ENDOCRINE DISRUPTORS UPDATE
Science and Technology Division
10 August 2000
TABLE OF CONTENTS
ENDOCRINE SYSTEM AND ENDOCRINE DISRUPTORS:
A. How the Endocrine System
Endocrine Disruptors and their Impact on the Endocrine System
CAN ACT AS ENDOCRINE DISRUPTORS
A Source of Endocrine Disruptors
B. Persistent Organic Pollutants
C. Heavy Metals
F. Other Substances
EFFECTS OF ENDOCRINE DISRUPTORS:
THE SCIENTIFIC POINT OF VIEW
A. Effects on Animals and Humans
on the Reproductive and Endocrine Systems
C. Heightened Effects on the
D. Non-estrogenic Effects
E. The Need for More Information
RECENT GOVERNMENT MEASURES
A. National Initiatives
B. International Initiatives
List of known and suspected hormone disruptors
Description of heavy metals studied by the Northern Contaminants
Scientific research is increasingly
highlighting the close links between human beings and their environment.
Every day, it becomes clearer that the quality of the air, water and soil
has a direct impact on the food chain and thus on human beings who are
situated at the top of the pyramid. For a few years now, endocrine-disrupting
substances or endocrine disruptors have become a source
of concern. Scientific studies carried out in Canada and in several other
countries have shown that those substances can act on the endocrine system
of certain invertebrates, fish and higher animals in general. Endocrine
disruptors can affect reproduction, growth and development in several
species. Scientists are therefore concerned by the role these substances
might play in the appearance or increase of hormonal system diseases in
human beings, particularly the still-unexplained increase in the incidence
of cancers, infertility and malformations of reproductive organs noted
in several countries.
The mechanisms through which
endocrine disruptors interfere with the hormonal system are complex and
not yet well understood. Researchers do know, however, that a wide range
of substances affect health, precisely because of the complexity of the
hormonal system, and that very low concentrations are sufficient to affect
the physiological processes of several animal species.
The extent of disruptors
effects on human beings is still being debated, as many factors limit
research and prevent researchers from drawing conclusions as easily as
they do for wildlife. Be that as it may, the Canadian government gives
this emerging international issue a high priority, recognizing the need
to produce the knowledge necessary for informed policy and regulatory
This document attempts to
provide an update on the question of endocrine disruptors. The first part
reviews how the endocrine system works, explains what endocrine disruptors
are, and how they act in the human body. The second part of the paper
introduces some of the substances that could be endocrine disruptors,
while the third part discusses the effects of endocrine disruptors on
animals and presents the scientific communitys various points of
view as to the extent of these effects on human beings. Finally, it examines
the Canadian governments most recent efforts to control endocrine
SYSTEM AND ENDOCRINE DISRUPTORS:
How the Endocrine System Works
The endocrine hormone system
plays a key role in growth and sexual development. It consists of the
endocrine glands, including the testicles, the ovaries, the thyroid, the
pancreatic and adrenal glands, the parathyroids and the pituitary gland
(which controls the other endocrine glands). These glands secrete substances
known as hormones, which are chemical messengers released directly into
the bloodstream, where they travel to and stimulate other organs (or receptors).
The pancreas, the thyroid, the parathyroids and the pituitary secrete
protein hormones; the adrenal glands and the gonads(1)
secrete steroid hormones.
Hormones are crucial to
morphology, metabolism, blood circulation and the nervous system (which
itself affects hormone secretion),(2)
and thus help maintain the individuals physiological balance.
Endocrine Disruptors and their Impact on the Endocrine System
When hormone secretion is
disrupted, a physiological imbalance occurs that can lead to such problems
as obesity, diabetes and decalcification of the bones. The natural or
artificial substances that may cause this imbalance are described as endocrine
disruptors. Disruptors are divided into three categories:
For example, if we look
at the development of a child from an embryonic stage to birth, the entire
process is regulated by specific chemical messengers that are programmed
to be released at one point and taken up at another in precise concentrations
and at specific times. If a chemical interferes with these messengers,
irreversible damage can result at some stage. The effects may include
changes in the development and function of the reproductive system, which
in turn produces abnormalities, including deformities.
The effects of endocrine
disruptors are not limited to male or female sex hormones; they also affect
other endocrine glands that play a role in growth, development and reproduction.(4)
SUBSTANCES THAT CAN
ACT AS ENDOCRINE DISRUPTORS
A. Pollution: A Source
of Endocrine Disruptors
The scientific community
clearly recognizes that a wide range of substances interfere with the
natural chemical messengers in animals.(5)
These substances are present throughout the environment, and even if we
do not yet know the extent of their effect on the human endocrine system,
the human organism is nevertheless in almost constant contact with them.
That is due, in particular, to the fact that a large number of these substances
can easily be transported by the wind in particle or droplet form, and
may travel thousands of kilometres from their source. Rain then deposits
the particles on soil or in waterways, where they accumulate and undergo
transformation. They are then absorbed by vegetation and end up in the
food chain, after which they become concentrated in the fatty tissue of
animals. The movement of substances over long distances seems to be confirmed
by a study of Inuit infants in Nunavik and Baffin Island, which found
that babies born in this region are exposed to higher levels of certain
products (such as PCBs) than are babies born in southern Canada.(6)
Variations in exposure to these pollutants are attributable primarily
to diet, although sociodemographic differences also come into play.
has established that several substances present in the environment may
act as endocrine disruptors (see Table 1). For instance, the presence
of industrial, agricultural and municipal waste in the environment may
expose organisms to abnormally high doses of natural substances such as
sexual hormones or phyto-estrogens (plant by-products or derivatives).
Synthesized chemical products such as pesticides, the by-products of industrial
activity (dioxins, furans), and industrial wastes (PCBs) can also affect
the normal functioning of the endocrine system.
The U.S. Endocrine Disrupter
Resource Center has identified about 50 of these substances (see Appendix 1).
According to that organization, very minute concentrations (parts per
trillion) of these products in an organism would be enough to affect its
endocrine system. Half of the substances mentioned in the Centers
list are part of the organochlorine group: a description of that group
is provided later in this paper.
TABLE 1: SOURCES, CATEGORIES AND EXAMPLES OF SUBSTANCES
HAVE BEEN REPORTED AS POSSIBLE ENDOCRINE DISRUPTORS
(Example of Uses)
Compounds (from industrial production or by-products of mostly
dioxins, polychlorinated biphenyls
runoff / Atmospheric transport
Pesticides (found in insecticides, many now phased out)
currently in use
(found in antifoulants used to paint the hulls of ships)
and municipal effluents
(Surfactants certain kinds of detergents used for removing
oil and their metabolites)
(found in placticisers)
phthalate, butylbenzyl, phthalate
effluent and agricultural runoff
Hormones (produced naturally by animals); synthetic steroids (found
estrone, testosterone; ethynyl estradiol
(found in plant material)
Source: Environment Canada,
Endocrine Disrupting Substances in the Environment, 2000.
Some scientists suspect
that ordinary products used in everyday life may also be endocrine disruptors.
Possible examples include cleaning products, beauty products and compounds
produced by the breakdown of plastics.
News reports and newspaper
articles tell startling stories that link chemical substances and diseases
related to the disruption of the hormonal system such as breast cancer
and non-Hodgkins lymphoma. For instance, some researchers suggest
that plastics, fuels and certain drugs or pesticides may stimulate excessive
hormone secretion and thus accelerate the development of cancer in a given
gland or the organ it affects. More than anything, these news reports
reflect the populations growing concern with the effects of pollution
Persistent Organic Pollutants
Until recently, most research
work on endocrine disruptors has been done on persistent, bioaccumulative
and toxic substances, many of which are mentioned in Table 1 (dioxins,
PCBs, organochlorine pesticides, etc.). Those chemical substances
persistent organic pollutants (POPs) come into the environment
as a result of human activities, and their list will probably continue
POPs share three broad characteristics:
POPs are called persistent because they resist degradation
in normal environmental conditions.
POPs are also liposoluble and very slightly water-soluble,
which means that the organism cannot excrete them, which is why they
accumulate in tissue. The accumulation of a contaminant over time
within one organism is known as bioaccumulation. The organism
that eats plants or animals that have already been contaminated can
accumulate a high concentration of contaminants, and that concentration
increases with every step up the food chain. This increase in the
concentration of POPs as you go up the food chain is known as bioamplification.(7)
POPs are semi-volatile, i.e., they move easily from a solid
state to a gaseous state at high temperatures and become solid again
if temperatures drop. Used in southern regions, these products partly
evaporate and are transported by the wind; they then condense when
they come in contact with cold arctic air and settle on the ground.
When these pollutants reach the North (all of the territory north
of the 60th parallel, i.e., the sub-arctic and arctic regions),
they tend to accumulate because the low temperatures are not conducive
to evaporation. POPs can repeat that cycle several times and over
long distances, which has caused this phenomenon to be known as the
Because of this travel over
long distances allied to their particular physical and chemical characteristics,
POPs affect arctic regions in particular.(8)
According to the literature, 80% of pollutants in the Arctic are thought
to be from countries other than Canada.(9)
Although the use of most
POPs is prohibited or restricted in Canada, they are produced, used or
discharged in a number of other countries; and because POPs are readily
transportable by air, they can still put the Canadian population (and
that of many other countries) at risk. That is why they are covered by
international agreements adhered to by Canada. These agreements currently
cover the following 16 POPs. Most of these pollutants are in organochlorines
organic substances that contain chlorine atoms; 11 of them
Chlordane, DDT, aldrin, dieldrin,
endrin, heptachlor, hexachlorobenzene, mirex, chlordecone, lindane
C. Heavy Metals
Canada has included three
heavy metals cadmium, mercury and lead (see Appendix 2)
in its research programs on the effects of toxic substances on health
and on the endocrine system in particular. Those three metals are thought
to act as endocrine disruptors and are among the substances being studied
under the Northern Contaminants Program sponsored by Indian and Northern
Affairs Canada (see Appendix 3).
These three metals are present
in the environment as a result of various natural processes. However,
since the beginning of the industrial era, human activity has raised the
levels of these metals in natural ecosystems, and as result of bioaccumulation
and bioamplification, in the food chain.
Organochlorines are chemical
products containing both carbon and chlorine. They are used for a variety
of purposes including pesticides, refrigerants or other industrial products.
Some organochlorines, such as dioxins and furans, are by-products of (various)
industrial processes that are released into the environment, and several
of them are believed to be endocrine disruptors (Table 1). Many of
them are POPs that are now prohibited in Canada, but traces of them can
still be found in the environment. They may even reach high concentrations
in the tissues of predators at the top of the food chain.
In Canada, the double-crested
cormorant (a fish-eating predator) is used as a national indicator of
persistent organochlorine levels because of its broad distribution across
southern Canada, especially in areas of concentrated human activity.(10)
The first pesticides,(11) which appeared during the 1940s, contained mostly organochlorines.
They were used in an intensive way both in agriculture and forest
management, as well as to protect wooden buildings and health in
order to control a variety of insects. Thus, it is not surprising to learn
that because of their characteristics, traces of organochlorine pesticides
still persist in the environment, even if several other groups of chemicals
have replaced them, at least in Canada, where more than 50 million
kilograms of herbicides, insecticides and fungicides are used each year.(12)
F. Other Substances
After having focused almost
exclusively on persistent, bioaccumulative and toxic substances, scientists
today are studying substances that may not persist as long in the environment,
but are nevertheless widespread. They may affect growth, development and
reproduction of organisms, even in low concentrations. These are substances
that are found in municipal and industrial effluents as well as in the
runoff from agricultural lands, natural plant estrogens, chemical products
such as alkyphenols and tributyltin (Table 1), and certain other
ingredients of pesticide formulations.(13)
EFFECTS OF ENDOCRINE DISRUPTORS:
THE SCIENTIFIC POINT OF VIEW
Effects on Animals and Humans
Canada has been a pioneer
in research on endocrine disruptors, thanks in particular to the efforts
of the Canadian Wildlife Service, whose work highlighted cases of disruption
of the endocrine system in animals.(14) Research showed effects on the reproduction
and development of fish and birds (Table 2); the observation of embryonic
malformations in various species and of the mortality of such embryos
confirmed embryotoxic effects(15) and teratogenic(16)
of certain pollutants. The research noted various anomalies: a decrease
in the size of the penis and testicles, a decline in sperm counts, reproductive
anomalies, feminization of males, and masculinization of females.
TABLE 2: SOME EXAMPLES OF ENDOCRINE-RELATED EFFECTS
IN WILD POPULATIONS
Source: Environment Canada, Endocrine
Disrupting Substances in the Environment, 2000.
These results have blazed
a trail for the world scientific community, which is now studying the
issue of active compounds in the environment in relation to the human
population. Over the past three decades, many countries have witnessed
an increase in diseases related to malfunctions of the endocrine system
(thyroid dysfunction, infertility, defects and cancer of the reproductive
organs).(17) In Canada, Ontario has experienced an
apparent 2% increase each year in the incidence of testicular cancer (60%
over the past 30 years);(18) and
as early as 30 years ago, endocrine disruptors were being suggested as
a possible cause.(19) Recent studies suggest that these substances also have
an effect on the human body; for instance, women who drank water daily
from Lake Michigan in the 1970s are reported to have been exposed to persistent
toxins and to have given birth to neurologically damaged babies.(20)
The learning ability and behaviour of the children with the highest exposure
levels are believed to have been irreversibly affected. Similar conclusions
were reached in a 1990 study of babies in New York whose mothers
had consumed fish from Lake Ontario in the 1980s while pregnant.(21)
There is a great deal of
debate concerning research on the human population, in particular because
scientists do not agree on the extent of the problem. A partial list of
recent studies suggests four main conclusions in connection with endocrine
studies conclude that more in-depth research is essential to a thorough
understanding of endocrine disruptors.
indicate that most of the studied products appear to have at least
some impact on mammals (including humans).
suggest that the effects of endocrine disruptors are seen primarily
in fetuses and developing children.
suggest that the extent of the effects varies according to a host
of parameters that are distinct from the effect of the products studied.
B. Effects on
the Reproductive and Endocrine Systems
Many authors agree that
the pollutants being studied can affect the endocrine system by coming
between the hormones and hormone receptors (paralyzing or triggering disruptors).
Benjamin Danzo is among those who support this view.(22)
His work on such products as DDT congeners,(23)
dieldrin, atrazine and pentachlorophenol has led him to observe that these
substances interfere to varying degrees with the binding of ligands(24)
to steroid receptors and binding proteins.
A Danish study of 18 organochlorine
products has linked the incidence of breast cancer to pesticides and has
shown that some organochlorines may have a slight estrogenic effect.(25)
In addition, some chemical pollutants with limited ability to stimulate
hormones may become more active (mimics) in synergy with other products.
In fact, Steven Arnold and various other researchers have hypothesized
that estrogen receptors have more than one site that can bind with pollutants.(26)
This is the case with chlordane, which has no effect on the endocrine
system by itself, but can make dieldrin more potent.(27)
However, other researchers have been unable to demonstrate this type of
synergy;(28)(29) these divergent observations further
complicate the subject of endocrine disruptors and the extent of their
Heightened Effects on the Fetus
Research was undertaken
after scientists in many countries had observed a decrease in sperm counts
and an increase in diseases affecting male genital organs. This research
suggests that, in such cases, there may have been exposure to chemical
pollutants that act like hormones in the fetal stage or in early childhood,
and that the effects are observed in adulthood. A literature review reported
on that hypothesis when male fetuses were inadvertently exposed (via the
mother) to abnormal doses of synthetic estrogens such as diethylstilbestrol
(a synthetic hormone used for the treatment of ovarian dysgenesis and
The greater sensitivity
of fetuses and children to toxins present in the environment is attributable
to their rapid growth and their physiological and metabolic immaturity.
The fact that children absorb larger quantities of air, food and fluids
than do adults, relative to their body mass, also increases their potential
for overexposure, as compared to adults.(31)
Research does not always
confirm that pollution has hormonal effects on living organisms; according
to some findings, chemical pollutants have only a minor impact on the
endocrine system while, according to others, the pollutants may harm health
through mechanisms independent of the hormone receptors.
W.G. Foster,(32) for instance, has questioned whether there is real cause
for concern about these disrupting environmental agents, in view of two
factors: 1) the products (in the case of this study, POPs) have only
a minor impact on the hormone system and 2) these products act through
mechanisms that are independent of the estrogen receptor. On the basis
of his work, he concluded that further studies must resolve a number of
points before this question can be answered, but emphasized that current
literature suggests that the potential effects of chemical pollutants
on public health should be a matter of concern.
The Need for More Information
Scientists agree on at least
one point: the current data on endocrine disruptors are inadequate. More
comprehensive studies of the endocrine system and toxic substances must
be conducted to establish clearly the scope of the problem and to develop
a strategy for prevention and intervention.(33) Every scientist has his or her own view of what must
According to Tracey M. Slayton,
among others, science must compile more information on how pollutants
act, the biological significance of the observed effects (reversible or
irreversible), the dose-response relationship, and the potential for chemical
interaction (for example, observation of synergistic or antagonistic effects
between estrogens and toxic compounds). Thomas Crisp and his team
focus on the imbalance in the central nervous system and the pituitary
integration(34) of hormonal and sexual
activity, the male and female reproductive systems, and thyroid function.
Their results suggest the need for analysis of the potential of the endocrine
disruptors to induce prostate, breast and testicular cancer and their
impact on endometriosis. In addition, attention is drawn to the importance
of a better understanding of the etiology(35) of the diseases that are attributed to
With regard to specific
research on the developing fetus and the newborn, research seems to be
needed on the following points: the developmental stage (which is most
sensitive to exposure); thyroid function, including steroid-dependent
processes as other than estrogen-dependent effects; and the combination
of chemical products present in the environment.
The Endocrine Disrupter
Screening Program, established in 1998 by the U.S. Environmental Protection
Agency (EPA),(36) offers the hope of additional scientific data, and perhaps
more systematic data. The program is designed to target pesticides and
other chemical substances that act or are presumed to act
in humans in the same way as natural hormones. It will first examine the
effects of some of these products on the three best-known hormone systems
(estrogen, androgen and thyroid systems), in order to: determine whether
these effects are similar to those produced by the hormones in question;
describe those effects; and quantify the effects. This work should allow
for the classification of products based on their capacity to simulate
hormones. Later, the research could target other hormonal systems.
RECENT GOVERNMENT MEASURES IN
The problem of endocrine
disruptors is complex, and finding solutions requires the participation
of governments as well as industries, universities and the public. Under
the terms of the new Canadian Environmental Protection Act (CEPA),
the Canadian government has set up a research investment fund, one part
of which deals specifically with endocrine disruptors. The Toxic Substances
Research Initiative (TSRI) subsidizes research in specific areas of environment
and health, including toxic substances that disrupt the hormonal system.(37) The TSRI is overseen by a Scientific
Management Committee made up of government and non-governmental scientists
specialized in the area of toxic substances. The Initiative is a result
of a partnership between the departments of Health, Environment, Fisheries
and Oceans, Natural Resources, Indian and Northern Affairs, and Agriculture
Environment Canada incorporates
research on endocrine disruptors into its multiple regional projects on
ecosystems, which allows it to increase what is known on the effects of
endocrine disruptors present in the environment. In addition to other
tasks, the Department is drawing up environmental assessment protocols
to be used in the field and in laboratories. Moreover, it is developing
its national leadership by putting information tools including
an Internet site and a recently created Fact Sheet on the topic of endocrine
disruptors at the disposal of scientists, decision-makers and the
Canada has taken several
other measures (see Appendix 3); if they do not apply directly to
endocrine disruptors, they will nevertheless allow for the gathering of
information on toxic substances that could eventually be targeted.
The Canadian government
is working with international organizations in order to address the issue
of endocrine disruptors as part of a list of serious world problems. These
organizations include the Organisation for Economic Co-operation and Development
(OECD), the United Nations Environment Program (UNEP), and the North American
Free Trade Agreement Commission for Environmental Cooperation (NAFTA-CEC).
Among other initiatives, Environment Canada will participate in international
activities involving the global harmonization of assessment methods designed
to help in the fight against endocrine-disrupting products.
Table 3 summarizes
the international accords that Canada has ratified or is in the process
of ratifying to solve the global problem posed by POPs. One of those accords,
prepared under the auspices of UNEP, should be ready in the year 2000.
This is a legally binding instrument for implementing international action
on certain organic pollutants; its purpose is to reduce emissions and
releases of substances such as DDT, toxaphenes and PCBs that accumulate
in the environment, particularly in the Arctic. During the first session
of the Intergovernmental Negotiation Committee, in June 1998, the
delegates from 92 countries defined the principles that were to guide
TABLE 3: NATIONAL AND
TAKEN BY CANADA ON TOXIC SUBSTANCES
The Green Lane, Environment Canada Internet site, October 1998.
Information from Marcos Silva, CEC Council Session held at Banff, Commission
for Environmental Co-operation, e-mail, 28 June 1999
North American Free Trade Agreement Commission for Environmental Co-operation
United Nations Economic Commission for Europe
Toxic substances management policy (these substances are to be eliminated
(quasi-elimination) according to the policy)
United Nations Environment Program
In addition, Canada
together with 43 European and North American countries has signed
two protocols on persistent organic pollutants under the auspices of the
United Nations Economic Commission for Europe. The first, New
Persistent Organic Pollutants Protocol to the Convention on Long Range
TransBoundary Air Pollution, covers 16 POPs as well as contaminants
and derivatives such as dioxins and furans. The second, the New Heavy
Metals Protocol to the Convention on Long Range TransBoundary Air Pollution,
deals with three heavy metals: cadmium, lead and mercury. Canada ratified
these agreements on 22 December 1998.(38)
Most of the toxic substances
suspected of having effects on the hormone system have appeared on the
market since World War II; many are pesticides from the organochlorine
group. Although available data are not sufficient to determine effects
on humans with absolute certainty, research has proven that those substances
do act on the endocrine system of animal species. Indeed, hundreds of
substances remain to be analyzed, and the conclusions compiled to date
are valid only for those products already specifically assessed.
Moreover, although some
scientists are extremely concerned about these substances, others are
more cautious. In fact, some studies show that a number of additional
factors other than endocrine disruptors such as changes in diet
and habits during pregnancy may be responsible for an increase
in the incidence of cancer.
In any event, most researchers
agree on one point: more studies must be carried out to provide further
information on the effects of endocrine disruptors. This information will
then make it possible to establish policies and standards for the assessment
and use of clinical products.
Canada is already participating
in a number of national and international efforts to counteract the effects
of these products on health and the environment. Other possible measures
include a review of the current Pest Control Products Act, which
has not been updated for more than 30 years. In addition, the Canadian
government could invest in detailed research on the effect of the endocrine
disruptors on the hormone system.
LIST OF KNOWN AND SUSPECTED HORMONE DISRUPTORS
A. Pollutants with Widespread
Distribution Reported to have Reproductive and
Dioxins and furans
Penta- to Nonyl-Phenols
Butyl benzyl phthalate
Di-hexyl phtalate (DHP)
Diethyl phthalate (DEP)
B. Pollutants with
Widespread Distribution Reported to Bind to Hormone Receptors and
Therefore Suspected to Have
Reproductive and Endocrine-disrupting Effects
list of substances considered to have endocrine-disrupting and reproductive
effects is compiled by the Endocrine Disrupter Resource Centre from
a variety of sources including:
and C. Clement. Chemically Induced Alterations in Sexual and
Functional Development: The Wildlife/Human Connection. Princeton,
N.J.: Princeton Scientific Publishing, 1992.
F. vom Saal and A.M. Soto. "Developmental Effects of Endocrine-Disrupting
Chemicals in Wildlife and Humans," Environmental Health Perspectives,
Vol. 101, No. 5, 1993.
Lyons, G. Phthalates
in the Environment, World Wildlife Fund, UK, 1995.
Agriculture, Fisheries and Food. Effects of Trace Organics on Fish,
Phase II, Foundation for Water Research, UK, 1995.
Note: All of
the substances currently identified as hormone disruptors are now widely
distributed throughout the environment; some are common constituents
of consumer products, and many are now found in human tissues.
DESCRIPTION OF HEAVY METALS STUDIED BY THE
NORTHERN CONTAMINANTS PROGRAM
Cadmium is a white, ductile, malleable metal from the same group as mercury.
It is used in alloys to protect other metals. Aside from its use by the
metallurgical industry, its most familiar use is in nickel-cadmium batteries.
In spite of the fact that the transportation sector, waste disposal activities
and land application of sewage sludge also contribute to the presence
of cadmium, metal smelters and refineries are the main source of cadmium
in the Canadian environment (82%, or 130 t/year); 92% of this metal
is found in the atmosphere.(39) Although cadmium does not break down
in the environment, chemical and physical processes affect its mobility,
its bio-availability and lifetime, and thus the extent of the danger that
it presents to mammals and human beings. For example, cadmium has been
found to accumulate in the organs of marine mammals (bioaccumulation).
According to experts at Environment Canada and Health Canada, current
information suggests that in certain cases, the accumulation of cadmium
in the environment may have adverse effects on human health. For instance,
there has been an increase in mortality attributable to lung cancer in
workers exposed simultaneously to cadmium and arsenic. Cadmium is also
associated with effects on the renal system.
production of chlorine and caustic soda, waste incineration, coal burning
and metallurgy are the principal anthropogenic sources of mercury, a white
metal that is liquid at room temperature. The methylated form of mercury
accumulates in the environment (bio-amplification), while the gaseous
elementary form of the metal found in the atmosphere is increasing globally
at a rate of approximately 1% per year.(40)
Mercury also accumulates in lake sediments. This metal is associated in
particular with sensory or neurological deficits. Dental amalgams made
the headlines when it was observed that the mercury they contained could
have effects on health. Although current evidence does not indicate that
these amalgams are causing illness in the general population, according
to a notice issued by Health Canada, a small proportion of the population
can suffer severe health effects from even a low exposure.(41)
More detailed studies are required for a proper assessment of this metal
and its real effects.
Lead, an extremely malleable bluish-grey metal, was found primarily in
gasoline until the 1975 adoption of regulations to reduce lead additives.
Because lead additives have been eliminated in gasoline and in the production
of food cans, the principal sources of this pollutant today include industrial
emissions (foundries, refineries), plumbing solders, hunting ammunition,
certain toys, domestic household products, and food containers. Lead exposure
occurs primarily (80% to 90%) through food.(42)
Because children absorb more food than do adults in relation to their
body mass, they have the highest blood concentrations of lead. Adult men
have higher concentrations than do women, because of their slightly higher
hemoglobin level. Lead poisoning can harm the hematological, gastrointestinal
and neurological systems. Wildlife (particularly waterfowl and their predators)
is particularly affected by the lead shot used by hunters; an estimated
250,000 aquatic water birds die each year of lead poisoning. To address
this problem, Canada now requires hunters to use non-toxic shot.(43)
The first phase of the NCP
ended in 1997, and its objective is to assess the risk of contamination
by various products associated with the traditional foods eaten by Aboriginal
people in the arctic region. The program is funded by Treasury Board and
four departments that also participate in its management to varying degrees.
For instance, Health Canada provides advice on the risks posed by certain
POPs and funds research on the analysis of the potential problems associated
with those substances. Three heavy metals have been added to the list
of substances being studied (see Appendix 2).
Toxic Substances Management
The Toxic Substances Management
Policy was adopted in 1995 to provide a scientific context for the identification
of toxic substances present in the environment. A two-part or "two
track" (according to the Policy) assessment grid is used for the
classification of substances:
substance" a substance that is bioaccumulative, persistent
and primarily the result of human activity, in which case it must
be eliminated from the environment ("quasi-elimination")
under the terms of the Canadian Environmental Protection Act (for
example, chlordane, in Table 3, is a Track-1 substance);
substance" a toxic or worrisome substance subject to life-cycle
management to prevent or minimize, as much as possible, its release
into the environment.
New provisions of the
Canadian Environmental Protection Act (CEPA)
Under the terms of the new
CEPA adopted 14 September 1999, all substances currently
in use in Canada will be categorized to determine if they are toxic. CEPA
also establishes deadlines for measures to be taken to control toxic substances
and will require the virtual elimination of the most dangerous of these.
These measures will include assessing 23,000 new and existing substances,
as well as managing and controlling toxic substances and tracking the
progress of the process.(44)
The scope of the Act is
illustrated by the story of dioxins (polychlorinated dibenzoparadioxins)
and furans (polychlorinated dibenzofurans), which were declared toxic
in 1999 under the old Canadian Environmental Protection Act, on
the basis of an assessment by Environment Canada and Health Canada. These
by-products were then added to the list of toxic substances in the Act.
The subsequent adoption of various regulations, including the Pulp
and Paper Effluent Regulations (in 1992), reduced the quantity of
dioxins and furans released into the environment by 98%.
Pest Management Regulatory
The PMRA was established
in 1995 to apply the Pest Control Products Act (PCPA). Under
this Act, all products imported, manufactured, sold or used in Canada
must be federally registered. A pest control product may not be registered
unless the risks to human health and to the environment are acceptable
and the product is useful for pest control. The PCPA also provides
a regulatory framework for aquacultural producers, unless the product
(parasiticide) is considered a drug, in which case the Food and Drugs
Various measures relating
to heavy metals and chlorinated substances
The North American Regional
Action Plan on Mercury, initiated by the Commission for Environmental
Cooperation of the NAFTA, is now in phase II. This plan is designed
to eliminate gradually, or to prohibit, uses of mercury that present unacceptable
or uncontrollable risks of release into the environment or risks to health.
The Canadian Plumbing
Code prohibits the use of lead solder in new plumbing systems and
in repairs to drinking water supply systems.(46)
In addition, in 1996, Canada adhered to the Organisation for Economic
Co-operation and Development Ministerial Declaration on Lead. As a
result, it is now sharing its skills in monitoring lead exposure with
other countries. The Declaration supports the elimination of leaded gasoline
as well as ending the exposure of children to lead through products designed
for them and through food containers. The Declaration includes a voluntary
action plan for lead-producing industries. For instance, producers are
encouraged to reduce lead exposure and to establish risk reduction programs.(47)
The Chlorinated Substances
Action Plan, adopted by Canadas Ministers of the Environment
and Health, presents Canadas approach to chlorinated substances.(48)
It consists of five components designed to meet specific objectives: targeting
critical uses and products through legislative or voluntary tools; improving
scientific knowledge; studying the effects on health and on socio-economic
aspects; providing Canadians with better information; and promoting and
directing international efforts.
(1) Testicles and ovaries.
(2) Petit Larousse de la médecine, Tome 1, 1976.
(3) The Endocrine Disrupter Resource Center, Institute
for Agriculture and Trade Policy
(4) Environment Canada, Endocrine Disrupting Substances
in the Environment, 2000.
(6) Gina Muckle, Éric Dewailly and Pierre Ayotte,
"Prenatal exposure of Canadian children to polychlorinated biphenyls
and mercury," Canadian Journal of Public Health, Vol. 89,
Suppl. 1, May/June 1998, pp. 22-26.
(7) Presentation concerning pesticide residues in the
Canadian Arctic and the Northern Contaminants Program, House of Commons
Standing Committee on the Environment and Sustainable Development, 9 December
(8) J. Jean, K. Adare and R. Shearer, Canadian
Arctic Contaminants Assessment Report, Northern Contaminants Program,
Indian and Northern Affairs, 1997; Draft of the report of the EcoSummit
(9) Brief submitted by the Inuit Tapirisat Circumpolar
Conference of Canada to the Standing Committee on Environment and Sustainable
Development, 9 December 1999.
Environment Canada, "Persistent organochlorines," S and E
Bulletin, January 1998, Environment Canada Internet site (http://www.ec.gc.ca/Ind/English/Toxic/default.cfm).
(11) A pesticide is any product designed to limit, destroy,
attract or repel pests that is used, sold or imported into Canada. Pesticides
include chemicals, devices and even organisms. Pest control products include
herbicides, insecticides and fungicides as well as algicides, animal and
insect repellants, cleaning and antimicrobial products, preservatives
for materials and wood, and devices for the control of insects and rodents.
This definition is based on the definition of control product in
Control Products Act.
(12) World Wildlife Fund, The Problems with Pesticides
in Canada, a Briefing Book for Parliamentarians, Canada, June 1999.
Environment Canada (2000).
(14) Standing Committee on Environment and Sustainable
Development, PESTICIDES: Making the Right Choice for the Protection
of Health and the Environment, May 2000.
(15) Embryotoxic: The character of a substance that can
harm the embryo.
(16) Teratogenic: The character of a substance that can
cause abnormal or monstrous forms in an organism.
(17) The Endocrine Disrupter Resource Center, Institute
for Agriculture and Trade Policy
(19) Shirley A. Briggs, Basic Guide to Pesticides
Their Characteristics and Hazards, Rachel Carson Council, 1992.
(20) Michael Gilbertson, "Linking Water Quality to
Wildlife and Human Health," FOCUS, International Joint Commission,
November 1998, pp. 18-19.
(21) International Joint Commission, FOCUS (http://www.ijc.org/focus).
(22) Benjamin J. Danzo, "Environmental
Xenobiotics May Disrupt Normal Endocrine Function by Interfering with
the Binding of Physiological Ligands to Steroid Receptors and Binding
Proteins," Environmental Health Perspectives, Vol. 105,
No. 3, March 1997, pp. 294-301.
(23) Congener: A product that belongs to the same chemical
group and is derived from the same initial compound.
(24) Ligand: In this case and in non-technical terms,
a molecule that has the necessary properties to attach itself to a receptor.
(25) Annette Pernelle et al., "Organochlorine
Exposure and Risk of Breast Cancer," The Lancet 352(9143),
1998, pp. 1816-1820.
(26) Steven Arnold et al., "In Vitro
Synergistic Interaction of Alligator and Human Estrogen Receptors with
Combinations of Environmental Chemicals," Environmental Health
Perspectives, Vol. 105, Suppl. 3, April 1994, pp. 615-618.
(27) Steven Arnold et al., "Synergistic
Activation of Estrogen Receptor with Combinations of Environmental Chemicals,"
Science, Vol. 277, 1997, pp. 462-463.
(28) K.F. Arcaro et al., "Lack of Synergy
by Mixtures of Weakly Estrogenic Hydroxylated Polychlorinated Biphenyls
and Pesticides," Environmental Health Perspectives, Vol. 106,
Suppl. 4, August 1998, pp. 1041-1046.
(29) K.F. Ramamoorthy et al., "Estrogenic
Activity of a Dieldrin/Toxaphene Mixture in the Mouse Uterus, MCF-7 Human
Breast Cancer Cells, and Yeast-Based Estrogen Receptor Assays: No Apparent
Synergism," Endocrinology, Vol. 138, No. 4, April 1997,
(30) Jorma Toppari et al., "Male Reproductive
Health and Environmental Xenostrogens," Environmental Health Perspectives,
Vol. 104, Suppl. 4, August 1996, pp. 741-803.
(31) Graham W. Chance and Eef Harmsen,
"Children are Different: Environmental Contaminants and Childrens
Health," Canadian Journal of Public Health, Vol. 89,
Suppl. 1, May/June 1998, pp. 10-14.
(32) Warren G. Foster, "Endocrine Disruptors
and Development of the Reproductive System in the Fetus and Children:
Is there a cause for concern?" Canadian Journal of Public Health,
Vol. 89, Suppl. 1, May-June 1998, pp. 41-45.
(33) Danzo (1997); Thomas M. Crisp et al.,
"Environmental Endocrine Disruption: an Effects Assessment and Analysis,"
Environmental Health Perspectives, Vol. 106, Suppl. 1, February 1998,
p. 11-56; Toppari et al. (1990); Tracey M. Slayton,
"Persistent Toxins that Bioaccumulate (PTbs) and Endocrine Disruptors,"
Internet site, 1996; Helen Tryphonas, "The Impact of PCBs and
Dioxins on Childrens Health: Immunological Considerations,"
Canadian Journal of Public Health, Vol. 89, Suppl. 1,
May/June 1998, pp. 54-57.
(34) Pituitary: site at which hormones are transferred
from the hypothalamus to the pituitary circulation.
(35) Etiology: the study of the causes of disease and
factors contributing to it.
Environmental Protection Agency, "Endocrine Disruptor Screening Program
11 August 1998.
(37) Environment Canada, "Federal Ministers Announce
that $40 million will be allocated to research on health and environment
in Canada," Communiqué, 7 December 1998.
(38) Environment Canada, "Canada First Country to
Ratify International Agreements to Reduce Toxic Airborne Pollutants,"
News Release, 22 December 1998.
(39) Environment Canada and Health Canada, Cadmium
and its compounds, 1994.
(40) Jensen et al. (1997).
(41) Health Canada, Health Canada Position Statement
on Dental Amalgams, Health Canada Internet site, 30 June 1999.
(42) Jensen et al. (1997).
(43) Environment Canada, Lead Shot, Fact Sheet,
the Green Lane Internet site, Environment Canada, 5 February 1999.
(44) Environment Canada, "New Funding to Implement
the New Canadian Environmental Protection Act," Communiqué, The
Green Lane, 4 September 1999.
(45) Health Canada, Food and Drugs
Act, March 1999.
(46) Health Canada, Its Your Health: Lead and
Human Health, Health Canada Internet site, 28 June 1996.
(47) Environment Canada, Canada Supports OECD Decisions
to Reduce Lead Exposure and Green Government Operations, The Green
Lane, Environment Canada Internet site, 5 February 1999.
(48) Environment Canada and Health Canada, Chlorinated
Substances Action Plan, Progress Report, Environment Canada Internet
site, October 1996.