1) An intermediate tier environmental exposure assessment is used when a lower tier assessment indicates potential risk from exposure. 2) This assessment uses an exposure model that accounts for the nanomaterial's environmental behavior, such as heteroaggregation, and models multiple environmental compartments and transfer between them. 3) The example models titanium dioxide nanoparticles released during road spraying into the Thames catchment area using the SimpleBox4nano model, finding higher predicted environmental concentrations for particles not retained in the polymer matrix compared to those retained.

1. Presentation Name
Name Surname
Date
Environmental Exposure Assessment Framework
Intermediate tier exposure assessment worked
example
- Workflow level 2
Prepared by Dr Stephen Lofts, UKRI-CEH
With Joris Quik (RIVM) and Samuel Harrison (CEH)
Sept. 2019
Detailed NanoFASE guidance here

2. Overview of tiered environmental exposure
assessment: Aim and logic of intermediate tier
Lower tier assessment
START
Data collection/collation, model choice
END
No
Intermediate tier assessment
No
Yes
Risk?
Data collection/collation, model choice
Higher tier assessment
Risk?
No
Yes
Yes
Additional risk
management measures
Yes
Risk?
Data collection/collation, model choice
END
END
An intermediate tier environmental exposure
assessment is engaged when the conservative
lower tier assessment yields an indication of
risk.
The assessment will then use:
 Exposure model parameterised for
environmental behaviour of nanomaterial
 Heteroagglomeration/heteroaggregation/attach
ment properties
 Dissolution
 Influence of size and density
 Environmental scenario
 Multiple environmental compartments and
transfer between them
 No spatial variability within environmental
compartments
 Flow of material out of system e.g. by burial in
deep sediments – allows steady state
computations
 Can do dynamic calculations

3. Recap – the example used for our assessment
workflow
Commercially sourced TiO2
Dispersed in polymer resin
Sprayed onto road surface Application rate 2.49 g/m2
Anatase type material
Primary particle size range 10–20 nm
Application rate 2.49 g TiO2/m2
Annual loss rate 0.95 g TiO2/m2
i.e. 38% of amount applied
Released as particles of polymer/nanoparticle aggregate, 0.5–5.0µm diameter
Standardized equipment used
to perform the wheel abrasion
simulation
Titanium dioxide (TiO2) used as a coating on urban roads
See our FCCCO case study and detailed release assessment in NanoFASE Report D4.2

4. Intermediate tier model
Screening level multimedia model: SimpleBox4nano
Linked, fully mixed
environmental
compartments
Constant annual
input rate of
nanomaterial
Dynamic and/or
steady state
calculation
Nanomaterial
properties
e.g. material density, particle
radius, attachment efficiency
to sediment, dissolution rate
Simultaneous emission to
different environmental
compartments
Natural, agricultural,
urban/industrial soil
Lake water, fresh water, sea water
Air

5. Parameters for Thames catchment example
Variable Units *Value
‘pristine’ ‘matrix’
Regional emission to air t a-1 0 0
Regional emission to lake water t a-1 0 0
Regional emission to fresh water t a-1 0.893 0.893
Regional emission to sea water t a-1 0 0
Regional emission to natural soil t a-1 0 0
Regional emission to agricultural soil t a-1 3.18 3.18
Regional emission to other soil t a-1 0 0
Area land km2 15875 15875
Fraction fresh water - 1.01×10-4 1.01×10-4
Fraction natural soil - 0.134 0.134
Fraction agricultural soil - 0.626 0.626
Fraction urban/industrial soil - 0.240 0.240
Temperature oC 10 10
Average precipitation mm a-1 633 633
Depth fresh water m 1.62 1.62
Soil erosion mm a-1 0.03 0.03
Radius natural colloids (NC, < 450 nm) in water nm 500 500
Density natural colloids (NC, < 450 nm) in water kg m-3 2200 2200
Radius natural suspended particulate matter (SPM > 450nm) in water µm 7 7
Density natural suspended particulate matter (SPM > 450nm) in water kg m-3 2200 2200
Radius natural colloids (NC, < 450 nm) in sediment pore water nm 500 500
Density natural colloids (NC, < 450 nm) in sediment pore water kg m-3 2200 2200
Radius natural colloids (NC, < 450 nm) in soil pore water nm 500 500
Density natural colloids (NC, < 450 nm) in soil pore water kg m-3 2200 2200
Radius primary ENP nm 7.5 1375
Density primary ENP kg m-3 4230 3900
Attachment Efficiency of ENPs and fresh water NCs (<450 nm) - 0.02 0.02
Attachment Efficiency of ENPs and fresh water SPM (>450 nm) - 0.02 0.9
Attachment Efficiency of ENPs and fresh sediment NCs (<450 nm) - 0.336 0.336
Attachment Efficiency of ENPs and fresh sediment grains - 0.336 0.336
* Two simulations were run, with different assumptions regarding the nanomaterial:
• ‘pristine’: nanomaterial assumed to be released from polymer matrix
• ‘matrix’: nanomaterial assumed to be retained in the polymer matrix Parameter differences highlighted in table

6. Results
Steady
state
One year
Soil PEC
0.000837 µg/g
Freshwater PEC
0.599 µg/dm3
Freshwater sediment PEC
0.192 µg/g
Soil PEC
5.00 µg/g
Surface water PEC
1.12 µg/dm3
Freshwater sediment PEC
0.192 µg/g
‘Pristine’
scenario
Steady
state
Freshwater PEC
0.998 µg/dm3
Freshwater sediment PEC
2.09 µg/g
Soil PEC
0.254 µg/g
One year
Freshwater sediment PEC
2.09 µg/g
Freshwater PEC
0.425 µg/dm3
Soil PEC
0.000870 µg/g
‘Matrix’
scenario

7.  As with the lower tier, the intermediate tier
provides a screening assessment
Screens out non-hazardous substances
Where risk is indicated, suggests higher tier
assessment may be useful
 Refinements possible within this tier:
Environment-specific parameters
Refined estimation of long-term release
Intermediate tier assessment and decision making