Why Paraquat is claimed to be associated with Parkinson

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Why Paraquat is claimed to be associated with
Parkinsons Disease
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Parkinsons Disease Association with paraquat

• 1. Objective
• Explain Parkinsons disease and why there is an
  increase in reports of an association between
  this disease and exposure to paraquat.
• The presentation is not a review of the risk
  assessment of paraquat, nor an explanation of the
  regulatory impact of this issue.

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Parkinsons Disease

• A loss of neurones in an area of the brain
  (substantia nigra) often associated with motor
  nerve activity (ie muscle activity).
• Usually a disease of old age.
• Has a prevalence of 2 per 1000.
• But over 65 years a prevalence of 1.8 per 100
  (Europe).
• It is a disease involving both genetic and
  environmental factors.
• The most certain environmental factor is
  cigarette smoke, which is strongly associated
  with a lower incidence of Parkinsons.

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Background of Paraquat association with
Parkinsons Disease

• In the early 1980s a chemist synthesised the
  compound MPTP while attempting to synthesise
  recreational drugs.
• Those who injected MPTP developed symptoms very
  similar to Parkinsons Disease and subsequently
  died within a few years.

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Background of Paraquat association with
Parkinsons Disease
cyperquat
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Background of Paraquat association with
Parkinsons Disease /continued

• In the 1980s, Canadian scientists (Barbeau et
  al) claimed there was an association between
  pesticide use and Parkinsons. This was not
  substantiated.
• In the early 2000s scientists in the USA showed
  that paraquat plus MANEB when given to mice
  caused loss of neurones in the substantia nigra.
• Following the above, several studies have been
  reported showing paraquat can cause the loss of
  neuronal cells in the brain.

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Background of Paraquat association with
Parkinsons Disease /continued

• There is no certainty that humans, even when
  exposed to paraquat will lose neurones in the
  substantia nigra.
• We know additional studies are underway in
  several laboratories to investigate the effect of
  paraquat on the substantia nigra in several
  species of experimental animal.
• The data from epidemiological studies are
  conflicting. Some epidemiological studies show
  an association between pesticide use, and in
  particular paraquat, and the development of
  Parkinsons Disease.

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Timelines for Syngenta

• We are in the process of reviewing all the
  relevant experimental data and epidemiological
  studies on paraquat and Parkinsons Disease with
  the help of external experts (end August 2007).
• A risk assessment will be carried out to
  establish Syngentas position on completion of
  this review (Sept 2007).
• We shall identify studies that could resolve
  unanswered questions (end Sept 2007).
• At present we have every reason to maintain our
  position that there is no causative association
  between the development of Parkinsons Disease
  and exposure to paraquat. However, we are
  likely to receive increasing challenges on this.

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No. of Publications referencing Paraquat and
Parkinson's (1980 - 2006)
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Managing the Paraquat, Parkinsonss Disease Issue

Strategy Establish if paraquat can cause
Parkinsons symptoms in humans and if it can,
under what circumstances of dose and time
Capability and capacity Identify what needs to
be done, how it can be achieved and who can do it

• Project Management
• Use expert committees on
• Experimental studies
• Epidemiological studies
• To investigate further the issue

Science Review the experimental data on the
effect of paraquat on the brain of mice and the
epidemiology studies that claim there is an
association between exposure to pesticides and
Parkinsons disease
Outcome Establish whether there is a
qualitative, or quantitative difference in the
effect of paraquat in the mouse compared with
humans and, if relevant, the extent of the
quantitative difference