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About the programme
The Ministry of Health’s environmental radioactivity monitoring programme analyses trends in radioactivity levels across New Zealand’s environment.
The programme also monitors naturally occurring radioactive materials beryllium-7 and lead‑210 for comparative and scientific purposes.
Despite recent nuclear incidents in the northern hemisphere, the programme confirms recent trends of decreasing environmental radioactivity levels in New Zealand.
Current testing
Air testing
- Atmospheric testing stations at Kaitaia, Chatham Island and Rarotonga use a SENYA ‘Snow White’ air sampler to draw air through 2025 cm2 filters (3M filter, polypropylene BMF) at a flow rate of approximately 900 m3/hour, with a daily sample volume of approximately 20,000 m3.
- High-resolution gamma spectrometry analyses these samples for gamma-emitting artificial and natural radionuclides.
- Samples collected at Baring Head are analysed for the presence of carbon-14.
Rainwater testing
- Rainwater samples are collected weekly at Hokitika (small-area rain collector, 0.021 m²) and analysed for total beta content by liquid scintillation counting.
- A large-area collector (area 1m²) is equipped for on-site continuous ion-exchange operation to increase sensitivity for artificial radionuclides.
- Beryllium-7 measurements are used as a quality control for the performance of the sampling system.
- Rainwater samples collected at Kaitoke are analysed for the presence of hydrogen-3.
Milk powder testing
- Milk powder sourced from three regions (Waikato, Taranaki and Westland) are analysed monthly using gamma spectrometry to measure Iodine-131, caesium-134 and caesium-137 concentrations.
Seawater testing
- Seawater samples are collected from the Canterbury coast and analysed using gamma spectrometry for Cs-134 and Cs-137. This commenced in 2015 and the testing program is expected to expand over coming years.
Results
- There is a continuing trend of decreasing radioactivity in our environment. Full details are provided on the Environmental radioactivity annual reports page.
- Concentrations of artificial radionuclides in the atmosphere are well below detection limits, which are in the range of 1 to 5 mBq/m³ for iodine-131, caesium-134 and caesium-137.
- Natural beryllium-7 continues to be the most significant radionuclide detected on the air filters.
- Beta-activity in rainwater is almost entirely due to naturally occurring radionuclides, such as potassium-40 and lead-210.
- There is a continuing trend of reducing radioactivity concentrations in milk powder, with caesium-137 being the only detectable artificial radionuclide.
- No evidence of radioactive contamination from the Fukushima Daiichi nuclear accident has been observed in the New Zealand environment. Further details are available at Fukushima Daiichi.
Historical radioactivity monitoring
2010s
In 2012/13, GNS Science provided information about hydrogen-3 and carbon-14 levels collected from its stations at Baring Head and Kaitoke, in Wellington.
Marine monitoring commenced in 2015 with seawater samples analysed for the presence of Cs-134 and Cs-137.
2000s
In 2000, the Kaitaia and Rarotonga stations were upgraded, and a new station was commissioned at Chatham Island. These stations now provide continuous daily monitoring with high-sensitivity air samplers.
The Ministry also monitored rainwater in Hokitika and milk powder in Waikato, Taranaki and Westland for evidence of radioactivity.
In 2004 the Ministry stopped monitoring levels of strontium-90 in milk powders because the concentrations had fallen below detectable levels.
1990s
New Zealand signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in 1996 and enacted the Nuclear-Test-Ban Act in 1999. To enforce the CTBT, seismic, radionuclide, infrasound and hydro-acoustic monitoring stations were set up around the world.
1980s
By 1985, levels of weapons-test debris had decreased to near the limits of detection for the monitoring techniques in use at the time. Monitoring was scaled down to three stations at Kaitaia, Hokitika and Rarotonga. More sensitive sampling equipment was installed.
1960s
The Ministry began environmental radioactivity monitoring in the New Zealand and South Pacific regions to assess radioactive fallout from nuclear weapons tests.
