Light pollution is one of the most rapidly increasing forms of environmental degradation. There is increasing evidence that draws potential linkages between artificial light at night (ALAN) and certain human health conditions. For example, a study by Rybnikova et al. [1
], based on World Bank databases, reported a statistically significant association between ALAN and prostate cancer incidence. A potential correlation between outdoor LAN and breast cancer incidence was also reported by Peter et al. [2
]. In addition, ALAN has been linked to diabetes [3
], fatigue, and depression [4
]. In addition to the effects of ALAN on the well-being of humans, sky glow resulting from ALAN is a major interference to astronomical activities [5
]. Furthermore, excessive and unnecessary ALAN is a key contributing factor to energy waste [7
As such, these rapidly increasing adverse effects of ALAN on humans and the general interactions between ecosystems have led to subsequent legal actions against improper usage of light, especially at night. The involvement of governmental institutions, in the form of ordinances or laws against ALAN, has increased over the years [8
]. Light pollution laws, ordinances, and prescriptive measures are becoming common in many parts of Europe [9
], Asia [10
], and America [12
Although the effects of ALAN are primarily the same in all areas, different countries have adopted diverse legal approaches to reduce light pollution. For example, as discussed by Martin-Taylor [13
], the United Kingdom has extended the previously existing law on air pollution to include light pollution. Many Italian regions have employed individual ordinances to prevent or reduce specific light-related issues prevalent in given regions [14
]. There is a variety of factors that influence the type of light pollution laws employed by a country or region. For instance, bolt-on laws are likely to be less expensive than stand-alone laws adopted for the specific issue of light pollution [12
]. In addition, ordinances are likely to provide better solutions in countries with cities or regions that experience diverse forms of light pollution [14
]. China and Korea are among the countries that recently established light pollution preventive measures through city ordinances. Given the social similarities between China and Korea, which may give rise to similar artificial lighting trends, the current study provides a comparative analysis of the Seoul light pollution ordinance and the regional light pollution laws and preventive measures in China. The contents of this study provide an extensive technical guideline to countries or regions that wish to draft their own regional or city-based light pollution laws.
5. Comparative Analysis of the Seoul and Chinese Light Pollution Ordinances
As indicated in Table 7
; Table 8
, the lighting divisions are listed separately according to the CIE standard for Shanghai and Beijing. Since there is no dark–light area in the Beijing area, it does not appear on the standard. Guangzhou City has proposed to organize the development of light environment control areas with relevant departments. However, the provision does not give a specific division, which cannot constitute legal benefits. By comparison, Shanghai is the most comprehensive in the lighting division, although Seoul City and Shanghai are almost the same. Therefore, China has followed international standards in the lighting division.
In the lighting division, Shanghai has mentioned the maximum value of the upward light output ratio. In road lighting design, people often underestimate the increase in light pollution caused by the direct upward discharge of lamps [29
]. The upward light output ratio is often used to compare these emissions. Cinzano and Diaz Castro [30
] suggested that the direction of light emission is important for determining the amount of light scattered in the atmosphere and the size of the contaminated area. The spread of light pollution is also related to the direction of the launch. Therefore, decreasing the light output ratio is necessary to curb light pollution.
Furthermore, in residential lighting, Shanghai not only gives the maximum vertical illumination of windows, but also gives the standard of lighting intensity for residential areas. Falchi et al. [31
] reported that human exposure to light at night (LAN) reduces the production and secretion of pineal melatonin (MLT). Restraining the production of MLT requires two optical variables: Light intensity and wavelength. Therefore, an increase in light intensity may inhibit the production of MLT and have serious negative impacts on health. Light intensity has a negative impact not only on humans, but also on animals. Anika et al. [32
] experimented with perch, using aquariums to simulate four different light intensities for 14 days of observation. Through analysis, it was found that nighttime melatonin was inhibited as light intensity increased.
Meanwhile, Shanghai has only proposed minimum horizontal illuminance and vertical illuminance, but has not given a maximum limit for public area lighting. It has been documented that the main factor of the human sensation of glare is high light source brightness [33
], and the overall brightness in human vision is closely related to the feeling of glare [36
]. Therefore, Shanghai has not paid much attention to the possibility of glare in public areas. The specification only mentions that the lighting in public activity areas should create a bright, clear, and friendly atmosphere. Therefore, its regulations do not constitute a standard for light pollution. In contrast, Guangzhou has clearly defined a design standard for public areas and proposed night lighting that effectively control the glare and light environment affecting pedestrians and motor vehicles.
However, although the specification mentions that lighting facilities need to meet design standards, the standards are subtly explained. In practical applications, there is a tendency for formalism and lack of maneuverability, and prevention and control of light pollution are not achieved. In addition, since commercial center lighting areas and administrative office lighting areas are in high-brightness areas, neither Shanghai nor Tianjin have given relevant restrictions on light pollution, and no specific solutions have been given. However, Guangzhou has pointed out that specific departments should solve the relevant complaints. As mentioned above in how to resolve related disputes, if there are no clear relevant standards, it is difficult for government departments to convince other departments, which brings difficulties to management. In addition, in green space and plaza landscape lighting, to avoid unnatural plant growth and generation of glare, Shanghai limits the distance, location, and time of illumination. Intense light pollution at night may disturb the growth of plants [37
]. More and more artificial lighting is used to grow plants in greenhouses, causing light pollution [38
]. Most creatures tend to be active at night, but, unfortunately, night lighting is also the most important for humans. Excessive artificial lighting not only interferes with the growth of plants, but also causes serious damage to the health of birds, fish, insects, and even humans [39
]. Therefore, a consideration of the effects on the human ecological environment is crucial. Although Shanghai has relatively curbed the production of light pollution, it has not proposed relevant standards. Similarly, Guangzhou has only limited the use of glass curtain walls, and Tianjin has only mentioned the prevention of glare.
In contrast, the emergence of floodlights has increased artistic beauty due to the emergence of modern buildings. Most floodlighting starts at the bottom of the object [43
]. This means that most of the luminous flux is directed to the sky, causing it to miss objects, especially in projects where inappropriate design or poor-quality fixtures are often used. This will lead to a huge loss of energy and light pollution [44
]. Krzysztof [45
] said that the ratio of luminous flux of floodlighting needs to be determined on the surface of the object and named this measure the floodlighting utilization factor, which is part of the luminous flux of an object. Therefore, the portion of light not directed at the object is the loss of luminous flux. He used formulas and computer simulations to calculate the floodlighting utilization factor and loss of luminous flux at different angles of illumination. Thus, the angle, the loss of luminous flux, and the floodlighting utilization factor can be used to determine the production of light pollution and the loss of energy. In Shanghai, clear regulations and standards are given for the floodlighting utilization factor and loss of luminous flux, which states that the luminous flux outside the building surface must not exceed 25% of the total luminous flux, and it gives the maximum limit of the brightness of a building surface. All in all, this measure can relatively reduce the occurrence of light pollution.
In advertising lighting, both the Illuminating Engineering Society of North America (IESNA) [46
] and the International Commission on Illumination (CIE) [22
] recommend limiting outdoor lighting. Although both give attention to this issue, the limits given by the two are different. IESNA gives the limitation of surface brightness, while the CIE150 report gives the limits of the brightness and vertical illumination of the sign. We all know that the surface brightness limit term adjusts the brightness of a single sign, while vertical illuminations are used to prevent outdoor light from entering a room [11
]. Although the latter is more suitable for evaluating the light intrusion status of advertising signs, Shanghai has not ignored the limitation of surface brightness and provides two limits.
In advertising lighting, Shanghai not only gives the limit values for surface brightness and vertical illumination, but also limits the LED display. In recent years, with the widespread use of LED displays in China, the LED advertising screens arranged in the city have seriously affected the normal life of residents. However, current international standards cannot be fully applied to the pollution status of Chinese cities. Therefore, research on LED display pollution in various cities in China is urgent [47
]. LED displays consume 12 times more energy per day than common signage lighting and severely increase the vertical illumination of the building façades in commercial areas, greatly increasing light intrusion [48
]. In addition, high-brightness dynamic picture LED displays create visual interference for drivers [49
In summary, Shanghai has the most comprehensive limits on light pollution, followed by Guangzhou. However, the specifications of Guangzhou City are only drafts and do not have legal benefits. On the official website of the Guangzhou Municipal Government, to communicate with the people in a timely manner and solve problems, the government has a leadership mailbox. Some citizens have asked whether the regulations on environmental radiation management in Guangzhou have been officially promulgated and implemented. What is the basis? The government replied that it does not specifically regulate light pollution. It gives the Guangzhou building glass curtain wall management measures and the Guangzhou outdoor advertising and signboard management methods as measures related to light pollution [50
]. However, in these two regulations, only the relevant restrictions of LED display screens and glass curtain walls on second floors are specified in the relevant buildings [28
]. Finally, it can easily be seen from Table 6
that Beijing and Tianjin have not paid special attention to the relevant regulations on light pollution. Therefore, the relevant specifications given by Shanghai for the light pollution problem are the most comprehensive.
On the other hand, Seoul gives limits not only for decorative lighting, but also for lighting in the overall space. China’s local laws and regulations are mainly reflected in one aspect, such as landscape lighting or decorative lighting, which lacks operability. On the contrary, this single mode has given some inspiration to Seoul, such as the ULOR proposed by Shanghai, the intensity of lighting, the brightness of building surfaces, the surface brightness of advertising signs, and the hard regulations related to light pollution. Seoul can improve the effectiveness of its laws and regulations according to the actual situation and the above noted provisions.
The authors believe that improving China’s light pollution laws and regulations requires improvements to the legislative model, such as special legislation on light pollution. Depending on the actual situation of each city, light pollution impact assessment should be performed according to clear criteria. For example, Seoul proposes that the mayor should strive to maintain the Korean industrial standard street lighting as the standard for light pollution environmental impact assessment and can seek expert advice accordingly. In addition, special department supervision is needed. For example, Seoul clearly stipulates that the mayor should formulate and implement policies to prevent light pollution and establish a light pollution committee. There should be clear accountability and incentive mechanisms, such as in Seoul, and the mayor may choose to reward those who contribute to the prevention of light pollution [16
Furthermore, in the actual control, data analysis is needed, and the night sky brightness of different cities is collected to conduct a comparative analysis, and the results are obtained and then controlled point-to-point. For example, Wei Jiang et al. [52
] used the Luojia 1–01 satellite to analyze and compare the night sky brightness with the brightness of different degrees in Wuhan, Seoul, Haifa and Mexico.
On the other hand, in future research of laws and regulations, the brightness of the night sky should be compared before and after the data in a range of years, so that the practicability of the current rules can be confirmed—for example, Wei Jiang et al. [53
] used the Defense Meteorological Satellite Program Operational Linescan System (DMSP/OLS) for data collection from 1992 to 2012 in assessing light pollution in China based on nighttime light imagery and analyzed the degree of light pollution in various regions of China. It was concluded that China’s light pollution has significantly expanded in provincial capital cities in the past 21 years. Therefore, by analyzing this, we can see that the degree of light pollution is on the rise when no relevant light pollution regulations are proposed. In the future, it is necessary to continue collecting proper data to compare and analyze the practicability of current rules on light pollution.
At the same time, in future research, the ecosystem needs to be paid attention to in light pollution. We can also conduct data comparison analysis. For example, Jonathan et al. [54
] used DMSP/OLS in combination with GLC2000 to collect nighttime lights from 1992 to 2012 and evaluated the latest changes in nighttime artificial illumination for 43 global ecosystem types. The results indicated that the Mediterranean climate–ecosystem has experienced an enormous increase in exposure and that all terrestrial ecosystem types have experienced a certain degree of artificial light exposure and that this exposure is increasing. Through the analysis of the ecosystem, the relevant laws and regulations can be strengthened in the future.
In the era of big data, we not only need to use data collection but also need to listen to the opinions of the public—for example, the public’s views on light pollution and its impact on the environment. Lyytimaki et al. [55
] investigated the public’s views on light pollution as an environmental problem using a questionnaire survey. Of the 2053 responses to the study, 84.6% said light pollution had spread to all areas. A total of 82.9 per cent of the respondents said it was essential to be dark. Various light pollution sources were found in the problem of light pollution sources. The most commonly mentioned sources were street lamps, courtyard lamps, commercial lights, and outdoor decorative lights. Therefore, the author believes that only by combining a questionnaire survey, interviews, and DMSP/OLS data collection, etc. can the occurrence of light pollution be effectively controlled, and the effectiveness of laws and regulations be improved in the future.