Manitoba’s government has reopened the public debate on cosmetic pesticides.
The provincial regulations, which banned the use of chemical herbicides on lawns and public properties used by children, came into effect less than two years ago.
On July 20, the province launched a public consultation process on the ban with a Twitter post that posed the question, “Pesticide free or weed free?” It seems an unfortunate way to engage residents in an important discussion about a public policy that is directed towards the protection of public health.
Municipalities and provinces began banning the use of cosmetic pesticides two decades ago, in response to concerns expressed by their citizens about the serious health impacts that appeared to be associated with them. While companies do conduct laboratory tests on active ingredients in pesticide products in order to get them approved for sale, those tests are far from perfect. They do not always pick up on chronic health impacts associated with long-term exposures. They do not pick up serious health impacts that can result from subtle changes in the hormone or immune systems of humans. They are seldom conducted on the mixture of chemicals contained in each pesticide product. They do not reflect the cumulative exposures that humans experience from many different sources. For this reason, epidemiological studies, conducted on populations of humans, are used by health scientists to identify health impacts from exposures that people experience in real life.
Thousands of epidemiological studies have been directed at pesticides. In 2002, Toronto Public Health conducted a systematic review of 300 scientific studies conducted on pesticides used on lawn and gardens. When the reviewers examined studies of occupationally exposed workers, they found that pesticides were associated with moderate increases in the risks for some cancers, some reproductive effects, and some neurological disorders. When they examined the long-term studies directed at children, they found that pre-conception, prenatal and postnatal exposure to pesticides were associated with moderate increases in the risks from some cancers and some birth defects.
In 2012, the Ontario College of Family Physicians conducted a systematic review of pesticide studies published after 2003. These reviewers closely examined 142 well-designed studies and found that pesticide exposures were associated with adverse reproductive effects (e.g. low birth weights in babies), measurable deficits in the neurodevelopment of children (e.g. deficits in their mental and/or motor development), and respiratory diseases (e.g. asthma). In many of these studies, the adverse effects observed in children were related to the exposure of their mothers during pregnancy or to exposures early in life.
The reviewers concluded that steps should be taken by individuals and communities to minimize pesticide exposures for all members of society, and for pregnant women and children in particular. They also noted that previous bans directed at pesticides that had heavy health burdens were effective in reducing both, the health risks in children, and the frequency with which pesticides were detected in samples collected from children and the environment.
When health professionals look at these results, we weigh the health risks against the health benefits associated with their use. We recognize that there may be times when the health benefits associated with the use of a pesticide may outweigh the health risks associated with them (although even in those cases, we would ask ourselves if there were safer alternatives). However, in the case of cosmetic pesticides, where the purpose is to guarantee a beautiful lawn or garden, we feel that the health risks to our children must take precedence. This is the thinking behind municipal and provincial bans of cosmetic pesticides. It is to apply the precautionary principle; to decide to act for the protection of our children in the face of scientific uncertainty.
Dr. John Howard is a pediatric gastroenterologist who practised medicine in London, Ontario for 31 years. Kim Perrotta is a public health advocate who has worked on environmental health issues for over 30 years.