Download Chemicals and their properties

Chemicals and their properties
Day 1.
Adam Peters and Graham Merrington
2017
1
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Identification
Chemical Properties
Environmental Fate
Information Sources
Missing Information
Example Chemicals
Summary
2017
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Identification
 Chemicals or Substances?
» Unique structure or complex mixture?
 Ambiguity in chemical identification
» Multiple CAS numbers , stereo isomers
» Commercial products (mixtures)
 CAS or EC numbers (EINECS, ELINCS)
 IUPAC name, Trade name, Common name
» Identify most suitable CAS/EC number and name for
searching
2017
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Chemical Properties
 Partition coefficient
» Log KOW, partitioning, accumulation,
 Water solubility
» Environmental mobility, bioavailability
 Vapour pressure
» Environmental mobility, long range transport
 Potential for ionisation?
 May be predictable from the chemical structure if
not available (USEPA EPISuite)
2017
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Environmental Fate
 Partitioning
» KOC, KD, KP, soil, suspended sediment
» Henry’s Law Constant
 Degradation
» Photolysis
» Hydrolysis
» Biodegradation, primary or ultimate
 Bioaccumulation
» KOW, BCF, BAF, BMF
2017
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Finding Information
 Is an EQS available?
» Use the EQS as the basis for effects information, additional
information on fate may still be required
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Searching databases
ECHA dissemination portal
IUCLID, ESR risk assessments
OECD HPV programme
USEPA ECOTOX
Open literature…
2016
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Missing Information
 QSAR estimates
» USEPA EPI Suite models
 Requires structure
» Many structures in database
» SMILES code
 Requires some expert chemical knowledge
» Validity of applied models
» Comparison against measured data
» Peer review of outputs by experienced staff
2017
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Partitioning and Fate
 How will a substance behave in the environment?
» Volatile, transport and exposure via air, rapid removal and
dispersion
» Water soluble, transport and exposure via water, available for
biodegradation
» Highly insoluble, high partition coefficient, binds strongly to
soils and sediments, low availability for biodegradation,
resistant to degradation, accumulates in organisms
2017
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Predicting Fate
 Fugacity modelling – Don Mackay
 Affinity of a substance for different phases
» Air, soil, water, sediment, biota
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Simplistic systems and routes of entry
Level I, single input, equilibrium
Level II, continuous inputs, transformation
Level III, compartment specific inputs
2017
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Example Chemicals
 Example substances which will be used
throughout the course to demonstrate the
complete risk assessment process for a diverse
range of substances
 You will be obtaining, and assessing,
information on some substances yourselves
2017
10
Approaches
 Risk assessment approach taken may define some
of the information requirements
 Many models require a selection of specific input
parameters
 In many cases the selection of the most
appropriate value for each input parameter will
need to be justified and recorded
2017
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2016
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