Reproductive Development, Congenital Anomalies and Endocrine Effects
What is the concern regarding reproductively toxic substances?
Substances that are reproductive toxicants alter the normal development,
differentiation and adult functioning of the reproductive system.
As recent reviews have suggested, the threat of exposure to reproductive
toxicants 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 that can alter reproductive development
are liberally emitted into our environment. There is also evidence
of adverse effects from some of these substances at current Canadian
Lastly, there is a great deal of uncertainty when it comes to reproductive
toxicity from environmental exposures. There appears to be an increasing
prevalence of fertility problems. Researchers suggest this is linked
to the considerable volumes of hormonally active agents emitted
regularly into the environment.
What substances can affect reproduction and reproductive development?
Among the major substances that are toxic to developing reproductive
systems and that Canadians may encounter are:
- Heavy metals such as lead, mercury, manganese, cadmium, arsenic
- Organic solvents such as benzene, toluene, xylene, acetone,
vinyl chloride, trichloroethylene, phenols, etc.
- Persistent organic pollutants (POPs) such as PCBs, dioxins,
DDT and other organochlorine pesticides
- Other hormonally active agents including plasticizers such as
- Pesticides of the organophosphate and carbamate type
How are children exposed to reproductive toxicants?
The routes of exposures to reproductive toxicants are broad and
vary depending on the specific agent. Most of our harmful exposures
to reproductive toxicants come through the diet, through food and
water, although in some cases they can be inhaled via air. Of particular
importance to children is that they may be exposed in the womb,
during infancy via breast milk, and from consumer products that
contain or harbour such contaminants. Parental exposures prior to
conception that lead to genetic damage in gametes may cause effects
What are the potential health effects from reproductive toxicants?
There is a spectrum of reproductive and developmental effects depending
upon a) the dose, b) the timing of exposure, c) the site of action
and d) the sex of the exposed individual (or fetus).
The range of potential reproductive effects includes
- impaired fertility
- fetal death
- congenital abnormalities
- malformations of reproductive structures
- altered growth
- altered (delayed or early) reproductive developmental milestones
Attention has been focused of late on the potential role of low
levels of hormonally active agents that disrupt normal endocrine
functioning. While most information comes from studies of the effects
in animals, there is concern that humans are at risk because of
widespread low-level exposure to such agents.
Why are the young more vulnerable to effects from reproductive
Athough there is incomplete evidence on sensitivity of the developing
human reproductive system, it is likely that there are several windows
of vulnerability for the reproductive system because of the complexity
and distinct timing of the many processes involved. Critical windows
of exposure occur preconceptionally, prenatally (during gonad differentiation,
urogenital system and early breast development) and during early
infancy, late childhood and puberty.
How does one prevent such exposures on a personal level?
There is a relatively broad window of susceptibility for reproductive
effects, from prior to conception through to adolescence. The effects
from reproductive toxicants may go unnoticed until an individual
is reproductively mature and attempts to conceive a child. Therefore,
avoiding exposures before they happen and before they can
do greatest harm is the key strategy for personal prevention. Physicians
can counsel patients, particularly if they are considering having
children or are pregnant, regarding personal activities, choices
in their diet and avoiding potential exposures in the workplace,
home and community.
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 children’s health
from reproductive toxicants. In particular, the identification and
elimination of hormonally active agents in the environment is crucial
because of the considerable scientific uncertainty combined with
the risk of exposure and harmful effects for significant numbers
of children and future generations.