Introduction The Japanese Ministry of the Environment has begun a birth cohort study, Japan Eco & Child Study, to clarify the influence environmental risks on children (http://www.env.go.jp/chemi/ceh/index.html). This study will be conducted on 100 000 pregnant mothers and their children from across Japan from 2011. Twenty-six areas across Japan offered to participate in this project, and 15 sites, including Fukushima Medical University, were chosen. The purpose of this birth cohort study is to elucidate an important hypothesis: that environmental factors, including the exposure of children from the fetal period to early childhood to chemical compounds, affects pregnancy/reproduction, the incidence of congenital anomalies, mental development, immunology/allergy, and metabolism/endocrine systems. If environmental agents affecting the growth/development of children can be clarified and reported to a risk management bureau, appropriate risk management steps, such as self-imposed restraints, examination chemical compound control, and the implementation of environmental quality standards in water and soil, can be applied.

Methods Investigation scale: 100 000 pregnant mothers and their children from across Japan (we plan to enrol 6840 pregnant mothers from Fukushima City, South Soma City, and Futaba County). Investigation period: 16 years (3 for recruitment, 13 for tracking) commencing 31 January 2011.

Results and Conclusion Recruitment number and rate in a half year will be presented. The prospects of Japan Eco & Child Study in Fukushima will be also described in presentation. It is important to discuss the problems on long term study.