Politicized science communication and motivated reasoning: social media responses to the Fukushima radioactive water discharge in Japan, South Korea, and China

The Fukushima radioactive water discharge became a major international controversy in East Asia, where scientific risk, evaluations of government and institutional actors, and diplomatic conflict intersected. While the Japanese government promoted the discharge policy by emphasizing its scientific safety, the South Korean government adopted a relatively cooperative stance toward Japan, whereas the Chinese government strongly criticized the discharge. This study comparatively examines how social media users in Japan, South Korea, and China interpreted and circulated discourse surrounding the Fukushima radioactive water discharge within these differing political and social contexts. To this end, X data from Japan and South Korea and Weibo data from China were collected and analyzed using repost network analysis and political orientation analysis. The findings show that pro-discharge discourse was relatively dominant in Japan and was closely associated with government-supportive and conservative users. In contrast, anti-discharge discourse overwhelmingly dominated in South Korea and was primarily linked to anti-government users. On Chinese Weibo, the high-engagement posts examined were predominantly critical of the discharge and included political, diplomatic, and anti-Japanese narratives, with state-affiliated media accounts visible among highly circulated content. These findings suggest that public responses to the Fukushima discharge were shaped not only by perceptions of scientific risk, but also by political identity, evaluations of government and institutional actors, and international relations. The study demonstrates how science communication in East Asian social media environments becomes politicized and embedded within broader political and nationalistic discourse structures.