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Why NZ Has High Rates of Skin Cancer

New Zealand has one of the highest skin cancer rates in the world.

A conservative estimate suggests that over 90,000 New Zealanders are diagnosed with skin cancer every year.

However, due to widespread under-diagnosis as well as a lack of required reporting the true number is likely to be much higher. This far surpasses all other cancers combined at around 16,000 annually.

New Zealand’s UV levels are high compared to corresponding countries in the Northern Hemisphere. This is because:

  • New Zealand gets 40% higher UV levels compared to equivalent latitudes in the Northern Hemisphere.
  • The sun’s elliptical orbit means that it is much closer to Earth during our summer, compared to the Northern Hemisphere summer. This factor contributes to a 7% increase in UV radiation.
  • Ozone is generated at the equator and is transported to higher latitudes (towards the poles). This transportation is more effective in the Southern Hemisphere resulting in lower levels of ozone over New Zealand. This effect contributes about 10% towards New Zealand’s increased UV radiation.
  • Because New Zealand has cleaner air, it is easier for UV radiation to reach the ground in New Zealand than in some other countries. This results in 20% extra UV radiation.

Australia has higher UV, so why does NZ have higher rates of skin cancer?

Most of Australia has even higher rates of UV radiation so we would expect Australia to have higher rates of melanoma than New Zealand, however, the reverse is true. The possible reasons for this are:

  • New Zealand has a higher proportion of the population with UK heritage, i.e. fairer skin. People with fairer skin are at the highest risk for skin cancer. Australia has a larger proportion that are descendants of southern Europe.
  • New Zealand’s climate is cooler than Australia’s – this is of particular relevance over summer, which means it is more comfortable to enjoy outdoor activities for longer periods. Furthermore, when it is cooler people don’t feel like they need to protect themselves from the sun even though the UV index could be high.
  • New Zealand has had less effective public health campaigns around sun protection.

References

  1. McKenzie R. UV radiation in the melanoma capital of the world: What makes New Zealand so different? AIP Conference Proceedings 1810, 020003 (2017); doi: 10.1063/1.4975499
  2. Lucas RM, Neale RE, Madronich S, McKenzie RL. Are current guidelines for sun protection optimal for health? Exploring the evidence. Photochemical & Photobiological Sciences. 2018; 17: 1956-63; doi: 10.1039/C7PP00374A
  3. McKenzie, Richard. Why Are UV Levels High in New Zealand Summer? Science Learning Hub, The University of Waikato, 29 July 2008, https://www.sciencelearn.org.nz/videos/87-why-are-uv-levels-high-in-new-zealand-summer

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