Request for blood test results of 52 past or present residents of Paritutu

Legislation display text:
Official Information Act 1982, s 9(2)(a)
Ministry of Health
Beverley A Wakem
Case number(s):
Issue date:

Section 9(2)(a) OIA did not apply—results could not be linked with identifiable individuals—information released

In 2001, the Ministry of Health contracted the Institute of Environmental Science and Research (ESR) to investigate non-occupational exposure to dioxins amongst residents of the New Plymouth town of Paritutu who were living, or had lived, close to the Dow AgroSciences plant, formerly operating as Ivon Watkins-Dow Ltd (IWD).

ESR conducted blood serum testing of 52 past or present residents identified as having possible high exposure to dioxins from the IWD plant. The Ministry published the results of its investigation, but not results of the blood tests. A journalist complained to the Ombudsman when their request for the de-identified blood test results was refused under section 9(2)(a) of the Official Information Act (OIA), in order to protect the privacy of the participants.

Section 9(2)(a) applies where withholding is necessary to protect the privacy of natural persons.

The results did not identify the individual participants by name. Each participant was denoted by a number. However, the Ministry argued that the small sample and small area in which the samples were collected might enable people to identity the participants and their individual blood test results.

The Ministry also noted that some participants in the study had publicly identified themselves and their dioxin levels. As a consequence, the pool of anonymised participants had become smaller. The Ministry was concerned that this increased the risk that disclosure would reveal the test results of individual identifiable participants.

The Ombudsman consulted the Privacy Commissioner. The central issue was whether any of the results could be linked to a particular individual. The Ombudsman and Privacy Commissioner did not think there was a realistic prospect of this. Even if it was possible to identify a group of people who may, by virtue of their age or the length of time they had spent in Paritutu, have participated in the study, it would not be possible to identify their individual test results. Even if some of the participants had come forward and identified themselves and their dioxin levels, it would not be possible to identify the blood results for the remainder of the group, down to an individual level. (Clearly, if some participants self-identified their results, that was entirely their own choice.) The Ombudsman and Privacy Commissioner concluded there was no privacy interest attaching to the blood test results.

The Privacy Commissioner noted that fairly small participant numbers (and sub-groups within that) do increase the chance that individual results will be identifiable. However, she was not convinced in this case that the low participant numbers could lead to identification. She also noted that the information in this case was not especially sensitive. To the vast majority of the population, the results would be incomprehensible. This had a privacy protective effect. In other instances, where the numbers were very small or the information extremely sensitive, particular care might have to be taken to group the results. However, the sensitivity of the information in this case did not seem to demand it.

The Ombudsman formed the opinion that section 9(2)(a) did not apply, and the Ministry agreed to release the information.

This case note is published under the authority of the Ombudsmen Rules 1989. It sets out an Ombudsman’s view on the facts of a particular case. It should not be taken as establishing any legal precedent that would bind an Ombudsman in future.

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