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Search on for former Paritutu residents

Search on for former Paritutu residents

The first phase of the study to investigate non-occupational exposure to dioxins among former and current residents of the New Plymouth suburb of Paritutu has been completed.

The community's concerns relate to uncertainty over whether they were exposed to dioxin as a result of past emissions from the nearby Ivon Watkins-Dow, now Dow AgroSciences, chemical plant, and whether health effects have occurred as a result of that exposure. Ivon Watkins-Dow manufactured the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) from 1960 to 1987. Dioxin is a contaminant of this process.

The study will assess historical exposure by measuring the levels of dioxin in selected residents' blood. These results can be compared with those obtained from a national serum study carried out in 1997 by the Ministry for the Environment.

This first phase of this study, conducted by the Institute of Environmental Science and Research (ESR), has been to discuss this issue with affected residents and other key members of the community, resulting in agreement from the majority that blood serum testing was the appropriate mechanism for assessing this exposure.

"We are very pleased the second part of this work can now go ahead," Associate Health Minister Damien O'Connor said. "We know this issue has been weighing on the community for some time and the serum dioxin study is another part of the jigsaw the government is building on organochlorine chemicals to help address these concerns."

He said the next phase is focusing on people who may have been exposed during the 1960s and 1970s, and he was encouraging people who lived in the area during this time to take part in the study. These people will be contacted through a variety of methods such as electoral rolls, council records and newspaper advertisements. "We want this process to be as robust as possible and it is important that all the people who may have been affected are considered for inclusion in this study."

Mr O'Connor said it was encouraging to see the community working so well alongside government agencies to address this issue. "During the consultation process, a number of people representing groups within the community have worked extremely hard not only to convey the concerns and issues of their constituents but to contribute very decisively to an end result. We thank the Paritutu community and its representatives for their time and assistance and hope this work moves us all forward in our understanding of this complex issue."


What is dioxin? Dioxin belongs to a larger group of chemicals called organochlorines, which contain carbon and chlorine atoms joined together. Because it is a stable chemical, it does not break down easily and can stay in the environment for a long time. Dioxin can build up in people's bodies and in animals where it is stored in the fatty tissue.

Where does dioxin come from? Dioxin is created by any kind of burning process. It is released into the air from fires at landfills, the burning of rubbish in commercial incinerators and from backyard fires. The burning of coal and wood and, to a much lesser extent, the combustion of petrol and diesel in motor vehicles is also a source of dioxin. Forest fires may also create dioxin. Metal processing can release dioxin. Previously dioxin was made during the bleaching of pulp and paper. This dioxin was released into waterways. Dioxin was also released into the environment in the past when certain chemicals were manufactured or used. This includes the herbicide 2,4,5-T. As the cheapest and most effective means to control gorse, scrub and other woody weeds at the time, 2,4,5-T was used extensively in New Zealand from 1948 to 1970. Until 1969, the manufacture of 2,4,5-T by Ivon Watkins-Dow was based on imported trichlorophenol (TCP). After 1969, TCP was manufactured locally. Dioxin is a by-product of this process

How are people exposed to dioxin? For most people, about 90 percent of dioxin intake is through diet. Animal-based foods such as meats, dairy products and fish, have the highest amounts of dioxin. This happens when dioxin in the air settles on the land and is then taken up by grazing animals or fish. Additional exposure of Paritutu residents to dioxin may also have occurred by eating contaminated soil or foods (such as meat, milk or eggs) from animals raised on contaminated land and, to a lesser extent, by eating home-grown vegetables, breathing in dust, and skin contact with contaminated soil As dioxin is stored in the body's fat cells, the fat content in a blood test will extracted and tested.

Serum vs adipose tissue testing The US Centers for Disease Control states that there is no analytical justification for the use of adipose (fat) tissue (requiring the removal of about 10g of adipose tissue via a needle biopsy) rather than serum for lipophilic compounds even if exposure occurred years ago. A synopsis of this evidence was presented to the community consultation group, and after due consideration it was decided that blood serum was a far more practical proposition (less invasive, more likely to encourage people to participate) for use in the first instance than any other body tissue. Some other reports on Taranaki dioxin issues

Ministerial Inquiry The issue was the subject of a Ministerial inquiry in 1986, which found no substantiated evidence that the manufacture of 2,4,5-T had any adverse effect on residents' health (the Brinkman report).

Taranaki health status In 2001, Dr Patrick O'Connor, Medical Officer of Health, Taranaki District Health Board analysed cancer registrations (1990-97), cancer mortality (1988-97) and birth defects notifications (1988-99) for Moturoa (which includes Paritutu), and multiple sclerosis data for Paritutu, in response to public concerns about health effects associated with living near the former IWD plant. No difference in cancer registrations and a lower rate of birth defects notifications was found. Dr O'Connor found a six percent higher cancer mortality compared to the New Zealand population (although this was within the range of variation expected by chance). However, the results do not exclude a small increased cancer risk. Data for multiple sclerosis were insufficient to draw conclusions about comparative incidence rates of the disease.

Birth defects In 2002, Dr Patrick O'Connor investigated the rate of neural tube defects (NTDs) in response to birth defects data for 1965-1971 collected by a former nurse from Westown Maternity Hospital, New Plymouth. The local rate of NTDs was slightly higher than the estimated national rate but the difference was not statistically significant. Three cases were identified from an area near IWD. This finding is two cases more than what was expected based on the New Plymouth rate. Although not a statistically significant difference in NTDs this is not definitive given uncertainties with the data and the definition of the study area.

Cancers The Ministry of Health is also carrying out a study of certain cancer incidence and mortality in New Plymouth. The cancers under study (soft tissue sarcoma, non-Hodgkin's lymphoma and Hodgkin's disease) are those cancers for which there is evidence of an association with exposure to herbicides such as 2,4,5-T.

Soils A study of residential soils, undertaken in 2002 by the Ministry for the Environment (MfE), found that there were detectable levels of 2,3,7,8-TCDD (a particular congener of dioxin) at all sites investigated. The low levels found are considered to pose a negligible health risk as all results were within New Zealand health-based residential soil guidelines and all but one within the most conservative residential guidelines that exist internationally. Concentrations found were generally consistent with distance from the plant, topography and prevailing wind direction. These findings are consistent with historical emissions from the former IWD plant as the source of 2,3,7,8-TCDD in the area. A previous MfE study, which was published in 1998, did not find 2,3,7,8-TCDD in soils from urban centers in New Zealand other than New Plymouth.


In 2001 the Taranaki Regional Council (TRC) investigated dumpsites allegedly used by IWD to dispose of chemical wastes. The Council conducted interviews with 80 informants to identify possible locations resulting in the investigation of 36 suspected sites through ground penetrating radar surveys, soil, sediment, leachate, marine biota, surface and groundwater sample analysis. No evidence was found of disposal of agrichemical wastes beyond those already known to the Council (which consisted of municipal landfills), there was no evidence of environmental risk at any site, and recommended no further action.

For more background on dioxin please visit the Ministry of Health website, or the Ministry for the Environment website The report on phase one of the study will also be available on the Ministry of Health website.

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