Survey of Indoor Air Pollution Health Literacy among Community-dwelling Adults in Taiwan

This study aimed to investigate the level of indoor air pollution health literacy (IAPHL) among adult residents of Taiwan and the associated covariates. A cross-sectional web-based online survey of 647 adults in Taiwan was conducted from May to October 2021 using a reliable and valid IAPHL instrument. We used weighted multiple linear regression models to identify covariates significantly associated with overall and four matric-specific IAPHL scores. The weighted sample size was 616 subjects aged between 20 and 88 years old (mean: 45.8 years, standard deviation: 18.1). Generally, adult residents of Taiwan showed only a moderate level of overall IAPHL, with the highest and lowest matric-specific score for “understanding” and “appraising,” respectively. The key factors associated with adults’ IAPHL included sex, age, work related to indoor air pollution, smoking status, exposure to second-hand smoke, budget for improving indoor air quality, and number of beneficial goods used. The community-dwelling adults in Taiwan had only moderate levels of IAPHL. Adults with certain characteristics associated with low IAPHL should be the objects of further educational interventions or public health policy-making aiming to improve IAPHL. To improve the IAPHL level of adults, we might need to focus on characteristics such as indoor air pollution information provision and health risk perceptions.


INTRODUCTION
The National Human Activity Pattern Survey reported that humans spend over 85% of their time in indoor environments, including homes, schools, offices, or other buildings, during the day (Klepeis et al., 2001).Therefore, indoor air quality (IAQ), which is defined as the quality of the air in and around buildings, may strongly affect the health, productivity, and comfort of individuals living and working in buildings (U.S. EPA, 2023).Very fine droplets, particles, and microbiomes may accumulate in and spread through the air in indoor environments.In developed countries, including Taiwan, indoor air pollutants include total volatile organic compounds (Chen et al., 2016),

Study Design and Participants
A cross-sectional study was conducted between May 2021 and October 2021 through an online video survey owing to the COVID-19 pandemic.The sample size required for this survey was calculated through multiple linear regression (Jan and Shieh, 2019).The sample size of 478 achieved 90% power to detect an effect size (f 2 ) of 0.050 attributable to 8 independent variable(s) using an F-test with a significance level (alpha) of 0.050.The variables tested were adjusted for 13 additional independent variable(s).The calculations assumed an unconditional (random X's) model.The study sample finally consisted of 647 participants from Taiwan, aged 20 years and above, who completed the survey, with a higher-than-expected response rate of 89.6%.The participants were selected via convenience quota sampling.While a convenient sample through the snowball sampling of the study participants was included in this study, quota sampling was also performed to assure the representativeness of the sample concerning the region (north, central, south, and east/remote island), gender, and age group (20-39 years, 40-65 years, and over 65 years) distribution of Taiwan's population in 2020.For additional information on the sample, see the previous study (Wu et al., 2022).Ethical approval for this study was obtained from the Institutional Review Board of the National Cheng Kung University .

IAPHL Instrument and Measurements
Information on reliability and validity was published in our previous study (Wu et al., 2022).The IAPHL instrument was developed on the basis of the integrated health literacy conceptual model proposed by HLS-EU-Q, and the psychometric properties of the IAPHL instrument were validated.A 38-item instrument was established, covering 12 constructs, including 4 information competencies, namely, access, understanding, appraisal, and application, in 3 health domains, that is, healthcare, disease prevention, and health promotion, from individuals to communities to assess IAPHL.The 38-item IAPHL instrument was rated on a 4-point Likert-type scale ranging from 1 (very difficult) to 4 (very easy) and used to indicate the participants' IAPHL level.If the response of a participant was "I do not know" or "I have no experience," then it was coded as a missing value.The overall IAPHL score was calculated as the mean of the scores of all the relevant items.Thus, the score ranged from 1 to 4, and the higher the score, the better the health literacy.In addition to the overall IAPHL score, four matric-specific scores, that is, accessing, understanding, appraising, and applying, were calculated to indicate the information competencies.

Covariates
Studies showed that a number of factors, including personal, sociodemographic, socioenvironmental, and situational determinants, might influence an individual's health literacy (Sørensen et al., 2012).Sociodemographic characteristics include gender, age, education level (middle school or lower, high school, college, postgraduate studies), current occupation (10 occupational categories), living arrangement (living alone, living with children, living with older students, or living with elderly individuals), and region of residence (north, central, south, or east).The occupational classification was based on the Standard Occupational Classification System of Taiwan, in which the inter-rater reliability was substantial (Li et al., 2000).
The questionnaire was administered to collect IAPHL-related information, specifically work related to indoor air pollution (i.e., "Is your or your household members' work related to indoor air pollution, or may you and your co-inhabitants obtain indoor air pollution information at work?" Yes or No), smoking status ("Nonsmoker," "Former smoker," or "Current smoker"), exposure to second-hand smoke (No or Yes), budget for improving IAQ (e.g., "How much are you willing to spend on products that can improve indoor air quality?" with four spending categories: not willing to spend on such products, less than 10%, 11%-20%, or more than 21% of my income), factors affecting IAQ (e.g., "Which of the following situations do you think will affect indoor air quality?"using air freshener or perfume, using insecticide or disinfectant, using curtains, using detergent, using carpet, cooking without a range hood, turning on a window-or split-type air conditioner in an interior space, keeping a furry animal, efflorescence on walls, worshipping with an incense stick, smoking, some of the situations, or all the situations), use of beneficial products in your residence (e.g., "Which of the following do you have or use in your residence?"-airpurifier, air freshener, dehumidifier, wallpaper, incense burner/candles/and so on, eco-friendly paint, curtains, potted plants, carpet, any, or none), and hours per day spent indoors.

Statistical Analysis
In this study, weighted analysis was conducted using stratification weights based on the region (north, central, south, and east/remote island), gender, and age group (20-39 years, 40-65 years, or over 65 years) distribution of Taiwan's population in 2020 to mitigate the effect of any sample imbalances.
Continuous variables were expressed as means (standard deviation [SD]), and categorical variables were expressed as numbers (percentage) to describe the demographics and quantitative parameters of the study participants.The IAPHL score was presented as means (± SD) and medians (interquartile range), and a comparison of the differences between the four matric-specific IAPHL scores was conducted with a linear regression model with generalized estimating equations (GEEs), which considered the within-subject correlations of the matric-specific scores from the same subject.
After the descriptive analysis, a multivariate linear regression model was employed with the stepwise method to identify the covariates significantly associated with the overall and matric-specific IAPHL scores.The linear relationships were verified through scatterplots, which were visually inspected for linearity.The assumptions of normality, homoscedasticity, independence, and multicollinearity were also validated for the linear regression model by examining the residual plots and calculating the variance inflation factor, and no violation of the above assumptions was found.The robustness for handling missing data was assessed through sensitivity analysis, with a single imputation as "1."We employed quantitative bias analysis to assess the potential impact of unmeasured confounding.To quantify this impact, we calculated E-values (VanderWeele and Ding, 2017), measuring the minimum effect needed for an unmeasured confounder on both exposure and outcome to nullify observed exposure-outcome associations.All the statistical analyses and graphing were performed using R version 4.1.3or SAS version 9.4 (SAS Institute, Cary, NC).All the tests were two sided, and statistical significance was defined as a p-value of less than 0.05.

Results
After the unequal probability of sample selection was accounted for in terms of age, sex, and geographical stratifications, a total of 616 participants were included in the weighted analyses.The analyzed sample comprised 304 males (49%) and 312 females (51%).Table 1 shows that the participants had a mean age ± SD of 45.8 ± 18.1 years, were highly educated (71% completed college or higher), and lived with co-inhabitants (n = 528, 86%).The majority (71%) of the participants did not obtain additional information about indoor air pollution from work.
Table 3 presents the results of the weighted multiple linear regression models, which indicated the variables significantly associated with the overall and four matric-specific IAPHL scores.The covariates significantly associated with the overall IAPHL score included gender, age, work related to indoor air pollution, smoking status, exposure to second-hand smoke, budget for 1 Living with someone is a multiple-choice question, that is, an interviewee may be living with a child under the age of 12 years and a person above the age of 65 years.Thus, the total for children under 12 years of age, a student over 12 years of age, and individual over 65 years of age (n = 783) is greater than the total number of the respondents living with someone (n = 528).improving IAQ, and number of IAQ-benefiting products used.In contrast to people whose work related to indoor air pollution had significantly higher overall IAPHL score (adjusted β = 0.26), those who were former smokers (adjusted β = -0.27)and current smokers (adjusted β = -0.46)had lower IAPHL scores.The participants willing to spend on products that can improve IAQ had significantly high IAPHL scores.The results of the four matric-specific IAPHL scores were similar to the results of the overall score.
To explore potential interactions, we conducted analyses examining the correlation between demographic characteristics and occupations associated with indoor air pollution.Across all analyses, the consistent findings indicated the absence of a statistically significant interaction between the selected variables.For quantitative bias analysis, we prioritized factors influencing the level of IAPHL, namely work content related to indoor air pollution.As the exposure effect of work content is presented as an additive effect rather than multiplicative effect, i.e., a risk ratio scale, we converted the naive point estimate to an approximate risk ratio (VanderWeele and Ding, 2017), which is estimated at 1.02.Based on the risk ratio of 1.02 and its corresponding confidence limits, the E-value was computed at 2.54, with a lower confidence interval limit of 2.05.An E-value of 2.54 means that there could be unmeasured confounders associated with both the exposure and the outcome, and its strength of association would need to be at least 2.54 to explain away the observed association.For nullifying the association, an unmeasured confounder must be linked to both work content related to indoor air pollution and the level of IAPHL, with a risk ratio of at least 2.54.Given that we have included most of the known factors associated with indoor air pollution health literacy including personal sociodemographic, socioenvironmental and situational determinants, unmeasured confounders were less likely to surpass the corresponding E-values in associations with exposure and the level of IAPHL.It suggests that the association between work content and indoor air health literacy is less likely to be completely explained by unmeasured confounding.

Discussion
People spend a considerable amount of time in enclosed buildings (Klepeis et al., 2001), so the resolution of indoor air-related health problems and the improvement of people's indoor health literacy are essential.Nonetheless, research on the degree of IAPHL and its contributors is scarce.This paper is believed to be the first one that presents the community-dwelling adults' overall and four matric-specific IAPHL scores, as well as their correlates.
The community-dwelling adults in Taiwan had only a moderate (2.36-2.58out of 4) level of IAPHL, with the lowest and highest matric-specific scores for "appraising" and "understanding" competencies, respectively.In Taiwan, people had high competency of understanding and applying/using the information available to them to avoid overexposure to indoor air pollution but had low competency in the access to indoor air pollution information that they needed.They also had low ability in interpreting and evaluating (i.e., appraising) the information regarding indoor air pollution.This finding is similar to the result of a previous general health literacy survey conducted in eight European countries, which suggested that the ability to "appraise" health information is perceived as more difficult than "understanding" it (Pelikan and Ganahl, 2017).Ref.
Ref. Our study results confirmed another health literacy survey in Germany, in which the lowest percentage of respondents (47.7%) indicated that they had difficulties understanding health information (Schaeffer et al., 2021).

Yes
A systematic review has highlighted critical problems with regard to health-related fake news shared on social media platforms, either by mistake or on purpose.Such fake news could markedly threaten an individual's health quality (Melchior and Oliveira, 2022), especially when one lacks the competence to appraise adequate and applicable indoor air pollution-related information.The barrier in appraising health literacy was associated with lack of careful consideration and relevant knowledge and familiarity with fake news, whose dissemination has increased substantially in recent years (Pennycook and Rand, 2021).One study demonstrated that the public has a limited health risk perception of indoor air pollutants.Nonetheless, the public perceives universities and research institutes as the most credible sources of health-related information, even though the media are considered the most important source of information on the health risks of indoor air pollutants (Dingle and Lalla, 2002).The overall and matric-specific IAPHL scores from the present study's survey are similar to the results of a previous survey on ambient air pollution health literacy (AAPHL), which reported that understanding information related to air pollution is easier than appraising it (Hou et al., 2021).Among the four matric-specific competencies of IAPHL and AAPHL, the "appraising" matrix was the most difficult, which is similar to that in chronic disease health literacy research, where the lowest-scoring domain was the appraisal of health information (Dinh et al., 2020).Elevating civil awareness and increasing the public's appraisal ability to distinguish between correct information, erroneous information, and "fake news" through the dissemination of health information are important.This outcome implied that evidence-based risk communication can help translate evidence into risk messages and provide accurate, understandable, and meaningful information to individuals with varying levels of basic and scientific literacy (Finn and O'Fallon, 2017).
Among the potential determinants of health literacy proposed by the European Commission, the distinct factors impacting health literacy include personal (e.g., age, education, gender, race, socioeconomic status, occupation, and income literacy), societal and environmental (e.g., culture, social systems, and political forces), and situational (e.g., social support, family and peer influence, media use, and the physical environment) determinants (Sørensen et al., 2012).The present study indicated that the determinants of IAPHL include gender, age, educational attainment (personal determinants), smoking status (situational determinants), and work related to indoor air pollution (socioenvironmental determinants), which are generally consistent with what the European Commission proposed.
Apart from the European Commission proposal, our study findings are also consistent with those of a previous systematic review, reporting that old age and low education level are independent predictors of low health literacy among patients with heart failure and breast cancer (Cajita et al., 2016;Shen et al., 2019).Similarly, a cross-sectional study on community-dwelling elderly individuals identified old age and low educational attainment as significant predictors of low health literacy (Baker et al., 2000;Hou et al., 2021).The present study demonstrated that residents with work related to indoor air pollution or nonsmoking status were associated with a high level of IAPHL.Quick et al. (2009) found that nonsmokers exhibited a significantly strong awareness of tobacco-associated risks, a preventive attitude toward the dangers of environmental tobacco smoke, and support for clean indoor air policies.This finding corresponds to understanding, appraising, and applying health literacy compared to smokers (Quick et al., 2009).
Although most smokers do not care about IAQ and tend to neglect the related diseases caused by indoor air pollutants, a Korean study reported no significant association between smokers' IAQ perceptions and smoking status (Kim et al., 2019).On the contrary, a study supports the notion that the perception of IAQ is mainly related to smoking status (Langer et al., 2017).Smokers usually fail to accomplish the four domains of the indoor air pollution health information processing because they have insufficient awareness of indoor air pollution and its impact on health and do not perceive smoke-free indoor environments as important.Consequently, they typically do not actively seek information or knowledge about indoor air pollution, and their ability to mitigate excessive exposure to indoor air pollution is compromised.A previous study noted that an individual's knowledge, attitude, subjective norms, favorable support, and awareness of the risks associated with environmental exposure, such as to tobacco smoke, may be increased if his/her family members and/or coworkers encourage preventive behavioral intention and support clean indoor air policies (Quick et al., 2009).The more individuals believe that overexposure to indoor air pollution is risky, the more likely that they will remind their co-inhabitants to support clean indoor air environmental conditions (Badland and Duncan, 2009).
To the best of our knowledge, this study is the first nationwide survey of community dwellers on IAPHL levels, which also identified potential determinants of IAPHL.Unlike most prior studies that emphasized perceived health symptoms related to IAQ (Raufman et al., 2020) or aimed to capture participants' perceptions of IAQ and to explore the factors that influence participants' behavior (Tomsho et al., 2022), our study assessed an individual's comprehensive domain of health literacy on indoor air pollution among inhabitants.The IAPHL based on the HLS-EU-Q conceptual model not only assessed an individual's knowledge and behaviors toward IAPHL but also emphasized an individual's competence of obtaining and evaluating health information related to indoor air pollution (Wu et al., 2022).Several studies reported the global burden of indoor air pollution-induced cardiorespiratory, pediatric, and maternal diseases, especially in low-income countries (Badland and Duncan, 2009;Lee et al., 2020;Pandey et al., 2021;Yin et al., 2020).Most previous studies indicated a positive association between air pollution exposure and risk perception through the influence of behavior, experience, socioeconomic factors, and information/communication (Cho et al., 2020;Dong et al., 2019;Pu et al., 2019).A study indicated that increased levels of EHL may contribute to the improvement of health outcomes related to household air pollution (Finn and O'Fallon, 2017).Improved EHL levels, through enhancing individuals' knowledge and understanding of the risks and mitigation strategies associated with indoor air pollution, can empower individuals to make informed decisions and adopt healthy practices within their households (Mendell et al., 2011).The current study contributes to the understanding of IAPHL, emphasizing the importance of targeted risk communication and awareness campaigns.
This study has several important limitations that need mentioning.First, the participants recruited via convenience sampling might not be representative of the whole adult population in Taiwan.Nonetheless, we managed to weigh our sample with the region of residence, gender, and age group of Taiwan's population to increase the representativeness of the study sample.Second, potential selection bias was a challenge in this study because data were collected through an online video survey, resulting in the study sample being composed disproportionally of adults with considerable capability in operating communication devices and access to the Internet (Andrade, 2020;Wright, 2005).This matter was particularly true for some elderly individuals willing to participate in an online survey only when they live with someone who has relatively good health and high education level and can help them (Dodge et al., 2014).Such a limitation was unavoidable in research conducted during the COVID-19 pandemic period, in which an on-site face-to-face interview was almost impossible.Third, one potential selection bias was related to the voluntariness.People who choose not to participate in the study tend to have low interest in the research topic.Fourth, the presence of two potential sources of information bias in our study was noted.The first potential source of information bias from health literacy depends on cognitive and communicative skills (Nutbeam, 2000), but the cognitive and communicative functions of the participants were not assessed in this study.Nevertheless, additional response categories (i.e., "I do not know" or "I have no experience") were recorded to preserve the participants' comprehension of the questionnaire items.The second source of potential information bias was related to the questionnaire length.A lengthy questionnaire can potentially introduce response burden and affect the quality of responses.Participants may experience fatigue or lose interest as the questionnaire progresses, leading to incomplete or inaccurate answers.A good questionnaire should aim for an optimal length, typically consisting of 25-30 questions within 30 min (Sharma, 2022).Lastly, the findings from a study with cross-sectional designs like ours preclude the causal inference.

CONCLUSIONS
The adult residents in Taiwan had only a moderate level of IAPHL, with the highest and lowest matric-specific scores for "understanding" and "appraising" competencies, respectively.In addition, attendance to a job related to indoor air pollution and nonsmoking status were significantly associated with enhanced IAPHL.From a public health perspective, the study results may provide insights into the development of tailored educational intervention programs considering personal, situational, and socioenvironmental determinants to improve the IAPHL of community dwellers.Identification of people who do not have adequate IAPHL may help determine who should be prioritized.Exploring the effectiveness of diverse intervention measures on health literacy or conducting in-depth studies on specific populations, such as the elderly, women, and occupational exposure groups, to understand their health literacy status may provide insights for future research directions.Understanding the subjective health-literate decision-making process regarding perceptions of health risks from indoor air pollution is crucial.Thus, reinforcing health gains by providing effective health communication strategies for improving IAQ may encourage healthy behaviors through accessing, understanding, assessing, and applying IAPHL across communities.Moreover, IAQ can benefit not only from educational interventions but also from strategic public policy enhancements.Recommendations for policy improvements should be formulated to address pollution sources and reduce fake news, aligning with efforts to improve overall indoor environmental quality.Integrating public health literacy considerations into these policies can contribute to fostering awareness and understanding among the general population.A comprehensive approach can be established by combining educational initiatives with targeted policy measures to create healthy indoor environments and raise public health literacy levels.

Table 2 .
Descriptive statistics of overall and matric-specific scores for IAPHL.Note: SD-standard deviation; Q1-25 th percentile; Q3-75 th percentile; Min.-minimum; Max.-maximum. 1p-values for comparison between the four matric-specific IAPHL scores by using a linear regression model with generalized estimating equations.

Table 3 .
Multiple linear regression models of overall and matric-specific scores for IAPHL.