Source-specific nitrate and nitrite intakes and associations with sociodemographic factors in the Danish Diet Cancer and Health cohort

Background

The dietary source and intake levels of nitrate and nitrite may govern its deleterious versus beneficial effects on human health. Existing evidence on detailed source-specific intake is limited. The objectives of this study were to assess nitrate and nitrite intakes from different dietary sources (plant-based foods, animal-based foods, and water), characterize the background diets of participants with low and high intakes, and investigate how sociodemographic and lifestyle factors associate with intake levels.

Methods

In the Danish Diet, Cancer and Health Cohort, sociodemographic and lifestyle information was obtained from participants at enrolment (1993-1997). Source-dependent nitrate and nitrite intakes were calculated using comprehensive food composition databases, with tap water nitrate intakes estimated via the national drinking water quality monitoring database linked with participants' residential addresses from 1978 to 2016. Underlying dietary patterns were examined using radar plots comparing high to low consumers while sociodemographic predictors of source-dependent nitrate intakes were investigated using linear regression models.

Results

In a Danish cohort of 55,754 participants aged 50-65 at enrolment, the median [IQR] intakes of dietary nitrate and nitrite were 58.13 [44.27-74.90] mg/d and 1.79 [1.43-2.21] mg/d, respectively. Plant-based foods accounted for ~76% of nitrate intake, animal-based foods ~10%, and water ~5%. Nitrite intake was sourced roughly equally from plants and animals. Higher plant-sourced nitrate intake was associated with healthier lifestyles, better dietary patterns, more physical activity, higher education, lower age and lower BMI. Females and participants who had never smoked also had significantly higher plant-sourced nitrate intakes. Higher water-sourced nitrate intake was linked to sociodemographic risk factors (smoking, obesity, lower education). Patterns for animal-sourced nitrate were less clear.

Conclusion

Participants with higher plant-sourced nitrate intakes tend to be healthier while participants with higher water-sourced nitrate intakes tended to be unhealthier than their low consuming counterparts. Future research in this cohort should account for the sociodemographic and dietary predictors of source-specific nitrate intake we have identified.

Integrating different tools and technologies to advance drinking water quality exposure assessments

Contaminants in drinking water are a major contributor to the human exposome and adverse health effects. Assessing drinking water exposure accurately in health studies is challenging, as several of the following study design domains should be addressed as adequately as possible. In this paper, we identify the domains Time, Space, Data Quality, Data Accessibility, economic considerations of Study Size, and Complex Mixtures. We present case studies for three approaches or technologies that address these domains differently in the context of exposure assessment of drinking water quality: regulated contaminants in monitoring databases, high-resolution mass spectrometry (HRMS)-based wide-scope chemical analysis, and effect-based bioassay methods. While none of these approaches address all the domains sufficiently, together they have the potential to carry out exposure assessments that would complement each other and could advance the state-of-science towards more accurate risk analysis. The aim of our study is to give researchers investigating health effects of drinking water quality the impetus to consider how their exposure assessments relate to the above-mentioned domains and whether it would be worthwhile to integrate the advanced technologies presented into planned risk analyses. We highly suggest this three-pronged approach should be further evaluated in health risk analyses, especially epidemiological studies concerning contaminants in drinking water. The state of the knowledge regarding potential benefits of these technologies, especially when applied in tandem, provides more than sufficient evidence to support future research to determine the implications of combining the approaches described in our case studies in terms of protection of public health.

Health-economic valuation of lowering nitrate standards in drinking water related to colorectal cancer in Denmark

Nitrate in drinking water is a contaminant which can affect human health and has been associated with an increased risk of, amongst other diseases, colorectal cancer. Based on epidemiologic data from Denmark on the association between drinking water nitrate and colorectal cancer, the health and economic consequences of lowering the standard of nitrate in drinking water from 50 mg/L to 9.25 mg/L and 3.87 mg/L, respectively are analyzed. The drinking water nitrate attributable number of cases was estimated using the risk in the exposed and unexposed population based on current nationwide exposure distributions. The analysis shows that a lower limit of 9.25 mg/L would decrease the annual number of colorectal cancer cases by 72 (95 % confidence interval: 34-114) and by an additional 55 (95 % CI: 10-100) for a stricter limit of 3.87 mg/L. The resulting avoided health-related costs are $179 million per year for the 9.25 mg/L nitrate limit and another $138 million per year for a further reduction to 3.87 mg/L nitrate. The new requirements would incur costs linked to either i) changes in land use management, ii) well reallocation or iii) use of treatment technologies. The additional costs are estimated to $0.03-1.84 per m3 abstracted water from public water companies, which together with costs for owners of private wells, will result in an average additional cost of $9 and $6 million per year for the two levels. The economic health benefits are higher than the costs for both limits with net gains of $170 million (9.25 mg/L) and additionally $132 million (3.87 mg/L) a year. Even in a worst-case scenario (lowest health-related benefits and highest mitigation costs), there is a likely economic gain for society from lowering the limit to 9.25 mg/L, but this might not be the case for the lower limit of 3.87 mg/L.

Prenatal exposure to nitrosatable drugs and timing of puberty in sons and daughters: A nationwide cohort study

BACKGROUND

N-nitroso compounds (NOCs) can be formed by endogenous reactions between nitrosatable drugs and nitrite. Animal studies have found that several NOCs are teratogenic, and epidemiological studies report associations between prenatal exposure to nitrosatable drugs and adverse birth outcomes. It is unknown whether prenatal exposure to nitrosatable drugs is harmful to the child's reproductive health, including pubertal development.

OBJECTIVES

We investigated whether prenatal exposure to nitrosatable drugs was associated with timing of puberty and whether nitrate, nitrite and antioxidant intake modified any association.

METHODS

The population-based Danish National Birth Cohort (DNBC) Puberty Cohort, which includes 15,819 children, was used to investigate the association between prenatal exposure to nitrosatable drugs and timing of puberty. Around gestational week 11 and gestational week 18, mothers provided information about drug use during pregnancy. The children's self-reported information on onset of pubertal milestones was collected every six months from 11 years of age and throughout puberty. To investigate potential effect modification by nitrite, nitrate and antioxidant intake, information on these factors was obtained from a food frequency questionnaire completed by the mothers in gestational week 25, and information on nitrate concentration in maternal drinking water at her residential address was obtained from monitoring data from public waterworks. Data were analysed using a multivariable regression model for interval-censored data estimating difference in months in timing of puberty between exposure groups.

RESULTS

A total of 2,715 children were prenatally exposed to nitrosatable drugs. We did not find an association between prenatal exposure to nitrosatable drugs and timing of puberty. This finding was supported by null-findings in the following sub-analyses investigating: 1. subtypes of nitrosatable drugs (secondary and tertiary amines and amides), 2. dose-dependency (duration of drug intake), 3. effect modification by maternal intake of nitrate, nitrite, and antioxidants. 4. confounding by indication.

CONCLUSIONS

Prenatal exposure to nitrosatable drugs was not associated with timing of puberty. Nitrosatable drugs are commonly used drugs in pregnancy, and further research is needed to allow firm conclusions on the potential effect of prenatal exposure to nitrosatable drugs on the child's reproductive health.

Prenatal Exposure to Nitrate in Drinking Water and Adverse Health Outcomes in the Offspring: a Review of Current Epidemiological Research

PURPOSE OF REVIEW

Recently, several epidemiological studies have investigated whether prenatal exposure to nitrate from drinking water may be harmful to the fetus, even at nitrate levels below the current World Health Organization drinking water standard. The purpose of this review was to give an overview of the newest knowledge on potential health effects of prenatal exposure to nitrate.

RECENT FINDINGS

We included 13 epidemiological studies conducted since 2017. Nine studies investigated outcomes appearing around birth, and four studies investigated health outcomes appearing in childhood and young adulthood. The reviewed studies showed some indications of higher risk of preterm delivery, lower birth weight, birth defects, and childhood cancer related to prenatal exposure to nitrate. However, the numbers of studies for each outcome were sparse, and some of the results were conflicting. We suggest that there is a need for additional studies and particularly for studies that include information on water consumption patterns, intake of nitrate from diet, and intake of nitrosatable drugs.

Exposures to perfluoroalkyl substances and asthma phenotypes in childhood: an investigation of the COPSAC2010 cohort

BACKGROUND

Exposure to perfluoroalkyl substances may affect offspring immune development and thereby increase risk of childhood asthma, but the underlying mechanisms and asthma phenotype affected by such exposure is unknown.

METHODS

In the Danish COPSAC2010 cohort of 738 unselected pregnant women and their children plasma PFOS and PFOA concentrations were semi-quantified by untargeted metabolomics analyses and calibrated using a targeted pipeline in mothers (gestation week 24 and 1 week postpartum) and children (age ½, 1½ and 6 years). We examined associations between pregnancy and childhood PFOS and PFOA exposure and childhood infections, asthma, allergic sensitization, atopic dermatitis, and lung function measures, and studied potential mechanisms by integrating data on systemic low-grade inflammation (hs-CRP), functional immune responses, and epigenetics.

FINDINGS

Higher maternal PFOS and PFOA exposure during pregnancy showed association with a non-atopic asthma phenotype by age 6, a protection against sensitization, and no association with atopic asthma or lung function, or atopic dermatitis. The effect was primarily driven by prenatal exposure. There was no association with infection proneness, low-grade inflammation, altered immune responses or epigenetic changes.

INTERPRETATIONS

Prenatal exposure to PFOS and PFOA, but not childhood exposure, specifically increased the risk of low prevalent non-atopic asthma, whereas there was no effect on atopic asthma, lung function, or atopic dermatitis.

FUNDING

All funding received by COPSAC are listed on www.copsac.com. The Lundbeck Foundation (Grant no R16-A1694); The Novo Nordic Foundation (Grant nos NNF20OC0061029, NNF170C0025014, NNF180C0031764); The Ministry of Health (Grant no 903516); Danish Council for Strategic Research (Grant no 0603-00280B); and The Capital Region Research Foundation have provided core support to the COPSAC research center. COPSAC acknowledges the National Facility for Exposomics (SciLifeLab, Sweden) for supporting calibration of the untargeted metabolomics PFAS data. BC and AS has received funding for this project from the European Union's Horizon 2020 research and innovation programme (BC: grant agreement No. 946228 DEFEND; AS: grant agreement No. 864764 HEDIMED).

Airway and systemic biomarkers of health effects after short-term exposure to indoor ultrafine particles from cooking and candles - A randomized controlled double-blind crossover study among mild asthmatic subjects

BACKGROUND

There is insufficient knowledge about the systemic health effects of exposure to fine (PM_2.5) and ultrafine particles emitted from typical indoor sources, including cooking and candlelight burning. We examined whether short-term exposure to emissions from cooking and burning candles cause inflammatory changes in young individuals with mild asthma. Thirty-six non-smoking asthmatics participated in a randomized controlled double-blind crossover study attending three exposure sessions (mean PM_2.5 µg/m³_; polycyclic aromatic hydrocarbons ng/m³): (a) air mixed with emissions from cooking (96.1; 1.1), (b) air mixed with emissions from candles (89.8; 10), and (c) clean filtered air (5.8; 1.0). Emissions were generated in an adjacent chamber and let into a full-scale exposure chamber where participants were exposed for five hours. Several biomarkers were assessed in relation to airway and systemic inflammatory changes; the primary outcomes of interest were surfactant Protein-A (SP-A) and albumin in droplets in exhaled air - novel biomarkers for changes in the surfactant composition of small airways. Secondary outcomes included cytokines in nasal lavage, cytokines, C-reactive protein (CRP), epithelial progenitor cells (EPCs), genotoxicity, gene expression related to DNA-repair, oxidative stress, and inflammation, as well as metabolites in blood. Samples were collected before exposure start, right after exposure and the next morning.

RESULTS

SP-A in droplets in exhaled air showed stable concentrations following candle exposure, while concentrations decreased following cooking and clean air exposure. Albumin in droplets in exhaled air increased following exposure to cooking and candles compared to clean air exposure, although not significant. Oxidatively damaged DNA and concentrations of some lipids and lipoproteins in the blood increased significantly following exposure to cooking. We found no or weak associations between cooking and candle exposure and systemic inflammation biomarkers including cytokines, CRP, and EPCs.

CONCLUSIONS

Cooking and candle emissions induced effects on some of the examined health-related biomarkers, while no effect was observed in others; Oxidatively damaged DNA and concentrations of lipids and lipoproteins were increased in blood after exposure to cooking, while both cooking and candle emissions slightly affected the small airways including the primary outcomes SP-A and albumin. We found only weak associations between the exposures and systemic inflammatory biomarkers. Together, the results show the existence of mild inflammation following cooking and candle exposure.

Perspectives on environment and health research in Denmark

AIMS

We provide an overview of nationwide environmental data available for Denmark and its linkage potentials to individual-level records with the aim of promoting research on the potential impact of the local surrounding environment on human health.

BACKGROUND

Researchers in Denmark have unique opportunities for conducting large population-based studies treating the entire Danish population as one big, open and dynamic cohort based on nationally complete population and health registries. So far, most research in this area has utilised individual- and family-level information to study the clustering of disease in families, comorbidities, risk of, and prognosis after, disease onset, and social gradients in disease risk. Linking environmental data in time and space to individuals enables novel possibilities for studying the health effects of the social, built and physical environment.

METHODS

We describe the possible linkage between individuals and their local surrounding environment to establish the exposome - that is, the total environmental exposure of an individual over their life course.

CONCLUSIONS

The currently available nationwide longitudinal environmental data in Denmark constitutes a valuable and globally rare asset that can help explore the impact of the exposome on human health.

Association Between Estimated Geocoded Residential Maternal Exposure to Lithium in Drinking Water and Risk for Autism Spectrum Disorder in Offspring in Denmark

Importance

Lithium is a naturally occurring and trace element that has mood-stabilizing effects. Maternal therapeutic use of lithium has been associated with adverse birth outcomes. In animal models, lithium modulates Wnt/β-catenin signaling that is important for neurodevelopment. It is unknown whether exposure to lithium in drinking water affects brain health in early life.

Objective

To evaluate whether autism spectrum disorder (ASD) in offspring is associated with maternal exposure to lithium in drinking water during pregnancy.

Design, Setting, and Participants

This nationwide population-based case-control study in Denmark identified 8842 children diagnosed with ASD born from 2000 through 2013 and 43 864 control participants matched by birth year and sex from the Danish Medical Birth Registry. These data were analyzed from March 2021 through November 2022.

Exposures

Geocoded maternal residential addresses during pregnancy were linked to lithium level (range, 0.6 to 30.7 μg/L) in drinking water estimated using kriging interpolation based on 151 waterworks measurements of lithium across all regions in Denmark.

Main Outcomes and Measures

ASD diagnoses were ascertained using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes recorded in the Danish Psychiatric Central Register. The study team estimated odds ratios (ORs) and 95% CIs for ASD according to estimated geocoded maternal exposure to natural source of lithium in drinking water as a continuous (per IQR) or a categorical (quartile) variable, adjusting for sociodemographic factors and ambient air pollutants levels. The study team also conducted stratified analyses by birth years, child's sex, and urbanicity.

Results

A total of 8842 participants with ASD (male, 7009 [79.3%]) and 43 864 control participants (male, 34 749 [79.2%]) were studied. Every IQR increase in estimated geocoded maternal exposure to natural source of lithium in drinking water was associated with higher odds for ASD in offspring (OR, 1.23; 95% CI, 1.17-1.29). Elevated odds among offspring for ASD were estimated starting from the second quartile (7.36 to 12.67 μg/L) of estimated maternal exposure to drinking water with lithium and the OR for the highest quartile (more than 16.78 μg/L) compared with the reference group (less than 7.39 μg/L) was 1.46 (95% CI, 1.35-1.59). The associations were unchanged when adjusting for air pollution exposures and no differences were apparent in stratified analyses.

Conclusions and Relevance

Estimated maternal prenatal exposure to lithium from naturally occurring drinking water sources in Denmark was associated with an increased ASD risk in the offspring. This study suggests that naturally occurring lithium in drinking water may be a novel environmental risk factor for ASD development that requires further scrutiny.

Prenatal exposure to tap water containing nitrate and the risk of small-for-gestational-age: A nationwide register-based study of Danish births, 1991-2015

BACKGROUND

Prenatal nitrate exposure from household tap water has been associated with increased risk of fetal growth restriction, preterm birth, birth defects, and childhood cancer. We aim to examine the association between maternal consumption of drinking-water nitrate during pregnancy and small-for-gestational-age (SGA) in a nationwide study of Danish-born children, as only one prior study has examined this association.

METHODS

We linked individual-level household estimates of nitrate in tap water and birth registry data to all live singleton Danish births during 1991-2015 from Danish-born parents where the mother resided in Denmark throughout the pregnancy. Exposure was both binned into four categories and modeled as an ln-transformed continuous variable. SGA was defined as the bottom 10% of births by birth weight per sex and gestational week. Multiple logistic regression models with generalized estimating equations were used to account for siblings born to the same mother while controlling for relevant confounders.

RESULTS

In the cohort of 1,078,892 births, the median pregnancy nitrate exposure was 1.9 mg/L nitrate. Compared to the reference group (≤2 mg/L), we found an increased risk of SGA in the second category (>2-5 mg/L) (OR = 1.04, 95% CI: 1.03-1.06) and third category (>5-25 mg/L) (OR = 1.02, 95% CI: 1.00-1.04) but not in the highest (>25 mg/L). There was strong (p = 0.002) evidence of an increase in SGA with nitrate in the model with continuous exposure (OR = 1.02, 95% CI: 1.01-1.04 per 10-fold increase in nitrate). Results were robust when restricting to households with nitrate levels at or below the current Danish and European Union regulatory drinking water standard (50 mg/L nitrate).

CONCLUSIONS

Our findings suggest that exposure from nitrate in household tap water, even below current regulatory standards, may increase risk of SGA, raising concerns of whether current allowable nitrate levels in drinking water protect children from SGA.

Prenatal nitrate exposure from diet and drinking water and timing of puberty in sons and daughters: A nationwide cohort study

BACKGROUND

In Western countries, age at pubertal development has declined during the last century in girls, and probably also in boys. No studies have investigated whether nitrate, a widespread environmental exposure with teratogenic and hormone disrupting properties, might affect timing of puberty.

OBJECTIVES

We investigated if prenatal exposure to nitrate from drinking water and diet was associated with timing of puberty.

METHODS

This cohort study included 15,819 children born from 2000 to 2003 within the Danish National Birth Cohort. Self-reported information on current status of various pubertal milestones was provided every six months by a questionnaire from 11 years of age until 18 years or full maturity, whichever came first. Maternal nitrate intake from diet (mg/day) was derived from a mid-pregnancy food frequency questionnaire and individual level nitrate exposure from drinking water (mg/L) was derived using measurements from Danish public waterworks. Adjusted average differences in months in age at attaining several pubertal milestones as well as the average age difference in age at attaining all the milestones were estimated separately for diet and water using a regression model for interval-censored data. C- and E-vitamin, red meat and processed meat intake were explored as potential effect modifiers in sub-analyses.

RESULTS

No strong associations were observed between prenatal exposure to nitrate and timing of puberty in children. However, sons born of mothers with a nitrate concentration in drinking water at their residential address of > 25 mg/L (half of the World Health Organisation (WHO) guideline value) compared with ≤ 1 mg/L showed a tendency towards earlier age at pubertal development with an average age difference of -1.2 months (95 % confidence interval,-3.0;0.6) for all the pubertal milestones combined.

DISCUSSION

Studies including more highly exposed children are needed before the current WHO drinking water guideline value for nitrate can be considered safe concerning pubertal development.

Analysis of the geological control on the spatial distribution of potentially toxic concentrations of As and F- in groundwater on a Pan-European scale

The distribution of the high concentrations of arsenic (As) and fluoride (F^-) in groundwater on a Pan-European scale could be explained by the geological European context (lithology and structural faults). To test this hypothesis, seventeen countries and eighteen geological survey organizations (GSOs) have participated in the dataset. The methodology has used the HydroGeoToxicity (HGT) and the Baseline Concentration (BLC) index. The results prove that most of the waters considered in this study are in good conditions for drinking water consumption, in terms of As and/or F^- content. A low proportion of the analysed samples present HGT≥ 1 levels (4% and 7% for As and F^-, respectively). The spatial distribution of the highest As and/or F^- concentrations (via BLC values) has been analysed using GIS tools. The highest values are identified associated with fissured hard rock outcrops (crystalline rocks) or Cenozoic sedimentary zones, where basement fractures seems to have an obvious control on the distribution of maximum concentrations of these elements in groundwaters.

Nitrate in Maternal Drinking Water during Pregnancy and Measures of Male Fecundity in Adult Sons

Animal studies indicate deleterious effects of nitrate exposure on fecundity, but effects in humans are unknown, both for the prenatal and postnatal periods. We aimed to investigate if exposure to nitrate in maternal drinking water during the sensitive period of fetal life is associated with measures of fecundity in the adult sons. In a sub-analysis, the potential effects of nitrate exposure in adulthood were investigated. This cohort included 985 young adult men enrolled in The Fetal Programming of Semen Quality Cohort (FEPOS). Semen characteristics, testes volume and reproductive hormones were analyzed in relation to nitrate concentration in maternal drinking water, using a negative binomial regression model. The nitrate concentration in drinking water was obtained from monitoring data from Danish waterworks that were linked with the mothers' residential address during pregnancy. The median nitrate concentration in maternal drinking water was 2 mg/L. At these low exposure levels, which are far below the World Health Organization's (WHO) guideline value of 50 mg/L, we did not find indications of harmful effects of nitrate on the investigated measures of male fecundity.

Drinking water nitrate and risk of pregnancy loss: a nationwide cohort study

BACKGROUND

Nitrate contamination is seen in drinking water worldwide. Nitrate may pass the placental barrier. Despite suggestive evidence of fetal harm, the potential association between nitrate exposure from drinking water and pregnancy loss remains to be studied. We aimed to investigate if nitrate in drinking water was associated with the risk of pregnancy loss.

METHODS

We conducted a nationwide cohort study of 100,410 pregnancies (enrolled around gestational week 11) in the Danish National Birth Cohort (DNBC) during 1996-2002. Spontaneous pregnancy losses before gestational week 22 were ascertained from the Danish National Patient Registry and DNBC pregnancy interviews. Using the national drinking water quality-monitoring database Jupiter, we estimated the individual and time-specific nitrate exposure by linking geocoded maternal residential addresses with water supply areas. The nitrate exposure was analyzed in spline models using a log-transformed continuous level or classified into five categories. We used Cox proportional hazards models to estimate associations between nitrate and pregnancy loss and used gestational age (days) as the time scale, adjusting for demographic, health, and lifestyle variables.

RESULTS

No consistent associations were found when investigating the exposure as a categorical variable and null findings were also found in trimester specific analyses. In the spline model using the continuous exposure variable, a modestly increased hazard of pregnancy loss was observed for the first trimester at nitrate exposures between 1 and 10 mg/L, with the highest. adjusted hazard ratio at 5 mg/L of nitrate of 1.16 (95% CI: 1.01, 1.34). This trend was attenuated in the higher exposure ranges.

CONCLUSION

No association was seen between drinking water nitrate and the risk of pregnancy loss when investigating the exposure as a categorical variable. When we modelled the exposure as a continuous variable, a dose-dependent association was found between drinking water nitrate exposure in the first trimester and the risk of pregnancy loss. Very early pregnancy losses were not considered in this study, and whether survival bias influenced the results should be further explored.

Effect of perfluoroalkyl exposure in pregnancy and infancy on intrauterine and childhood growth and anthropometry. Sub study from COPSAC2010 birth cohort

BACKGROUND

Perfluoroalkyl substances PFOS and PFOA are persistent and bioaccumulative exogenous chemicals in the human body with a range of suspected negative health effects. It is hypothesised that exposure during prenatal and early postnatal life might have particularly detrimental effects on intrauterine and childhood growth. In a Danish longitudinal mother-child cohort we investigate effect of PFOS and PFOA in pregnancy and infancy on intrauterine and childhood growth and anthropometry.

METHODS

COPSAC₂₀₁₀ is an ongoing population based mother-child cohort of 738 pregnant women and their children followed from 24 week gestation with longitudinal deep clinical phenotyping until age 10 years. In this observational cohort sub study plasma PFOS and PFOA concentrations were semi-quantified by untargeted metabolomics in the mothers at week 24 and 1 week postpartum and in the children at ages 6 and 18 months and calibrated using a targeted pipeline. We examined associations to intrauterine and childhood growth and anthropometry, including interactions with child sex. Untargeted and targeted blood metabolomics profiles were integrated to investigate underlying mechanisms.

FINDINGS

Pregnancy plasma PFOA concentrations were associated with lower birth size -0.19 [-0.33; -0.05] BMI z-score per 1-ng/mL and increased childhood height (z-scored) at age 6: 0.18 [0.05; 0.31], but there was no association between childs' own infancy plasma PFOA concentration and height. Pregnancy plasma PFOS concentrations were also associated with lower birth BMI (-0.04 [-0.08; -0.01]), but in childhood pregnancy plasma PFOS concentration interacted with child sex on BMI and fat percentage at 6 years with negative associations in girls and positive in boys. The effect of maternal plasma PFOS concentration on lower girl BMI was borderline mediated through increasing child plasma lactosyl-ceramide levels (p-mediation=0.08). Similarly the effect of maternal plasma PFOS concentration on higher boy fat percentage was borderline mediated through increasing child plasma lactosyl-ceramide levels (p-mediation=0.07). Infancy concentrations of plasma PFOS associated with lower height in childhood, -0.06 z-score at age 6 [-0.19; -0.03].

INTERPRETATION

Higher PFOS and PFOA plasma concentrations during pregnancy had detrimental effects on fetal growth. The effects on childhood growth were not similar as PFOA increased child height, opposite of PFOS in multipollutant models suggesting a differing fetal programming effect. Sex specific growth effects were borderline mediated through an altered lactosyl-ceramide metabolism, proposing a possible mechanism of PFOS that has long-lasting health consequences in this observational study.

FUNDING

All funding received by COPSAC are listed on www.copsac.com. The Lundbeck Foundation (Grant no R16-A1694); The Novo Nordic Foundation (Grant nos NNF20OC0061029, NNF170C0025014, NNF180C0031764) The Ministry of Health (Grant no 903516); Danish Council for Strategic Research (Grant no 0603-00280B) and The Capital Region Research Foundation have provided core support to the COPSAC research center. Effort from JALS is supported by R01HL123915, R01HL141826, and R01HL155742 from NIH/NHLBI. CEW was supported by the Swedish Heart Lung Foundation (HLF 20180290, HLF 20200693). BC has received funding for this project from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 946228). The funding agencies did not have any role in design and conduct of the study; collection, management, and interpretation of the data; or preparation, review, or approval of the manuscript.

Drinking water magnesium and cardiovascular mortality: A cohort study in Denmark, 2005-2016

INTRODUCTION

Cardiovascular diseases are globally a major cause of death. Magnesium deficiency is associated with several diseases including cardiovascular diseases.

OBJECTIVE

To examine if a low concentration of magnesium in drinking water is associated with increased cardiovascular mortality and mortality due to acute myocardial infarction and stroke.

METHODS

A nationwide population-based cohort study using national health registries was used. A total of 4,274,132 individuals aged 30 years or more were included. Magnesium concentration in drinking water was estimated by linkage of residential addresses in the period 2005-2016 with the national drinking water quality monitoring database. The association between magnesium concentration in drinking water and cardiovascular mortality and mortality due to acute myocardial infarction and stroke was examined using a Poisson regression of number of deaths and logarithmic transformation of follow-up time as offset. The incidence rate ratio (IRR) was adjusted for differences in age, sex, calendar year, cohabitation, country of origin, and socioeconomic status.

RESULTS

Median magnesium concentration in drinking water at inclusion was 12.4 mg/L (range: 1.37-54.2 mg/L). The adjusted IRR for cardiovascular mortality was 0.96 (95% CI: 0.94; 0.97) for the lowest magnesium quintile (<6.5 mg/L) as compared to the highest magnesium quintile (>21.9 mg/L). The adjusted IRR for mortality due to acute myocardial infarction and stroke was 1.22 (1.17; 1.27) and 0.96 (0.93; 0.99), respectively, for the lowest magnesium quintile as compared to the highest quintile A decreasing mortality due to acute myocardial infarction was seen with an increasing magnesium concentration in a dose-response manner.

CONCLUSION

Low concentrations of magnesium in drinking water were associated with an increased mortality due to acute myocardial infarction. Low concentrations of magnesium in drinking water were associated with decreased cardiovascular mortality, and mortality due to stroke.

Nitrate in Drinking Water and Time to Pregnancy or Medically Assisted Reproduction in Women and Men: A Nationwide Cohort Study in the Danish National Birth Cohort

Purpose

No studies have investigated if drinking water nitrate affects human fecundity. Experimental studies point at detrimental effects on fetal development and on female and male reproduction. This cohort study aimed to explore if female and male preconception and long-term exposure to nitrate in drinking water was associated with fecundability measured as time to pregnancy (TTP) or use of medically assisted reproduction (MAR) treatment.

Methods

The study population consisted of pregnant women recruited in their first trimester in 1996–2002 to the Danish National Birth Cohort. Preconception drinking-water nitrate exposure was estimated for the pregnant women (89,109 pregnancies), and long-term drinking water nitrate exposure was estimated from adolescence to conception for the pregnant women (77,474 pregnancies) and their male partners (62,000 pregnancies) by linkage to the national drinking water quality-monitoring database Jupiter. Difference in risk of TTP >12 months or use of MAR treatment between five exposure categories and log-transformed continuous models of preconception and long-term nitrate in drinking water were estimated. Binominal regression models for risk ratios (RR) were adjusted for age, occupation, education, population density, and lifestyle factors.

Results

Nitrate in drinking water (median preconception exposure: 1.9 mg/L; median long-term exposure: 3.3 mg/L) was not associated with TTP >12 months or use of MAR treatment, neither in the categorical nor in the continuous models.

Conclusion

We found no association between preconception or long-term exposure to drinking water nitrate and fecundability.

Maternal exposure to arsenic in drinking water and risk of congenital heart disease in the offspring

INTRODUCTION

Prenatal exposure to arsenic is suspected to impair fetal health, including congenital malformations. Few studies investigated an association between maternal exposure to arsenic and congenital heart disease.

OBJECTIVE

To examine the association between maternal exposure to arsenic through drinking water and congenital heart disease among offspring.

METHODS

This nationwide cohort study included all liveborn children in Denmark, 1997-2014. Maternal addresses at fetal age 4 weeks were linked to drinking water supply areas. Exposure was arsenic concentration in drinking water in first trimester in four categories (<0.5 μg/L, 0.5-0.9 μg/L, 1.0-4.9 μg/L, ≥5.0 μg/L). Outcomes were defined as congenital heart disease diagnosed within the first year of life, with sub-categorization of severe, septal defects and valvular heart defect. Associations between arsenic levels and congenital heart disease were analysed using logistic regression, presented as odds ratios (OR) with 95% confidence interval (CI), and adjusted for year of birth, mother's educational level and ethnicity.

RESULTS

A total of 1,042,413 liveborn children were included of whom 1.0% had a congenital heart disease. The OR of congenital heart disease was higher among children exposed to all levels of arsenic above 0.5 μg/L; the OR was 1.13 (95% CI: 1.08-1.19) for exposure of 0.5-0.9 μg/L, 1.33 (95% CI: 1.27-1.39) for 1.0-4.9 μg/L and 1.42 (95% CI: 1.24-1.63) for ≥5.0 μg/L. Similar associations were observed for congenital septal defects. The OR was also higher for severe congenital heart disease but at the same level among all exposure levels ≥0.5 μg/L. The OR of congenital valvular heart defects was only higher among children with maternal exposure to arsenic in drinking water ≥5.0 μg/L. The associations were similar for boys and girls.

CONCLUSION

The findings indicate that maternal exposure to arsenic in drinking water even at low concentrations (i.e., 0.5-0.9 μg/L) increased the risk of congenital heart disease in the offspring.

Geographical Distribution and Pattern of Pesticides in Danish Drinking Water 2002-2018: Reducing Data Complexity

Pesticides are a large and heterogenous group of chemicals with a complex geographic distribution in the environment. The purpose of this study was to explore the geographic distribution of pesticides in Danish drinking water and identify potential patterns in the grouping of pesticides. Our data included 899,169 analyses of 167 pesticides and metabolites, of which 55 were identified above the detection limit. Pesticide patterns were defined by (1) pesticide groups based on chemical structure and pesticide-metabolite relations and (2) an exploratory factor analysis identifying underlying patterns of related pesticides within waterworks. The geographic distribution was evaluated by mapping the pesticide categories for groups and factor components, namely those detected, quantified, above quality standards, and not analysed. We identified five and seven factor components for the periods 2002-2011 and 2012-2018, respectively. In total, 16 pesticide groups were identified, of which six were representative in space and time with regards to the number of waterworks and analyses, namely benzothiazinone, benzonitriles, organophosphates, phenoxy herbicides, triazines, and triazinones. Pesticide mapping identified areas where multiple pesticides were detected, indicating areas with a higher pesticide burden. The results contribute to a better understanding of the pesticide pattern in Danish drinking water and may contribute to exposure assessments for future epidemiological studies.

Nitrate in drinking water and risk of birth defects: Findings from a cohort study of over one million births in Denmark

Background

A few studies have reported an increased risk of birth defects (BD) with maternal exposure to nitrate in drinking water. We examined this association in a large cohort study with well-characterized exposure.

Methods

Danish singletons liveborn to Danish-born parents from 1991–2013 were identified using civil and patient registries (n=1,018,914). Exposure to nitrate was estimated using a spatial model based on national data linked with individual addresses. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using logistic regression.

Findings

In total, 33,182 cases of BD were identified. Nitrate concentrations were generally well below US and EU standards. We observed an exposure-response relationship (p=0·004) between nitrate during pregnancy and eye BD, and increased risk in the highest exposure group (≥25 mg/L nitrate) (OR: 1·29; 95% CI: 1·00, 1·66). An interaction was observed between maternal age and continuous nitrate exposure for nervous system BD (p<0·001) indicating an increased risk among mothers <25 years-of-age (OR for 10 mg/L (OR₁₀): 1·20; 95% CI: 1·06, 1·35). An interaction (p<0.01) with maternal age and continuous nitrate exposure was also observed for ear, face, and neck BD indicating an increased risk among babies born to mothers <25 years-of-age (OR₁₀: 1·35; 95% CI: 1·11, 1·66). There was evidence of an inverse exposure-response relationship for any, digestive system, female genital, and urinary BD.

Interpretation

Our study is the first to report an association between nitrate and eye BD and BD of the ear, face, and neck. It also provides support to prior reports of increased risk of nervous system BD.

Funding

This study was supported by a grant from the United States National Institute of Environmental Health Sciences (R01 ES027823-01A1).

Association between magnesium in drinking water and atrial fibrillation incidence: a nationwide population-based cohort study, 2002-2015

BACKGROUND

Atrial fibrillation (AF) is a common heart rhythm disorder and a risk factor of adverse cardiovascular diseases. Established causes do not fully explain the risk of AF and unexplained risk factors might be related to the environment, e.g. magnesium in drinking water. Low magnesium levels in drinking water might be associated with higher risk of cardiovascular diseases including AF. With detailed individual data from nationwide registries and long-term magnesium exposure time series, we had a unique opportunity to investigate the association between magnesium in drinking water and AF.

OBJECTIVE

We evaluated the association between magnesium concentration in drinking water and AF risk.

METHODS

A nationwide register-based cohort study (2002-2015) was used including individuals aged ≥30 years. Addresses were linked with water supply areas (n = 2418) to obtain time-varying drinking water magnesium exposure at each address. Five exposure groups were defined based on a 5-year rolling time-weighted average magnesium concentration. AF incidence rate ratios (IRRs) between exposure groups were calculated using a Poisson regression of incidence rates, adjusted for sex, age, and socioeconomic position. Robustness of results was investigated with different exposure definitions.

RESULTS

The study included 4,264,809 individuals (44,731,694 person-years) whereof 222,998 experienced an incident AF. Magnesium exposure ranged from 0.5 to 62.0 mg/L (mean = 13.9 mg/L). Estimated IRR (95% CI) compared to the referent exposure group (< 5 mg/L) was 0.98 (0.97-1.00) for the second lowest exposure group (5-10 mg/L), and 1.07 (1.05-1.08) for the two highest exposure groups (15-62 mg/L). Strongest positive associations were observed among those aged ≥80 years and with lowest education group. An inverse association was found among individuals with highest education group.

CONCLUSION

There might be a small beneficial effect on AF of an increase in magnesium level in drinking water up to 10 mg/L, though an overall positive association was observed. The unexpected positive association and different associations observed for subgroups suggest a potential influence of unaccounted factors, particularly in vulnerable populations. Future research on magnesium in drinking water and cardiovascular diseases needs to focus on contextual risk factors, especially those potentially correlating with magnesium in drinking water.

Trace elements in drinking water and the incidence of attention-deficit hyperactivity disorder

BACKGROUND

Trace elements have been suggested to have neurotoxic effects and increase the risk of neurodevelopmental disorders, but studies of a potential role of trace elements in relation to Attention-Deficit/Hyperactivity Disorder (ADHD) are very limited. The objective of this study was to conduct an exploratory analysis investigating the associations between 17 geogenic trace elements (Ba, Co, Eu, I, Li, Mo, Rb, Re, Rh, Sb, Sc, Se, Si, Sr, Ti, U and Y) found in Danish drinking water and the risk of developing ADHD.

METHODS

In this cohort study, 284,309 individuals, born 1994-2007, were followed for incidence of ADHD from the age of five until the end of study, December 31, 2016. We conducted survival analyses, using Poisson regression to estimate incidence rate ratios (IRRs) with 95 % confidence intervals (CI) in three different confounder adjustment scenarios.

RESULTS

In a model including adjustments for age, sex, calendar year, parental socio-economic status, neighborhood level socio-economic status and parental psychiatric illness, we found that six of the 17 trace elements (Sr, Rb, Rh, Ti, Sb and Re) were associated with an increased risk of ADHD, whereas two (Ba and I) were inversely associated with ADHD. However, when including region as a covariate in the model, most trace elements were no longer associated with ADHD or the association changed direction. Four trace elements (I, Li, Rb, and Y) remained significantly associated with ADHD but in an inverse direction and for three of these (I, Li and Y), we found significant interactions with region in their association with ADHD.

CONCLUSION

The trace elements under investigation, at levels found in Danish drinking water, do not seem to contribute to the development of ADHD and our findings highlight the importance of examining consistency of associations across geographic areas.

Prenatal nitrosatable prescription drug intake, drinking water nitrate, and the risk of stillbirth: a register- and population-based cohort of Danish pregnancies, 1997-2017

BACKGROUND

Nitrosatable drugs commonly prescribed during pregnancy can react with nitrite to form N-nitroso compounds which have been associated with an increased risk of stillbirth. Whether maternal residential drinking water nitrate modifies this association is unknown. We investigated, if household drinking water nitrate was associated with stillbirth, and if it modified the association between nitrosatable prescription drug intake and the risk of stillbirth.

METHODS

We conducted an individual-level register- and population-based cohort study using 652,810 women with the first recorded singleton pregnancy in the Danish Medical Birth Registry between 1997 and 2017. Nitrosatable drug exposure was recorded by use of the Danish National Patient Registry defined as women with a first redeemed prescription of a nitrosatable drug the first 22 weeks of pregnancy. The reference group was women with no redeemed prescription of a nitrosatable drug in this period. The average individual drinking water nitrate concentration level (mg/L) was calculated in the same period. We categorized nitrosatable drugs as secondary amines, tertiary amines, and amides. Cox hazard regression was used to estimate crude and adjusted hazard ratios with 95% confidence intervals for stillbirth stratified into five categories of nitrate concentrations: ≤1 mg/L, > 1- ≤ 2 mg/L, > 2- ≤ 5 mg/L, > 5- ≤ 25 mg/L, and > 25 mg/L.

RESULTS

Drinking water nitrate exposure in the population was not associated with the risk of stillbirth. Among 100,244 women who had a nitrosatable prescription drug redeemed ≤22 weeks of pregnancy of pregnancy, 418 (0.42%) had a stillbirth compared to 1993 stillbirths (0.36%) among 552,566 referent women. Women with any nitrosatable prescription drug intake and > 1- ≤ 2 mg/L nitrate concentration had an increased risk of stillbirth [adjusted hazard ratio 1.55 (95% confidence interval, 1.15-2.09)] compared with referent women. In the stratified analyses, the highest risk of stillbirth was found among women with secondary amine intake and > 25 mg/L nitrate concentrations [adjusted hazard ratio 3.11 (95% CI, 1.08-8.94)].

CONCLUSIONS

The association between nitrosatable prescription drug intake and the risk of stillbirth may depend on the level of nitrate in household drinking water. Evaluations of the effect of nitrosatable drug intake on perinatal outcomes might consider nitrate exposure from drinking water.

Exposure to nitrate from drinking water and the risk of childhood cancer in Denmark

BACKGROUND

There is limited evidence that nitrate, a common contaminant in drinking water, increases the risk of childhood cancers. Our objective was to examine this association in Denmark.

METHODS

We conducted a nationwide case-control study based on all singletons liveborn to Danish-born parents from 1991 to 2015 (N = 1,219,140) that included 596 leukemias, 180 lymphomas, and 310 central nervous system cancers (CNC) who were ≤15 years of age at diagnosis and were identified from the Danish Cancer Registry. Approximately 100 controls were randomly selected and matched to each case on date of birth and sex. Nitrate measurements in public water systems were linked with an address registry to estimate individual average nitrate concentrations during preconception, prenatal, and postnatal periods. Odd ratios (OR) and 95% confidence intervals (95%CI) were estimated using conditional logistic regression controlling for the matching variables, and birth order, birthweight, urbanicity, maternal education, employment, income and smoking, and parental age.

RESULTS

There was no evidence of an association of nitrate with leukemia or lymphoma. An association between CNC and the highest category of nitrate exposure (>25 mg/L nitrate) was observed for preconception (OR = 1.82, 95%CI:1.09 to 3.04), prenatal (OR = 1.65, 95%CI:0.97 to 2.81), and postnatal exposure (OR = 1.48, 95%CI:0.82 to 2.68) in fully adjusted models. There was also some evidence of an exposure-response in models of continuous nitrate exposure and CNC.

CONCLUSIONS

Our findings provide some evidence that exposure to nitrate from drinking water may increase the risk of childhood CNC cancer, but not leukemia or lymphoma.

Drinking Water Criteria for Arsenic in High-Income, Low-Dose Countries: The Effect of Legislation on Public Health

Due to the potential health risks at very low concentrations, the criterion for arsenic in drinking water has been debated. High-income, low-dose countries are uniquely positioned to follow WHO's recommendation of keeping concentrations "as low as reasonably possible." In this policy analysis, 47646 arsenic analyses from Denmark are used to follow the effect of lowering the national criterion from 50 to 5 μg/L. The first 3 years (2002-2004) following the criterion change, 106 waterworks were identified as noncompliant. An additional 64 waterworks were identified as noncompliant in the next 12 years (2005-2016). Of the 106 waterworks initially (2002-2004) aware of the violation, an average concentration drop from 6 to 3 μg/L was observed during a 6 year period following a lag time of 1 year. After this point, no further improvements were observed. Thirteen years after regulation was imposed, 25 of 170 waterworks were still in violation. The results suggest that legislation alone is insufficient to ensure better drinking water quality at some waterworks and that stakeholders' drivers and barriers to change also play an important role. In an exploration of five legislation scenarios, this study showed that a criterion of 1 μg/L would require action by more than 500 Danish waterworks, with treatment costs from 0.06 to 0.70 €/m³. These scenarios illustrate that it can be technically feasible and affordable to lower the arsenic criterion below 5 μg/L in low-dose, high-income countries. However, more information is needed to apply a cost-benefit model, and comparative studies from other counties are warranted.

Prenatal Exposure to Nitrate from Drinking Water and Markers of Fetal Growth Restriction: A Population-Based Study of Nearly One Million Danish-Born Children

BACKGROUND

High levels of nitrate (NO3-) in drinking water cause methemoglobinemia in infants; however, few studies have examined the potential effects of low-level exposure on fetal growth, and the results have been inconsistent.

OBJECTIVES

We sought to assess the association between maternal exposure to nitrate in drinking water during pregnancy and offspring size at birth in a nationwide study of full-term (≥37 wk gestation) live-born singletons.

METHODS

We estimated maternal nitrate exposure for 898,206 births in Denmark during 1991-2011 by linkage of individual home address(es) with nitrate data from the national monitoring database. Maternal address during pregnancy, infant size at birth [i.e., birth weight, low birth weight (LBW), body length, and birth head circumference] and covariates were compiled from the Danish Civil Registration System, the Danish Medical Birth Register, and The Integrated Database for Longitudinal Labor Market Research. Linear and logistic models with generalized estimating equations were used to account for multiple births to an individual. Nitrate exposure was modeled using five categories and as a log-transformed continuous variable.

RESULTS

There was evidence of a decreasing trend in models for term birth weight using categorical or continuous measures of exposure. Modeling exposure continuously, a difference of -9.71 g (95% confidence interval: -14.60, -4.81) was predicted at 25 mg/L (half the value of the European Union drinking water standard) compared with 0 mg/L NO3-. Body length also decreased as nitrate concentrations increased in categorical and continuous models. There was little evidence of an association between NO3- and head circumference or LBW.

DISCUSSION

Although the estimated effects were small, our findings for live singleton births to Danish-born parents suggest that maternal intake of nitrate from drinking water may reduce term birth weight and length, which are markers of intrauterine growth. However, there was little evidence for an association between nitrate and head circumference or LBW. Future studies in other populations and with data on dietary sources of nitrate are encouraged to confirm or refute these findings. https://doi.org/10.1289/EHP7331.

A high-resolution nitrate vulnerability assessment of sandy aquifers (DRASTIC-N)

Groundwater protection against agricultural diffuse nitrate pollution is of paramount importance for safeguarding groundwater-dependent aquatic ecosystems and protecting human health by securing clean groundwater for drinking water production. Nitrate vulnerability assessment of aquifers is the core of a scientifically sound strategy for management and protection of groundwater by authorities. A multitude of methods exists for assessing intrinsic aquifer vulnerability. The objective of this paper is to develop a nitrate-specific groundwater vulnerability assessment method based on the globally recognized DRASTIC method, which was developed by the US Environmental Protection Agency in the 1980s. We propose a new method "DRASTIC-N″ for assessing aquifer nitrate vulnerability, which for the first time expands the seven original geological and hydrogeological parameters with a geochemical parameter for redox condition. The development of DRASTIC-N is based on the longstanding Danish practice of performing detailed groundwater mapping based on dense sampling of geophysical, geological, and geochemical data. DRASTIC-N is compared to the widely used and documented Danish nitrate vulnerability assessment method SCANVA in a study area where the primary aquifer used for drinking water production is composed of heterogeneous sandy glacial deposits. Both SCANVA and DRASTIC-N result in vulnerability maps, which show similar patterns of nitrate vulnerability with a fair overall agreement of 71%. DRASTIC-N provides a framework for systematic and transparent application, which can facilitate stakeholder involvement and help authorities in groundwater protection and decision-making with regards to nitrate pollution. DRASTIC-N is suitable for nitrate vulnerability assessments of glacially deposited sandy aquifers, an abundant and important water resource worldwide, potentially threatened by nitrate pollution from anthropogenic activities.

Exposure to Manganese in Drinking Water during Childhood and Association with Attention-Deficit Hyperactivity Disorder: A Nationwide Cohort Study

BACKGROUND

Manganese (Mn) in drinking water may increase the risk of several neurodevelopmental outcomes, including attention-deficit hyperactivity disorder (ADHD). Earlier epidemiological studies on associations between Mn exposure and ADHD-related outcomes had small sample sizes, lacked spatiotemporal exposure assessment, and relied on questionnaire data (not diagnoses)-shortcomings that we address here.

OBJECTIVE

Our objective was to assess the association between exposure to Mn in drinking water during childhood and later development of ADHD.

METHODS

In a nationwide population-based registry study in Denmark, we followed a cohort of 643,401 children born 1992-2007 for clinical diagnoses of ADHD. In subanalyses, we classified cases into ADHD-Inattentive and ADHD-Combined subtypes based on hierarchical categorization of International Classification of Diseases (ICD)-10 codes. We obtained Mn measurements from 82,574 drinking water samples to estimate longitudinal exposure during the first 5 y of life with high spatiotemporal resolution. We modeled exposure as both peak concentration and time-weighted average. We estimated sex-specific hazard ratios (HRs) in Cox proportional hazards models adjusted for age, birth year, socioeconomic status (SES), and urbanicity.

RESULTS

We found that exposure to increasing levels of Mn in drinking water was associated with an increased risk of ADHD-Inattentive subtype, but not ADHD-Combined subtype. After adjusting for age, birth year, and SES, females exposed to high levels of Mn (i.e., >100μg/L) at least once during their first 5 y of life had an HR for ADHD-Inattentive subtype of 1.51 [95% confidence interval (CI): 1.18, 1.93] and males of 1.20 (95% CI: 1.01, 1.42) when compared with same-sex individuals exposed to <5μg/L. When modeling exposure as a time-weighted average, sex differences were no longer present.

DISCUSSION

Mn in drinking water was associated with ADHD, specifically the ADHD-Inattentive subtype. Our results support earlier studies suggesting a need for a formal health-based drinking water guideline value for Mn. Future Mn-studies should examine ADHD subtype-specific associations and utilize direct subtype measurements rather than relying on ICD-10 codes alone. https://doi.org/10.1289/EHP6391.

Incidence Rates and Cumulative Incidences of the Full Spectrum of Diagnosed Mental Disorders in Childhood and Adolescence

IMPORTANCE

Knowledge about the epidemiology of mental disorders in children and adolescents is essential for research and planning of health services. Surveys can provide prevalence rates, whereas population-based registers are instrumental to obtain precise estimates of incidence rates and risks.

OBJECTIVE

To estimate age- and sex-specific incidence rates and risks of being diagnosed with any mental disorder during childhood and adolescence.

DESIGN

This cohort study included all individuals born in Denmark from January 1, 1995, through December 31, 2016 (1.3 million), and followed up from birth until December 31, 2016, or the date of death, emigration, disappearance, or diagnosis of 1 of the mental disorders examined (14.4 million person-years of follow-up). Data were analyzed from September 14, 2018, through June 11, 2019.

EXPOSURES

Age and sex.

MAIN OUTCOMES AND MEASURES

Incidence rates and cumulative incidences of all mental disorders according to the ICD-10 Classification of Mental and Behavioral Disorders: Diagnostic Criteria for Research, diagnosed before 18 years of age during the study period.

RESULTS

A total of 99 926 individuals (15.01%; 95% CI, 14.98%-15.17%), including 41 350 girls (14.63%; 95% CI, 14.48%-14.77%) and 58 576 boys (15.51%; 95% CI, 15.18%-15.84%), were diagnosed with a mental disorder before 18 years of age. Anxiety disorder was the most common diagnosis in girls (7.85%; 95% CI, 7.74%-7.97%); attention-deficit/hyperactivity disorder (ADHD) was the most common in boys (5.90%; 95% CI, 5.76%-6.03%). Girls had a higher risk than boys of schizophrenia (0.76% [95% CI, 0.72%-0.80%] vs 0.48% [95% CI, 0.39%-0.59%]), obsessive-compulsive disorder (0.96% [95% CI, 0.92%-1.00%] vs 0.63% [95% CI, 0.56%-0.72%]), and mood disorders (2.54% [95% CI, 2.47%-2.61%] vs 1.10% [95% CI, 0.84%-1.21%]). Incidence peaked earlier in boys than girls in ADHD (8 vs 17 years of age), intellectual disability (5 vs 14 years of age), and other developmental disorders (5 vs 16 years of age). The overall risk of being diagnosed with a mental disorder before 6 years of age was 2.13% (95% CI, 2.11%-2.16%) and was higher in boys (2.78% [95% CI, 2.44%-3.15%]) than in girls (1.45% [95% CI, 1.42%-1.49%]).

CONCLUSIONS AND RELEVANCE

This nationwide population-based cohort study provides a first comprehensive assessment of the incidence and risks of mental disorders in childhood and adolescence. By 18 years of age, 15.01% of children and adolescents in this study were diagnosed with a mental disorder. The incidence of several neurodevelopmental disorders peaked in late adolescence in girls, suggesting possible delayed detection. The distinct signatures of the different mental disorders with respect to sex and age may have important implications for service planning and etiological research.

Trihalomethanes in Drinking Water and Bladder Cancer Burden in the European Union

BACKGROUND

Trihalomethanes (THMs) are widespread disinfection by-products (DBPs) in drinking water, and long-term exposure has been consistently associated with increased bladder cancer risk.

OBJECTIVE

We assessed THM levels in drinking water in the European Union as a marker of DBP exposure and estimated the attributable burden of bladder cancer.

METHODS

We collected recent annual mean THM levels in municipal drinking water in 28 European countries (EU28) from routine monitoring records. We estimated a linear exposure-response function for average residential THM levels and bladder cancer by pooling data from studies included in the largest international pooled analysis published to date in order to estimate odds ratios (ORs) for bladder cancer associated with the mean THM level in each country (relative to no exposure), population-attributable fraction (PAF), and number of attributable bladder cancer cases in different scenarios using incidence rates and population from the Global Burden of Disease study of 2016.

RESULTS

We obtained 2005-2018 THM data from EU26, covering 75% of the population. Data coverage and accuracy were heterogeneous among countries. The estimated population-weighted mean THM level was 11.7μg/L [standard deviation (SD) of 11.2]. The estimated bladder cancer PAF was 4.9% [95% confidence interval (CI): 2.5, 7.1] overall (range: 0-23%), accounting for 6,561 (95% CI: 3,389, 9,537) bladder cancer cases per year. Denmark and the Netherlands had the lowest PAF (0.0% each), while Cyprus (23.2%), Malta (17.9%), and Ireland (17.2%) had the highest among EU26. In the scenario where no country would exceed the current EU mean, 2,868 (95% CI: 1,522, 4,060; 43%) annual attributable bladder cancer cases could potentially be avoided.

DISCUSSION

Efforts have been made to reduce THM levels in the European Union. However, assuming a causal association, current levels in certain countries still could lead to a considerable burden of bladder cancer that could potentially be avoided by optimizing water treatment, disinfection, and distribution practices, among other possible measures. https://doi.org/10.1289/EHP4495.

Exposure to neuroactive non-organochlorine insecticides, and diabetes mellitus and related metabolic disturbances: Protocol for a systematic review and meta-analysis

OBJECTIVES

To assess whether exposure to specific classes of neuroactive non-organochlorine insecticides is associated with diabetes mellitus or related metabolic traits.

METHODS

Eligibility criteria: Any type of epidemiological and human exposure studies providing an exposure contrast to neuroactive non-organochlorine insecticides and a measure of association to diabetes mellitus or related metabolic traits. We will include published peer-reviewed studies in both English and non-English language.

INFORMATION SOURCES

Articles will be located in the NCBI PubMed, Embase, Scopus, Web of Science and LILACS databases, supplemented with manual searching of reference lists and articles citing the included studies. Risk of bias assessment: Risk of bias in individual studies will be assessed using tools from the Navigation Guide systematic review methodology, while the risk of bias at the outcome level will be assessed according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) guidelines. Data synthesis and analysis: When studies are sufficiently similar in population, exposure, comparator and effect estimate to meaningfully allow quantitative synthesis, we will perform meta-analysis. Otherwise, results will be summarized qualitatively.

FUNDING

The authors are paid employees of their respective institutions. MRHH is a Ph.D. student working under grants from Aarhus University and the National Research Centre for the Working Environment.

REGISTRATION

PROSPERO CRD42017068861.

Stability of Major Geogenic Cations in Drinking Water-An Issue of Public Health Importance: A Danish Study, 1980⁻2017

Concentrations and spatial variations of the four cations Na, K, Mg and Ca are known to some extent for groundwater and to a lesser extent for drinking water. Using Denmark as case, the purpose of this study was to analyze the spatial and temporal variations in the major cations in drinking water. The results will contribute to a better exposure estimation in future studies of the association between cations and diseases. Spatial and temporal variations and the association with aquifer types, were analyzed with spatial scan statistics, linear regression and a multilevel mixed-effects linear regression model. About 65,000 water samples of each cation (1980–2017) were included in the study. Results of mean concentrations were 31.4 mg/L, 3.5 mg/L, 12.1 mg/L and 84.5 mg/L for 1980–2017 for Na, K, Mg and Ca, respectively. An expected west-east trend in concentrations were confirmed, mainly explained by variations in aquifer types. The trend in concentration was stable for about 31–45% of the public water supply areas. It is therefore recommended that the exposure estimate in future health related studies not only be based on a single mean value, but that temporal and spatial variations should also be included.

Nitrate in drinking water and colorectal cancer risk: A nationwide population-based cohort study

Nitrate in drinking water may increase risk of colorectal cancer due to endogenous transformation into carcinogenic N-nitroso compounds. Epidemiological studies are few and often challenged by their limited ability of estimating long-term exposure on a detailed individual level. We exploited population-based health register data, linked in time and space with longitudinal drinking water quality data, on an individual level to study the association between long-term drinking water nitrate exposure and colorectal cancer (CRC) risk. Individual nitrate exposure was calculated for 2.7 million adults based on drinking water quality analyses at public waterworks and private wells between 1978 and 2011. For the main analyses, 1.7 million individuals with highest exposure assessment quality were included. Follow-up started at age 35. We identified 5,944 incident CRC cases during 23 million person-years at risk. We used Cox proportional hazards models to estimate hazard ratios (HRs) of nitrate exposure on the risk of CRC, colon and rectal cancer. Persons exposed to the highest level of drinking water nitrate had an HR of 1.16 (95% CI: 1.08-1.25) for CRC compared with persons exposed to the lowest level. We found statistically significant increased risks at drinking water levels above 3.87 mg/L, well below the current drinking water standard of 50 mg/L. Our results add to the existing evidence suggesting increased CRC risk at drinking water nitrate concentrations below the current drinking water standard. A discussion on the adequacy of the drinking water standard in regards to chronic effects is warranted.

Lithium in drinking water and the incidence of bipolar disorder: A nation-wide population-based study

OBJECTIVE

Animal data suggest that subtherapeutic doses, including micro doses, of lithium may influence mood, and lithium levels in drinking water have been found to correlate with the rate of suicide. It has never been investigated whether consumption of lithium may prevent the development of bipolar disorder (primary prophylaxis). In a nation-wide population-based study, we investigated whether long-term exposure to micro levels of lithium in drinking water correlates with the incidence of bipolar disorder in the general population, hypothesizing an inverse association in which higher long-term lithium exposure is associated with lower incidences of bipolar disorder.

METHODS

We included longitudinal individual geographical data on municipality of residence, data from drinking water lithium measurements and time-specific data from all cases with a hospital contact with a diagnosis of mania/bipolar disorder from 1995 to 2013 (N=14 820) and 10 age- and gender-matched controls from the Danish population (N= 140 311). Average drinking water lithium exposure was estimated for all study individuals.

RESULTS

The median of the average lithium exposure did not differ between cases with a diagnosis of mania/bipolar disorder (12.7 μg/L; interquartile range [IQR]: 7.9-15.5 μg/L) and controls (12.5 μg/L; IQR: 7.6-15.7 μg/L; P=.2). Further, the incidence rate ratio of mania/bipolar disorder did not decrease with higher long-term lithium exposure, overall, or within age categories (0-40, 41-60 and 61-100 years of age).

CONCLUSION

Higher long-term lithium exposure from drinking water was not associated with a lower incidence of bipolar disorder. The association should be investigated in areas with higher lithium levels than in Denmark.

Association of Lithium in Drinking Water With the Incidence of Dementia

IMPORTANCE

Results from animal and human studies suggest that lithium in therapeutic doses may improve learning and memory and modify the risk of developing dementia. Additional preliminary studies suggest that subtherapeutic levels, including microlevels of lithium, may influence human cognition.

OBJECTIVE

To investigate whether the incidence of dementia in the general population covaries with long-term exposure to microlevels of lithium in drinking water.

DESIGN, SETTING, AND PARTICIPANTS

This Danish nationwide, population-based, nested case-control study examined longitudinal, individual geographic data on municipality of residence and data from drinking water measurements combined with time-specific data from all patients aged 50 to 90 years with a hospital contact with a diagnosis of dementia from January 1, 1970, through December 31, 2013, and 10 age- and sex-matched control individuals from the Danish population. The mean lithium exposure in drinking water since 1986 was estimated for all study individuals. Data analysis was performed from January 1, 1995, through December 31, 2013.

MAIN OUTCOMES AND MEASURES

A diagnosis of dementia in a hospital inpatient or outpatient contact. Diagnoses of Alzheimer disease and vascular dementia were secondary outcome measures. In primary analyses, distribution of lithium exposure was compared between patients with dementia and controls.

RESULTS

A total of 73 731 patients with dementia and 733 653 controls (median age, 80.3 years; interquartile range, 74.9-84.6 years; 44 760 female [60.7%] and 28 971 male [39.3%]) were included in the study. Lithium exposure was statistically significantly different between patients with a diagnosis of dementia (median, 11.5 µg/L; interquartile range, 6.5-14.9 µg/L) and controls (median, 12.2 µg/L; interquartile range, 7.3-16.0 µg/L; P < .001). A nonlinear association was observed. Compared with individuals exposed to 2.0 to 5.0 µg/L, the incidence rate ratio (IRR) of dementia was decreased in those exposed to more than 15.0 µg/L (IRR, 0.83; 95% CI, 0.81-0.85; P < .001) and 10.1 to 15.0 µg/L (IRR, 0.98; 95% CI, 0.96-1.01; P = .17) and increased with 5.1 to 10.0 µg/L (IRR, 1.22; 95% CI, 1.19-1.25; P < .001). Similar patterns were found with Alzheimer disease and vascular dementia as outcomes.

CONCLUSIONS AND RELEVANCE

Long-term increased lithium exposure in drinking water may be associated with a lower incidence of dementia in a nonlinear way; however, confounding from other factors associated with municipality of residence cannot be excluded.

Groundwater nitrate response to sustainable nitrogen management

Throughout the world, nitrogen (N) losses from intensive agricultural production may end up as undesirably high concentrations of nitrate in groundwater with a long-term impact on groundwater quality. This has human and environmental health consequences, due to the use of groundwater as a drinking water resource, and causes eutrophication of groundwater-dependent ecosystems such as wetlands, rivers and near-coastal areas. At national scale, the measured nitrate concentrations and trends in Danish oxic groundwater in the last 70 years correlate well with the annual agricultural N surpluses. We also show that the N use efficiency of agriculture is related to the groundwater nitrate concentrations. We demonstrate an inverted U-shape of annual nitrate concentrations as a function of economic growth from 1948 to 2014. Our analyses evidence a clear trend of a reversal at the beginning of the 1980s towards a more sustainable agricultural N management. This appears to be primarily driven by societal demand for groundwater protection linked to economic prosperity and an increased environmental awareness. However, the environmental and human health thresholds are still exceeded in many locations. Groundwater protection is of fundamental global importance, and this calls for further development of environmentally and economically sustainable N management in agriculture worldwide.

Lithium in Drinking Water and Incidence of Suicide: A Nationwide Individual-Level Cohort Study with 22 Years of Follow-Up

Suicide is a major public health concern. High-dose lithium is used to stabilize mood and prevent suicide in patients with affective disorders. Lithium occurs naturally in drinking water worldwide in much lower doses, but with large geographical variation. Several studies conducted at an aggregate level have suggested an association between lithium in drinking water and a reduced risk of suicide; however, a causal relation is uncertain. Individual-level register-based data on the entire Danish adult population (3.7 million individuals) from 1991 to 2012 were linked with a moving five-year time-weighted average (TWA) lithium exposure level from drinking water hypothesizing an inverse relationship. The mean lithium level was 11.6 μg/L ranging from 0.6 to 30.7 μg/L. The suicide rate decreased from 29.7 per 100,000 person-years at risk in 1991 to 18.4 per 100,000 person-years in 2012. We found no significant indication of an association between increasing five-year TWA lithium exposure level and decreasing suicide rate. The comprehensiveness of using individual-level data and spatial analyses with 22 years of follow-up makes a pronounced contribution to previous findings. Our findings demonstrate that there does not seem to be a protective effect of exposure to lithium on the incidence of suicide with levels below 31 μg/L in drinking water.

Nitrate, Nitrite, and Ammonium Variability in Drinking Water Distribution Systems

Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system variability and (2) short-term (seasonal) concentration variability have to be made. We assess concentration variability in the distribution system of nitrate, nitrite, and ammonium, and seasonal variability in all Danish public waterworks from 2007 to 2016. Nitrate concentrations at the exit of the waterworks are highly correlated with nitrate concentrations within the distribution net or at the consumers' taps, while nitrite and ammonium concentrations are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate concentrations. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies.