Click to edit Master text styles
Second level
Third level
Fourth level
Fifth level
Today’s children are growing up in an environment that is radically different from that of their parents and grandparents.  That environment is teeming with many thousands of chemicals and toxins. We can detect traces of synthetic chemicals in the tissues of just about all people and animals on the globe.  Our knowledge of the environmental and health effects of the vast majority of these chemicals is incomplete. 
Children’s health in relation to environmental exposures is of great concern.
Since the early 1990s there has been a rapidly growing body of knowledge that has shone a light on the specific vulnerabilities of children and the potentially devastating effects from even low levels of exposure to many different contaminants.  This research is also highlighting the need for greater efforts to protect children from environmental risks to health.  This can be achieved through an awareness, avoidance and advocacy framework.  We need to create greater awareness of the potential environmental risks to child health, to implement risk avoidance measures and to advocate for overall improvement in environmental quality.  This will involve education of all those who influence the well-being of children including parents, caregivers, health professionals and policymakers.  All of these groups need to better understand that environmental risks to children’s health are preventable.
Environmental health, as defined by the World Health Organization, includes aspects of human health and disease that are determined by environmental factors. It can also include the theory and practice of assessing and controlling factors in the environment that can potentially affect health. It includes both the direct pathological effects of chemicals, radiation and some biological agents, and the effects (often indirect) on health and well-being of the broad physical, psychological, social and aesthetic environment which includes housing, urban development, land use and transport (WHO Regional Office for Europe, 1989).
A child’s environment includes everything around the child, in both indoor and outdoor settings, and including all that is taken into the body. It includes consumer products where these contribute to toxic exposures. Since babies develop for nine months in utero, the mother’s body is a child’s first environment and her breast milk the first food. The physical environment includes natural and built environments.
Experts in the field of children’s environmental health sometimes refer to the “new pediatric morbidity” when discussing child health trends for which environmental factors may be contributing causes (Landrigan et al, 1998). Alongside the traditional measures or indicators of child health, such as infant mortality or infectious diseases, they look at trends in respiratory health (especially asthma), cancer, neurodevelopmental and neurobehavioural outcomes and various reproductive and developmental indicators such as fertility rates or birth defects. This new perspective embraces the broad definition of child health described above. It looks at both developmental and functional health endpoints in investigations that try to unravel the complexity of the environment-human health interface
In contrast to adults children represent a particularly vulnerable group because their bodies and physiological systems are undergoing substantial growth and development.  Starting from in utero to adolescence there are numerous periods of cell proliferation and tissue differentiation representing critical windows of vulnerability.  These are the times when it is most likely that toxic exposures might have permanent effects.  Immature physiological systems also mean that children are particularly ill-equipped to handle toxic contaminants.  They absorb more contaminants from their environment and their body defenses lack the functionality to properly excrete or de-toxify such chemicals. There are also key behavioural differences between children and adults at every stage prior to maturity that influence the exposures of the young.  They play closer to the ground and explore their environment using all their senses.  They have particular food preferences.  They spend more time indoors but are also very active when they play outdoors. Children are more often passively exposed since they cannot protect themselves but depend on adults for their protection. To use the term coined by Lynn Goldman a former U.S. EPA scientist, children have longer shelf-life.  They have more years of life ahead of them during which the effects of environmental exposures may manifest themselves. For many of these reasons, we cannot always extrapolate from our knowledge of the effects of contaminants in adults to understand how they will affect children’s health.    
In general, organisms are exposed to environmental hazards via several possible pathways.  Pathways trace the route that the contaminant travels from its source to the living organism (the receptor).  Health Canada’s scheme divides exposure pathways in to three sets of factors that include: 1) Contamination source: this is the ultimate origin of a contaminating substance. 2) Environmental media: are the elements through which the contaminant travels and that represent the points at which humans become exposed.  Water, air, soil and food are the main environmental media. 3) Routes of exposure: are the means by which contaminants are then transferred to, or absorbed by the human body.  These may include any or all of inhalation, skin absorption or ingestion, depending upon the media. The degree to which a chemical is absorbed by the body depends mainly upon the physical and chemical properties of the substance, as well as the nature of the exposure route and the exposure amount. The main portals of entry, the lungs, digestive system and skin, may in the case of some substances, effectively inhibit absorption.  If a substance does pass into the body it may be metabolized in the liver and excreted as a waste product although this does not necessarily mean that the body tissues will fully escape the harmful effects of that substance.  Some chemicals are not readily excreted but become stored in the body.  For example, chemicals that are fat soluble are not only easily absorbed, but also become stored in the body’s fatty tissues.
Children are exposed via many potential pathways AND they are often relatively more exposed to environmental contaminants compared to adults This figure illustrates a model that more accurately depicts all exposures of children.  There’s a lot to take in here, but I will highlight some key points.
Children are exposed via many potential pathways AND they are often relatively more exposed to environmental contaminants compared to adults What distinguishes the child’s exposure pathways is that their exploratory behaviour, hand-to-mouth activity and the fact that they are closer to the ground, mean they have greater contact with sources of contamination. 
Beyond the four main environmental media through which contaminants travel to people (namely air, water, soil, food), there are additional exposure media for children that are not relevant to the adult.  These include, contaminant transfer via the placenta, breast milk and non-food products, such as toys, carpets, floor surfaces, etc., which may harbour contaminants.
The routes of exposures for children are also quantitatively and qualitatively different.  Underdeveloped, immature organ systems (especially the lungs, skin and gastrointestinal tract) allow greater absorption of chemical contaminants via inhalation, absorption and ingestion.  As well, the smaller size of the child means that they have relatively greater intake of substances via breathing, ingestion and skin contact by comparison to their body weight.
There are also accompanying behavioural changes at every stage of life that influence the exposures of the young. 
Infants are dependent on parents for the security of their environment.  They are generally always near their mother and will have similar exposures to her. They may spend a lot of time lying in one location.  Toddlers and older infants are mobile and can readily explore their environment.  They frequently put items and their hands into their mouths.  Infants, toddlers and young children spend most of their time indoors. 
Once children reach school age, they are coming into much greater contact with the external world beyond their homes, and thereby have greater chance of exposure from a variety of sources, including schools, day-care, parks, playgrounds and the homes of others.  Older children are also more likely to be unsupervised and to participate (often unwittingly) in adventurous or risky behaviour.  For example, in 1993 a dozen Hamilton school children between the ages of 9 and 14 found liquid mercury in the laboratory facilities of an abandoned industrial plant.  From that small group, over 250 other children were rapidly exposed to the mercury through school chums, the majority of these children having direct contact with the mercury from touching, playing with it, spilling or pouring.
As children reach adolescence, they are even  more exposed to the outside world and therefore come into increasing contact with a broad range of sources of environmental contaminants. Behaviourally, adolescents also have greater opportunities for exposure through occupational scenarios and are even more likely to be involved in health risk behaviours
A mother’s body is in fact, the first environment. 
The nine months from conception to birth represent the most vulnerable in an individual’s existence with respect to environmental exposures.  It is during this time that exposure may result in physical abnormalities. We have learned that many contaminants can cross the placental barrier from mother’s to the fetal bloodstream, and therefore, can alter in profound and subtle ways the development of a child at this earliest stage. In the medical context, it is still not routine to caution women to avoid exposure to various harmful substances such as pesticides (or, at least there is a presumption that if manufacturer’s directions are followed there will not be a problem).  Here in Canada, we have a unique service in the Motherisk Program operated out of Sick Children’s Hospital, a phone-in information source for both the public and health professionals.  However, staff at Motherisk state that they receive very few calls related to exposure to contaminants, and their fact sheets provide information mainly on acute exposures.
Growth and development is a complex process.  At each stage in a child’s developmental path unique biological processes occur. The physiological and morphological milestones that mark a child’s development equate to “windows of vulnerability” or critical periods during which interference with the developmental process by exposure to an environmental contaminant may result in irreversible changes.  The outcome of exposure varies depending upon the timing of exposure in a child’s life. 
·In utero exposure of the embryo or fetus to environmental contaminants, many of which are able to cross the placenta, may permanently alter the course of development, even at very subtle exposure levels.  The prenatal stages of development of major organs, body structures, nervous and reproductive systems, represent especially sensitive times.
·Postnatally, certain organ systems and body structures are also more vulnerable to effects from exposure because they undergo continued differentiation before adulthood. The brain, nervous system and lungs undergo extensive growth after birth and are particularly sensitive throughout much of childhood as a result. For example, we now know that lead exposure prior to age 2 has marked effects on nervous system development. Endocrine disruptors and air pollutants may operate at an early stage in development, predisposing children to health effects later on in life. 
·At the same time, the fact that several other body systems are immature in the infant and child renders them particularly ill equipped to handle toxic contaminants. The digestive tract and skin are extremely permeable and the developing lungs present large surface areas through which chemicals may be easily absorbed.  The physiological mechanisms that normally help protect the body from chemicals that do invade it, such as the immune, excretory and de-toxifying systems are also underdeveloped in the earliest stages of life. 
Not all children in this country are equally at risk of harm to their health from environmental exposures.
There are individual genetic, social, economic or cultural factors that influence the extent to which different groups of children are exposed or respond to environmental contaminants.  Poor children and indigenous children suffer the worst of all possible worlds in being perhaps the most highly exposed to contaminants by virtue of their unique circumstances.  With lead for instance, we know that a proportion  of children are defined as being at greater risk of exposure, especially those from lower income homes where physical conditions within the home, proximity to sources of contaminants, as well as inadequate nutrition levels, may all predispose these children to higher lead exposures.
Inuit children in Northern Quebec are exposed to the highest known levels of organochlorine contaminants in mother’s milk– four to five times that of non-native women in southern Quebec.  This is because of traditional dietary staples such as seal and fish.
Researchers at Sick Children’s hospital were able to show that mothers who were exposed to solvents through their work had greater risk of having a child born with a birth defect. 
Health researchers have come to recognize that a broad array of conditions in childhood are influenced by many different environmental contaminants.
Experts in the field of children’s environmental health sometimes refer to the “new pediatric morbidity” when discussing child health trends for which environmental factors may be contributing causes (Landrigan et al, 1998).
Alongside the traditional measures or indicators of child health, such as infant mortality or infectious diseases, they look at trends in respiratory health (especially asthma), cancer, neurodevelopmental and neurobehavioural outcomes and various reproductive and developmental indicators such as fertility rates or birth defects. The items listed here include health conditions such as asthma and respiratory problems, childhood cancers and learning disabilities, among others.
The child environmental burden of illness is increasing in Canada and other industrialized countries.
The causes of childhood cancer are not well understood, but greater exposure to environmental contaminants is a potential factor associated with its appearance. Several studies suggest that exposures perinatally and of parents prior to conception, to things like organic solvents, benzene and pesticides are linked with appearance of cancer in offspring.
Childhood cancers are relatively rare (in epidemiological terms) and therefore, difficult to study in samples of adequate size. Although the number of children affected is small, there is some thought that childhood cancers have increased over the last 25 years.  In Canada, we have few enough cases that it is difficult to establish the long term trends.  Over the last 10 to 15 years, incidence has hovered at around 16cases per 100K children. 
Certain types of childhood cancers have shown considerable increases, namely, acute lymphoid leukemia, tumours of the CNS and bone tumours.  Exposures to pesticides pre-conceptionally, prenatally and during childhood, both in the environmental and occupational settings have been associated with moderate increases in childhood brain tumours and leukemias.
Although most other types of cancers are more difficult to link to the causal exposures (and do not directly affect children), there is still good reason to prevent exposure to carcinogenic substances at the youngest ages possible.
Developmental neurotoxicity and behavioural effects are of particular concern as more is learned about the nature of more subtle degrees of impairment that can occur with even low level exposures.  The window of susceptibility to neurotoxic effects is broad because of the extensive age-related development that the brain and nervous system undergoes from fetal stage, through childhood and into adolescence.  
Pesticides have also come under scrutiny as preventable exposures.  There is recognition of the need to reduce pesticide residues in the North American diet, as recommended by the seminal work of the National Academy of Sciences. This is driving the thrust for new child-centred standards in the U.S.
The anthropologist Dr. Elizabeth Guillette, has been studying pre-school children in northwestern Mexico for neurobehavioural impacts from pesticide exposure. Children from the agricultural Yaqui Valley Indian community are routinely exposed to aerial pesticide spraying as well as daily household bug spraying and there have been high levels of organochlorine pesticides measured in newborn cord blood and breast milk in this community. 
She compared this group to children from the foothills region, who are less exposed but are similar for other features (such as genetic origin, living conditions, diet, social and cultural behaviours) that might influence growth and development. These drawings done by the Yaqui Indian children show dramatic evidence of the neurodevelopmental effects from high exposure to pesticides. Children from the exposed valley community had impaired motor co-ordination, balance and memory and less stamina. Dr. Guillette reports recently that a second visit to the community two years later found that the valley children are sick more often and are still displaying delayed development.
Pollutants in both indoor and outdoor air, are associated with respiratory problems in children. The “Health Effects Pyramid” here illustrates how with decreasing severity of symptom, there is an increasingly larger proportion of the population that is affected.  In other words, fewer people die from the effects of air pollutants, however, many more people do suffer some degree of respiratory impairment or illness. Pollution-related respiratory symptoms in kids range from subtle, non-specific symptoms such as sore throat, cough and wheeze, to increased frequency of asthma attacks, physician and hospital emergency visits, permanent reduction in lung capacity and an increased risk for Sudden Infant Death Syndrome (SIDS). 
Canadian children are more likely to be hospitalized for respiratory problems, especially asthma, than due to any other cause.  Epidemiological studies do show clear associations between episodes of high air pollution and subsequent hospital visits for respiratory problems.  Outdoor air pollutants such as ground-level ozone, particulates and acid aerosols are important risk factors that worsen existing disease or trigger asthma attacks.
The chart here also shows you data indicating that the poorest children in Toronto have nearly double the risk of respiratory hospitalizations compared children from families in the highest income bracket.  (This phenomenon has been observed in other populations where low SES children suffer relatively greater from asthma symptoms.)
Pollution-related respiratory effects in all kids range from subtle, non-specific symptoms such as sore throat, cough and wheeze, through to more serious effects such as an increased risk for Sudden Infant Death Syndrome (SIDS).  (Essentially they fall into a the health effects pyramid as described by Dr. Basrur in her address this morning.)
Exposure to air pollution in the young may also permanently affect lung capacity.  It may also predispose children to developing chronic respiratory illness or put them at higher risk of ill effects from other environmental exposures later in life.
Exposure to air pollution is widespread and obviously not just affecting children as you heard this morning.  The TPH report of May, 2000 estimated that in 1995, 1000 premature deaths in Toronto were attributable to air pollution.
it’s also not just exposure to outdoor pollution that affects respiratory health in kids.
Gaps in Knowledge
·Of all chemicals in use and being produced, only a relatively small fraction have been tested to assess for any or all types of health effects.  Aside from lead, mercury and PCBs, there is relatively little information on the health impact of many environmental contaminants specifically in children.
·Frequently there is imperfect knowledge of the mechanisms by which environmental contaminants may lead to particular health effects.  For example, although there is modest evidence for cancer stemming from childhood exposure to pesticides, the process remains speculative.  In part, this stems from our incomplete knowledge of many aspects of normal developmental processes and physiological parameters.
·Much less is understood of low-level exposures (to organic chemicals and toxic metals) but they may predispose to chronic illness, decrease higher brain function, especially learning, or impair fetal and childhood development.
·We don’t know how long after exposure at an early age health effects might appear (i.e. the latency period), what the effects of life-long, low-dose exposure are, as well as what effects might occur in one generation as a result of the previous generation’s exposures (transgenerational effects).  Research is suggesting these are all important areas of inquiry.
·Real-world exposures to environmental contaminants rarely mirror those seen in the controlled laboratory experiment.  We don’t have a clear understanding of the effects of cumulative and multiple (mixed), synergistic (combined or interactive) exposures to environmental chemicals, which we presume every one of us undergoes.
Our report describes many contaminants, health effects, environmental media and routes of exposure and why children are particularly susceptible because of both increased exposure and increased sensitivity.  What are the issues of greatest concern for children, their parents, communities, researchers and policy?  These can be prioritized according to two criteria: 1) the numbers of children affected and, 2) the severity of outcome.
Number of Children Affected
We identify three very different issues that are of concern because they affect (actually or potentially) large numbers of children.  For two of these the health effects in children are extremely well characterized. The third represents an area of research that is much less well defined , yet the major uncertainties are of critical concern to society.  This creates new challenges for policy. 
Breast milk is the most important (and often the only) source of nutrition for the infant during the first few months of life.  Chemicals in breast milk largely stem from the mother’s stored body burden of contaminants which are mainly from foods such as meat, fish and dairy products.
Nursing babies are at the top of the food chain and therefore, there is concern that they may receive close to an adult level dose at the beginning of their lives when they are breast-fed.  However, the potential for health effects from contaminants in breast milk is not easily determined  mainly because it is impossible to separate the effects from prenatal (via placenta) versus postnatal (via breast milk) exposure.
Long term studies of children whose mothers had measurable levels of PCBs in breast milk, have found slight effects on neuromuscular development in the first 2 years, with development progressing normally after that.  Others have observed cognitive and behavioural problems but indicated that prolonged breast-feeding was linked to improved memory and verbal scale test performance.  Health studies of breastfed Inuit infants have indicated an increased incidence of ear infections and “modest” compromise to immune function. 
After repeated evaluation of the risks versus benefits of breastfeeding, it has been widely acknowledged that the benefits from breast-feeding, for both infant and mother, (including psychological, nutritional, immune and health protective benefits) far outweigh the risks from exposure to breast milk contaminants.  Hence, virtually no health researcher or practitioner would deny that “breast is best”.
Children are particularly vulnerable to health effects from lead, even at very low levels of exposure.  Children are also predisposed to higher exposure to sources of lead contamination.  We now believe that lead may permanently alter a child’s physical, mental, intellectual and behavioural development and that there may be no “safe” threshold for these developmental delays.  Many of the previous sources of lead exposure have been eliminated or significantly reduced.  However, this was not before literally millions of children suffered the consequences from exposure to lead in gasoline and consumer products.  (We not that there are also likely millions of children in developing countries where leaded gasoline is frequently still used who are suffering health effects.)  There is still reason to remain vigilant about the possibility for many children to be exposed through new or unexpected and virtually unregulated sources of lead (e.g., from a variety of consumer products), because of their unique behaviour and because of the persistence of lead in the environment.
There has been a dramatic increase in the prevalence of asthma in the last 20 years, affecting 672,000, or over 11% of Canadian children in 1994/95. Asthma is the most common chronic condition of childhood; a major public health issue.
We do not know what is driving the increased prevalence of childhood asthma, but areas of research must include familial, allergenic and environmental factors. We do know that exposure to both outdoor and indoor pollutants, and Environmental Tobacco Smoke, makes asthma worse in asthmatics. The role of pollution in the causation of asthma must be studied more since exposure to air pollution is widespread.  In Canada, the south Atlantic region, Ontario and Lower Fraser Valley in B.C. are three regions where air pollution is greatest.
Endocrine disruption is a relatively new concept in environmental health. There has been an explosion of research and understanding, but it remains an area of enormous scientific uncertainty.  The story of lead suggests that uncertainty should not supersede a precautionary approach when the stakes are so high (i.e. widespread exposure combined with profound health effects). 
We are all exposed to many thousands of endocrine disruptors and researchers speculate that they are capable of exerting population-wide effects at current levels of exposure. They are measurable at very low levels in the body fluids and tissues of all our children.  Some of them (persistent organochlorines) are stored in the body for long periods of time.  The significance of this is unclear. Wildlife, exposed to higher levels of persistent organochlorines, has been found to suffer reproductive dysfunction and sexual abnormalities.  At present we live with uncertainty as to whether endocrine disruptors might be affecting cancer rates, reproductive function and development, neuro-development, the immune systems and thyroid function of children. Of immediate concern are the levels of two persistent organochlorines with endocrine disruption action, dioxin and PCBs, in the breast milk of mothers in the Great Lakes Region.  (Recent Health Canada estimates indicate that exclusively breastfed infants under 6 months of age in the Great Lakes region are likely exposed to almost six times the Tolerable Daily Intake of 10 pg TEQ/kg bw/day for dioxin.) Although breast milk is clearly considered best for the baby, this is an area that warrants continued scientific and immediate policy attention.  We need to focus on reducing the chances that these substances continue to end up in the environment and ultimately, in human tissues, being passed on from generation to generation. Colborn, T, D. Dumanoski, and J. Peterson Myers, Our Stolen Future (Dutton,  New York, 1996), see in particular, Chapter 11 (Beyond Cancer) and Chapter 11 (Flying Blind). Haines M., et.al.,. Dioxins & Furans. Chapter 6.0 and Polychlorinated Biphenyls. Chapter 11.0In: Persistent Environmental Contaminants and the Great Lakes Basin Population:  An Exposure Assessment.  Health Canada.  Minister of Public Works and Government Services, Canada.  Catalogue No. H46-2/98-218E. (1998).
Severity of Outcome:  Childhood Cancer
Cancer is the most feared of childhood diseases.  It is the second leading cause of death in 0-14 year olds. Childhood cancers are relatively rare (in epidemiological terms) and therefore, difficult to study in samples of adequate size.  Of great concern is the apparent increased incidence of certain childhood cancers, especially leukemia, brain tumors and, testicular cancer in young men. What role do environmental agents play in the etiology of cancer? What is the relationship between genetic, developmental and environmental factors? Great strides have been made in the treatment of childhood cancer, offering hope to affected children and families. But the ultimate victory over cancer will be prevention of the disease. Hopefully the search for, and elimination of, environmental causative or promoting agents, will be a huge step in this direction. The causes of childhood cancer are not well understood, but greater exposure to environmental contaminants is a potential factor associated with its appearance.
Although most types of cancers are difficult to link to the causal exposures (and do not directly affect children), there is still good reason to prevent exposure to carcinogenic substances at the youngest ages possible.
Neurodevelopmental Effects
Lead levels in the blood of Ontario's children dropped steadily as lead was removed from gasoline. How many children were affected prior to this we do not know, although conservative estimates are that likely tens of thousands of children across Canada were exposed. We do know that lead, even at levels previously common in Ontario, and certainly common in other parts of the world that still use leaded gasoline, has been consistently associated with lower scores on tests of intellectual function, and with reading disabilities and failure in school. Meta-analyses of the numerous studies on lead and neurological effects in children conclude that an increase in blood lead levels from 10 to 20 ug/dL results in approximately a 2-point deficit in IQ (Shannon, 1999).  The figure on the right shows how the difference between the normal distribution of IQ values in a population with a mean of 100 (shown by the solid line) and what happens when there is an overall population IQ shift downward by 5 points (the dashed curve).  In the population with lower average IQ, if you consider the shaded tails of the new distribution, there are 2.5 times fewer individuals with IQ;s greater than 130 and double the number of persons with IQ’s less than 70 which is the clinical definition of mental retardation.   The loss of human potential has probably been substantial.
There are other chemical exposures that affect the child’s brain in this period of rapid and critical development. Less is known of them than lead. There are concerns with regard to mercury, organochlorines, pesticides, and manganese.  (Manganese has been added to Canadian gasoline since the 1970s and was the subject of a failed attempt by the federal government to eliminate its use in gasoline.) The gaps in knowledge should not restrict us in our efforts to protect the potential that is our children.
 CELA & OCFP, EHC.  Environment5al Standard Setting and Childrens Health.  (2000).
Need to raise awareness of the greater susceptibility of children to adverse effects from environmental exposures.  Education of parents and caregivers as they play a large role in determining the factors in the child’s environment.
BUT  ..(U)pstream strategies (are) essential if our efforts to protect children’s health are to succeed in the long term.”   Monica Campbell
Requires changes on individual and societal levels
Recognizing the far-reaching consequences of our everyday behaviour, the interconnectedness of actions, choices, etc…  (PREVENTION)
e.g. driving SUVs; driving period - generation of air pollution; contributing to alterations in global climate change
e.g. energy needs - we in N Am make a far greater ecological footprint vs. people in developing countries.  In Ontario we have two coal-fired electrical plants (Lakeview & Nanticoke) that contribute significantly to air pollution in Southern Ontario & beyond
Changes also have to come through strong policies, backed by local, provincial/territorial and national gov’ts as well as international agreements   (ADVOCACY)
e.g. POPs treaty in Stockholm;  Kyoto protocol
Ultimately protecting children’s health, health of future generations is a powerful motivator for change.  (Notion of “Do no harm”)  Especially important when science isn’t equal to the task of proving something “safe”  (PRECAUTION)