  In August 2023, the long-planned discharging of radioactive wastewater from
the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) started after the
confirmation of its feasibility and safety. As this water contains elevated
amounts of tritium even after being diluted, a lot of resources have been
invested in the monitoring of the Fukushima coastal region where the discharge
outlet is located. We compare the first $^3$H surface activity concentrations
from these measurements (up to the end of November 2023) with the available
background values to evaluate a possible impact of the long-term discharging on
humans and environmental levels of the radionuclide of interest in the same or
nearby area. From our results, we can conclude that the joint effect of
horizontal and vertical mixing has been significant enough to reduce tritium
concentrations at the monitored locations in the region close to the FDNPP port
two days after the end of the respective phase of the discharging beyond the
detection limit of the applied analytical methods (~ 0.3 Bq L$^{-1}$) which is
by five orders of magnitude lower than safety limit for drinking water set by
the World Health Organization (WHO). Moreover, the distant correlation analysis
showed that tritium concentrations at stations located further than 1.4 km were
very close to pre-discharge levels (~ 0.4 Bq L$^{-1}$). We also estimated that
the $^3$H activity concentration in the offshore Fukushima region would be
elevated by 0.01 Bq L$^{-1}$ at maximum over a year of continuous discharging,
which is in concordance with the already published modelling papers and much
less than the impact of the FDNPP accident in 2011.
