Night Sky Brightness in Climatic Health Resorts – Association between outdoor artificial light at night and cancer in selected communities of Bavaria, Germany

Background

Light is essential for life on earth; but so is its absence. Life is adapted to natural cycles of light and darkness, and changing its rhythm has an impact on well-being. This is becoming increasingly clear as medical research has begun pointing toward adverse effects of artificial light at night on human health. Artificial light at night (ALAN) was brought into discussion as causation for cancer in 1987. Since then the relationship was investigated for different types of the disease: in women focus was on breast cancer while in men focus was on prostate cancer. Whereas the knowledge about the impact of indoor artificial light at night is fairly advanced and shift work was declared as carcinogenic by WHO in 2007, insights into the health-effects of outdoor artificial light in the sense of light pollution (e.g. outdoor illumination shining in through bedroom windows) is still in emergence.

Designation schemes exist that promote the preservation of areas with near-natural conditions both in terms of their lightscapes and in terms of health benefits. Currently, the designation schemes that aim to preserve darkness in areas that are fairly unaffected by artificial illumination, such as the International Dark-Sky Association's Dark Sky Parks and Dark Sky Reserves, do not consider aspects of human health. This is not surprising given the emergent nature of inquiry into the health effects of light pollution. Conversely, artificial light at night is not currently an aspect relevant to the designation of areas supporting human health, such as the German Spa Organisation's Climatic Health Resorts. These focus on the local climate's qualities in order to ensure the absence of adverse effects on human health and the occurrence of health-promoting effects. Climatic Health Resorts work with atmospheric conditions as remedies – and with the strict rhythm of day and night.

This contribution will investigate to which extend communities labelled as Climatic Health Resorts suffer from light pollution. Furthermore, it will be tested whether an association between the incidence of selected types of cancer and light pollution can be observed on community level.

Procedure

In Germany, 58 communities labelled as Climatic Health Resorts were identified. Non-classified communities of similar size according to their number of inhabitants (no. of inh. ± 2 %) were taken as controls (n = 4 566). Evaluation was conducted in two steps: First, night time brightness was determined for Climatic Health Resorts and for their non-classified counterparts by existing remote sensing data. Second, for Resorts in the German Federal State of Bavaria and their Bavarian matches data on cancer incidence was compiled by the Population Based Cancer Registry for 10 years (2002 to 2011).

The Night Sky Brightness of the Resorts and their non-classified counterparts was evaluated by two means:

• The new Visible Infrared Imaging Radiometer Suite (VIIRS) of the Soumi National Polar-orbiting Partnership (SNPP) for the year 2012 gives information about the upwards emitted and reflected light. Thus, it is reporting the light's place of origin in detail.

• Data of the “World Atlas of Artificial Night Sky Brightness” (WA: World Atlas) shows zenith artificial night sky brightness at sea level. Here, emitted light is combined with atmospheric conditions to model the skyglow luminance at zenith with the radiance calibrated DMSP-OLS data for the year 2001. Thereby, values do not reflect a measurement at a single point but can be influenced by surrounding light sources.

Results of both datasets show that Night Sky Brightness is smaller in Climatic Health Resorts on average than in non-classified communities.

For those communities situated in Bavaria data on cancer incidence was compiled by the Population Based Cancer Registry for 10 years (2002 to 2011). Altogether, 17 Climatic Health Resorts and their 386 non-classified counterparts were chosen. As outcome, breast cancer and ovarian cancer will be analysed for women and prostate cancer and testicular cancer for men, respectively. For the same period, incidences in intestine and lung cancer will be chosen as control for both sexes. Analysis of data is still in progress and results of cancer incidence and light will be handed in later.

Conclusion

As Climatic Health Resorts aim to offer atmospheric conditions with stressors absent or reduced compared to other/ normal / the majority of communities, next to a reduction of stressors like heat or air pollutants Climatic Health Resorts offer low levels of light pollution. Whether an association between Night Sky Brightness and cancer incidence can be observed or not is still open.