This year, the S20 was held in Japan, featuring the emerging issue of marine plastic waste. As a result, the G20 Academies of Sciences calls for 6 recommendations including the use of evidence-based advice, capacity building for both essential research infrastructures and human capital, and establishment of an improved data storage and management system that ensures open access by scientists globally. To implement these recommendations, there is a growing need for scientists to work multidisciplinary and to promote evidence-based policy toward the SDGs. There is, however, a risk of conflict; scientists from different disciplines have opinions that collide with one another and biased view in public image on particular science hinders the other with different objectives. It is almost unclear what are “known knowns”, “known unknowns” and “unknown unknowns” related to many sustainable development issues, such as SDGs including the new problems of plastic waste. The amount of microplastics in the ocean is uncontrollably increasing (known knows). However, how much amount of microplastics are lethal to marine organisms or humans is still unknown (known unknowns). There might be a further potential risk of smaller plastics (nanoplastics) (unknown unknowns). Such recently recognized environmental issues need public awareness and urgent action to protect and preserve natural resources. On the other hand, the negative public image on plastics may hinder the promotion or development of associated industrial science.