainlyneeded on this controversial subject, theexposure incurred by applicators and by-standers to pesticides is so minimal thatan association between pesticides and en-docrine effects in humans is unlikely.

Pesticides and NeurologicalEffects in Children

A 1998 study conducted by Guilletteet al. suggested that pesticide exposurecauses effects on the developmental/neu-romuscular function and fine motor skillsin children". The authors studied childrenof two separate villages in Mexico - onelocated in an agricultural valley wherepesticides were used frequently, and theother located in the foothills where ranch-

ing was practiced and pesticides were notusually sprayed.

There are many flaws in this study in-cluding lack of proof of the genetic simi-larity of the two populations studied andfailure to conduct chemical analyses offood, water, environment, blood or urineto confirm pesticide exposure and to ruleout the possible contribution of other con-taminants such as PCBs which are knownto cause neurological impairment.

The children of the two villages do ap-pear to differ in terms of their fine motorskills and neurological development; how-ever, the data do not prove that pesticideexposure is the cause of the difference.Eye exams were not even given to the par-ticipants. Guillette et al. did not collectsamples to identify what substances thechildren were actually exposed to, nor didthey attempt to adjust or identify con-founding factors such as parental alcohol

and drug abuse, parenting skills, level ofparental education, genetics, etc.

Exposure MitigationThe best way to mitigate occupational

exposure to pesticides applied to turf is toread and follow the label directions, ap-ply the correct application rate, wear therecommended personal protective equip-ment (gloves, respirator, chemical-resist-ant coveralls, etc.), change respiratorcartridges frequently, launder clothingdaily and follow proper hygiene practices.

To reduce bystander exposure to pesti-cide treated turf, the recommended appli-cation rate should never be exceeded,spraying should never occur during con-ditions conducive to drift, surfaces mustbe dry before allowing contact with treatedturf (obey re-entry intervals), and bystand-ers must not be allowed in the area whenpesticides are being applied.

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Conclusions (of this three partseries)

Pesticides are thoroughly tested and thedata are reviewed by the Canadian PestManagement Regulatory Agency (PMRA)prior to registration. Pesticide productsthat PMRA concludes have incompletedatabases or that cannot be used safely arenot granted registration and cannot besold, imported, or used in Canada. Ourcountry has the most stringent regulatoryrequirements in the world. Pesticides, likeprescription drugs, can be used safely,provided label directions are followed.The recommended personal protectiveequipment should always be worn whenhandling and applying pesticides.

The benefits of using pesticides on turfinclude reduced potential for allergic re-actions caused by weed pollen and insectstings and bites, positive health benefitsassociated with increased participation inoutdoor sports such as soccer and golf,fewer sports injuries, reduced soil erosionresulting in less pollution of waterwaysetc., and the psychological benefits ofimproved aesthetics. The use of pesticideson residential property is a matter of per-sonal choice which should be respected.

Reviews of sound, scientific, peer-re-viewed data indicate that allegations sug-gesting occupational and bystanderexposure to pesticides is associated withhealth effects such as asthma, cancer, en-docrine disruption, developmental effectsand neurological impairment in children,is currently unfounded. Unfortunately, themedia's presentation of possible associa-tions between pesticide use and health ef-fects has served to create an irrational fearabout pesticides among the general public.

As mentioned in Part 1 of this article,any pesticide ban approved by a munici-pality is a political decision based on emo-tion and not one based on sound science.This fact should be clearly communicatedto the constituents of the municipalitiesinvolved .•

Editor's Note: The STA thanks Dr.Houghton for her informative article onPesticide Exposure and Human Health.Our appreciation is extended to her for notonly sharing her expertise but for all thetime and energy spent in editing this infor-mation into three parts.

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