1. Definition and Classification of Light Pollution
Light Pollution, an emerging environmental hazard, refers to the adverse effects on the nocturnal environment and human health caused by the excessive or improper use of artificial light sources, or inappropriate alterations to natural lighting conditions. The concept originated in the field of astronomical observation in the 1930s and has now been incorporated into the regulatory scope of environmental laws such as the Environmental Protection Code (2026).
Based on the pollution source and mode of impact, light pollution can be primarily categorized into three types:
- Glare Pollution: Harsh light reflected or emitted from surfaces with high reflectivity (e.g., glass curtain walls) or high-brightness display devices (e.g., LED advertising screens).
- Skyglow: Excessive artificial lighting scattered into the atmosphere at night, forming a luminous veil over cities, which severely disrupts astronomical observations.
- Light Trespass and Color Pollution: This includes colored light sources that are not ecologically friendly, as well as intrusive light that directly illuminates non-target areas (e.g., residential windows).
For the fixed road and garden lighting discussed in this paper, the primary manifestations of light pollution are: upward light spill (skyglow) from luminaires, intrusive illumination onto residential buildings, and the disruption of biological rhythms by spectral composition, particularly short-wavelength blue light.
2. Analysis of Light Pollution Hazards
2.1 Impacts on Human Health
Nocturnal exposure to excessive artificial light, particularly short-wavelength blue light (400-500 nm) contained in high color temperature (>4000K) sources, significantly suppresses melatonin secretion in humans. A 2025 World Health Organization (WHO) research report indicates that excessive blue light exposure can reduce melatonin secretion by approximately 40%. Melatonin is the core hormone regulating the human circadian rhythm, and its suppression can lead to:
- Sleep Disorders: Manifested as difficulty falling asleep, disrupted sleep architecture, and shortened effective sleep duration.
- Chronic Disease Risks: Long-term sleep disorders are associated with decreased immunity, increased risk of cardiovascular diseases, and certain cancers.
- Psychological and Cognitive Impacts: May trigger anxiety, irritability, and decreased attention.
Legally, Chinese judicial practice has established clear precedents supporting accountability for light pollution infringement, such as the 2005 Lu Yaodong v. Yongda Company case, which established the judicial principle that excessive lighting constitutes an infringement on residents’ rights to a healthy living environment.
2.2 Ecological Impacts
Light pollution systematically disrupts nocturnal ecosystems:
- Birds: Migratory birds rely on celestial navigation; urban bright lights can cause them to deviate from their migratory routes. Birds are particularly sensitive to short-wavelength blue light.
- Insects: Many insects are phototactic. Studies show that LED streetlights can lead to significant declines in local moth populations. The reproductive behavior of species like fireflies, which rely on bioluminescence for mating communication, is also severely inhibited.
- Marine Life: For example, newly hatched sea turtles rely on moonlight to guide them to the ocean; artificial lights on shore can disorient them, increasing mortality rates.
2.3 Energy Waste and Astronomical Observation Interference
According to a 2026 Science study, approximately 83% of the global population lives under light-polluted skies, and about one-third of regions can no longer see the Milky Way with the naked eye. Upwardly scattered lighting essentially represents inefficient use of electrical energy. Estimates suggest that about 30% of global outdoor lighting is excessive or misused, leading to massive carbon emissions.
3. Technical Approaches for Controlling Light Pollution from Road and Garden Lighting
The core of controlling such lighting pollution lies in achieving precise light distribution, intelligent control, and ecological compatibility. Specific technical measures are as follows:
3.1 Source Control: Luminaire Selection Standards
- Mandatory Use of Full-Cutoff Luminaires: The maximum luminous intensity of the luminaire should be concentrated within the downward 0° to 65° range, ensuring minimal light flux in directions ≥90°. This effectively controls light from spilling into non-target areas (e.g., building facades or the sky). Garden lights should be selected with models featuring glare shields and deeply recessed light sources.
- Strict Control of Upward Light Output Ratio (ULOR): According to the International Commission on Illumination (CIE) Environmental Zone standard:
- E1 Zone (Dark Sky Preserve): e.g., nature reserves, areas around observatories; ULOR should be 0%.
- E2 Zone (Low-Brightness Residential Zone): e.g., residential areas; ULOR should be ≤1%.
- E3 Zone (General Urban Zone): e.g., urban main roads; ULOR should be ≤5%.
- Standardization of Color Temperature and Spectral Selection:
- Residential and garden lighting should prioritize warm white light sources in the range of 2700K-3500K.
- In ecologically sensitive areas during late-night hours (e.g., after 22:00), sources can be switched to amber (~1800K) or red/amber light with wavelengths >560 nm to significantly reduce disturbance to wildlife. The national standard Code for Service Quality Evaluation of Urban Light Environment Construction (GB/T 43992-2024) explicitly prohibits the use of pure blue light sources with wavelengths <500 nm as main lighting in residential areas.
- Decorative lighting should use products with a high Colour Rendering Index (CRI ≥85) and low Unified Glare Rating (UGR ≤19).
3.2 Engineering Installation Design Criteria
- Control of Installation Geometric Parameters:
- Streetlight tilt angles should generally not exceed 15°.
- Overhang length should generally not exceed one-quarter of the mounting height.
- In areas adjacent to residences, measures such as lowering pole height, adjusting the tilt angle, or adding shielding baffles can be adopted to prevent direct light intrusion into living room windows.
- Layout and Power Density Optimization: The number and layout of luminaires should be determined based on lighting calculations rather than subjective judgment to avoid over-lighting. The power density for main garden lighting areas is recommended not to exceed 50 W/㎡.
3.3 Intelligent Operation Management
- Time-Based Dimming Strategy:
- Peak Hours (e.g., 18:00-22:00): Maintain 100% of the designed illuminance.
- Late-Night Hours (e.g., 22:00-05:00 next day): Can be dimmed to 50%-70% of the designed illuminance.
- Transition and Responsiveness: Luminance changes should use smooth transitions (e.g., not exceeding 10% change per minute) to avoid visual discomfort. Microwave radar or AI video analytics can be employed to achieve adaptive lighting that “brightens when vehicles/pedestrians approach and maintains low illuminance when absent.” Practice shows that reasonable midnight dimming measures can achieve 30%-40% energy savings and significantly reduce resident complaints.
- Time-Based Dimming Strategy:
3.4 Special Measures for Ecologically Sensitive Areas
In specific areas such as ecological reserves, targeted technologies are required:
- Bird-Friendly Lighting: Using red or amber light sources with wavelengths >560 nm can effectively reduce bird collision risks.
- Insect-Directed Control: Employing narrow-band ultraviolet light (e.g., 365 nm) in specific areas to trap pests, replacing widespread high-brightness lighting, thereby reducing attraction to non-target insects.
- Control of Installation Geometric Parameters:
4. Conclusion and Outlook
Effective light pollution prevention and control does not imply lowering lighting standards or sacrificing functionality, but rather achieving a balance between lighting efficiency, environmental friendliness, and human health through refined engineering design and intelligent management.
With the implementation of the Environmental Protection Code, light pollution prevention in China has entered a new stage of legalization and standardization. From a technical perspective, the widespread adoption of full-cutoff luminaires, strict limitation of ULOR, ecologically conscious spectral choices, and demand-based intelligent dimming constitute the core technical system for current light pollution control in road and garden lighting. In the future, with the further integration of sensor technology, the Internet of Things (IoT), and artificial intelligence, dynamic, precise, and adaptive “dark-sky-friendly” lighting systems will become an industry trend.
The ultimate goal is to construct a scientific lighting environment that, while ensuring public safety and functional needs, minimizes adverse impacts on the natural night sky, ecosystems, and resident health.