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Hello, my name is Jean-Lou.
I’m a toxicologist at EFSA.
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My work involves developing
methods for assessing
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the safety of chemicals in
food and the environment.
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Today, I’m going to talk
about the risk assessment of
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multiple chemicals in food often
called chemical mixtures.
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First of all, what do we mean
by ‘chemical mixtures’?
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“Chemical mixtures” refer to combined
exposure to multiple chemicals.
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Food may contain many different
chemicals naturally occurring such as
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nutrients and plant toxins produced
by weeds, or man-made chemicals
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such as pesticides and
environmental contaminants like dioxins.
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The number of combinations
of chemicals is practically infinite
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and they can come from
a variety of sources:
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food, medicines or consumer
products such as cosmetics.
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These chemicals may raise health
concerns depending on their toxicity
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and the level of exposure in
food or the environment.
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So, how do scientists assess consumer
safety for a single chemical?
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For a single chemical scientists
review all the toxicological data
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to set a safe level of use
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and compare it with consumer
exposure through food,
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to conclude on any
potential health risk.
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What about multiple chemicals?
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For multiple chemicals, scientists
have developed risk assessment methods
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which use the same principles as for
single chemicals with some differences.
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First of all, the beginning of the
process is the problem formulation
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to define whether a risk assessment
for a group of chemicals is needed
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based on the nature of the exposure in
consumers or depending on their toxicity.
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Who is exposed and by how much?
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Is the exposure a one-off or
is spread over time?
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The next step is to assess
the toxicity of the group of chemicals
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and identify how they act,
often referred to as “mode of action”.
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Scientists analyse the information
available on the toxicity
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using scientific criteria in a so-called
“weight of evidence approach”.
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Three assumptions about the toxicity
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are used to then conclude
on the health risks
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– dose addition, response addition
and interaction –.
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Dose addition means that the chemicals
have a similar toxicity/mode of action
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and after determining
their individual potency,
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the doses are added for
the risk assessment.
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Response addition means
that the chemicals have independent
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toxic effects and the measures of toxicity
are added for the risk assessment.
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Interactions are more complex.
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Chemicals can become more toxic
when combined, which is called “synergism”.
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On the other hand, they
can be less toxic
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when combined, which is
known as “antagonism”.
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The mechanisms behind
synergism and antagonism
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are complex, however,
two important ones
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involve an increase or decrease
in the body’s ability to detoxify
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and eliminate the compounds,
which is called toxicokinetics,
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and an increase or decrease in toxicity,
which is called toxicodynamics.
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If there is evidence of such interactions,
scientists collect the information
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