*3.1. Sample Socioeconomic Demographics*

There was no difference in number of male and female respondents in both groups of vendors and clients, and the populations of vendors and clients differed in number of socioeconomic and demographic parameters (Table 2). Overall, 103 night-market vendors and 102 non-night-market vendors were surveyed, providing a total size of 205. However, 11 respondents (eight vendors and three non-vendors) did not fully answer all questions; therefore, the number of respondents used for data analysis was 194 (95 vendors and 99 non-vendors).

Concerning the ages of both groups, there was a slight difference between two respondent groups' ages: more surveyed non-vendors fell into the age range from 30 to 40 than surveyed vendors. Respondents of the vendor group were more likely to have higher education (70.5% vs. 42.4% having university, *p* < 0.001), because working in night markets is usually a source of income in additional to a main occupation, so vendors had a higher overall income (1423.57 ± 899.38 vs. 661.609 ± 588.0 Baht/day, *p* < 0.001), but more exposure to artificial light (7.78 ± 2.63 vs. 5.17 ± 1.21 h/night, *p* < 0.001), and they stayed closer to lamps (around 103.89 ± 61.48 cm vs. 195.53 ± 96.09, *p* < 0.001).

Both groups (67.4% for vendors and 73.7% for clients) applied energy-saving measures, but around half of both two groups didn't know about lamp and lighting regulations (43.2% for vendors and 57.6% for non-vendors). The majority in both groups perceived light color of the environment around them as "white".

**Table 2.** Sample demographics and comparisons among respondents of two groups of night-market vendors and non-vendor participants.


### *3.2. Public Perception of Excessive-Light-Related Health Problems*

Our result showed that night-market vendors reported suffering from more health problems than non-vendors. The main problems of the vendors were eye-related, including eyestrain, sensitivity, burning, squinting, impaired vision, etc. They also suffered from difficulty initiating sleep, difficulty maintaining sleep, and daytime sleepiness, which is in agreemen<sup>t</sup> with the disruptions of circadian rhythms caused by lighting reported in the literature. In general, more night-market vendors have these problems than non-vendors (Figure 4).

**Figure 4.** Percentages of vendors and non-vendors reporting health problems they perceived as being associated with excessive lighting.

The calculated χ2 revealed a significant difference between non-vendors and vendors in terms of eye problems (χ<sup>2</sup> = 12.52, *p* < 0.001, df = 1). There is a much higher number of vendors reporting eyestrain and sleeping problems associated with excessive lighting in the market than non-vendors.

The χ2 was also performed to compare the difference in percentages between male and female respondents reporting health problems they perceived as being associated with excessive lighting. The results revealed that women seem to report these problems more than men. Female respondents had difficulty initiating sleep (χ<sup>2</sup> =3.73, *p*-value = 0.05, df = 1), experienced daytime sleepiness (χ<sup>2</sup> = 15.13, *p*-value < 0.001, df = 1), and suffered from eye-related problems (χ<sup>2</sup> =6.31, *p*-value = 0.01, df = 1) more than male respondents. These results may be due to the remarkable hormonal differences between men and women.

### *3.3. Public Awareness of the Impact of Excessive Light on Human Health*

The results indicated that the majority of survey respondents were aware of the excessive-lighting impacts on human health (Figure 5). Both vendors and non-vendors tended to be neutral about or agree with the proposal that excessive lighting levels are linked to circadian-rhythm-related problems. T-test data showed that vendors tended to agree more and agree strongly than non-vendors on how excessive light can change a human's biological clock (*t* = 3.75, df = 185.8, *p* < 0.001), disturb human sleep *(t* = 2.55, df = 191.26, *p* = 0.012) and increase health problem *(t* = 2.10, df = 189.96, *p* = 0.04), while there was no difference of awareness about the impact of excessive lighting on vision between two groups.

**Figure 5.** Excessive lighting impacts on human health. Mean values calculated from individual scores (1 = strongly disagree; 2 = disagree; 3 = uncertain; 4 = agree; 5 = strongly agree) (N = 194).

### *3.4. Public Attitude Toward the Contribution of Night Market to Local Development*

Table 3 shows that vendors tended to be neutral about the contribution of night markets to local development, while non-vendors were more likely to agree with that. T-test data revealed the difference of attitudes between the two groups for all aspects of night markets' contributions to local livelihoods, local development, and community cohesion.

**Table 3.** Difference between vendors' and non-vendors' attitudes toward the contribution of night markets to local development. Mean values calculated from individual scores (1 = strongly disagree; 2 = disagree; 3 = uncertain; 4 = agree; 5 = strongly agree) (N = 194).


T-test was also performed to see the difference of attitudes between females and males within the vendor group. The results in Table 4 revealed that men were more likely to disagree or be neutral about the role of night markets in poverty reduction, urbanization, efficient use of public space, and community connection.

ANOVA was performed to see the differences of attitude toward the contribution of night markets to local development among four age groups. The results revealed no significant difference among these groups.

The study results show that night markets are a source of livelihoods and incomes for local populations. The income per day gained from selling in the night market is higher than the daily salary of an ordinary worker. That is the reason why many university graduates choose to be vendors in the night markets as their main or second job. One of the reasons behind this success can be in their very striking lighting. This is in agreemen<sup>t</sup> with other studies, like the one of Johnstone et al., in 2019 [24], which showed that LED lighting impacts night-market businesses' prosperity in Kenya because of its attractiveness to customers.

However, the findings also depicted that more night-market vendors suffered from circadian-rhythm-related problems than non-vendors, including vision problems, difficulty initiating sleep, and difficulty maintaining sleep. The experience with health problems made vendors unlikely to have positive attitudes toward the contribution of night markets to local development, in spite of their dependence on night markets and the higher incomes they received from them, when compared to other jobs.

**Table 4.** Difference between female and male attitudes toward the contribution of night market to local development within vendors' group. Mean values calculated from individual scores (1 = strongly disagree; 2 = disagree; 3 = uncertain; 4 = agree; 5 = strongly agree) (N = 194).


Because individuals' own experiences and environments often influence their awareness and attitude [25,26], both vendors and clients were aware of lighting impacts on vision, as lighting's impacts on the eyes are more perceptible than other problems. Vendors were more likely to accept that excessive light can alter the human biological clock, disturb human sleep, and increase health problem, because many of them had experienced the health problems related to high levels of illumination.

This is the first field study up to date demonstrating these effects and perceptions in real conditions applicable to the topic under consideration: people developing their activities under too intensive or spectrally inaccurate lighting in night markets.
