The document discusses several chemical and physical hazards in the environment including pesticide use, Minamata disease, the Bhopal disaster, and mobile phone use. It defines hazard and risk, and explains how risks are quantified and assessed using epidemiological studies despite uncertainties. The precautionary principle is described as it relates to environmental regulation.

1. CHEMICAL AND PHYSICAL
HAZARDS IN THE ENVIRONMENT
David Coggon
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2. “People move to the countryside thinking it will be a
healthy environment to bring up their children and do not
know about the dangers and risks inherent in the spraying
of poisonous chemicals on surrounding fields, until they
themselves suffer adverse effects on their health”
Georgina Downs (pesticides campaigner)
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5. MINIMATA DISEASE
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6. BHOPAL
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7. “With a third of all the food we eat
containing them, pesticide residues
have become a routine ingredient in
our diet. Something needs to
change.”
Guardian 20.10.01

8. HAZARD
A hazard is a potential harmful effect
of exposure to an agent, activity or
stressor

9. RISK
Risk is the probability that a hazard will
be realised, given the circumstances of
exposure to an agent, activity or
stressor

10. Risk depends importantly on
the circumstances and extent
of exposure
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13. QUANTIFICATION OF RISK
• Relative risk
• Attributable risk
• Population attributable risk

14. RISK AND UNCERTAINTY
• Risks in individuals correspond to rates in
populations
• Risk estimates are subject to uncertainty
because of incomplete scientific information
• Unlike risk, uncertainty cannot be quantified
empirically. It can only be characterised in terms
of subjective beliefs.
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15. ASSESSING RISK
• Extrapolation from existing scientific
knowledge
• Laboratory experiments in vitro and
in vivo
• Epidemiology
• Experimental studies in humans

16. RISK MANAGEMENT
• Weighs risks and costs against benefits,
taking account of uncertainties
• Depends on value judgements

17. THE PRECAUTIONARY
PRINCIPLE
“Where there are threats of serious or
irreversible damage, lack of full scientific
certainty shall not be used as a reason for
postponing cost-effective measures to
prevent environmental degradation.”
UN Conference on Environment and Development
1992

18. AIM OF PESTICIDE REGULATION
Residues of plant protection products
consequent on application consistent with
good plant protection practice must not
have any harmful effects on human or
animal health
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19. METHOD OF RISK ASSESSMENT
• Reasonable upper estimates of daily
exposure are compared with
appropriate toxicological reference
values derived principally from animal
studies
• Tiered approach with assessment
factors to allow for uncertainty
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20. MAIN SOURCES OF UNCERTAINTY
• Extrapolation from animals to humans
• Variation between individuals
• Exposure modelling
• Statistical uncertainties in underpinning data
• Aggregated and cumulative exposures
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21. “The government allows the
phone industry to focus
pulse-modulated microwave
beams, pass them through
our homes – and slow-cook
us day and night. We are in
the microwave oven against
our will – and it is switched
on.”
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22. MOBILE PHONES – THE CHALLENGE
• New technology rapidly introduced
on massive scale
• Continually evolving
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23. APPROACH TO RISK ASSESSMENT
• Heating of tissues is the only established
hazard. Exposure-response is well-
understood.
• Seek evidence of other possible hazards
from biophysics, in vitro and in vivo
toxicology, human experiments and
observational epidemiology
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24. MAIN SOURCES OF UNCERTAINTY
• In vitro and animal models less
developed and less standardised
• Exposure characterisation
• Bias, confounding and statistical
uncertainty
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25. NOCEBO EFFECTS
Adverse health effects, sometimes
with physical manifestations, that arise
through psychological mechanisms
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26. EVIDENCE FOR NOCEBO EFFECTS
• Patterns of illness do not fit with known
toxicological mechanisms of disease
• Psychological characteristics and health
beliefs predict later illness
• Double-blind randomised experiments
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