# A New Indicator to Assess Public Perception of Air Pollution Based on Complaint Data
## 1 Introduction  
Air pollution is a major environmental problem that affects every country and everyone. To solve the problem of air pollution, local monitoring and practical evaluation of pollution levels are needed [1]. Many countries have established air quality monitoring stations to measure pollution levels in real time [2]. However, monitoring stations are limited, and the public is everywhere. As the direct feeler of air quality and the assessor of environmental protection performance, the public is crucial to improving air pollution. Therefore, it is essential to study further the public's attitudes and opinions on air quality [3, 4, 5]. Public perception of air pollution assessment can be summarized as the public's subjective evaluation of air pollution events based on subjective feelings and risk perceptions [6, 7]. It is a supplement to objective air quality monitoring, although there is a certain deviation between them [8, 9]. According to the different methods of obtaining data, theexisting research on public perception of air pollution can be classified into two categories: one based on questionnaires and the second one based on the social media platform. A questionnaire survey records people's feelings and emotions about air pollution in the form of a questionnaire according to different research purposes [10; 11; 12]. The questionnaire survey forms include offline and online; offline is through on-site interviews and paper questionnaires, online is through the mobile devices or professional questionnaire survey platform [13; 14]. For example, [PERSON] et al. [15] collected data through a questionnaire survey of 1202 residents in four cities. They found that there are moderate differences in subjective evaluation of local air pollution, as well as the degree of worry and pain caused by the air pollution. [PERSON] et al. [16] selected three cities in China: Beijing, Nanjing, and Guangzhou, by the questionnaire survey and found that the public's awareness of the health effects and familiarity of air pollution was significantly higher in winter than in summer. The haze weather is also considerably higher than the typical weather. [PERSON] et al. [17] explored public satisfaction with air pollution and found that the public's air pollution views would be affected by industrial emissions. However, the perception of air quality based on the questionnaire survey will be affected by many factors, such as investigators and cities' differences. Moreover, due to the high costs, the questionnaire survey is challenging to perform frequently and regularly. With the development of information and communication technology, people actively express their attitudes and feelings through social media. Some scholars used the social media data such as Tweet, Facebook, or Sina Weibo in China to extract public responses and abundant information on air quality or air pollution [18; 19; 20]. For example, [PERSON] et al. (2019) explored the text content of Twitter data to understand the public's response to air quality changes over time and their understanding of air quality issues [18]. [PERSON] et al. [19] proposed a method to infer air quality in Chinese cities based on Sina Weibo and meteorological data. [PERSON] et al. [20] used Tweet data and sentiment analysis methods to evaluate the feasibility of using social media to monitor outdoor air pollution in London from public perception. [PERSON] and [PERSON] et al. [21] proposed the air quality perception index (AQPI) based on the Internet search volume data to evaluate air quality views. The above research provides new methods and technologies for the public perception of air quality and expands subjective public emotion on air quality assessment. However, the social media data are complex and need to analyze the positive, negative, neutral, mixed, and other emotion types in the text. There may also be bias, and users may express unreal emotions for social purposes [22].