Social media never shake the role of trust building in relieving public risk perception

The avenues through which booming social media information provision reshape public environmental risk perceptions remained unclear. The release of a documentary titled “Under the Dome – Investigating China's Smog” in mainland China on February 2015 provides a natural experiment to fill the gap. In the experiment, the public was randomly divided into two groups: people who were exposed to the information (treatment group) and people who were not (control group). To track the dynamic changes of risk perceptions of environmental pollution, we conducted three surveys on the perceptions covering two groups within one week after the treatment (March 2015, survey 1) and six months and twelve months later (September 2015, survey 2 and March 2016, survey 3, respectively). Results show that social media information provision reshapes the public risk perception by increasing self-reported knowledge, reducing trust, and making them more fearful. Raised perceived risk encourage the public to take protective behaviours that are nonetheless accompanied by public panic and collapse of trust. Based on the findings, we recommend that the government and the media pay attention to the periodicity of information provision to ensure its effectiveness on promoting the behaviour shifts and minimize the uncertainties embedded in the information to avoid the violation of trust. In addition, the effects of information provision are found to attenuate over time for all perception factors but not for trust. It also reveals that the positive role of trust building in relieving perceived risk are independent of the information provision process. Therefore, trust building shall be considered as a priority to tackle the challenges posed by a dramatically changed communication environment. The findings have wider implications for the perceptions of general risks not limited to environmental pollution.