Intermediate tier: assessment using SimpleBox4Nano

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