# Development and Effect Analysis of UVB-LED General Lighting to Support Vitamin D Synthesis
## 3 Methods: Animal Testing to Confirm Vitamin D Synthesis  
The effect of the test UVB-LED general lighting on vitamin D synthesis at a given duration of light exposure was confirmed using animal testing. The experiment was performed at the nonclinical CRO Institution (KNOTUS, Jeonbuk, Korea). All procedures were approved by the KNOTUS IACUC (Institutional Animal Care and Use Committees)'s animal testing ethics committee (KNOTUS Co. Ltd.'s animal testing ethics committee) (Approval no. : KNOTUS IACUC 18-KE389). Two cages with dimensions of \(150\times 150\times 200\) cm (W \(\times\) D \(\times\) H) were used, which were designed to completely block light from entering. One was installed with UVB-LED general lighting (supposed lighting) and the other with normal lighting installed in the interior ceiling. The cages were situated inside the test institution at a room temperature of \(23\ ^{\circ}\)C \(\pm\) 3\({}^{\circ}\)C, humidity of \(55\%\pm 15\%\), and ventilation per hour of 10-20 times. Figure 4 show the animal testing environment. The animals used in this experiment are widely used for drug efficacy and toxicity testing, and a wide range of data has been collected using Wistar rats as test subjects. Of the Wistar rats, 22 SPF, 8-week-old rats were chosen [25]. To allow the rats to acclimatize to their new environment, they were introduced to the cages seven days prior to the start of the experiment. During the seven days, 20 out of the 22 rats were chosen based on their health and consistent normal behavior. The weights of these 20 rats were measured and ranked. Next, they were categorized into either the test group or the control group so that the body weight distribution was as even as possible in random order. The G1 group was the experimental group with the UVB-LED general lighting, and the G2 group was the control group with normal lighting. However, the illuminance of the lighting applied to the two groups was \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Toxicity Category**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{**Results**} & \multicolumn{4}{c}{**IEC 62471 Category**} \\ \cline{4-6}  & & & **Exempt** & **Risk Group 1** & **Risk Group 2** \\ \hline Actinic UV hazard Radiation (AUV) & W/m\({}^{2}\) & 0.001 & 0.001 & 0.003 & 0.03 \\ \hline Near UV hazard Radiation (NUV) & W/m\({}^{2}\) & 1.075 & 10 & 33 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: IEC 62471, UV light spectrum toxicity category and results. Figure 4: Animal testing environment. (**a**) Cages for animal testing. (**b**) Test group G1: UVB-LED general lighting. (**c**) Test group G2: normal lighting. adjusted to be equal to 300 lux at the bottom of the cage in order to follow the recommended standard of animal experiments. In addition, considering the general lighting exposure time of modern people, the lights were turned on for the same time from 06:00 to 22:00 every day. The UVB irradiance was set, considering the fact that the indoor users were sitting on a chair and some parts of their face, shoulder, and arm were exposed to light. However, the rats used for the animal experiment stayed on the floor at a distance of 1.5 meters from the lighting; therefore, the UVB dose to the exposed part of the animal would be reduced. The reduction rate of UVB irradiance (y), according to the distance (x), was calculated by deriving Equation (3) based on the experimental case provided in the preceding research [17]. \[y=\frac{270.2265}{\text{x}^{2}}+0.009096 \tag{3}\]  
In order to supplement the shortage of UVB dose due to distance, which was calculated using Equation (3), the UVB irradiance to the animal was increased by about 1.3 times. In addition, the expected vitamin D synthesis was proportional to the exposure of the skin [26]. Therefore, we increased the intensity of UVB light by double, considering that the rat's body was mostly covered with hair, so the skin exposure condition was set to 50% lower than that of humans.