How Pesticides Affect Our Health
Long-term exposure
Long-term health effects
Medical scientists are less certain about how regular exposure to low levels of pesticides affects our long-term health. This is because these types of studies are very difficult to design and carry out, there are conflicting results and data gaps.
However, recent studies do point to some possible long-term health effects from repeated low level exposure to certain pesticides.
Ongoing research
It often takes many decades of research and hundreds of studies to reach a solid conclusion about how an environmental factor affects our health.
Ongoing research adds to our knowledge, but there are still many unanswered questions about low level long-term pesticide exposure and its health effects.
The following summarizes the research on pesticides.
Pesticides and possible health effects
- Pesticides & reproduction
- Pesticides & the nervous system
- Parkinson's disease
- Effects on brain development
- Effects on learning
- Pesticides & cancer
- Pesticides & the immune system
- Childhood cancers
- More information
In recent years health researchers have studied the relationship between pesticides and reproductive effects, neurological (nervous system) effects, and certain cancers.
Keep in mind that not all studies show a connection (events that occur more frequently together than they would by chance). Some show no association at all, or an association that isn’t significant.
We have only limited data available at this time, and not all researchers draw the same conclusions. So while the research shows some cause for concern, nothing is absolutely certain regarding how pesticides affect cancer rates or particular parts of your body.
Relatively few studies have been done looking for associations between health effects and exposure to the specific pesticides you would use on your lawn and garden. Most studies have looked at people who work with pesticides (farmers, landscapers, people who work in pesticide factories) who have been exposed to higher levels for a longer time.
Pesticides & reproduction
Research suggests that if you work directly with pesticides you have a slightly higher risk for reproductive effects. Some pesticides have been linked to fertility problems, reduced sperm count, difficulties in getting pregnant, spontaneous abortion, fetal death, certain birth defects and altered growth of the fetus.
Pesticides & the nervous system
Several pesticides — such as organophosphates, carbamates, and some fungicides — are known to affect the nervous systems of animals and humans.
Some workers exposed to neurotoxic pesticides (pesticides that are toxic to the brain) have experienced sensory, motor, mental and psychological effects. However, there is little known about long-term, low level effects.
Parkinson’s disease
There is mounting evidence that if you work consistently with pesticides — particularly if you’re a farmers or a gardener — you do run a a greater risk of developing neurodegenerative disorders such as Parkinson’s Disease (PD).
However, this increased risk for PD from pesticide exposure may be related to your individual genes, so you should take this into account. This is an important area of research.
Effects on brain development
The effect on human brain development is still unclear.
Several studies on young animals show that the nervous system is especially vulnerable to some insecticides, such as those from the organophosphates and carbamates family. For example, when tested on pregnant animals, chlorpyrifos was found to reduce the number of brain cells in newborns. Infant rats exposed to low levels of chlorpyrifos showed long-term cognitive problems. (Chlorpyrifos hs been phased out for home use in Canada).
Effects on learning
Studies are on-going on this issue.
One intriguing study examined the effects of low-level, long-term exposure to many different pesticides (including DDT, which has been banned in Canada for many years) in a group of preschool children from an agricultural community in Mexico.
These children scored lower in stamina, coordination, memory, and drawing ability than children from a non-agricultural community. (The children from the non-agricultural community were exposed to a much lower levels, but otherwise shared similar genetic, economic, and social traits).
Although this study is not directly applicable to children in Ontario because of the pesticides involved and the intensity of exposure, it’s conclusions about how children’s nervous systems are affected by different exposures to pesticides is concerning.
Pesticides & cancer
The possibility of a link between cancer and pesticides has received the most attention. Yet, after much study, the role of pesticides in causing cancer still is not clear.
However, some recent workplace studies do show a greater risk of testicular, prostate, and cervical cancers, Non-Hodgkin’s Lymphoma (NHL), and multiple myeloma if you’re regularly exposed to pesticides through your work.
Some studies also show higher cancer rates among people living in agricultural areas.
Pesticides and the immune system
A number of studies on animals show that some pesticides (such as chlorpyrifos, malathion, some pyrethroids, and phenoxy herbicides) can change how our immune system functions.
If your immune system is weak, you might be more susceptible to infectious diseases. A weak immune system might also play a part in the development of certain cancers, but not all researchers agree on this.
We need further research to better understand how pesticides affect our immune systems.
Childhood cancers
While many studies suggest a connection between pesticide exposure and some cancers in children, a definite link is far from being proven.
Certain childhood cancers may be a result of a parent’s being exposed to pesticides.
Several studies show a reason to suspect that pre-conception, prenatal, and early childhood exposures to pesticides are linked to increases in brain tumours, leukemia, NHL, and neuroblastoma in children.
While using pesticides in your home appears to increase the risk of your children developing these cancers, the research on childhood cancer rates and yard and garden pesticides isn’t definite.