Ministry Report Shows Dioxin Levels In New Zealander’s Low Internationally

A report released today shows that dioxin levels in New Zealanders are low relative to the levels in other countries, but that we can’t afford to be complacent about their effects, says the Ministry for the Environment.

Ministry senior policy analyst Dr Simon Buckland says the report – Concentrations of selected organochlorines in the serum of the non-occupationally exposed New Zealand population – shows that though our levels are low on the international scale, dioxins are extremely toxic chemicals. Other toxic chemicals were also frequently present in the New Zealand population, including polychlorinated biphenyls (PCBs) and pesticides, the report shows.

“The information we’re getting from our research is that we need to be cautious – and that’s why we’re working on ways to reduce New Zealanders’ exposure to dioxins,” Dr Buckland says.

Other key findings from the report show that dioxin levels in our bodies increase with age and that there is minimal difference in levels between male and females or between Maori and non-Maori.

An earlier Ministry for the Environment report, the Health Risk Assessment (HRA) released in February, found that New Zealanders’ exposures to dioxins had an insufficient margin of safety and that steps should be taken to reduce exposure.

Dr Buckland says the findings in today’s report were consistent with the results of the Ministry’s environmental and dietary studies and with the Ministry of Health’s breast milk study – also released today.

“This report is part of a series looking at the dioxin situation in New Zealand. It backs up our earlier studies and the information it contains will feed into an action plan we’re putting together on ways to reduce dioxin emissions to air,” Dr Buckland says.

The serum (blood) study set out to determine the background concentrations of dioxins, PCBs and organochlorine pesticides in the serum of New Zealanders. It was based on blood serum taken from a representative sample of the New Zealanders population aged 15 years and over who had not been exposed to organochlorines through their work.

The serum results confirm the findings in a Ministry of Health report that show that the levels of persistent organochlorine chemicals in the breast milk of New Zealand women at the low end of the range of values compared with other industrialised countries. The breast milk study showed levels of dioxins in breast milk have fallen by about two-thirds in the last decade.

The Ministry for the Environment and Ministry of Health studies, and other work undertaken over the last five years, puts New Zealand in a favourable position to comply with any future requirements that may come from the recent signing of the POPs (Persistent Organic Pollutants) convention.

Copies of the full report are available from the Ministry’s website – www.mfe.govt.nz – under the ‘What’s new’ section. An executive summary is attached.

For more information, please contact:
Dr Simon Buckland, 04-917-7421
Karl Ferguson, media advisor, 04-917-7482 or 025-243-7486

SERUM STUDY: A SUMARY OF THE FINDINGS
May 2001

BACKGROUND
This paper summarises the Ministry’s publication, Concentrations of selected organochlorines in the serum of the non-occupationally exposed New Zealand population. The serum study set out to:
(a) obtain estimates of baseline concentrations of these organochlorine chemicals in serum sampled from individual New Zealanders who had not been occupationally exposed to these chemicals
(b) determine the relationship of these chemicals to age, ethnicity, sex and geographic region, and
(c) obtain data that could be used, under the RMA, to develop national environmental standards for the protection of human health and the environment from organochlorine contaminants.
The study was not intended to identify or characterise highly exposed or at-risk populations or to assess where the exposure may have come from.
The exposure data from this study has been used in a health risk appraisal of the New Zealand population to dioxins, which has been published by the Ministry for the Environment as a separate report (Evaluation of the toxicity of dioxins and dioxin-like PCBs: A health risk appraisal for the New Zealand population – February 2001). The Health Risk Appraisal found that the current background exposures to dioxin-like compounds for the New Zealand population had an insufficient margin of safety and recommended that steps should be taken to further reduce human exposure.

STUDY DESIGN
The study looked at the concentrations of organochlorine contaminants in serum taken from a representative sample of the NZ population. The samples were taken from December 1996 through to November 1997 from New Zealanders aged 15 years and over.
Analysis was done by the Centres for Disease Control and Prevention in Atlanta, Georgia, USA.
The serum samples were analysed for:
• dioxins (a generic name for the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans)
• polychlorinated biphenyls (PCBs). Some PCBs show similar toxicity to the dioxins
• organochlorine pesticides and their degradation products.
Samples were pooled because there was insufficient blood for analysis from any one individual. Of the original 3376 people who provided a blood sample, only 1834 samples were actually used. (To be included, people needed to (a) have had no occupational exposure to organochlorines and (b) provide at least 2 millilitres of serum. Plus when the serum was pooled for analysis into strata, equal volumes from each individual had to be used, so this excluded some people.)
The blood serum was pooled into strata based on age, ethnicity, sex and geographic region. Strata had to have sufficient numbers of people and volume of serum in order to be included in the study.
60 strata were used in the study. Some strata were not used for analysis; for example there were insufficient samples to provide data for Maori in the higher age groups.

RESULTS
The serum study found that for:
Dioxins
• the amount of dioxin in our blood increased with age
• the amount of dioxin was marginally higher in people living in the more northern parts of New Zealand (concentrations were higher in people living in Northland/Auckland and Waikato/Bay of Plenty, than those living in the lower North Island or the South Island)
• there were no consistent differences between Maori/non Maori or between female/male
• non-Maori women aged 65+ had higher concentrations of dioxins than non-Maori men of the same age.
PCBs
• there was a general trend of increasing concentration with age
• concentrations were marginally higher in the northern regions
• there was no difference between males and females for the dioxin-like PCBs
• there were markedly higher concentrations of PCBs in non-Maori women aged 65+ compared to non-Maori men aged 65+.
Organochlorine Pesticides
• pp’-DDE, dieldrin and beta-HCH were the most frequently detected pesticides
• concentrations of dieldrin, pp’-DDE and beta-HCH in New Zealanders’ serum increased with age of the individual
• pp’-DDE concentrations in serum increased towards the south of the country
• beta-HCH concentrations were significantly higher in non-Maori males aged 35-49 and especially in Northland. There was minimal variability between males and females and regions for dieldrin and beta-HCH.

Overall, the study showed:
• dioxins and PCBs were consistently found across all ages, regions and ethnic groups and across both sexes
• three pesticides were also consistently found; beta-HCH, dieldrin and pp’-DDE. Of these, pp’-DDE concentrations were 50-100 times the level of any other pesticide
• serum concentrations of these chemicals increased
with age.
One likely reason for this is that earlier exposures to all the chemicals may have been much higher than in more recent time periods. This would be consistent with results of studies in other countries which have found that exposure to organochlorines have fallen in the last two decades. The Ministry of Health has recently released the results of a study of organochlorines in breast milk, and this study found that concentrations were lower than concentrations measures a decade ago.
• there were regional differences:
(a) dioxins and PCBs were marginally higher in the northern study regions than the two southernmost regions. This may be due to higher population densities and levels of industrialisation in the north relative to the south
(b) pp’-DDE concentrations were higher in the south than the north of New Zealand. This reflects the findings of studies of organochlorines in the breast milk of New Zealand women, which have found higher concentrations of pp’-DDE in women living in the South Island (Christchurch and Canterbury) than in women living in the upper North Island (Northland and Auckland).
• no consistent differences between the sexes or between Maori and non-Maori were found
• there was some evidence that women in the highest age group tended to have higher serum concentrations than men in the same age group even though the average ages of men and women in this age category were identical.

This is believed to be the first time such a study has been carried out for dioxins and PCBs on a sample representative of an entire national population for any country.

COMPARISON WITH INTERNATIONAL DATA
In comparing results from one country with those from another, there is always a caveat that needs to be made, because no studies are ever alike.
Studies may vary in terms of design, data reporting, analytical methodologies etc, and these variations may mask or heighten real differences in results between studies form different countries. For example, a Japanese study cited in the report had as its sample base a group of women with a mean age of 20.5 years, which is much lower than the mean age of women in the New Zealand serum study. Therefore, comparisons need to be made carefully, ensuring the study designs are as comparable as possible, and differences in results interpreted with caution.
As far as we are aware, no other studies have attempted to measure the concentrations of dioxins and PCBs in a representative population-based sample for an entire country. Most overseas studies have focused on relatively small regions. As a result, it is difficult to compare this with overseas studies that may have used samples from different groups.
A comparison with international data found that for:
Dioxins
• concentrations of dioxins found in New Zealand tended to be towards the lower end of the international range, particularly for the younger age groups
• the lower concentrations of dioxins in New Zealand serum reflected the fact that, on an international scale, concentrations are comparatively lower in the New Zealand environment (ie in air, soil, rivers, estuaries and fish)
• exposures through dietary intake were also generally low compared to dietary intakes of dioxins overseas in other industrialised countries where studies have been undertaken.

PCBs
• New Zealand concentrations were at the low end of the range relative to concentrations found in other developed countries
• this was in keeping with the fact that environment concentrations of PCBs in New Zealand are typically lower by an order of magnitude or more relative to those in overseas countries
• similarly, dietary intake of PCBs has also been shown to be lower in New Zealand than in other industrialised countries where studies have been undertaken.

Organochlorine pesticides
• there was limited comparative data available for dieldrin
• beta-HCH concentrations were low compared to those in overseas populations
• pp’-DDE concentrations were similar to concentrations measured in overseas populations.

COMPARISON WITH BREAST MILK RESULTS

This report compares the concentrations of organochlorines measured in the serum of New Zealand women with concentrations measured in the breast milk of women as reported in a recently released Ministry of Health study. This comparison found that, overall, there was excellent agreement in the concentrations measured in the two media when reported on a lipid weight basis. This results demonstrates the applicability of serum as the most relevant human matrix to assess population exposures for males and females across a range of ages.

Visit our website at www.mfe.govt.nz for more information on organochlorines.

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