Supplementary file 1_Educational gradients and sex-by-education differences in environmental health literacy among adults from selected urban communities in Nanning, China.docx

In the analytic community sample, 1,574 participants (88.8%) met the 70-point criterion for sufficient EHL; the total-score distribution was left-skewed and concentrated above this threshold. Internal consistency was acceptable for the total instrument (Cronbach’s alpha = 0.718), whereas domain-specific coefficients were interpreted descriptively. Educational attainment showed the strongest and most consistent association with EHL.

Compared with participants with primary school education or below, those with a master’s degree or above had an 11.32-point higher total score (95% CI: 7.84 to 14.80) and higher odds of sufficient EHL (aOR = 10.06; 95% CI: 3.82 to 28.98). Significant sex-by-education interactions were observed for total EHL, basic knowledge, and basic skills. The exploratory indirect association from basic knowledge to basic skills through basic concepts was small but statistically evident in the total sample and among women.</p>Conclusion<p>Educational attainment was the strongest correlate of EHL in this selected urban community sample.

The findings should be interpreted as sample-specific associations rather than population-representative estimates for all adults in Nanning. The observed sex-by-education heterogeneity and exploratory knowledge-concept-skill association suggest that EHL promotion should prioritize residents with limited education and use concept-centered, skill-oriented communication strategies.</p>