Global environmental transfer of 129 I

•A compartmental model is used to estimate the transfer of 129I through various environmental segments.•Scenario of initial release to each of the compartments is considered.•Dose due to natural production of 129I is constant and continuous i.e. 2.07×10−11mSv/y.•Maximum dose due to 129I for nuclear weapon tests carried for a period of 10 y is 2.42×10−7mSv/y.•Dose due to infinite releases of 129I from NPP and FRP is highest but insignificant as compared to regulations.