Reviews endorse serum dioxin study

Three independent reviews have endorsed a 2005 study assessing historical dioxin exposure for the Paritutu community, Health Minister Pete Hodgson said today.

Pete Hodgson released the reviews from:

• Dr Chris Frampton, Associate Professor of Biostatistics from the University of Canterbury,
• Dr Allan Smith, Professor of Epidemiology at the University of California at Berkeley and
• Dr Marie H Sweeney, Chief of the Surveillance Branch of the United States National Institute for Occupational Safety and Health. Dr Sweeney was nominated by the World Health Organization.

Pete Hodgson said he was satisfied from the reviews that the study was fit for purpose and its conclusions were valid.

"It is important to say again that the report of the study, released in 2005, did find evidence of historical exposure to dioxins for people who lived close to the former Ivon Watkins Dow agrochemical plant, in particular for at least 15 years between 1962 and 1987. This major finding remains unchanged," Pete Hodgson said.

Dioxin, or more particularly tetrachlorodibenzo-p-dioxin (TCDD), is an unwanted byproduct of the manufacture of the herbicide 2,4,5-T, which was made at the IWD plant from 1962 till 1987.

The minor errors in the report of the study, released late last year, have been reviewed and they do not affect the major findings of the study.

"The most obvious errors are transcription in one of the appendices of the report (Appendix O). Another was the misclassification of one of the participants in the final report. Both of these have been corrected and included as errata, which will accompany the report. They do not change the findings of the study."

Claims were also made that the information provided by the participants was misinterpreted by the Institute of Environmental Science and Research (ESR) who conducted the study. The Medical Officer of Health for Taranaki has been discussing this with the claimant with a view to collecting information which may better help pinpoint the duration of residence during the exposure period and better define the bounds of the exposure area.

The errors and the claims made about them by accountant John Leonard were reported in a TV3 programme. There were subsequent transcription errors found in one of the appendices of the report. It is unfortunate that the substance of these errors was not raised first with the scientific organisation that actually did the study.

These errors and the claims made about them appear to have been presented in such a way as to attack the credibility of the entire study. Allowing ESR to give its view of the errors when presented to the public would have allowed the public to better judge the importance of these errors.

The reviews also confirmed that the way researchers calculated the highest levels of dioxin in residents was appropriate and robust.

As this is a matter of considerable controversy, there is an onus of responsibility on the media reporting and commentators participating in this debate.

"These three further reviews confirm that this is a credible scientific study and it does give the government a basis for further action," Pete Hodgson said.

"We know that people who lived within one kilometre east and 400m south of the IWD plant between 1962 and 1987 are likely to have higher dioxin levels than other New Zealanders. On average that level is four times that of the general public but in some age/sex groups it is as much as seven times as high.

"While these levels are considerably lower than workers who made phenoxyherbicides such as 2,4,5-T, it may put those individuals at increased risk of cancer and this provides sufficient platform for us to act."

Pete Hodgson said some form of enhanced health, support or information service is proposed and the details are currently being worked through.

"The ESR study provides clear direction as to who was affected and this allows us to offer a package to people who would be regarded as being exposed whether they were blood tested or not.

The Ministry of Health is currently negotiating with a provider to develop this health support service.

Background Information

• Dr Sweeney concluded the study met its overall objectives and was comprehensive in its approach to assessing the range of serum 2, 3,7.8-TCDD concentrations in the residents of Paritutu, potential routes of exposure and modes of contamination. She noted that it is impressive that the research team used all the available current technology to measure and model potential exposures to determine which segments of the population may have had highest exposures. She found that the while the sample size is small, there is unlikely to be sufficient gain in analyzing additional serum samples.
• Professor Frampton concluded that he had found nothing in the commentary by Mr Leonard that invalidated claims made from ESR's report. Prof Frampton stated that he was dismayed that the commentary by Mr Leonard had caused a furore when in the first instance ESR's report was appropriately and sensibly peer reviewed by independent, international experts who have a familiarity with epidemiological study design, analysis and interpretation.
• Professor Smith concluded: A precautionary approach should be adopted concerning dioxin and dioxin-like compounds with an on-going goal of reduction in population body burdens of TCDD. This has been taking place in New Zealand. It is clearly evident that some Paritutu residents had additional exposure well above the average in the general population. The ESR study provides excellent and valuable information concerning this, although it has a limitation in that there were quite a number of residences with potentially high exposure without participants coming forward from them.

It is indeed regrettable that the Paritutu community had these exposures but it can only cause them greater harm if they are unduly alarmed by misguided political and media attention to their past exposure. There is no treatment, and their blood concentration will continue to gradually decrease. The blood concentrations for the large majority of participants in this study were quite commonly found in the general population just 20 or so years ago.

Changes to the text of the report

The changes to the text of the report are included below.

Errata for the 2005 ESR report, titled: A study of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposures in Paritutu, New Zealand. ESR Report No. FW0521.

ERRATA

There is an error in the text on page ii. Third paragraph:

“Specifically, participants with 15 years or more residence time between 1962 and 1987 had mean and geometric mean TCDD levels of 14.6 and 12.4 pg/g lipid respectively (n = 15), compared to age and gender-adjusted backgrounds of 2.4 (mean) and 2.2 (geometric mean) pg/g lipid. Those with less than 15 years exposure during this period had a mean TCDD concentration of 3.2 pg/g lipid (n = 37), compared to an expected mean of 1.5 pg/g lipid for a group of similar age and gender.”

The text should instead read:

“Specifically, participants with 15 years or more residence time between 1962 and 1987 had mean and geometric mean TCDD levels of 14.7 and 12.4 pg/g lipid respectively (n = 14), compared to age and gender-adjusted backgrounds of 2.4 (mean) and 2.2 (geometric mean) pg/g lipid. Those with less than 15 years exposure during this period had a mean TCDD concentration of 3.6 pg/g lipid (n = 38), compared to an expected mean of 1.5 pg/g lipid for a group of similar age and gender.”

Consequently, on page iii. Discussion. The second bullet point: “…(14.6 pg/g lipid, on average)” should be: “…(14.7 pg/g lipid, on average)”.

There is an error in the text on Section 3.2, page 18:

“Of the 37 people who had lived in the area for less than 15 years, from 1962-1987, only one was demonstrably elevated (17.9 pg/g), and the next highest serum result in this group was only moderately elevated at 7.1 pg/g. The mean serum TCDD level in the 37 participants living less than 15 years in this area was 3.2 pg/g. In contrast, those 15 people having lived at least 15 years in the area from 1962-1987 had a mean serum TCDD level of 14.6 pg/g lipid.”

The text should instead read:

“Of the 38 people who had lived in the area for less than 15 years, from 1962-1987, two were demonstrably elevated (17.9 and 14 pg/g). The next highest serum result in this group was only moderately elevated at 7.1 pg/g. The mean serum TCDD level in the 38 participants living less than 15 years in this area was 3.6 pg/g. In contrast, those 14 people having lived at least 15 years in the area from 1962-1987 had a mean serum TCDD level of 14.7 pg/g lipid.”

The line 7 of the Discussion should similarly replace “14.6 pg/g lipid” with “14.7 pg/g lipid”.
On page 14 "...15 long term residents" should be "14 long term residents"; "... 31.6 pg/g..." should be "....31.1 pg/g...", "...15 individuals..." should be "...14 individuals..." and "...16.9 pg/g lipid observed..." should be "...16.4 pg/g lipid observed...".

None of the above corrections impact the tables, figures, or conclusions of the report in any way. The lead author apologizes for any confusion that might have resulted from these errors.

There is also a further error in Appendix 2: Also on page 2 of Appendix O, the first column, starting with the 6th row from bottom:
“PCB TEQ 3
PCB TEQ 4
PCB-189”

These analytes are out of order and should be:
“PCB-189
PCB TEQ 3
PCB TEQ 4”

None of the values in these rows require any further change. None of these errors affect the analyses in the report since this table was assembled AFTER the analyses were performed. The errors are therefore typographical only.

None of the above corrections impact the tables, figures, or conclusions of the report in any way.