Chernobyl's Asymptomatic Legacy: Effects of Low Level Prenatal Irradiation on Adult Cognitive Performance

该项目研究低水平产前照射对成人人力资本的影响，特别关注认知能力。为此，它利用了1986年4月26日在乌克兰发生的切尔诺贝利核事故所产生的自然实验。事故发生后不久的天气状况意味着放射性尘埃的传播范围很广。瑞典收到了大约5%的辐射尘。该项目将1983-1988年出生的瑞典儿童的成年结果与事故发生后采取的局部放射性测量相匹配。放射性尘埃的变化，结合出生日期和地点的信息，被用来创建实验组和对照组。对子宫内受切尔诺贝利放射性尘埃辐射的瑞典儿童进行的一项研究提供了一个独特的机会，以评估迄今为止被认为是安全和/或无法检测到的辐射水平的潜在损害。本项目探讨胎儿起源假说的普遍性。特别是，它试图确定子宫内的低水平辐射暴露是否会影响随后的认知结果。这些联系是否存在目前尚不清楚。切尔诺贝利为评估这些联系提供了一个令人信服的自然实验。更广泛的影响如果初步结果得到全面研究的证实，这些发现将偏离关于什么水平的辐射暴露是安全的传统指导方针。因此，这项工作将刺激其他国家对切尔诺贝利放射性尘埃的进一步分析。这种分析是可行的，因为东经7度以东的大部分欧洲国家受到的放射性尘埃水平与瑞典相当；其中一些国家（如挪威）产生了类似的学生成绩微数据集。此外，该项目计划跟踪1986年出生的瑞典人完成学业并进入劳动力市场。这样就可以更精确地评估切尔诺贝利事故的长期经济代价。辐射暴露并不局限于切尔诺贝利事故。例如，切尔诺贝利释放的辐射量远远低于大气核武器试验释放的辐射量。因此，低水平辐射暴露是常态，而不是例外。切尔诺贝利只是为这些影响提供了一个特别明确的辐射暴露基准。因此，这一分析有助于了解与未来辐射照射有关的费用。核能在发展中国家正在扩张，主要是在人口密集的印度和中国。虽然未来熔毁的可能性只能是一种猜测，但核电站的故障只是可能暴露于放射性的一个来源。其他包括但不限于现有发电厂的退役、核武器或脏弹的使用、高海拔地区本底辐射水平升高（影响到经常飞行的旅客和航空公司机组人员）、工业和医疗中使用的辐射以及室内接触氡气及其衰变产物所产生的辐射。在未来发生大规模辐射释放的情况下，这项工作可以为受影响人群提供建议（例如，限制当时孕妇的户外暴露）。这项研究也可能提高对胎儿健康如何影响以后生活结果的理解。了解这种关系对于制定有效的公共政策至关重要。特别是，胎儿起源的证据可以帮助确定寻求改善认知和相关社会经济结果的公共政策在生命过程中的最佳时机。最后，胎儿起源为社会经济结果的差异提供了另一种视角。这种差异，例如美国平均受教育率的种族差异，是出了名的难以缩小的。胎儿起源框架强调了另一个众所周知的差异的作用——在儿童早期健康方面存在的巨大种族差距。

The project studies the effect of low level prenatal irradiation on adult human capital with a particular focus on cognitive ability. To that end, it exploits the natural experiment generated by the Chernobyl nuclear accident that took place April 26, 1986, in Ukraine. Weather conditions in the accident's immediate aftermath meant that fallout traveled widely. Sweden received about 5 percent of fallout. The project matches adult outcomes of Swedish children born 1983-1988 to localized measures of radiocaesium taken after the accident. Variation in fallout, combined with information on date and place of birth, is used to create treatment and control groups. A study of Swedish children exposed in utero to radiation from Chernobyl fallout provides a unique opportunity to assess potential damage of irradiation at levels hitherto considered safe and/or undetectable.This project probes the generality of the fetal origins hypothesis. In particular, it seeks to establish whether low-level radiation exposure in utero may shape subsequent cognitive outcomes. Whether these linkages exist is not currently known. Chernobyl represents a compelling natural experiment for assessing these linkages.Broader Impact Should the preliminary results be confirmed by the full study, these findings would depart from conventional guidelines on what level of radiation exposure is safe. Thus, this work would spur additional analyses of Chernobyl fallout in other countries. Such analyses are feasible, as most of Europe east of the 7th degree east received fallout at levels comparable to Sweden; Some of these counties (e.g., Norway) produce analogous microdatasets of student outcomes. Moreover, this project plans to follow the Swedish cohort born in 1986 as they complete schooling and enter the labor market. This permits more precise assessment of the long-term economic costs of the Chernobyl accident.Radiation exposure was not restricted to the Chernobyl accident. For example, the amount of radiation released by Chernobyl is substantially less than that released by atmospheric nuclear weapons tests. Thus, low-level radiation exposure is the rule rather than the exception. Chernobyl simply affords a particularly well-identified radiation exposure for benchmarking these effects. Therefore, this analysis helps inform the costs associated with future radiation exposures. Nuclear power is expanding in the developing world, principally in population-dense India and China. While the probability of a future meltdown can only be a speculation, nuclear power plant failures are only one source of possible exposure to radioactivity. Others include, but are not limited to the decommissioning of existing power plants, the employment of nuclear weapons or dirty bombs, heightened levels of background radiation at high altitudes (affecting frequent fliers and airline crews), radiation employed in industrial and medical treatments, and irradiation stemming from indoor exposure to radon gas and its decay products. In the event of large-scale future radiation release, this work may inform recommendations to affected populations (e.g., limiting outdoors exposure by those pregnant at the time).This research may also improve understanding of how fetal health in general affects outcomes later in life. Knowledge of this relationship is essential to the formulation of efficient public policies. In particular, evidence of fetal origins can help identify the optimal timing over the life course of public policies that seek to improve cognitive and related socioeconomic outcomes. Finally, fetal origins provide an alternative perspective on disparities in socioeconomic outcomes. Such disparities, e.g., racial differences in average schooling rates in the U.S., are notoriously difficult to reduce. A fetal origins framework highlights the role of another well-known disparity - the wide gap by races that exists in early childhood health.