Increased 137Cs metabolism during pregnancy

Internal exposure risk due to radiocesium and the consuming behaviour of local foodstuffs among pregnant women in Minamisoma City near the Fukushima nuclear power plant: a retrospective observational study

OBJECTIVES

This study aimed to evaluate the internal cesium (Cs) level among pregnant women in Minamisoma City (the area straddling the evacuation zones) over a 5-year period after Japan's 2011 Fukushima nuclear accident and assess the status and transition of their food-acquiring preferences during this period.

DESIGN

A retrospective observational study of a screening along with a questionnaire survey.

SETTING

This study was conducted in an obstetrics and gynaecology service in Minamisoma City in Fukushima, Japan.

PARTICIPANTS

Participants included pregnant women who applied for the voluntary internal radiation exposure screening programme.

PRIMARY AND SECONDARY OUTCOME MEASURES

Internal radiation exposure was evaluated using the whole-body counter (WBC) in the screening programme. Data from a food acquisition preference questionnaire administered to the participants were analysed and compared across the 5-year period after adjusting for covariates.

RESULTS

Overall, 804 screening programmes were conducted with 579 participants during the study period. All participants had internal contamination levels below the detection limit of the WBC unit (220 and 250 Bq/body for Cs-134 and Cs-137, respectively). Based on the most conservative assumption, their maximum annual effective doses by Cs-134 and Cs-137 together were estimated at 16 µSv/year. Contrary to limited internal contamination risks and counter-dose initiatives by the government, a considerable number of pregnant women were still concerned about consuming potentially contaminated local food products when purchasing them at supermarkets between 2012 (78.4%) and 2015 (75.0%).

CONCLUSIONS

Health effects from post-accident internal radiation exposure were likely to be insignificant in pregnant women. National/local action is urgently needed to promote scientific understanding in pregnant women regarding limited internal exposure risks from local food products in the market. However, few mothers chose to participate in the internal radiation exposure screening programme, and thus, caution is required in interpreting the results of analyses.

Considerations on the ICRP model predictions of the transfer of (137)Cs from food to the milk and urine of lactating mothers

A recent work has shown that the current ICRP biokinetic model for the transfer of caesium radionuclides from food to human breast milk was able to describe with satisfactory accuracy (137)Cs activity concentrations in human breast samples collected a few weeks after the Chernobyl accident as well as in samples collected some years later. However, systematic discrepancies were observed for the predictions of the activity concentrations in urine samples. In the present work, modifications to the model were investigated with the aim of improving the agreement between model predictions and data. It turned out that the disagreement for the urine data was ascribable to the mathematical simplifications used by the ICRP to describe urinary excretion in the first few days after delivery. However, the predictive performances of the model remained unchanged even when differences in the bioavailability of caesium from the ingested food types were considered or metabolic interactions between caesium and potassium were introduced into the model formulation.

Radioactive cesium (¹³⁴Cs and ¹³⁷Cs) content in human placenta after the Fukushima nuclear power plant accident

AIM

The degree of contamination with radioactive cesium (¹³⁴Cs and ¹³⁷Cs) in the human placenta after the accident at Fukushima nuclear power plant (FNP), which occurred on 11 March 2011, has not been assessed.

MATERIAL AND METHODS

¹³⁴Cs and ¹³⁷Cs contents were determined in 10 placentas from 10 women who gave birth to term singleton infants during the period between October 2011 and August 2012 using high-purity germanium detectors for gamma ray spectrometry. Five women resided within 50 km of FNP (neighbor group) and gave birth by the end of February 2012, while the other five women resided within 210-290 km of FNP (distant group) and gave birth in July and August 2012.

RESULTS

All except one of the 10 placentas contained detectable levels of ¹³⁴Cs and ¹³⁷Cs, ranging 0.042-0.742 Bq/kg for ¹³⁴Cs and 0.078-0.922 Bq/kg for ¹³⁷Cs. One placenta from a woman living in Tokyo contained 0.109 Bq/kg ¹³⁷Cs and no detectable level of ¹³⁴Cs (<0.054 Bq/kg). ¹³⁷Cs content was more than 0.2 Bq/kg in four and one placentas in the neighbor and distant groups, respectively.

CONCLUSION

Degree of contamination of the placenta with radioactive Cs was lower even in women who resided within 50 km of FNP compared to Japanese and Canadian placentas in the mid-1960s after repeated nuclear tests and in northern Italian placentas from 1986-1987 after the Chernobyl power plant accident.

Mercury exposure from fish consumption within the Japanese and Korean communities

Public health guidance pertaining to fish consumption requires that we be cognizant of the health concerns associated with eating contaminated fish and the nutritional benefits obtained from fish consumption. In doing so, a need exists for an improved understanding of the extent of contamination within various fish species consumed by populations of concern and the extent of exposure to contamination by these populations. As part of the Arsenic Mercury Intake Biometric Study involving the Japanese and Korean communities, it was possible to obtain fish intake data, determine mercury (Hg) fish tissue concentrations for various species consumed, and examine hair for Hg levels of study participants. This longitudinal study (n = 214) included 106 Japanese and 108 Korean women of childbearing age. Hair Hg levels for the two populations and weight-normalized, species-specific, individual-consumption pattern data that estimated Hg intake levels were compared with published National Health and Nutrition Examination Survey (NHANES) data. Sensitivity analyses and population-specific probabilistic assessments of exposure were conducted. The estimated Hg intake levels for the Japanese (0.09 microg/kg/d) and Koreans (0.05 microg/kg/d) were above the NHANES estimates (0.02 microg/kg/d), as were the hair Hg levels (1.23, 0.61, 0.2 ppm, respectively). Results indicate that (1) there are significant differences between the fish-species-consumption behavior of these two populations; (2) even when fish-consumption rates are equal between two populations, Hg intakes between them can vary significantly; and (3) these population and Hg intake differences present public health challenges when attempting to provide fish consumption guidance.