Rhodes serum dioxin study: Mid Point Summary Report

By Adam Craig
Rhodes Serum Study Coordinator 2007/8
Public Health Officer Trainee

Background

The Rhodes Serum Dioxin Study's aim is to determine if there is a change in the serum dioxin levels of the Rhodes community relative to a control group (recruited from the Clarence Street Red Cross Blood Donation Centre) during the period of remediation of the Rhodes peninsula.

Blood samples have been collected from the Rhodes community and controls at baseline (before the remediation started in 2004/5) and at mid-point of remediation (in 2007). A third sample will be taken at the completion of remediation, envisaged to be in 2009. A description of the study methodology can be found in the Technical Report: Rhodes Serum Dioxin Study: Methodology and Baseline Data.

At baseline, 60 Rhodes residents and 594 controls provided blood samples for this study. Each of the Rhodes residents provided a 50ml sample while the controls provided a 5ml sample. At mid-point sample collection 52 (87%) of the Rhodes community group and 243 (41%) of the control group provided their second sample. Table 1 summarises the number of samples collected from each group at baseline and mid-point sample collections.

All samples have been stored at -20 degrees Celsius in specified freezers at the National Measurement Institute (NMI) in Pymble. In 2008 NMI extracted a portion of the samples of those participants who had given blood at both sample collection time points (52 Rhodes and 243 controls). These portions were combined into four pooled samples based on group and sample collection time points (2004 Rhodes, 2007 Rhodes, 2004 controls & 2007 controls) and were subsequently analysed by the Eurofins Analytik GmbH laboratory in Germany for the standard suite of dioxins and polychlorinated biphenyls (PCBs).

At baseline, Rhodes residents tended to be slightly older compared to the control group (mean age of Rhodes residents = 56; mean age of controls = 51.4). When excluding participants that have not provided mid-point samples (and hence have not been included in the analysis) the difference in mean age between the residents and control group reduces from 4.6 to 3.5 years. At baseline, controls were more likely to be regular smokers than Rhodes residents; this was reversed at mid-point sampling. Other comparison characteristics such as education levels, dietary intake of fish or dairy, and consumption of home grown vegetables or home reared meat/eggs tend to be similar between the groups (Table 1).

Table 1 Comparison between Rhodes residents and controls at baseline and mid-point sample collection.

Study parti​cip​ants Rhodes residents Baseline (n) Rhodes residents Baseline (%) Rhodes residents Mid-point (n) Rhodes residents Mid-point (%) Controls Baseline (n) Controls Baseline (%) Controls Mid-point (n) Controls Mid-point (%)
Provided sample 60 100 52 87 593 100 243 41
Unable to donate 290 49
Withdrawn - 7 12 - 35 6
Not contactable - 1 2 - 25 4
Male, 30-45 years at 31/10/04 (baseline) 7 12 6 12 145 24 39 16
Male, 46-60 years at 31/10/04 (baseline) 17 28 15 29 170 29 56 23
Male, >60 years at 31/10/04 (baseline) 10 17 7 13 63 11 30 12
Total males​​ 34 57 28 54 378 64 125 51
Female, 30-45 years at 31/10/04 (baseline) 0 0 0 0 0 0 0 0
Female, 46-60 years at 31/10/04 (baseline) 20 33 18 35 163 27 89 37
Female, >60 years at 31/10/04 (baseline) 6 10 6 12 52 9 29 12
Total females 26 43 24 46 215 36 118 49
Regular cigarette smoker 3 5 7 13 53 9 6 4
Other smokers at home 9 15 10 19 72 12 15 9
Vegetarian 0 0 1 2 11 2 1 1
Nil daily serves of dairy* 2 3 3 6 82 14 6 2
1-3 daily serves of dairy* 53 88 48 92 481 81 227 93
>3 daily serves of dairy* 3 5 0 0 21 4 5 2
Invalid response regarding daily serves of dairy* 2 3 1 2 9 1 5 2
Nil serves of seafood* 2 3 2 4 33 6 5 2
Monthly serves of seafood* 13 22 13 25 99 17 56 23
Fortnightly serves of seafood* 15 25 9 17 164 28 52 21
Weekly serves of seafood* 24 40 28 54 280 47 119 49
Daily serves of seafood* 4 7 0 0 10 2 7 3
Invalid response regarding serves of seafood* 2 3 0 0 7 1 4 2
Eat locally caught fish 1 2 1 2 6 1 1 1
Eat home grown veg. 4 7 2 4 55 9 21 13
Eat home reared poultry/eggs 0 0 0 0 10 2 3 2
Body Mass Index (median) 28 28 26 26

* Note: Figures for Controls at baseline differ to those in the Technical Report: Rhodes Serum Dioxin Study due to a corrected data coding error.

The full report of the dioxins analysis is included as Appendix 1.

Results

Table 2, below, shows that between 2004 and 2007 blood serum dioxin levels have decreased for both residents and control groups. The concentration of dioxin-like chemicals in the pooled serum samples, expressed as 2,3,7,8-TCDD toxicity equivalent (TEQ) concentrations, decrease was greater in the control group than in the residents. However the decrease for TCDD, the key contaminant associated with the remediation site, was greater over the three year period in the residents compared to the controls.

Table 2. Comparison between residents and controls blood serum dioxin test results for at baseline and mid-point testing.

Sample Code Client Code Matrix Lipid concentration in % 2,3,7,8-Tetra-CDD in pg/g, lipid based WHO2005 TEQ (PCDDs/PCDFs) in pg/g, lipid based WHO2005 TEQ (DL-PCBs) in pg/g, lipid based WHO2005 TEQ (PCDDs/PCDFs & DL-PCBs) in pg/g, lipid based
703-2008-00393490 Residents Pooled 2004 N08/008292 Whole blood 0.54 2.25 11.3 2.65 13.9
703-2008-00393491 Residents Pooled 2007 N08/008293 Whole blood 0.43 1.73 11.2 2.09 13.3
703-2008-00393492 Blood bank control 2004 N08/008294 Whole blood 0.50 1.34 10.3 1.97 12.3
703-2008-00393493 Blood bank control 2007 N08/008295 Whole blood 0.48 1.29 8.89 1.46 10.3

WHO2005 TEQs presented here are calculated according to the lower bound procedure

Conclusion

The purpose of this mid point analysis was to identify if there has been a substantial exposure to clinically significant levels of dioxin associated with the remediation at Rhodes that would require immediate further investigation and/or public health action. The results indicate that the blood serum dioxin levels have decreased in both the residents and control group from 2004 to 2007 and thus any significant contribution to dioxin body burden in the local community from the remediation process is unlikely.

According to the criteria established for this study in 2004, these results do not warrant further investigation at this stage and a more comprehensive analysis will be undertaken at the end of the remediation period.

Appendix 1

Report AR-08-jj-055041-001​​​

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