Increases in perinatal mortality in prefectures contaminated by the Fukushima nuclear power plant accident in Japan: A spatially stratified longitudinal study

Decline in the Conception Rate of Wild Japanese Monkeys after the Fukushima Daiichi Nuclear Power Plant Accident

We examined the conception rate of wild Japanese monkeys (Macaca fuscata) in Fukushima City that were exposed to radiation as a result of the Fukushima Daiichi Nuclear Power Plant accident in March 2011. The conception rate in the year of delivery from 2009 to 2022 was estimated by dissecting individuals that were euthanized by the government for population control as a countermeasure against crop damage. To evaluate the effects of exposure, the cumulative exposure dose for each individual was calculated using the concentration of radiocesium deposited in the soil at the capture site and the concentration of radiocesium in muscle estimated from the aggregated transfer factor. There were no significant differences in conception rates across all age classes over time. In terms of conception rates by age class, there was a significant decrease post-exposure compared with pre-exposure in the age class ≥ 8 years, but no significant differences in the age class 5-7 years. The non-ovulation rate did not significantly differ between the pre- and post-exposure periods for any age class. Body fat index, which can affect fertility, was compared between the pre- and post-exposure periods, and no significant differences were found in either age class. In contrast, the median total cumulative exposure (cumulative internal exposure + cumulative external exposure) was significantly higher in the age class ≥ 8 years compared with the age class 5-7 years. These results suggest that the total cumulative exposure dose may be one of the reasons for the lower conception rate in the post-exposure period among the age class ≥ 8 years.

CDC Division of Reproductive Health's Emergency Preparedness Resources and Activities for Radiation Emergencies: Public Health Considerations for Women's Reproductive Health

Pregnant, postpartum, and lactating people, and infants have unique needs during public health emergencies, including nuclear and radiological incidents. This report provides information on the CDC Division of Reproductive Health's emergency preparedness and response activities to address the needs of women of reproductive age (aged 15-49 years), people who are pregnant, postpartum, or lactating, and infants during a radiation emergency. Highlighted preparedness activities include: (1) development of a quick reference guide to inform key questions about pregnant, postpartum, and lactating people, and infants during radiation emergencies; and (2) exercising the role of reproductive health experts during nuclear and radiological incident preparedness activities.

Effects of External Radiation Exposure on Perinatal Outcomes in Pregnant Women After the Fukushima Daiichi Nuclear Power Plant Accident: the Fukushima Health Management Survey

BACKGROUND

This study aimed to investigate the effects of maternal exposure to external radiation on perinatal outcomes among women who experienced the Fukushima Daiichi Nuclear Disaster (FDND) using the Fukushima Health Management Survey (FHMS).

METHODS

Data from the Pregnancy and Birth Survey and Basic Survey in the FHMS were combined to analyze external maternal radiation exposure following the FDND, and the relationship between radiation dose and perinatal outcomes was analyzed using binomial logistic regression analysis. Missing dose data were supplemented using multiple imputation.

RESULTS

A total of 6,875 individuals responded to the survey. Congenital anomalies occurred in 2.9% of patients, low birth weight (LBW) in 7.6%, small for gestation age (SGA; <10th percentile) in 8.9%, and preterm birth in 4.1%. The median maternal external radiation dose was 0.5 mSv (maximum, 5.2 mSv). Doses were classified as follows: <1 mSv (reference), 1 to <2 mSv, and ≥2 mSv. For congenital anomalies, the crude odds ratio for 1 to <2 mSv was 0.81 (95% confidence interval [CI], 0.56-1.17) (no participants with congenital anomaly were exposed to ≥2 mSv). At 1 to <2 mSv and ≥2 mSv, the respective adjusted odds ratios were 0.91 (95% CI, 0.71-1.18) and 1.21 (95% CI, 0.53-2.79) for LBW, 1.14 (95% CI, 0.92-1.42) and 0.84 (95% CI, 0.30-2.37) for SGA, and 0.91 (95% CI, 0.65-1.29) and 1.05 (95% CI, 0.22-4.87) for preterm birth.

CONCLUSION

External radiation dose due to the FDND was not associated with congenital anomalies, LBW, SGA, or preterm birth.

Radioactive releases from the nuclear power sector and implications for child health

Although radioactivity is released routinely at every stage of nuclear power generation, the regulation of these releases has never taken into account those potentially most sensitive-women, especially when pregnant, and children. From uranium mining and milling, to fuel manufacture, electricity generation and radioactive waste management, children in frontline and Indigenous communities can be disproportionately harmed due to often increased sensitivity of developing systems to toxic exposures, the lack of resources and racial and class discrimination. The reasons for the greater susceptibility of women and children to harm from radiation exposure is not fully understood. Regulatory practices, particularly in the establishment of protective exposure standards, have failed to take this difference into account. Anecdotal evidence within communities around nuclear facilities suggests an association between radiation exposure and increases in birth defects, miscarriages and childhood cancers. A significant number of academic studies tend to ascribe causality to other factors related to diet and lifestyle and dismiss these health indicators as statistically insignificant. In the case of a major release of radiation due to a serious nuclear accident, children are again on the frontlines, with a noted susceptibility to thyroid cancer, which has been found in significant numbers among children exposed both by the 1986 Chornobyl nuclear accident in Ukraine and the 2011 Fukushima-Daiichi nuclear disaster in Japan. The response among authorities in Japan is to blame increased testing or to reduce testing. More independent studies are needed focused on children, especially those in vulnerable frontline and Indigenous communities. In conducting such studies, greater consideration must be applied to culturally significant traditions and habits in these communities.

Perinatal mortality after the Fukushima nuclear accident: An ecological study

Objective

This study continues former studies on perinatal mortality in Japan after the Fukushima Daiichi nuclear power plant (FDNPP) accident in March 2011. An increased study region is chosen, and the study period is extended to 2019.

Methods

Japanese monthly perinatal mortality data are provided on a prefecture level by the Japanese government. The study region consists of 12 prefectures around the FDNPP; the rest of Japan is used as the control region. A combined non-linear regression of perinatal mortality rates in the study- and control regions is conducted. The regression model allows for a common asymptotic lower limit of perinatal mortality, seasonal variations, and periodic peaks in 2012–2019 in the study region. To determine the dependency of the effect on distance from the FDNPP, the study region is divided into four core prefectures and eight prefectures surrounding the core prefectures.

Results

Perinatal mortality rates in the study region show a significant 6.4% (95% CI: 1.8%, 13.4%) overall increase in 2012–2019 relative to the trend in preceding years with no attenuation during 2012–19. The increase translates to 590 (165, 1226) excess perinatal deaths (p = 0.016). It is characterized by annual peaks with maxima in April. A 13.6% increase is determined in the four core prefectures and a 4.3% increase in eight prefectures surrounding the core prefectures. Before 2012, there is a peak around April 2011 and a decline in October 2011; another significant peak is detected in November 2012. In the 4 core prefectures, large increases are found in the first quarter of 2018 (+70%) and in May 2019 (+130%).

Conclusion

This study finds periodic peaks in perinatal mortality in spring 2012–2019 in 12 prefectures of Japan surrounding the FDNPP. In light of massive increases in 2018 and 2019 in the four core prefectures, continued investigation of perinatal mortality in contaminated regions of Japan is recommended.

A hypothesis to derive the shape of the dose-response curve for teratogenic radiation effects

Reports of adverse pregnancy outcomes after in utero exposure to very low levels of ionizing radiation are inconsistent with a threshold dose of 100 mSv for teratogenic effects in humans. In the present study, it is hypothesized that the shape of the dose-response relationship for teratogenic effects is a cumulative lognormal distribution without threshold. This hypothesis relies on the assumption that both doses and radiosensitivities in human populations exposed to ionizing radiation are random variables, modeled by lognormal density functions. Here, radiosensitivity is defined as the dose limit up to which radiation damage can be repaired by the cellular repair systems, in short, the repair capacity. Monte Carlo simulation is used to generate N pairs of individual doses and repair capacities. Radiation damage occurs whenever the dose exceeds the related repair capacity. The rate of radiation damage is the number of damages, divided by the number N of pairs. Monte Carlo simulation is conducted for a sufficient number of ascending median doses. The shape of the dose-response relationship is determined by regression of damage rates on mean dose. Regression with a cumulative lognormal distribution function yields a perfect fit to the data. Acceptance of the hypothesis means that studies of adverse health effects following in-utero exposure to low doses of ionizing radiation should not be discarded primarily because they contradict the concept of a threshold dose for teratogenic effects.

Disproportionate Impacts of Radiation Exposure on Women, Children, and Pregnancy: Taking Back our Narrative

Narratives surrounding ionizing radiation have often minimized radioactivity's impact on the health of human and non-human animals and the natural environment. Many Cold War research policies, practices, and interpretations drove nuclear technology forward by institutionally obscuring empirical evidence of radiation's disproportionate and low-dose harm-a legacy we still confront. Women, children, and pregnancy development are particularly sensitive to exposure from radioactivity, suffering more damage per dose than adult males, even down to small doses, making low doses a cornerstone of concern. Evidence of compounding generational damage could indicate increased sensitivity through heritable impact. This essay examines the existing empirical evidence demonstrating these sensitivities, and how research institutions and regulatory authorities have devalued them, willingly sacrificing health in the service of maintaining and expanding nuclear technology (Nadesan 2019). Radiation's disproportionate impacts should now be the research and policy focus, as society is poised to make crucial and long-lasting decisions regarding climate change mitigation and future energy sources (Brown 2019b).

Nutrient Imbalance of the Host Plant for Larvae of the Pale Grass Blue Butterfly May Mediate the Field Effect of Low-Dose Radiation Exposure in Fukushima: Dose-Dependent Changes in the Sodium Content

The pale grass blue butterfly Zizeeria maha is sensitive to low-dose radioactive pollution from the Fukushima nuclear accident in the field but is also highly tolerant to radioactive cesium (¹³⁷Cs) in an artificial diet in laboratory experiments. To resolve this field-laboratory paradox, we hypothesize that the butterfly shows vulnerability in the field through biochemical changes in the larval host plant, the creeping wood sorrel Oxalis corniculata, in response to radiation stress. To test this field-effect hypothesis, we examined nutrient contents in the host plant leaves from Tohoku (mostly polluted areas including Fukushima), Niigata, and Kyushu, Japan. Leaves from Tohoku showed significantly lower sodium and lipid contents than those from Niigata. In the Tohoku samples, the sodium content (but not the lipid content) was significantly negatively correlated with the radioactivity concentration of cesium (¹³⁷Cs) in leaves and with the ground radiation dose. The sodium content was also correlated with other nutrient factors. These results suggest that the sodium imbalance of the plant may be caused by radiation stress and that this nutrient imbalance may be one of the reasons that this monophagous butterfly showed high mortality and morphological abnormalities in the field shortly after the accident in Fukushima.

Folic Acid Fortification Prevents Morphological and Behavioral Consequences of X-Ray Exposure During Neurulation

Previous studies suggested a causal link between pre-natal exposure to ionizing radiation and birth defects such as microphthalmos and exencephaly. In mice, these defects arise primarily after high-dose X-irradiation during early neurulation. However, the impact of sublethal (low) X-ray doses during this early developmental time window on adult behavior and morphology of central nervous system structures is not known. In addition, the efficacy of folic acid (FA) in preventing radiation-induced birth defects and persistent radiation-induced anomalies has remained unexplored. To assess the efficacy of FA in preventing radiation-induced defects, pregnant C57BL6/J mice were X-irradiated at embryonic day (E)7.5 and were fed FA-fortified food. FA partially prevented radiation-induced (1.0 Gy) anophthalmos, exencephaly and gastroschisis at E18, and reduced the number of pre-natal deaths, fetal weight loss and defects in the cervical vertebrae resulting from irradiation. Furthermore, FA food fortification counteracted radiation-induced impairments in vision and olfaction, which were evidenced after exposure to doses ≥0.1 Gy. These findings coincided with the observation of a reduction in thickness of the retinal ganglion cell and nerve fiber layer, and a decreased axial length of the eye following exposure to 0.5 Gy. Finally, MRI studies revealed a volumetric decrease of the hippocampus, striatum, thalamus, midbrain and pons following 0.5 Gy irradiation, which could be partially ameliorated after FA food fortification. Altogether, our study is the first to offer detailed insights into the long-term consequences of X-ray exposure during neurulation, and supports the use of FA as a radioprotectant and antiteratogen to counter the detrimental effects of X-ray exposure during this crucial period of gestation.

Response to the "letter to the editor" by Sani Rachman Soleman et al., "spatiotemporal association of low birth weight with Cs-137 deposition at the prefecture level in Japan after the Fukushima nuclear power plant accidents"

We thank Sani Rachman Soleman et al. for three specific points of criticism concerning our investigation of the ecological association between low birth weight (LBW) and radioactive contamination in Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accidents: 1. Ecological variables are not justified enough to adjust potential confounding. 2. The spatiotemporal regression model does not consider temporal reduction in radiation dose rate. 3. Dose-response plot between dose rates and odds ratios overestimates R² and underestimates p-value. This criticism is a good starting point to explain some of the technical backgrounds of our approach in more detail.

Spatiotemporal association of low birth weight with Cs-137 deposition at the prefecture level in Japan after the Fukushima nuclear power plant accidents: an analytical-ecologic epidemiological study

BACKGROUND

Perinatal mortality increased in contaminated prefectures after the Fukushima Daichi Nuclear Power Plant (FDNPP) accidents in Japan in 2011. Elevated counts of surgeries for cryptorchidism and congenital heart malformations were observed throughout Japan from 2012 onward. The thyroid cancer detection rate (2011 to 2016) was associated with the dose-rate at the municipality level in the Fukushima prefecture. Since the birth weight is a simple and objective indicator for gestational development and pregnancy outcome, the question arises whether the annual birth weight distribution was distorted in a dose-rate-dependent manner across Japan after Fukushima.

METHODS

The Japanese Ministry of Health, Labour, and Welfare provides prefecture-specific annual counts for 26.158 million live births from 1995 to 2018, of which 2.366 million births (9.04%) with weights < 2500 g. Prefecture-specific spatiotemporal trends of the low birth weight proportions were analyzed. Logistic regression allowing for level-shifts from 2012 onward was employed to test whether those level-shifts were proportional to the prefecture-specific dose-rates derived from Cs-137 deposition in the 47 Japanese prefectures.

RESULTS

The overall trend of the low birth weight prevalence (LBWp) in Japan discloses a jump in 2012 with a jump odds ratio (OR) 1.020, 95%-confidence interval (1.003,1.037), p-value 0.0246. A logistic regression of LBWp on the additional dose-rate after the FDNPP accidents adjusted for prefecture-specific spatiotemporal base-line trends yields an OR per μSv/h of 1.098 (1.058, 1.139), p-value < 0.0001. Further adjusting the logistic regression for the annual population size and physician density of the prefectures, as well as for the counts of the dead, the missing, and the evacuees due to earthquake and tsunami (as surrogate measures for medical infrastructure and stress) yields an OR per μSv/h of 1.109 (1.032, 1.191), p-value 0.0046.

CONCLUSIONS

This study shows increased low birth weight prevalence related to the Cs-137 deposition and the corresponding additional dose-rate in Japan from 2012 onward. Previous evidence suggesting compromised gestational development and pregnancy outcome under elevated environmental ionizing radiation exposure is corroborated.

Design characteristics and statistical methods used in interrupted time series studies evaluating public health interventions: a review

OBJECTIVES

Interrupted time series (ITS) designs are frequently used in public health to examine whether an intervention or exposure has influenced health outcomes. Few reviews have been undertaken to examine the design characteristics, statistical methods, and completeness of reporting of published ITS studies.

STUDY DESIGN AND SETTING

We used stratified random sampling to identify 200 ITS studies that evaluated public health interventions or exposures from PubMed (2013-2017). Study characteristics, details of statistical models and estimation methods used, effect metrics, and parameter estimates were extracted. From the 200 studies, 230 time series were examined.

RESULTS

Common statistical methods used were linear regression (31%, 72/230) and autoregressive integrated moving average (19%, 43/230). In 17% (40/230) of the series, we could not determine the statistical method used. Autocorrelation was acknowledged in 63% (145/230) of the series. An estimate of the autocorrelation coefficient was given for only 1% of the series (3/230). Measures of precision were reported for 63% of effect measures (541/852).

CONCLUSION

Many aspects of the design, methods, analysis, and reporting of ITS studies can be improved, particularly description of the statistical methods and approaches to adjust for and estimate autocorrelation. More guidance on the conduct and reporting of ITS studies is needed to improve this study design.

Association between the detection rate of thyroid cancer and the external radiation dose-rate after the nuclear power plant accidents in Fukushima, Japan

A thyroid cancer ultrasonography screening for all residents 18 years old or younger living in the Fukushima prefecture started in October 2011 to investigate the possible effect of the radiological contamination after the Fukushima Daiichi Nuclear Power Plant accidents as of March 12 to 15, 2011. Thyroid cancer in 184 cases was reported by February 2017. The question arises to which extent those cancer cases are a biological consequence of the radiation exposure or an artefactual result of the intense screening of a large population.Experiences with the Chernobyl accident suggest that the external dose may be considered a valid surrogate for the internal dose of the thyroid gland. We, therefore, calculated the average external effective dose-rate (μSv/h) for the 59 municipalities of the Fukushima prefecture based on published data of air and soil radiation. We further determined the municipality-specific absolute numbers of thyroid cancers found by each of the two screening rounds in the corresponding municipality-specific exposed person-time observed. A possible association between the radiation exposure and the thyroid cancer detection rate was analyzed with Poisson regression assuming Poisson distributed thyroid cancer cases in the exposed person-time observed per municipality.The target populations consisted of 367,674 and 381,286 children and adolescents for the 1st and the 2nd screening rounds, respectively. In the 1st screening, 300,476 persons participated and 270,489 in the 2nd round. From October 2011 to March 2016, a total of 184 cancer cases were found in 1,079,786 person-years counted from the onset of the exposure to the corresponding examination periods in the municipalities. A significant association between the external effective dose-rate and the thyroid cancer detection rate exists: detection rate ratio (DRR) per μSv/h 1.065 (1.013, 1.119). Restricting the analysis to the 53 municipalities that received less than 2 μSv/h, and which represent 176 of the total 184 cancer cases, the association appears to be considerably stronger: DRR per μSv/h 1.555 (1.096, 2.206).The average radiation dose-rates in the 59 municipalities of the Fukushima prefecture in June 2011 and the corresponding thyroid cancer detection rates in the period October 2011 to March 2016 show statistically significant relationships.

Infant, neonatal, and postneonatal mortality trends in a disaster region and in Japan, 2002-2012: a multi-attribute compositional study

Background

The reductions achieved in infant mortality in Japan are globally regarded as remarkable. However, no studies in Japan have classified infant mortality trends into neonatal and postneonatal or considered regional issues. This study aimed to explore trends in neonatal and postneonatal deaths, both overall for Japan and in a region affected by a natural disaster.

Methods

Drawing on national infant death data, we used a multi-attribute compositional study design to examine all infant deaths occurring in a region affected by a disaster (Tohoku, which consists of Iwate, Miyagi, and Fukushima) between 2002 and 2012. We used conjoint analysis to clarify the associations between infant and maternal characteristics and age of infant death.

Results

We obtained data of a total of 31,012 infant deaths between 2002 and 2012, which included 1450 from Tohoku. Infant mortality rates in Japan overall declined over the period but increased in 2011. There were more postneonatal (29–364 days post-birth) than neonatal (0–28 days post-birth) deaths. Infant deaths in Tohoku declined slightly overall, with a fluctuation in 2011. In Tohoku, the trends in postneonatal death rates were similar; the overall rates for males increased, but those for females decreased in 2011. We found that the cause and place of infant death differed by gender for neonatal and postneonatal deaths in both Japan in general and Tohoku. The conjoint analysis showed that most variables affected the age of postneonatal death. The factor with the largest influence on the variation in infant death age was gestational week (55.5%). A maternal gestational week ≤36 was linked to an average age at death of 43.4 days, and > 37 was linked to an average of 83.7 days.

Conclusions

In Japan, infant death rates have declined steadily over the past 10 years. The recent trends indicated that postneonatal death rates were higher than neonatal rates, especially in Tohoku. However, not much attention has been focused on postneonatal deaths in Japan. Our findings may help health planners to prioritise work on the factors that are linked to infant deaths in the neonatal and postneonatal periods.

Trial registration

Not applicable.

Perinatal mortality after the Fukushima accident: a spatiotemporal analysis

OBJECTIVE

This study investigates the trend of perinatal mortality rates in Fukushima Prefecture and four neighboring prefectures (Miyagi, Gunma, Tochigi, and Ibaraki) after the disaster at the Fukushima Daiichi nuclear power plant in March 2011.

MATERIAL AND METHODS

Japanese monthly perinatal mortality data on a prefecture level are available on a website of the Japanese government. A combined regression of perinatal mortality rates from the study region and the rest of Japan (the control region) is conducted. The regression model allows for an asymptotic lower limit and a level change of perinatal mortality rates in 2012-2017 in the study region relative to the predicted trend.

RESULTS

In 2012-2017, perinatal mortality in the study region shows a significant 10.6% increase relative to the trend in preceding years (p = 0.006). The excess mortality translates to 195 (95% CI: 28, 462) excess perinatal deaths. The increase is three times greater in Fukushima Prefecture than in the four neighboring prefectures and the difference in excess rates is statistically significant (p = 0.010). Periodic peaks of perinatal mortality are found in 2012-2017 with maxima around April.

CONCLUSION

We find an increase in perinatal mortality in Fukushima and four neighboring prefectures after the Fukushima nuclear accident. The results agree with similar observations in Germany and Ukraine after the Chernobyl disaster. Due to its ecological design, the study cannot prove a causal link between radiation exposure and perinatal mortality. Continued observation of the trend of perinatal mortality in contaminated regions of Japan is recommended.

Design characteristics and statistical methods used in interrupted time series studies evaluating public health interventions: protocol for a review

INTRODUCTION

An interrupted time series (ITS) design is an important observational design used to examine the effects of an intervention or exposure. This design has particular utility in public health where it may be impracticable or infeasible to use a randomised trial to evaluate health system-wide policies, or examine the impact of exposures (such as earthquakes). There have been relatively few studies examining the design characteristics and statistical methods used to analyse ITS designs. Further, there is a lack of guidance to inform the design and analysis of ITS studies.This is the first study in a larger project that aims to provide tools and guidance for researchers in the design and analysis of ITS studies. The objectives of this study are to (1) examine and report the design characteristics and statistical methods used in a random sample of contemporary ITS studies examining public health interventions or exposures that impact on health-related outcomes, and (2) create a repository of time series data extracted from ITS studies. Results from this study will inform the remainder of the project which will investigate the performance of a range of commonly used statistical methods, and create a repository of input parameters required for sample size calculation.

METHODS AND ANALYSIS

We will collate 200 ITS studies evaluating public health interventions or the impact of exposures. ITS studies will be identified from a search of the bibliometric database PubMed between the years 2013 and 2017, combined with stratified random sampling. From eligible studies, we will extract study characteristics, details of the statistical models and estimation methods, effect metrics and parameter estimates. Further, we will extract the time series data when available. We will use systematic review methods in the screening, application of inclusion and exclusion criteria, and extraction of data. Descriptive statistics will be used to summarise the data.

ETHICS AND DISSEMINATION

Ethics approval is not required since information will only be extracted from published studies. Dissemination of the results will be through peer-reviewed publications and presentations at conferences. A repository of data extracted from the published ITS studies will be made publicly available.