Document 1



M E M O / N O T E  D E  S E R V I C E




To / Destinataire

Steve Kanellakos

Deputy City Manager, Community & Protective Services
Ned Lathrop

Deputy City Manager, Planning and Growth Management

From / Expéditeur

Dr. Robert Cushman

Medical Officer of Health


Subject / Objet

Update from the Medical Officer of Health on Cosmetic Use of Pesticides

Date: 19 August 2005



The Board of Health (City Council) has requested an update from the Medical Officer of Health (MOH) regarding the health effects of pesticides. Initially, this was to be released this fall prior to public consultation on the pesticide-free by-law. As those timelines fall after I leave the post of Medical Officer of Health to become the head of our Local Health Integration Network, I have made every effort to complete the work before my departure and am forwarding this information for you to present to City Council on my behalf. 




In December 2002, after hearing many hours of public debate on whether to pass a by-law prohibiting the cosmetic use of pesticides on lawns and gardens, Ottawa City Council approved a three-year public education campaign to reduce pesticide use which included mass media advertising, workshops on using alternatives to pesticides and surveys of current practices.  At the end of the three-year period, in the fall of 2005, City Council will discuss the implementation of a by-law prohibiting the cosmetic use of pesticides.


As has been stated, City Council, as the Board of Health, has also requested an update from the Medical Officer of Health (MOH) regarding the health effects of pesticides to help inform their debate.


This report provides a survey of the latest scientific evidence and offers the opinion of the MOH on the cosmetic use of pesticides, to be forwarded to the Board of Health for their consideration.




Review Methodology:


Research on the health effects of pesticides is complex. Because we don’t yet have a clear understanding of exposure risks, a variety of research on this matter must be taken into account. Taken together, hundreds of studies on pesticide exposure paint a disturbing picture. As much as we would like scientific exploration to be an easy task, this is a complex issue, and no single study will provide all the answers.


This report is not a full literature review, as that is beyond its scope. However, two recent, comprehensive reports on the health effects of pesticides are available. City Council, as the Board of Health, should be aware of these studies and their conclusions.


·        Former Toronto Medical Officer of Health Dr. Sheela Basrur, wrote an in-depth report in 2002 following a review of the scientific literature entitled “Lawn and Garden Pesticides: A Review of Human Exposure and Health Effects Research.”[1] The Toronto analysis concluded: “the evidence is persuasive that the greater susceptibility of pregnant women and foetuses, infants, children and the elderly justifies prudent avoidance and precautionary reasons to limit unnecessary exposure to pesticides for these vulnerable subpopulations.”  Soon after this report was released, the City of Toronto passed legislation to ban the cosmetic use of pesticides.


·        In 2004, after examining the results of hundreds of international studies, the Ontario College of Family Physicians judged that “evidence for harm is strong.”[2]  The College went on to publicize warnings about pesticides and encourage its physician membership to advise patients to reduce exposure to pesticides; supply information about organic methods; educate on the high skin absorption of pesticides; and offer instruction on the use of respirators for in home and occupational exposures. 


Included in this report is a summary of relevant, methodologically sound studies offering new insights. Much of the research is based on occupational studies, which are germane for several reasons – many of the chemicals used on farms are also used on lawns and gardens; occupational outcomes may serve as an advance warning to the population as a whole; and pesticide appliers should be aware of the potential health risks imposed by their jobs.


The research and policy challenge is to determine to what extent findings from the occupational setting can be applied to residential exposure rates. One cannot discount the information on the grounds that the exposure is minimal by comparison. For example, first, the volume of pesticides used per hectare in residential areas has been found to be greater than that in agricultural areas.[3] Second, residents may not protect themselves with safety equipment available to workers. Third, evidence shows that certain people are more vulnerable to the effects of pesticides (i.e. children, pregnant women and people with environmental sensitivities), meaning that even a relatively small dose may place them at greater risk for disease. And lastly, emerging literature on residential exposures and exposures to specific pesticides used on lawns - while in its infancy - has begun to identify disease risks such as a miscarriages, birth defects, leukemia and Parkinson’s disease.    


It is important to note that the following limits to current research would tend to underestimate health risks associated with pesticides:


·        Inadequate follow-up time – Because there is a long lag time between exposure and disease, many studies simply don’t follow subjects long enough to get a full picture.  


·        No unexposed control group – As is made clear by body burden data, virtually everyone is exposed to pesticides, making it difficult to find a study control group from which to make a decent comparison. 


·        A healthy worker effect – It is well known that people too ill to work leave the workforce and thus are often excluded from occupational health studies. An inherent bias exists because workers tend to be healthier than the general population.


·        Multiple exposures, multiple disease outcomes – The complexity of the interactions makes it difficult to assess direct causal relationships. One problem is determining which pesticides people have been exposed to.  However, newer and more sophisticated technology, such as measuring pesticides in umbilical cord blood, is allowing for more targeted research. Furthermore, now that we know which diseases are implicated, we can focus our research better.


·        Mortality vs. incidence – Most studies focus on death rates (mortality) and don’t consider people surviving with a disease (incidence). In one of the few studies measuring incidence, Florida researchers uncovered significantly elevated incidences of three of the more treatable cancers - prostate, testicular and cervical. (Fleming et al, 1999.)[4] With better diagnosis and treatments available, adverse effects can be missed in morality-only studies.


Arguably, the history of smoking may offer a parallel where the health impacts of second-hand smoke (a reduced exposure) became known some 20 to 40 years after the effects of smoking first-hand.


Finally, the current views of the federal Pest Management Regulatory Agency were considered. A common line of reasoning is that since pesticides are legal, they must be safe. This assumption ignores problems associated with our federal regulatory agency, including chronic under funding and an over-reliance on industry science.


City Council should be aware that the Office of the Auditor General of Canada has been extremely critical of the federal Pest Management Regulatory Agency. A 2003 audit said, “the federal government is not adequately ensuring that many pesticides used in Canada meet current standards for protecting health and the quality of the environment.”[5]


The audit also reported that:

·        Health Canada has done only limited research on the health effects of pesticides despite the federal government‘s stated priority in this area. It has very limited dedicated funding for research on human exposure to pesticides or the resulting health effects. Three researchers are working on current pesticides, and they rely primarily on outside funding. The Pest Management Regulation Agency did not receive the funding it originally expected.


·        Required steps are not always followed. Auditors found that evaluators often expedited the submission, cut the scientific review short, or skipped the public consultation stage.


·        Progress made in re-evaluating older, widely used pesticides has been very slow. In addition, all pesticides re-evaluated were either removed from the market or had greater restrictions placed on them.


·        For studies such as toxicological assessments, potential registrants are to provide results generated by laboratories inspected periodically by an independent body. There were several examples noted when studies meeting such quality standards were not provided.


·        Regulations stipulate that temporary registrations may be approved for up to a year. Yet over the last six years, more than 370 temporary registrations were extended and, in most cases, more than once – some up to five times. “We are concerned about the heavy and repeated use of temporary and emergency registrations,” stated the auditors.


·        Agency staff assume pesticides and users will follow label instructions, although the Agency’s own compliance reports show that they may not. “Other studies have documented only partial compliance with requirements to use personal protective equipment.”


·        In several cases, measures listed on pesticide labels, even if followed, appear not to have been enough to prevent environmental damage. For example, in P.E.I. more than 20 instances of fish kill since 1994 have been attributed to pesticides, with up to 35,000 dead fish collected in each incident.





It is worthwhile, at this point, to remind ourselves exactly what a pesticide is and what it is designed to do.


Pesticides are manufactured to interrupt biological systems and kill living species. This is obviously a concern because humans share many genetic and physiological characteristics with other organisms. Some pesticides inhibit important enzymes of an insect’s nervous system; others upset the normal hormonal balance that regulates cell division, protein synthesis, and respiration – important functions at the micro level shared by all members of the plant and animal kingdoms.


Pesticides can have acute (short-term) or chronic (long-term) effects. Acute pesticide poisonings underline the toxic nature of the chemicals. Such poisonings may result in effects ranging from diarrhea to nerve damage. ‘Seizures are characteristic of poisoning with 19 different pesticides and may occur with 12 others, including 2,4 D and the organophosphate and carbamate insecticides commonly used on lawns and gardens.’ (Sanborn et al, 2002).[6]


These products were intended for carefully applied industrial and agricultural use rather than as household products for everyday purposes. No one can discount the contributions pesticides have made in the modern age, such as reliable crop production and malaria control. However, the question before the Board of Health is whether cosmetic pesticide use is safe in residential settings where children play.


Vulnerable Populations:

a) Prenatal and Children

Researchers are learning that the timing of pesticide exposure is crucial in assessing risk. ‘Critical exposure windows’ may include the months just prior to conception or during pregnancy. The effects of exposure during pregnancy may show up decades later; since a woman’s eggs are formed during fetal development, a woman’s exposure could jeopardize the health of her grandchild – creating a health hazard across three generations.


·        An American study investigating cardiovascular malformations found a significant association between pesticide exposure in the womb and a heart defect called transposition of the great arteries. (Loffredo et al, 2001)[7].


·        Ma et al (2002)[8], investigating childhood leukemia, found that indoor pesticide exposures early in life appeared to be more significant than later exposures, and the highest risk was observed for exposure during pregnancy. It must be noted that this study found no association with outdoor pesticide use – the issue under discussion – but serves to illustrate the importance of timing of exposure, raising questions about leukemia as a fetal disease in some cases.   


·        Several studies suggest that the fetus clears toxicants less efficiently than the adult and may be more vulnerable to genetic damage and the resultant risk of cancer. In addition, the human nervous system involves an “exquisitely sensitive process. . . the production of 100 billion nerve cells and 1 trillion glial cells, which then must follow a precise stepwise choreography,” writes Perera et al (2002)[9]. “A mistake at any one step can have permanent consequences.”


·        Children, too, are disproportionately affected. For instance, their hand-to-mouth behaviour and play on the ground increases exposure; their organs are immature and therefore can’t manage toxins as well; and their longer future life span allows more time for diseases to arise. (Note also that people and pets track pesticides indoors on their shoes, inadvertently exposing children).


b) Vulnerable gene traits

People with certain gene traits called ‘polymorphisms’ seem more susceptible to the harmful effects of pesticides. This ‘polymorphism’ phenomenon has been studied on the pesticide question, as illustrated by the following examples:


·        A Montreal study looked at children exposed in the womb to residential (including outdoor) pesticides and found they were at higher risk for childhood leukemia when they carried certain gene mutations that lower one’s ability to detoxify cancer-causing agents (Infante-Rivard, 2001)[10].


·        For people exposed to pesticides in gardening and professional use, the risk of Parkinson’s disease was increased two-fold among those with ‘poor-metabolizing’ genes. (Elbaz et al, 2004)[11]. These ‘poor metabolizers’ have difficulty ridding their bodies of specific poisons including pesticides. The study also noted that in the absence of pesticide exposures, ‘poor metabolizers’ were not at increased risk for Parkinson’s disease.


Since we currently have a limited understanding of genetic polymorphisms, and because these particular gene mutations are relatively common, it is important to protect the population as a whole.



Another poorly understood yet important phenomenon is ‘synergism,’ where a mixture of pesticide exposures creates more total harm than the sum of the individual pesticide exposures. In other words, multiple interacting problems may push a person over a certain threshold. As well, some people are more vulnerable to pesticide exposure because of unrelated risk factors, such as age or family history, that are associated with certain illnesses. Because of these interactions, the heavily relied-upon animal toxicity studies (while important) suffer from limitations in terms of measuring human risk. The following two studies exemplify research that takes into account the complex web in which we live.


·        A study found Ontario farm women were at higher risk for spontaneous abortion (miscarriage) if exposed in the months prior to conception to certain pesticides including 2,4 D. (Arbuckle, 2001)[12]. In addition, the researchers noted women were at much higher risk of miscarriage if they were 35 years of age or older and exposed to a combination of pesticides rather than a single pesticide. Older women exposed to the pesticides carbaryl and 2,4 D had 27 times the risk of spontaneous abortion compared to similar women exposed only to carbaryl.


·        Complicating the picture is that regulators do not adequately study the many chemicals associated with the manufacture and environmental breakdown of pesticides. These include formulants (non-active ingredients), breakdown products and contaminants from the manufacturing process such as dioxins.   


·        Additional risk factors can place a person in the vulnerable category. A good example is an investigation by Alavanja et al (2003)[13], who discovered that ‘significant associations between specific pesticides and prostate cancer risk were observed largely among those with a family history of prostate cancer.’ This finding is important because prostate cancer is the most common malignancy among Canadian men, and despite its common occurrence, its cause remains largely unknown. 



It is increasingly recognized that many diseases are the result of complex gene-environment interactions.  In fact, a number of research studies have found an association between pesticide exposure and genotoxicity (DNA damage). Such damage may be a precursor to cancer and other illnesses. Since genes are the human blueprint, the relationship between genotoxicity and pesticide exposure is concerning and needs further exploration.


·        For instance, Garry et al (1996) found that pesticide appliers were more likely to have specific chromosomal breaks and ‘rearrangements’ that are associated with cancer risk[14].


·        Another study analyzed the DNA of greenhouse workers and concluded these workers had significantly more chromosomal aberrations just after a summer season of spraying compared to pre-season, especially among those who had not worn gloves (Lander, 2000)[15]. 


Reproductive and Neurological Outcomes:

While cancer risks are most often related to pesticide exposure, reproductive (including male and female exposure) and neurological outcomes are equally worrisome. The neurological findings are compelling, and in an era of rising infertility concerns, we should pay particular attention to the reproductive studies. For example:   


·        A Dutch study found that high farming exposure to pesticides during the spraying season made it more difficult for a couple to conceive. The measure of fertility used in the study, called ‘time to pregnancy,’ was normal outside the spraying season (de Cock, 1994)[16].


·        Weidner et al[17] found higher rates of chryptorchidism (undescended testes) to sons of women working in gardening. The researchers hypothesized this could be attributed to hormonal effects of pesticide formulations. 



·        Men in France occupationally exposed to pesticides were five times more likely to get Parkinson’s disease and twice as likely to get Alzheimer’s disease (Baldi et al)[18].


·        A literature review found that of 14 studies on the relationship between pesticide exposure and Parkinson’s disease, 11 found a positive association. (Priyadarshi et al)[19]. It is now well established that poisoning by a toxin called MPTP, similar in structure to a number of pesticides, results in a syndrome strikingly similar to Parkinson’s disease.  The authors concluded, “Since Parkinson’s disease may be occurring at a younger age at onset, perhaps because environmental risk factors are becoming more common,” there is a need for more sophisticated research.


Body Burden:

New information on the potential additive effects of chemicals in the human body should be considered when assessing the potential hazards of pesticides.


·        Data from the U.S. Centers for Disease Control and Prevention (CDC) revealed a high human pesticide ‘body burden.’ The study found that the average person has 13 pesticides in their body, and almost everyone has a breakdown product of the long-banned DDT[20]. 


·        More recently, a study conducted by the Environmental Working Group entitled “Body Burden – the Pollution in Newborns” – tested umbilical cord blood of 10 newborns and detected 287 industrial chemicals (including pesticides)[21].




Arriving at decisions on important community health issues, including the pesticide issue, requires not only a regulatory framework, but also a discussion of underlying ideas. The following principles serve as a useful guide:  


1) The Precautionary Principle

This principle, enshrined in international law, says that where potential risks outweigh benefits, scientific uncertainty should not be used as a reason to postpone taking action to protect health. It is increasingly recognized that ‘precaution’ should be based on scientific principles and viewed as an overarching societal philosophy. 


“Physicians are taught ‘primum non nocere’ (first of all, do no harm),” writes Dr. Neil Arya in a recent edition of the Canadian Journal of Public Health,

“Environmentalists seek the same basic protection for the ecosystems on which we depend for survival i.e. the Precautionary Principle. . . the obligation should not be on citizens and their representatives to demonstrate harm, but rather on those introducing new products to society to prove not only that the products themselves are safe, but that clean production processes are used with insignificant discharge of foreign, noxious substances. This is known as ‘Reverse Onus.’ These conditions are not met by currently used pesticides.”[22] 


An understanding of past errors is important. For example, herbicide spraying decades ago at CFB Gagetown has allegedly resulted in serious illnesses among personnel and residents exposed. (Incidentally, many of the first-generation pesticides have been pulled from the market for safety reasons; whether newer pesticides will suffer the same fate remains to be seen). In future, the precautionary principle will help us avoid similar incidents.  


2) Risks vs. Benefits

From a public health perspective, the potential risks outlined in the discussion section above far outweigh the benefits, especially given that both the industry and individuals can use pesticide-free alternatives.


3) “Second-hand” effects

Pesticides do not stay put – so one person’s actions may significantly impact on another person’s health and well-being. Pesticides drift into the air, seep into soil, and leak into our streams and rivers. In 2003, the Rideau River and its tributaries tested positive for a number of landscaping pesticides, including the particularly hazardous (and recently banned) neurotoxin diazinon.[23] 


Ottawa City Council has a vital role to play with respect to this issue, particularly because of its dual role as Board of Health. In addition:


·        The cities of Montreal, Toronto, and Halifax have already adopted pesticide-free by-laws. In fact, the Province of Quebec’s 2003 Pesticide Management Code (over three years) banned the use numerous pesticides including 2,4 D, MCPA and mecoprop on public, private and commercial lawns and prohibited the sale of these lawn pesticides, as well as fertilizer-pesticide mixtures. When the pesticide industry protested the first ban in Hudson, Quebec, the Supreme Court ruled in favour of the municipality, arguing that local governments best understand the health needs of communities.


·        A 2004 international study concluded that pesticide-reduction education and outreach programs are much less effective than pesticide by-laws. In fact, only those communities that passed a by-law and supported it with education were successful in reducing the use of pesticides by a high degree (51-90%). The researchers could not find an education/ outreach program that achieved more than a low reduction (10-24%) in pesticide use.[24]



Aggregate scientific evidence and the precautionary principle support the need for a cosmetic pesticide prohibition in Ottawa. While the City's three-year pesticide education strategy has been helpful, it has not resulted in adequate reduction of cosmetic pesticide use on lawns and gardens. Much more research is needed before conclusive evidence is available on this issue; however, the balance of research published to date urges extreme caution.


Therefore, as Medical Officer of Health, I recommend that Ottawa City Council pass a by-law to prohibit the cosmetic use of pesticides on lawns and gardens, to be implemented March 2006. Agricultural and forestry use should be exempted, as this does not qualify as cosmetic use.    





cc:     Kent Kirkpatrick, City Manager

          Dr. Dave Salisbury, Acting Medical Officer of Health  

[1] Basrur, S. Lawn and garden pesticides: a review of human exposure and health effects research. Toronto Public Health, April 2002.

[2] Sanborn M, Cole D, Kerr K, Vakil C, Sanin LH, Bassil K. “Pesticide Literature Review,” Ontario College of Family Physicians, 2004.

[3] Pim L, Cooper K, Keenan K. “Urban versus agricultural: pinning down the numbers on pesticide use.” Intervenor vol. 27, no. 1-2, Jan-June 2002.

[4] Fleming LE, Bean JA, Rudolph M, Hamilton K. Cancer incidence in a cohort of licensed pesticide applicators in Florida. Journal of Occupational & Environmental Medicine. 1999; 41: 279-288.

[5] “Managing the Safety and Accessibility of Pesticides,” Office of the Auditor General of Canada, Report of the Commissioner of the Environment and Sustainable Development, 2003.



[6] Sanborn, MD, Cole D, Abelsohn A, Weir E. Identifying and managing adverse environmental health effects: pesticides, CMAJ 2002; 166(11):1431-6.

[7] Loffredo CA, Silbergeld EK, Ferencz C, Zhang J. Association of transposition of the great arteries in infants with maternal exposures to herbicides and rodenticides. Am J Epidemiol 2001; 153:529-36.

[8] Ma X, Buffler PA, Gunier RB, Dahl G, Smith MT, Reinier K, Reynolds P. Critical Windows of Exposure to Household Pesticides and Risk of Childhood Leukemia. Environ Health Perspect 110:955-960 (2002)

[9] Perera, FP, Illman SM, Kinney PL, Whyatt RM, Kelvin EA, Shepard P, Evans D, Fullilove M, Ford J, Miller RL, Meyer IH, Rauh VA. The challenge of preventing environmentally related disease in young children: community-based research in New York City. Environ Health Perspect 110:197-204 (2002).

[10] Infante-Rivard C, Labuda D, Krajinovic M, Sinnett D. Risk of childhood leukemia associated with exposure to pesticides and with gene polymorphisms. Epidemiology 1999; 10(5):481-487.

[11] Elbaz A, Levecque C, Clavel J, Vidal JS, Richard F, Amouyel P, Alpérovitch A, Chartier-Harlin MC, Tzourio, C. CYP2D6 polymorphism, pesticide exposure, and Parkinson’s disease. Ann Neurol 2004; 55:430-434.

[12] Arbuckle TE, Lin Z, Mery LS. An exploratory analysis of the effect of pesticide exposure on the irsk of spontaneous abortion in an Ontario farm population. Environ Health Perspec 2001; 109:851-857.

[13] Alavanja MC, Samanic C, Dosemeci M, Lubin J, Tarone R, Lynch CF, Knott C, Thomas K, Hoppin JA, Barker J, Coble J, Sandler DP, Blair A. Use of agricultural pesticides and prostate cancer risk in the agricultural health study cohort. American Journal of Epidemiology. 2003; 157(9): 800-14.

[14] Garry VF, Tarone RE, Long L, Griffith J, Kelly JT, Burroughs B. Pesticide appliers with mixed pesticide exposure; G-banded analysis and possible relationship to non-Hodgkin’s lymphoma. Cancer Epidemiology, Biomarkers & Prevention. Vol 5, 11-16, 1996.

[15] Lander BF, Knudsen LE, Gamborg MO, Jarventaus H, Norppa H. Chromosome aberrations in pesticide-exposed greenhouse workers. Scand J Work Environ Health 2000; 26: 436-442.

[16] De Cock J, Westveer K, Heederik D, te Velde E, van Kooij R. Time to pregnancy and occupational exposure to pesticides in fruit growers in The Netherlands. Occup Envion Med 1994; 51:693-699.

[17] Weidner IS, Moller H, Jensen TK, Skakkebaek NE. Cryptorchidism and hypospadias in sons of gardeners and farmers. Environ Health Perspect 106:793-796 (1998). 

[18] Baldi I, Lebailly P, Mohammed-Brahim B, Letenneur L, Dartigues JF, Brochard P. Neurogenerative diseases and exposure to pesticides in the elderly. Am J  Epidemiol 2003; 157; 409-414.

[19] Priyadarshi A, Khuder SA, Schaub EA, Priyadarshi SS. Environmental risk factors and Parkinson’s disease: a metaanalysis. Environmental Research Section A 86, 122-127 (2001) 

[20] U.S. Centers for Disease Control and Prevention, “Second national Report on Human Exposure to Environmental Chemicals,” Jan. 2003

[21] Environmental Working Group, “Body Burden – The Pollution in Newborns,”  July, 2005.

[22] Arya, N. Pesticides and Human Health – Why Public Health Officials Should Support a Ban on Non-essential residential use, Canadian Journal of Public Health, March-April 2005.

[23] City of Ottawa Water Environment Protection Program, “Surface Water Pesticide Monitoring Program” Summary 2003-04.

[24] Cullbridge Marketing and Communications and Canadian Centre for Pollution Prevention. “The impact of by-laws and public education programs on reducing the cosmetic/non-essential, residential use of pesticides, A best practices review,” 2004.