Modern artificial lighting can be considered a key achievement in the technology revolution of the past century. However, even though artificial lighting is hugely beneficial to modern society, it still presents significant disadvantages, in the form of pollution, to human health and the ecological wellbeing of the environment. Light or photo pollution can be simply defined as excessive or misdirected artificial lighting. Scientifically, it has been defined as the changes in outdoor natural light levels as a result of artificial lighting [1
]. The IDA (International Dark-Sky Association) defines light pollution as the inappropriate or excessive use of artificial lighting [2
]. There are also several legal definitions of light pollution. For instance, the Korean government defines light pollution as “any situation where inappropriate use of artificial lighting may interfere with people’s health and comfort, or harm the ecological system” [3
Other than the radical issue of sky glow caused by artificial lighting [4
], light pollution is also the cause of a number of known ecological concerns. Among the known effects, health issues in humans caused by exposure to artificial lighting at night are the most pressing. To understand how light may affect humans, it is ideal to realize first how light is introduced into the body and how it is used by the body. Light is introduced to the body through the eye. Some of the light is then used for vision whereas the rest of the light mediates in other human biological processes, such as the synchronization of the light and dark cycles. In that context, the effects of light pollution in humans can also be divided into 2 categories; the image forming effects and the non-image forming effects. The image forming problems caused by artificial lighting are mostly associated with discomfort and disability glare. Photometric parameters of light have been indicated to be a contributing force to the occurrence of both types of glare; discomfort and disability glare [6
]. The non-image forming effects are mainly due to a disrupted circadian rhythm—an internal clock that regulates most of the physiological systems in mammals [7
]. The circadian cycle is a complex system that begins in the eye and ends in the pineal gland where melatonin hormone is secreted—a neuro hormone responsible for the rhythmic functioning of the human internal clock. Melatonin is secreted during the dark hours of the night. The peak secretion of melatonin has been reported to be between midnight and 4 a.m. in the morning [8
]. Consequently, exposure to light during this period of the day may inhibit the production of melatonin and thus a disruption of the entire circadian cycle. The desynchronization of the circadian rhythm is believed to be the cause of many clinical conditions in humans. It has been linked to simple discomforts such as fatigue [9
], reduced work productivity [10
] and so forth. It has also been linked to much more grave conditions including diabetes [11
] and many different forms of cancer [12
]. Some of the most prevalent studies in this area are those linking breast cancer to artificial lighting exposure, especially during the night. The idea that artificial lighting may indeed be a concern in regards to breast cancer was given even more credit after a number of pioneering studies in this field showed breast cancer cases to be comparatively lower in blind women than in women with functioning eyesight [13
]. Similarly, a couple of studies [15
], conducted in the US (United States) have shown correlations between high risk of breast cancer incidents and exposure to artificial lighting. The subjects for both studies were medical nurses who worked a minimum of three night shifts a month. In the first study [15
], 78,562 such nurses were investigated in a 10-year follow-up. Based on data obtained from the investigation, statistical analysis showed that women who worked night shifts had a higher risk of developing breast cancer. In addition, the risk of developing breast cancer tended to increase with the number of years spent working night shifts; women who worked night shifts for more than 30 years showed a higher risk of developing breast cancer than women who worked night shifts for less than 29 years. In the second study, Schernhammer et al. [16
] studied the relationship between rotating night shift work and the involved risk of developing breast cancer. 115,002 nurses were studied over a period of 12 years. The results revealed that high risk of breast cancer incidents is associated with longer periods of rotating shifts. Additionally, among 115,002 of the subjects who had no breast cancer at the beginning of the 12-year follow up, 1352 developed breast cancer during the time of the follow-up.
As evidenced through the existing literature, there is a potential link between light pollution and certain human health conditions. Concerns associated with light pollution have thus prompted a legal battle. A number of countries including Korea [17
], France and Italy [19
] have begun dictating lighting level limits through regulations in order to reduce the amount of light pollution. In places like Taiwan, light pollution research and policy is also becoming prevalent [20
]. Additionally, concerned institutions such as the International Commission on Illumination (CIE) also offer general lighting recommendations for proper and sustainable usage of artificial lighting. In Korea, it has been 29 years since the Seoul municipal government installed outdoor lighting to celebrate the 1988 Seoul Olympic Games. Since then, artificial lighting at night has become common practice in cities all over Korea. Moreover, a recent series of controversies related to light pollution have sparked a number of debates in Korea. For this reason, it has become of vital importance that prior to planning and installing new lighting concepts, all parties involved have a firm understanding of the direct and indirect impact of artificial lighting on the surroundings. Additionally, while solutions are being developed, lighting guidelines and recommendations must be put in place so that light designers can create sustainably lit-environments at night with minimum risk of light pollution.
The aim of this paper is to present recent findings and discussions regarding light pollution and sustainable lighting. The assessment provided in this study is based on data gathered from field measurements conducted in Seoul, South Korea. Furthermore, the authors are of the view that close collaboration between architects and lighting designers at the conceptual stage of lighting projects is one way to reduce the current impact of excessive artificial lighting on the environment, while at the same time encouraging sustainable lighting.