What is the concern regarding neurotoxic substances?
Substances that are neurotoxic alter the normal developmental path
of a childís brain and nervous system. We have learned that even
subtle changes in neurodevelopmental processes can permanently affect
the way the nervous system functions and can produce changes in
cognition and behaviour.
As recent reviews have suggested, the threat of exposure to neurotoxins
is not merely hypothetical or potential, but is absolutely real
and yet preventable. We know from both animal and human studies
that a number of substances liberally emitted into our environment
are neurotoxic. There is also evidence of adverse effects from some
of these substances at current Canadian environmental concentrations.
Lastly, there is a great deal of uncertainty when it comes to neurodevelopmental
effects. There appears to be an increasing prevalence of cognitive
and behavioural problems in children. Researchers suggest this is
linked to the considerable volumes of neurotoxins emitted regularly
into the environment. There is an enormous societal cost in terms
of the profound health compromise to the many children potentially
exposed to environmental neurotoxins.
What substances can affect neurobehavioural development?
Among the major substances that are toxic to developing nervous
systems and that are present in the Canadian environment at levels
of some concern are:
- Heavy metals such as lead, mercury, and manganese
- Persistent organic pollutants such as PCBs, dioxins, DDT and
other organochlorine pesticides
- Pesticides of the organophosphate and carbamate type
How are children exposed to neurotoxic substances?
Most of our harmful exposures to neurotoxins come through the diet,
through food and water, although in some cases they can be inhaled
via air. In addition, children may be exposed in the womb, during
infancy via breast milk and from consumer products that contain
or harbour such contaminants.
What are the potential health effects from neurotoxins?
There is a spectrum of effects depending upon a) the dose and b)
the timing of exposure. The range of neurotoxic effects includes
fetal death, malformations, altered growth and functional abnormalities.
Attention has been focused of late on the potential role of low
levels of neurotoxins in contributing to subtle, yet important,
functional changes such as developmental delays, behavioural problems,
attention problems/hyperactivity, poor school performance and learning
Why are children more vulnerable to effects from neurotoxins?
Children are more vulnerable due to a) developmental and b) behavioural
differences. There are numerous, sequential windows of vulnerability
for the brain and nervous system because of the complexity and distinct
timing of the many processes involved. The most critical periods
of exposure are in utero and during infancy. Childrenís exploratory
and hand-to-mouth behaviours mean they are more exposed to environmental
What can you do personally to prevent exposures?
Because of the broad window of susceptibility of the brain and
nervous system and the brainís inability to readily repair cells
after injury, once neurodevelopmental effects are apparent, they
are unfortunately often permanent. Therefore, avoiding exposures
before they happen and before they can do greatest harm is
the key strategy for personal prevention. Physicians can counsel
patients on choices in their diet and regarding personal activities,
particularly if they are considering having children or are pregnant.
What do we do as a society to prevent these exposures?
Personal prevention strategies are only half measures at best,
however. CAPE joins other health advocacy organizations in Canada
and the United States in calling for precaution in health policies
and environmental regulations to prevent harm to childrenís health
from neurotoxic contaminants. This is crucial when there is a great
deal of scientific uncertainty combined with the risk of exposure
and harmful effects for considerable numbers of children.