1.HOMEBUSH BAY 
HUMAN HEALTH AND ECOLOGICAL RISK ASSESSMENT
EVS ENVIRONMENT CONSULTANTS
1998-2000

2. HOMEBUSH BAY - HHRA & ERA DEFINITION
Risk Assessment;
a process for evaluating scientific information 
on the opportunity for adverse impacts
on human health and/or the environment 
Screening Level (SLRA) or Detailed (DRA) 
determine baseline risks
identify acceptable concentrations
chemicals of concern (COCs) in sediments

3. Diagram showing worms eat sediments, fish eat worms, people and birds eat fish (not reproduced here)

4. HOMEBUSH BAY - HHRA & ERA
1997 FIELD PROGRAM
sediment
43 grids 45*9, 90*90 and 180*180 m
59 composite surface samples, 0-10 cm
analyse D+F, moisture, grainsize, TOC
water
fish
70 sea mullet from one grid 
3 composite samples by size and weight
analyse D+F, lipids

5. Diagram showing grid and sampling (not reproduced here)

6. HOMEBUSH BAY - ECOLOGICAL RISK ASSESSMENT (ERA)
EVS Environment Consultants, Canada
Tony Chapman
ERA objectives
residual risk to invertebrates 
residual risk to birds (cormorant)
residual risk to fish

7. HOMEBUSH BAY - SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT 
Screening Level Risk Assessment (SLRA)
very conservative
contaminants of concern
receptors of concern
Detailed Risk Assessment (DRA)
hotspots outside remediation footprint

8. HOMEBUSH BAY - SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT 
Risk to Invertebrates
no adverse effect values for sediment = A
compare with sediment data = B
Hazard Quotient (HQ) = B/A
Results
Similar to Parramatta River 
chlordane, dieldrin, lead, zinc
Hotspots with high HQs
DDT and PAHs
mainly along seawall, some central hotspots

9. HOMEBUSH BAY - SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT 
Conculsions
moderate to high likelihood of adverse effects to benthos by a number of contaminants over broad areas
remediaiton footprint will greatly reduces ecological risks
detailed ERA for central hotspots

10. HOMEBUSH BAY - DETAILED ECOLOGICAL RISK ASSESSMENT
Site specific
hotspots and surrounds
15 locations
toxicity bioassays (worms, oysters, amphipods) 
benthic abundance and diversity

11. HOMEBUSH BAY - DETAILED ECOLOGICAL RISK ASSESSMENT 
Results 
very few adverse effects observed
diversity similar to Parramatta River
diversity not related to hotspots 
Conclusion
weight of evidence suggests that adverse ecological impacts are not expected outside the remediation footprint

12. HOMEBUSH BAY - DETAILED ECOLOGICAL RISK ASSESSMENT 
Risks to pisciverous birds and fish
little black cormorant and local fish species 
avian dioxin toxicity and exposure data
Results
current potential for impaired bird reproduction
early life stages of fish not adversely affected 
Conclusion
remediation footprint will significantly improve situation

13. HOMEBUSH BAY - HUMAN HEALTH RISK ASSESSMENT (HHRA) 
HHRA objective
define sediment remediation objective for D+F concentration to protect human heath 
HHRA focussed on:
baseline risk from eating recreational fish
safe D+F levels in fish and sediment

14. HOMEBUSH BAY - HHRA
CHEMICALS & RECEPTORS 
Chemicals of Concern (COCs)
D+F and dieldrin (not in sediments)
long lived, bind to C in sediment
lipophilic, bioaccumulate 
Receptors of Concern (ROCs) (us)
Auburn and Canada Bay Councils
residential, recreational, industrial
1 in 3 Australian households fishes

15. HOMEBUSH BAY - HHRA
FIELD PROGRAM
Sediment results
Organic compounds
D+F, highest near the seawall, 4.5 to 0.3 ppb
OCPs, major OCC, mainly higher near seawall
PAHs and Chlorobenzenes, highest near the seawall
Phenols, higher in river than bay
Metals
do not covary with organics, same as river
Pb <154 ppm and Zn <420 ppm, high for benthos
Cu < 7 ppm, Cr < 90ppm, Cd < 1.2 ppm

16. HOMEBUSH BAY - HHRA
FIELD PROGRAM
Fish results
2378 TCDD wet weight 
range of 144 to 232 ng/kg (ppt) 
mean of 179 ng/kg (ppt
2378 TCDD = 94% of TEQ in fish
previous study range of 150 to 160 ng/kg (ppt) 

17. HOMEBUSH BAY - HHRA
BASELINE RISK ASSESSMENT
TDI Selection
WHO
1000 pg/kg-day = no effect levels for animals
100 pg/kg/day = no-effects level for human
10 pg/kg-day in 1992 (100/10) 
USEPA 
draft report in 1994, final agreement not achieved
proposed level to low to be of use

18. HOMEBUSH BAY - HHRA
BASELINE RISK ASSESSMENT
TDI Selection
WHO
1-4 pg/kg-day in 1998
background = 2-6 pg/kg-day in developed nations
not an achievable remediation target
based on subtle effects that are highly controversial
policy based rather than science based
NSW HEALTH
advice to EPA NSW, interim recommendation 
proposed C’wealth provisional TDI of 1-4 pg/kg-d

19. HOMEBUSH BAY - HHRA
BASELINE RISK ASSESSMENT
Exposure Assessment
E = B + (C*R*K)/(365*BW)
E = exposure (pg TEQ/kg-day)
B = background (pg TEQ/kg-day)
C = concentration in fish (pg TEQ/g wet weight)
R = fish consumption rate (g wet weight/yr)
K = loss from cooking (fraction)
365 = days/year
BW = body weight (kg)

20. HOMEBUSH BAY - HHRA
BASELINE RISK ASSESSMENT
Exposure Assessment Result 
(E = B + (C*R*K)/(365*BW))
if C = 190 pg TEQ/g wet weight (mean) then E = 1.6 + 13 = 14.6 > TDI = 10 pg/kg-d
if TDI = 10 then 32% high
if TDI = 4 then 73% too high
if TDI = 2 then 86% too high 
safe level is C = 130 pg TEQ/g wet wt incl B
or C = 120 pg 2378 TCDD/g wet wt incl B

21. HOMEBUSH BAY - EVS HHRA
SEDIMENT REMEDIATION OBJECTIVE 
Current Sediment
exposure via surface feeding
fish weighted, E to W, 2 to 1
surface weighted, concentration * area
surface weighted average = 0.932 ug/kg
Future Sediment
32% reduction needed for TDI of 10
new weighted mean of 0.62 ug/kg

22. HOMEBUSH BAY - EVS HHRA
SEDIMENT REMEDIATION SCOPE 
Minimum scope (TDI 10 pg/kg-d)
reduce D+F surface weighted average 35%
excavate 3 blocks, NE-08S, NE-03S, NE-04S
Maximum scope (TDI 10 pg/kg-d)
recognises variability of sediment data
very high degree of confidence
reduce D+F surface weighted average 66%
excavate 13 blocks

23. Map showing scenario A - remediate 3 blocks of grid, lower confidence of 10pg/kg/day (not reproduced here)

24. Map showing Thiess proposal - remediate 13 blocks - high confidence of below 10 pg/kg /day but not sure of getting 4 pg/kg/day (not reprodeuced here)

25. HOMEBUSH BAY - HHRA
SEDIMENT REMEDIATION SCOPE WHAT’S CHANGED 
New data
double the density of locations 
discrete samples not composites
triple the data
reduced the TDI 
excavate 9 blocks
reduce surface weighted D+F average 48%

26. Chart showing differences in amount of sediments to be remediated to achieve a specified average dioxin level in the sediments (not reproduced here)

27. Map showing scenario B - remediate 15 blocks of grid, higher confidence of 10pg/kg/day (not reproduced here)