Impact Of Air Pollution On Public Psychological Health-Evidence From Environmental Physio-Psychological Experiment

In the past 10 years,with the speeding up of urbanization and industrialization,China experienced serious air pollution.As the dominant air pollutants,wide-range and high-concentration fine particulate matter(PM2.5)posed great threats to public health.In addition to physical health losses,the mental health risk attributable to air pollution also caused great public concerns and international research interests.Due to the difficulties of defining and quantifying mental health,existing studies were limited to the following two branches.One is to use the epidemiological method to establish the relationship between atmospheric pollution and psychology disease(depression,suicide,etc.)and the other is to explore the associations of air pollution and selfreported wellbeing obtained from household surveys.However,these approaches are challenged by the experimenter effect and the crowd bias deviation.With the development of physio-psychological experimental technology,another novel solution was provided to measure people’s mental health.In this study,we designed two environmental physio-psychological experiments with three kinds of measurements for mental health to quantify the impacts of air pollution on mental health.In the first experiment,standardized static images matched with varied PM2.5 concentration as the stimulus were viewed by 110 participants with similar personal characteristics through E-prime 3.0 software in a quiet lab.E-prime 3.0 also recorded participants’ immediate wellbeing response in different metrics of annoyance and adjusted Self-Assessment Manikin(SAM)with two-dimensional emotional indices(arousal and valence)after each picture stimulus.In addition,participants are divided into four groups by whether they were told the experimental objective and whether there were landmarks in the background of PM2.5 pictures to examine the stigma effect of air pollution in China and the interference of picture background,respectively.In the second experiment,there were three steps.First,after entering the lab and sit in front of a computer monitor,participants were asked to relax for 1 minute.Second,participants then took 10-minutes oral English tasks in the form of TOEFL test for evoking the stress.Immediately after the stress evocation,110 participants were randomly divided into seven groups.Then they were asked to relax for 3 minutes in the front of the monitor that displayed one group of blank pictures and six target groups of air pollution pictures with PM2.5 concentrations ranging from 11,32,51,108,165,to 231 μg/m3,respectively.During the experiment,Galvanic Skin Reaction(GSR)and ECG(Electrocardiograph)were selected as stress indicators and acquired using a BIOPAC MP 150 System and aggregated for obtaining the mean and maximum of GSR for each 10-seconds interval using Acqknowledge 4.0.Based on the first experiment,in terms of annoyance,critical PM2.5 concentrations were around 42-65 μg/m3.Under critical concentration interval PM2.5 increase didn’t cause any additional annoyance while above critical levels the annoyance increased obviously by 1.95%per 10 μg/m3 PM2.5 increase.In addition,we found participants who were told experimental objective reported significantly higher annoyance than the counterpart,which proved the stigma effect of air pollution in China.All the findings above are robust,which are independent from the interference of picture background.At the same time,our study also established the relationship between atmospheric pollution and two-dimensional emotional indices(arousal and valence).The results showed that the averaged valance scores increased by 1.56%per 10 μg/m3 PM2.5 increase,with a broader critical concentration interval of 42-65 μg/m3 where the valance shifted from positive ratings(score≥ 4)to negative ones(score<4).The averaged arousal scores presented a U curve with the bottom level located in 42-50μg/m3,Even using different wellbeing metrics from annoyance,the same findings were concluded that PM2.5 caused negative wellbeing consequences with the threshold of 42-65 μg/m3.It strongly supported the rationality and reliability of this study about the impact of air pollution on human mental health.Similarly,we found participants who were told experimental objective reported significantly lower valance than the counterpart,which proved the stigma effect of air pollution in China.All the findings above are robust,which are independent from the interference of picture background.Based on the second experiment,the impact of air pollution on stress recovery was explored through physiological signal changes of GSR and ECG.The results showed that environment with high PM2.5 concentration seriously interfered with the subjects’ stress recovery levels,even increased the stress levels.According to the stress recovery patterns,six target groups were regrouped into three categories that matched the Air Quality Grading system in China well.For the first one with PM2.5 of 11-32μg/m3(Grade:Good),participants presented the most obvious stress reductions of around 20%by the end of the third minutes.For the second one with PM2.5 of 51-108μg/m3(Grade:Fine and Mild Pollution),moderate stress reductions of less than 10%were observed.For the third one(Grade:Moderate and Severe Pollution),participants’stress levels have not been reduced,but increased since the second minute.It revealed that there was a novel staircase-function response mechanism of stress restoration to air pollution exposure.This also proved that the good air quality could effectively improve public psychological stress level,which also supported the results from the first experiment powerfully.In summary,air pollution brings negative assessment with the critical value in range of 42-65 μg/m3 to public psychological health.This is an innovation of interdisciplinary integration with environmental science,public health,social psychology and so on.It also fits the reality background of improving concerns to living environment quality.The most importantly,our research provides policy reference and theoretical basis to government and related NGOs(Non-Governmental Organization).