My first postpartum scientific publication is out now! I am getting back to my PhD topic; it has been a while, but I was truly excited to dig-in the “new” monitoring data on iodine in Danish groundwater. In this blog-post I’ll first give the highlights (the tweetable summary, or is it now X-able summary?) and mention why these findings are important, and then I’ll share few thoughts about the process.
What did I find?
There are 3 key findings from this work:
- Iodine in Danish groundwater varies over time (0–124%, median = 10%)
- In one quarter of the well screens this variation exceeds 20%
- This variation cannot be attributed solely to analytical uncertainty at 14% of the well screens
Why does this matter?
Iodine is an essential element for our health; it plays an important role in our early development, but also throughout our life-span, as both high and low intakes could impact negatively our health. A recent meta-analysis  showed that iodine status is directly correlated to iodine content in drinking water and that iodine concentration in drinking water can be used as an indicator of dietary intake.
Danish drinking water is entirely of groundwater origin. The spatial variation of iodine in both drinking water and groundwater in Denmark has been studied before, but this is the first time the temporal variation is quantified. Previously, it was hypothesized that iodine in Danish groundwater and drinking water is stable. There were only handful of studies that provided some qualitative evidence for it (see the paper for some direct quotes). Therefore, in this paper, I decided to quantify the variation.
The findings are important, because they provide an evidence against the hypothesis for “stable iodine”. Therefore, 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.
Another important point I wanted to make is that the work on temporal variation of iodine in Danish groundwater is far from over. There is a need to continue with the groundwater monitoring, because currently there is not enough data to cover the entire concentration range (especially for concentrations > 50 ug/l). And for a quarter of the monitoring well screens, there was only one sample available in the 2011–2021 period, which made it impossible to evaluate the temporal variation there.
Few details about the data and methods
The data used in this paper comes from the Danish groundwater monitoring program (GRUMO). The dataset I worked with included 2924 samples analyzed for iodine between 2011 and 2021, from 1242 well screens at 893 wells throughout the country. The sampling frequency varied, as it does with all other elements, which reflects the different program periods for the GRUMO monitoring.
The main methodology was to compare the variability, expressed as a robust coefficient of variation (%), with the analytical uncertainty for all well screens where this could be done. The idea was that if the observed variability is higher than the analytical uncertainty, there must be other environmental factors governing or causing the variability. It was out of scope to go deeper than that in the causalities, as I wanted first to identify the locations where further more detailed studies, using other geochemical, geological, hydrological, landuse data, etc. should be used.
Some reflections on the process
As I mentioned, this is my first postpartum publication. I started the data-analyses before I went on pregnancy leave. I changed my mind (switched the paper focus) during my pregnancy leave and did more data-analyses some time during the maternity leave. I simplified my idea during the pregnancy leave, as I thought that the temporal analysis could stand on its own. And maybe I needed to adjust my ambitions a bit. I don’t know when exactly I found time to work on this paper, as my maternity leave is a little bit of a blur of breastfeeding multiple times per night and pushing a pram uphill in Odder with a sleeping baby. I finished writing the manuscript when I came back to work after the maternity leave (clocked 25 hours on that) and submitted it before my summer holiday. Two reviews (minor revisions) were waiting for me when I came back from summer holiday, and I spent 10 hours editing and writing answers to the reviewers’ comments, and few more hours on copyediting and proof checks. That process will probably never going to be repeated, so this paper is special in that way.
This is also the first time when I am trying to write a paper on my own, without relying on my co-authors for help with the outline, scope, and writing or polishing of the text. I must say, it is a completely different experience! One thing about science I love, is that it is collaborative. I feel the need to discuss results, or just to think out loud in front of other people. However, I also wanted to experience how it is to rely only on yourself while going through the entire process. I also felt a bit of external pressure to try and do it on my own, as I keep on hearing how you should also have some work without your usual collaborators. But why? Who comes up with those rules and why should you? Different discussion…
And last reflection, once a paper is published online, I always feel a little bit “And, so what?“, “Would it really matter if it wasn’t?“, “Definitely someone else could have also done that!“, and if I am very negative that day, I even go as far as to think “Maybe I should not have wasted time with this, who cares.” In this case, I am glad I did this work, because when I was writing my PhD thesis, I thought it would be really cool, if I could also focus on the temporal aspect, not only on the spatial. Unfortunately, at that time there was not enough data to do it. Ten years later, I could finally fulfill this “wish”. I also keep on reminding myself, that the work is never done, there is always something that can be done better, as our methods and knowledge expand.
So, I’ll end with that. I hope you would find my paper easy to read 🙂 I tried my best to do it as simple as possible this time (as usually I tend to overcomplicate things and get lost in the details.
 Azevedo, F.M., Machamba, A.A.L., Candido, A.C., Pinto, C.A., Lopes, S.O., Macedo, M.D.S., Ribeiro, S.A.V., Priore, S.E. & Franceschini, S.D.C.C. 2023: Correlation between drinking water and iodine status: A sys-tematic review and meta-analysis. Biological Trace Element Research 201(1), 129–138. https://doi.org/10.1007/s12011-022-03127-4