Appendix 6.3          Methodology for Cumulative HUman Risk Impact Assessments

 

Assessment Approach

 

1.1               The assessment approach for the cumulative risk impact was same as the one for the Human Health Risk Assessment (HHRA) for the chlorination by-products (CBPs), which has been discussed in Appendix 6.1.

 

Problem Formulation

 

1.2               The objective, scope, Site Conceptual Model and assessment endpoints of the cumulative risk impact assessment are same to those for HHRA, which have been presented in Section 6 and Appendix 6.1.

 

1.3               The cumulative risk impact assessment focused on assessing the potential risks/impacts to human health due to chronic exposure to the CBPs and other pollutants present in the HATS effluent discharge.

 

Identification of COPC and Selection of COC

 

            Identification of COPC  

 

1.4               A comprehensive chemical analysis was conducted under the HATS EEFS (2004) to determine the pollutant concentrations in HATS CEPT effluent (Stage 1 and Stage 2A) and CEPT plus Biological Aerated Filters (BAF) effluent (Stage 2B).  One hundred of analytes including metals, inorganic pollutants, organic pollutants, pesticides and organo-metallics were identified as COPC and analyzed. 

 

Selection of COC

 

1.5               A number of selection rules were established in HATS EEFS (2004) for selection of COCs and determination of COC effluent concentrations for risk assessments.  COCs selected for Project Scenarios 1 to 4 and Scenario 5 for cumulative risk impact assessment are presented in Tables 1 and 2 respectively.

 

Table 1         Results of COCs Selection for Scenarios 1 to 4

COPC	Selected as COC for HHRA	Max. Conc. in CEPT Effluent (mg/L)*	Max. Total Conc. in Ambient Seawater (mg/L)*	Note
Aluminium		122	156
Antimony	Yes	0.804	0.21
Arsenic	Yes	1.49	1.48
Barium	Yes	25.5	7.19
Chromium III	Yes	18	0.43
Copper	Yes	55.7	2.25
Lead	Yes	1.21	0.723
Mercury	Yes	29.4ng/L	0.06ng/L
Nickel	Yes	28.5	1.02
Selenium	Yes	0.4	0.05
Silver	Yes	3.83	0.058
Tin		0.93	0.205	A
Vanadium	Yes	29.1	2.15
Zinc	Yes	44.1	3.54
Ammonia		22,000	230	A
Sulphide		4,900	48	A
TCDD (I-TEQ)	Yes	0.1pg/L	0.039pg/L
Toluene	Yes	12	<1
Diazinon		0.048	<0.01	A
Malathion	Yes	0.031	<0.01

Note:  * Total concentration of metals for human health risk assessment

A) No available toxicity data for human health

Table 2         Results of COCs Selection for Scenario 5

COPC	Selected as COC for HHRA	Max. Conc. in secondary treated Effluent (mg/L)*	Max. Conc. in Ambient Seawater (mg/L)*	Note
Aluminium		15.4	156
Antimony	Yes	0.631	0.21
Arsenic		0.88	1.48
Barium	Yes	24.5	7.19
Chromium III	Yes	8.38	0.43
Copper	Yes	9.98	2.25
Lead		0.135	0.723
Mercury		3.48ng/L	0.06ng/L	A
Nickel	Yes	22.3	1.02
Selenium	Yes	0.14	0.05
Silver	Yes	0.387	0.058
Tin		0.612	0.205	B
Vanadium	Yes	30.5	2.15
Zinc	Yes	11.8	3.54
Ammonia		4,200	230	B
Sulphide		53	48	B
TCDD (I-TEQ)	Yes	0.062pg/L	0.039pg/L
Toluene		<1	<1
Diazinon		0.058	<0.01	B
Malathion	Yes	0.015	<0.01

Note:  * Total concentration of metals for human health risk assessment

A) Rinsate blank of dissolved mercury is greater than 20% of sample value

B) No available toxicity data for human health

 

 

Identification of Potential Human Receptors

       

1.6               The potential human receptors for cumulative risk impact assessment are:

·            People who swim or engage in other water related activities in the sea area which is contaminated by the selected COCs discharged from the outfall of SCISTW

·            People who consume seafood which is contaminated by the selected COCs discharged from the outfall of SCISTW

 

Exposure Assessment

 

1.7               The exposure assessment is same to the one for HHRA for CBPs

 

1.8               The water-to-fish bioconcentration factor and food chain multiplier (for trophic level 4) were presented in Table 3 whereas the parameters related to dermal exposure were presented on Table 4.

 

Table 3                Bioconcentration Factor and Food Chain Multiplier of COC

COC	Water-to-fish Bioconcentration Factor	FCMa
Aluminum	2.7c	1.0
Antimony	40b	1.0
Arsenic	114b	1.0
Barium	633b	1.0
Chromium (III)	19b	1.0
Copper	710c	1.0
Lead	0.09b	1.0
Mercury	3,190d	1.0
Nickel	78b	1.0
Selenium	129b	1.0
Silver	87.7b	1.0
Tin	138d	1.0
Vanadium	N/A	-
Zinc	2,060b	1.0
Ammonia	N/A	-
Sulphide	N/A	-
Dioxins and furans (TEQ)	34,400b	27
Toluene	171b	1.0
Diazinon	171b	1.0
Malathion	13.1b	1.0

N/A: Not Available        

Note: ^a FCMs were developed using K_ow values reported in USEPA (1995), as in USEPA (1999b).

^b        BCF values documented in USEPA (2005).

^c No recommended BCF value identified.  Regression equation was used to calculate the BCF values (Bintein et al. (1993), as in USEPA (1999b)).

^d MW (1998).

 

Table 4                Parameters related to Dermal Exposure

COC	Kp (cm/hr)	T (hr)	t* (hr)	B
Antimonya	1E-3	-	-	-
Arsenica	1E-3	-	-	-
Bariuma	1E-3	-	-	-
Chromium (III) a	1E-3	-	-	-
Coppera	1E-3	-	-	-
Leada	1E-3	-	-	-
Mercurya	1E-3	-	-	-
Nickela	1E-3	-	-	-
Seleniuma	1E-3	-	-	-
Silvera	1E-3	-	-	-
Tina	1E-3	-	-	-
Vanadiuma	1E-3	-	-	-
Zinca	1E-3	-	-	-
Ammonia	N/A	N/A	N/A	N/A
Sulphide	N/A	N/A	N/A	N/A
Dioxins and furans (TEQ)a	1.4	8.1	38	6.3E+2
Toluenea	4.5E-2	3.2E-1	7.7E-2	5.4E-2
Diazinonb	1.34E-3	6.29	45.5	0.64
Malathionb	8.76E-4	9.01	21.6	0.023

                Note:  ^a parameter values were adopted from USEPA (1992).

                              ^b No recommended values documented, values were calculated using equations documented in USEPA (1992).

 

Dose-response Assessment

 

1.9               The Cancer Slope Factor (CSF) and reference dose of the COCs adopted in World Health Organization (WHO) and USEPA[1] were presented in Table 5.  More stringent value was typed in bold adopted.  For the identified COCs, adjustment of oral toxicity data (cancer slope factor and/or reference dose) for calculation of the risk/hazard due to absorbed doses was not needed according to USEPA (2001b).  Therefore, the oral cancer slope factor and reference dose selected for oral exposure were used for the risk calculation in dermal exposure pathway. 

 

Table 5                Cancer Slope Factor and Reference Dose of COCs

COC	Cancer Slope Factor (oral, (mg/kg/d)-1)		Reference Dose (mg/kg/d)
	WHO	USEPA	WHO	USEPA
Antimony	N/A	N/A	6b	0.4a
Arsenic	N/A	1.5a	N/A	0.3a
Barium	N/A	N/A	N/A	0.3a
Chromium (III)	N/A	N/A	N/A	1,500a
Copper	N/A	N/A	N/A	N/A
Lead	N/A	N/A	3.5b	N/A
Mercury	N/A	N/A	0.71b	N/A
Nickel	N/A	N/A	5b	20
Selenium	N/A	N/A	4b	5a
Silver	N/A	N/A	N/A	5a
Tin	N/A	N/A	N/A	N/A
Vanadium	N/A	N/A	N/A	9a,c
Zinc	N/A	N/A	N/A	300a
Ammonia	N/A	N/A	N/A	N/A
Sulphide	N/A	N/A	N/A	N/A
Dioxins and furans (TEQ)	N/A	1.5E+5d	N/A	1E-6d
Toluene	N/A	N/A	223c	80a
Diazinon	N/A	N/A	N/A	N/A
Malathion	N/A	N/A	N/A	20a

             Note:  N/A: Not Available

                        ^a Source: USEPA IRIS Database

                         ^b Source: WHO (2004b)

^c Based on vanadium peroxide

^d USEPA Office of Air Quality Planning and Standards

 

Risk/Hazard Characterization

 

1.10           The risk/hazard characterization for the cumulative risk impact was same as the risk assessments for the CBPs. 

 

 

References  

 

1.                  NHMRC (2004).  Australian Drinking Water Guidelines 2004.

2.                  The Risk Assessment Information System. Available online: http://risk.lsd.ornl.gov/tox/tox_values.shtml.

3.                  USEPA. Integrated Risk Information System (IRIS) Database. Available online at www.epa.gov/iris.

4.                  USEPA (1992).  Dermal Exposure Assessment: Principles and Applications.

5.                  USEPA (1998).  Methodology for Assessing Health Risks associated with Multiple Pathways of Exposure to Combustor Emissions.

6.                  USEPA (2001b).  Risk Assessment Guidance for Superfund, Volume 1: Human Health Evaluation Manual, Part E, Supplemental Guidance for Dermal Risk Assessment.

7.                  USEPA (2005).  Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities – Final.

8.                  WHO (2004b). Guidelines for Drinking-water Quality (Third Ed.) – Volume 1.