This document provides an overview of the precautionary principle, including its origins, key elements, and approaches to implementation. It discusses the principle in the context of environmental health problems caused by human activities that have led to issues like climate change, fishery collapses, and chemical contamination. The precautionary principle aims to take anticipatory action to prevent harm when threats exist, even in cases of scientific uncertainty, and places the burden of proof on those introducing potentially hazardous activities. The document examines uncertainties in science, different types of errors, and limits to proof when assessing environmental health issues. It also outlines values like respect, humility and responsibility that underlie the precautionary principle.

1. THE PRECAUTIONARY
PRINCIPLE:
Policy Responses to
Environmental Health Problems
***
Carolyn Raffensperger
Ted Schettler
Exploring Links to Environmental
Diseases
December 5, 2003

2. Why we need the precautionary
principle
• Humans have caused major global change
• Some change has serious implications
– Hole in the ozone layer
– global climate change
– collapse of marine fisheries
– alteration of major biogeochemical cycles, including
carbon, nitrogen, water, metals
– synthetic chemicals contaminate virtually all wildlife
and humans
• The magnitude of human caused change is
unprecedented

3. Why the precautionary principle?:
additional perspectives
(the world is big and complex)
• Assessing cumulative, systems level or interactive effects
is difficult.
• Surprises have occurred too frequently ( Ex. CFCs and the
hole in the ozone layer).
• Future generations have interests and needs that are
difficult to protect with some decision-making strategies
• Many current choices have high decision stakes because of
the scale at which they are made. (Global choices have
global consequences.)

4. An additional public health
perspective
• Patterns of illness and disease are changing:
e.g., asthma, neurodevelopmental disorders,
incidence of some malignancies and birth
defects; chronic, degenerative diseases.

5. What is the precautionary
principle?
Wingspread Statement: “When an activity
raises threats of harm to human health or
the environment, precautionary measures
should be taken even if some cause and
effect relationships are not fully established
scientifically.”

6. Wingspread statement
Jan., 1998
1. People have a duty to take anticipatory action to
prevent harm.
2. The burden of proof lies with the proponents, not
with the public.
3. Before using a new technology, process, or
chemical, or starting a new activity, people have
an obligation to examine "a full range of
alternatives.”
4. Decisions applying the precautionary principle
must be "open, informed, and democratic" and
"must include affected parties."

7. Common elements of the precautionary
principle in international treaties
All formulations include:
1) Threat of harm
2) Lack of scientific certainty
3) Action to prevent harm

8. The precautionary principle
incorporates both science and
ethics
– Ethics and values
• Do no harm
– Science
• What we know
• How we know
• What we don’t know

9. Values underlying the
precautionary principle
1) Respect - for the needs and rights of this and future
generations as well as others who cannot speak for themselves
2) Humility - towards the natural world and our ability to
understand it through science
3) Democracy - giving people a voice in matters that affect their
lives
4) Responsibility - government’s public trust responsibility to
manage the commonwealth for this and future generations.
Individuals’ and their institutions’, including industry,
obligation to take responsibility for their actions in the world.

10. History of the precautionary
principle
• The use of Vorsorge in Germany
• Sweden
– Goal setting
– “Sunsetting” chemicals
– Presence of chemical sufficient; evidence of harm not
necessary
• Treaties
• International Joint Commission
• Wingspread
• California (EPA and San Francisco)

12. Harm
1) Serious
2) Irreversible
3) Cumulative
4) Broad spatial and temporal dimensions
5) Easily avoidable

13. Scientific uncertainty
• Uncertainty about cause or magnitude
• Uncertainty, indeterminacy, ignorance
– Value of more data
– Unpredictability of complex systems
– Asking the right questions

14. Kinds of uncertainty
• Statistical
• Model
• Fundamental

15. Statistical uncertainty
• Easiest to reduce or quantify
• Results from not knowing the value of some
variable at a particular point in space or
time, but knowing, or being able to
determine, the probability of a given value

16. Model uncertainty
• Results from not fully understanding the
relationships between variables in a system
• May know that a particular outcome is
possible, but probability of that outcome is
difficult to predict; may be indeterminant.

17. Fundamental uncertainty
• Increasing indeterminacy
• Partially results from ignorance
• Ignorance of ignorance a big problem (we
don’t know what we don’t know)
• Fail to ask the right questions

18. Science and the precautionary
principle
• Kinds of errors and error bias
• “Proof”
• What do we need to consider in order to say
that something “causes” something else?
• The limits of science

19. Kinds of errors when assessing
“safety”
• Type 1 (false positive)—conclude that
something is harmful when it is not
• Type 2 (false negative)—conclude that
something is safe when it is not
• Type 3—the right answer to the wrong
question

20. Error bias
• Scientific studies are usually interpreted to favor
type 2 over type 1 errors
• This is because we have chosen not to conclude
that evidence is “significantly positive” without it
being “strong”
• ? Should the interpretation of “science” for
establishing health- and environmentally-
protective policies favor Type 1 errors? Who
should decide?

21. How do we know what “causes”
a disease?
• Hume (1700s)—we don’t perceive or see
causes; we observe sequences and events
and infer causes
• Robert Koch (1890)—Koch’s postulates for
infectious disease
• Bradford Hill (1960’s)—the “Hill” criteria
for causation

22. Hill criteria for causation in
epidemiology
• Consistency of findings
• Strength of association
• Biological gradient (dose-response)
• Temporal sequence (“cause” before effect)
• Biologic plausibility (mechanism)
• Coherence with established facts
• Specificity of association

23. Comments from Bradford Hill
• “None of my criteria can bring indisputable
evidence for or against a cause and effect
hypothesis and none, except for time sequence,
can be required as a sine qua non”
• “All scientific work is liable to be upset or
modified by advancing knowledge. That does not
confer upon us a freedom to ignore the knowledge
that we already have, or to postpone the action that
it appears to demand at a given time.”

24. Cigarettes and lung cancer—
evidence for causation
• 1945—Ochsner—Incidence rises together
• 1950—Doll & Hill—case-control study
• 1953—Wynder—tar causes cancer in mice
• 1954—Follow up studies show association,
and that greater exposure > greater risk
• 1990s—biological mechanism(s) described
(genetic factors; mutations)

25. “Proof”
• Scientific “proof” depends on the kind of
study and the criteria that are agreed upon
to establish proof
• What constitutes “proof” is a mixture of
scientific, social, and political factors

26. When is “proof” difficult to
establish?
• Non-specificity-
– many exposures “cause” multiple diseases; e.g
smoking
– many diseases have multiple “causes”; interactions
• Long latent period between exposure and disease
• Windows of vulnerability: exposure is most
hazardous when it occurs at a particular time
• Exposures are ubiquitous; no “control” population
• Unidentified susceptible populations mixed in
with the general population

28. Precautionary Action
• Anticipatory and preventive
• Increases rather than decreases options
• Can be monitored and reversed
• Increases resilience, health, integrity of
whole system
• Enhances diversity (one size does not fit all)

29. Shifting the burden of proof
• Industry has an obligation
– to test their product (ask the right questions and use the
right scientific disciplines)
– heed early warnings
– seek safer alternatives
– publicly disclose information about harm.
– pay for damage and restoration.
• Shifting the burden of proof does NOT mean that industry has
to prove absolute safety.
• Shifting the burden of proof does mean that the environment
and public health get the benefit of the doubt.

30. Implementing the precautionary
principle
1) Establish a general duty to act with
precaution
2) Set goals
3) Use science wisely
Establish a public interest research agenda
Use the right discipline.
Use multiple disciplines.
4) Enhance information flows
5) Create early warning systems

31. Implementing the precautionary
principle (cont)
6) Shift the burden of responsibility/proof
(Locate responsibility in the system)
7) Create new torts and other legal
mechanisms
8) Choose the least harmful alternative
9) Engage in democratic decision-making
processes
10) Explicitly incorporate values

32. Can we say “yes” using the
precautionary principle?
1) Ongoing monitoring
2) Performance bonds
3) Alternatives assessment (Similar to an EIS
under NEPA)
4) Adaptive management

33. June 17th the San Francisco Board of
Supervisors adopted the precautionary
principle as city and county policy
“every San Franciscan has an equal right to a healthy
and safe environment. This requires that our air, water,
earth, and food be of a sufficiently high standard that
individuals and communities can live healthy,
fulfilling, and dignified lives. The duty to enhance,
protect and preserve San Francisco's environment rests
on the shoulders of government, residents, citizen
groups and businesses alike.”