Science Used is Inadequate

Why a Bylaw?

Federal Regulations Don’t Work to Protect Human Health and the Environment

Some Reasons Why The Science Used is Inadequate

1. Testing only addresses one chemical at a time

The testing required by the Pest Management Regulatory Agency (PMRA) for health safety purposes is usually being done only on the active ingredients in the pesticide formulations.  Not much testing is required for the chemicals that make up the formulations (e.g. agents to improve spreading or sticking).  Testing is usually not done on mixtures of pesticides in products, such as weedkillers with three active ingredients (2,4-D, mecoprop and dicamba - “Killex”).  There are so many possibilities involved, it would require too much killing of lab animals to test every formulation or combination. Also, this would not take into account the practice of applying various pesticides during actual use, for instance to kill weeds and insects. So while pesticides are usually used in combination, PMRA assessments usually address toxicity of a single chemical at a time. (1)

“Some evidence from animal testing suggests the commercial formulation of a pesticide may cause greater biological effect on the animal than does the pure active ingredient.” (2) The commercial product  ‘Roundup,’ containing the active ingredient glyphosate, is one such product.  Some scientists suggest that it is the non--active ingredients in pesticide formulations that increase the biological effects. Surfactant chemicals, that help the formulation penetrate leaf surfaces, may cause more of the formulation to be absorbed through the skin or respiratory system of animals. (7)

Another study showed that mixtures of pesticides have a greater health effect than individual active ingredients AND that mixtures of pesticides with nitrates have even more of an effect on health. Nitrates are a common ingredient in fertilizers and are often used with pesticides, or can be found in the environment with pesticides. (7)

2.  Lab animals results may not apply to humans

The PMRA largely relies upon rat studies.  In April 2004 the genome of the rat was published in the prestigious journal "Nature".  (3) An important finding was that rats have genes that do not exist in people for detoxification of chemicals, and therefore are a poor model for toxicity testing.  (There is a reason that rats can live in sewers and garbage dumps, and people cannot.)  Dogs are much more sensitive to 2,4-D, but the dog data was put aside in favour of the more robust rats. (from Coalition for a Healthy Ottawa’s web-site, PMRA page)

3.  Essential tests are missing

A knowledgeable Saskatchewan health advocate summarizes what many scientists have said:

Many essential tests to establish safety are missing from the tests mandated by the PMRA. Much is still unknown about the potential health effects of pesticide exposure, especially on the health of fetuses and children. Almost nothing is known about the long-term impacts of multiple chemicals in the body over long periods. Neither Canada nor the United States currently requires the following tests before registering pesticides: endocrine disruption,. . .   low dose effects, or neurotoxicity (unless a pesticide is already a known [or suspected] neurotoxin), nor does either government demand tests for the health effects of exposure to pesticides in combination with each other or with other toxins. Consequently, these factors are not taken into account when evaluating or re-evaluating pesticides although recent scientific evidence indicates negative health effects. (4) 

Developmental neurotoxicity (i.e. how toxins affect the development of the nervous system in fetuses and children) that might anticipate problems such as autism and attention deficit hyperactivity disorder in children, or environmental sensitivities later in life, are usually neglected in the testing of pesticides. (5)

Some developmental neurotoxicity tests are now being required by the PMRA for some pesticides. Most of the pesticides on the market, though, have not gone through these assessments.

4.  Only healthy workers are tested

Research on workers who are exposed to pesticides is skewed by the “healthy worker effect,” that workers with a physiology such that they do not tolerate the chemicals will find other work. Thus, the self-selected group of employees would not include people with a pre-disposition to chemical sensitivities or other health problems.  Furthermore, avoiding obvious toxicities in healthy adults will not translate into protection for the unborn. (1)

5.  Tests Only Address High Dose Response, Not Low Doses Over Time

In the tests submitted to the PMRA, lab animals are fed high doses of chemicals to test how they respond. In ordinary human life though, we are exposed to low doses of many different pesticides over time through the food and water we take in and also through our skin and the air we breathe. (5, 7)  The human body often responds well to a high dose, recognizing it as toxic, and getting rid of the toxins. With low ongoing doses, the amount of toxins can build in the body, causing damage. (4)

Some studies show that adult susceptibility to “pesticides can be acquired by low-dose pesticide exposure earlier in life.” (5: page 14) Other studies show that low doses of pesticides can have more of a harmful effect than higher doses. (5, 6)

 The nervous system, endocrine (hormonal) system and immune system are so linked that small effects on one system can affect the system as a whole, especially when the effect happens early in life when these systems are developing, for example in the womb or even up to teen years. Pesticides have been linked to effects on all of these systems. A small low dose at a critical development window in the fetus may lead to “permanent developmental changes.” (7: p. 144)

6.  Tests are Not Peer Reviewed by Other Scientists

Usually the tests submitted to the PMRA are not public information and are not published elsewhere. Thus this testing does not undergo the typical scientific process of publishing results of work and having other scientists read and respond to the work. (8)

7. Literature Reviews are Not Published

Part of the PMRA assessment process is a review of the literature related to the chemical being assessed. The PMRA does not publish the literature that is used in this assessment. The literature review process does not then undergo the typical scientific process of having other scientists evaluate how thoroughly the literature was reviewed. (8)


1) Dr. Meg Sears, Adjunct Investigator of the Children’s Hospital of Eastern Ontario Research Institute. Personal communications. 2007.

2) Alavanja, Michael C.R., Bonner, Matthew R. "Pesticides and Human Cancers". Cancer Investigation, 23:700-711, 2005.  They note that glyphosate formulations  (e.g. Roundup) have been found to cause DNA abnormalities that can lead to cancer and also can cause genetic mutations or increase the mutation rate.  Read more on glyphosate . . .

3)  Lindblad-Toh K. Genome sequencing Three's company. Nature. 2004;428:475-476.

4) Hjertaas, Paule, "Why, given that pesticides are regulated in Canada, is extra protection for children needed." Briefing Note submitted to the Government of Saskatchewan. p. 6 Citing PANNA; “Chemical Trespass”; May 2004 J.P. Myers, Ph.D; “From Silent Spring to Scientific Revolution”; Our Stolen Future ( (essay first published in San Francisco Medicine, Nov 2002.  “In Harm’s Way”; Greater Boston Physicians for Social Responsibility;  Mona Thiruchelvam, et al; “The Nigrostriatal Dopaminergic System as a Preferential Target of Repeated Exposures to Combined Paraquat and Maneb: Implications for Parkinson's Disease”; The Journal of Neuroscience, 20(24):9207-9214 15dec00.

5) Colborn, Theo. “A Case for Revisiting the Safety of Pesticides: A Closer Look at Neurodevelopment.” Environmental Health Perspectives.114: 10-17.  January, 2006.  Read more . . .

6) Cavieres, Maria Fernanda et al. “Developmental Toxicity of a Commercial Herbicide Mixture in Mice: 1. Effects on Embryo Implantation and Litter Size.” Environmental Health Perspectives, 110: 1081-1085, September, 2002.  This study showed that low doses of a common pesticide mix had a stronger effect than higher doses on the number of babies mice had (with low doses mice had 20 % less babies).  Read more . . .

7) Porter, Warren P.; Jaeger, James W.; Carlson, Ian H. “Endocrine, immune, and behavioral effects of aldicarb (carbamate), atrazine (triazine) and nitrate (fertilizer) mixtures at groundwater concentrations.” Toxicology and Industrial Health, 15 (1-2), pages 133-150. 1999.
For an interview with Warren Porter, the man who supervised the studies mentioned in 6 and 7, click here

8) M.Sears, CR Walker, RHC van der Jagt, P Claman. “Pesticide Assessment: Protecting public health on the home turf.” Paediatric Child Health 2006; 11 (4); 229-234.

Click here for a scientist’s view on Why Science Can’t Prove a Pesticide is Safe .

Click here to download a team of scientists’ assessment of the review process for 2,4-D.

Click here to download a scientist’s call for a new approach to determining the safety of pesticides. 

Click here
for actions you can take to support a pesticide bylaw.

Click here for how to use natural landscaping in your yard.