International Joint Commission

iomagnify at each step in the food chain. Thus, when we consume predatory fish or wildlife
at the top of food chains our bodies become the next reservoirs for these substances.
Children frequently are more vulnerable than adults to toxic chemicals. The developing
offspring, for example, lives from its mother's body, and operates one step higher on the food
chain. Crucially, the fetus is going through a once-in-a-lifetime development, a process
delicately orchestrated and timed that can be upset by toxic chemicals. In short, our children
may be better indicators of environmental quality than adults.
The extent of the diminished human potential resulting from exposure to toxic substances,
however, remains to be determined. Subtle manifestations of human damage are
unlikely to attract attention of health authorities, unless our definition of health changes. The
World Health Organization (WHO) addressed this issue 40 years ago, when it offered an
expanded view of what constitutes health: "Health is a state of complete physical, mental and
social well-being, and not merely the absence of disease or infirmity."
Whether or not one needs the services of a doctor does not define the state of one's health.
Good health, according to WHO, represents more than a collection of negatives, more than not
suffering any clinically defined disorder. The child exposed to high doses of toxic substances,
resulting in diminished 1.0. or learning disabilities, falls into the WHO definition of someone
who does not have a healthy state of well-being.
Paradoxically, the sciences underpinning methodologies for assessing human health risk
work best for after-the-fact solutions. Unfortunately, the human is not seen as a part of the
ecosystem. Neat, easily recognized human medical problems (e.g. cancer, morphological birth
defects) or death are the dominant criteria on which decisions about the risk to humans are
based. A defined outcome and an exact cause, beyond a shadow of doubt, is the goal. Defining
harm in such narrow terms, and requiring definitive evidence on the cause of that harm, has
excluded from consideration the less dramatic harms such as subtle insults to the organ
systems, e.g. the immune system, or the developmental process.
The sciences of toxicology and epidemiology, on which environmental policymakers
have traditionally depended, were not designed to answer questions about exposure to a
multiplicity of chemicals. As a result, the larger picture of chemical exposure, multichemical
body burdens, chemical interactions and simultaneous impacts on human biological processes
has been missed. A preventive ecosystem approach requires us not only to consider all
chemicals and all exposure routes - air, land, water, food - but all of the harms as well. The
adoption ofthe preventive or public health model meansthat although we risk being wrong, we
must accept as possible a hypothesis for a causal relationship between a toxic substance and
a particular health impact. Where human health is concerned, all available data, including in
vitro and animal studies, must be considered. In the absence of irrefutable human studies,
common sense dictates that appropriate actions be taken to prevent potential harm.
In 1989 the Health Committee recommended and the Science Advisory Board (SAB)
accepted that a weight-of-evidence approach be adopted for environmental health determinations
and policy making. One assembles all the evidence: adverse effects on wildlife, adverse
effects on humans, adverse effects on ecological processes together with a fundamental
understanding of how biological systems, such as the reproductive system or the immune
system, can be harmed. As in solving a crime, the weight ofthe evidence together builds a basis
for judgement.
The weight-of-evidence approach supports the objectives of the International Joint
Commission because it provides a basis for judgements within a preventive framework, and
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