Supplementary files for: "Temporal variation of iodine in Danish groundwater"

Iodine is an essential element for human health, and both high and low iodine intake could have negative health outcomes. The spatial variation of iodine in Danish groundwater has been studied before, but to the author’s knowledge, this is the first time that the temporal variation is characterised. Nationwide data from the Danish groundwater monitoring programme (GRUMO) were analysed between 2011 and 2021, including 2924 samples from 1242 well screens at 893 wells. The sampling frequency varied and so the robust coefficient of variation (rCV) was calculated for 930 (75%) of well screens, and time-series analysis was performed for 23 (2%). Key findings are (1) iodine in Danish groundwater varies over time (0–124%, median = 10%), (2) in one quarter of the well screens rCV exceeds 20% and (3) this variation cannot be attributed solely to analytical uncertainty at 14% of the well screens. The impact of temporal variation of iodine in Danish drinking water of groundwater origin should be evaluated in future exposure or epidemiological studies with respect to the study goal, location and time period. Since the temporal variation could not be quantified over the entire concentration range, monitoring of iodine in Danish groundwater should continue.

碘元素对人体健康至关重要，无论是碘摄入量过高还是过低，均可能对健康产生负面影响。此前，丹麦克里斯蒂安松地区地下水碘的时空变化已有所研究，但据作者所知，这是首次对碘的时间变化特征进行刻画。本研究分析了2011年至2021年间丹麦地下水监测计划（GRUMO）的全国数据，涉及893个井位中的1242个井筛的2924个样本。采样频率不一，因此对930个（占总数的75%）井筛计算了稳健系数变化（rCV），并对23个（占总数的2%）井筛进行了时间序列分析。主要发现如下：（1）丹麦地下水中的碘含量随时间推移而变化（0-124%，中位数为10%）；（2）在四分之一的井筛中，rCV超过20%；（3）在14%的井筛中，这种变化不能完全归因于分析不确定性。未来应评估丹麦地下水饮用水中碘的时间变化对暴露或流行病学研究的影响，特别是针对研究目标、地理位置和时间段的考量。鉴于在整个浓度范围内无法量化时间变化，丹麦地下水中的碘监测应持续进行。