Influence of mercury exposure on blood pressure, resting heart rate and heart rate variability in French Polynesians: a cross-sectional study

Background The potential harm from exposure to nonessential metals, particularly mercury (Hg) and lead (Pb), has been the focus of research for years. Initial interest focused on relatively high exposures; however, recent evidence suggests that even high normal exposures might have adverse consequences for child development. Identifying the extent of these consequences is now a priority. Methods We assessed blood Pb and Hg levels in a biracial sample of 9–11 year-old children (N = 203). Neurodevelopment and psychological functioning assessments included hostility, disruptive behaviors, emotion regulation, and autism spectrum disorder behaviors. Parasympathetic (vagal) responses to acute stress were indexed by heart rate variability (HRV) at rest and during stress. Results With increasing Pb levels, children exhibit higher levels of hostile distrust and oppositional defiant behaviors, were more dissatisfied and uncertain about their emotions, and had difficulties with communication. These significant associations were found within a range of blood Pb levels from 0.19 to 3.25 μg/dL, well below the “reference value” for children of >5 μg/dL. Vagal reactivity interacted with Hg such that increasing Hg was associated with increasing autism spectrum behaviors for those children with sustained vagal tone during acute stress. Conclusions This study is the first to demonstrate an association between very low-level Pb exposure and fundamental psychological mechanisms that might explain prior associations with more complex outcomes such as delinquency. Analyses of vagal reactivity yielded entirely novel associations suggesting that Hg may increase autism spectrum behaviors in children with sustained vagal tone during acute stress. The novelty of these later findings requires additional research for confirmation and the cross-sectional nature of the data caution against assumptions of causality without further research.

Section: Discussioncontrasting

confidence: 99%

Background lead and mercury exposures: Psychological and behavioral problems in children

Gump

Dykas

MacKenzie

et al. 2017

“…The cardiovascular risk of methylmercury exposure has also been more extensively explored in adults than in children. Methylmercury exposure has a known effect on the autonomic nervous system, and in particular on heart rate variability (Lim et al 2010; Valera et al 2008; Valera et al 2011; Valera et al 2012; Yaginuma-Sakurai et al 2010). Mercury exposure has also been associated with an increased risk of myocardial infarction and accelerated progression of carotid atherosclerosis (Choi et al 2009; Salonen et al 2000).…”

Section: Discussionmentioning

confidence: 99%

Associations of prenatal maternal blood mercury concentrations with early and mid-childhood blood pressure: A prospective study

Kalish

Rifas‐Shiman

Wright

et al. 2014

Background Childhood blood pressure (BP) is an important determinant of adult cardiovascular disease. Prenatal exposure to methylmercury through maternal fish consumption has been reported to increase the BP of children years later. Methods Mother-child pairs were enrolled from Project Viva, a prospective cohort study in Massachusetts. From second trimester maternal blood samples, we measured erythrocyte mercury concentration. Systolic BP in children, measured up to 5 times per visit in early and mid-childhood (median ages 3.2 and 7.7 years), was the primary outcome. We used mixed-effect regression models to account for variation in the number of BP measurements and to average effects over both time points. Results Among 1,103 mother-child pairs, mean (SD) second trimester total erythrocyte mercury concentration was 4.0 (3.9) ng/g among mothers whose children were assessed in early childhood and 4.0 (4.0) ng/g for children assessed in mid-childhood. Mean (SD) offspring systolic BP was 92.1 (10.4) mm Hg in early childhood and 94.3 (8.4) mm Hg in mid-childhood. After adjusting for mother and infant characteristics, mean second trimester blood mercury concentration was not associated with child systolic BP (regression coefficient, 0.1 mm Hg; 95% CI, −1.3 to 1.5 for quartile 4 vs. quartile 1) at either time period. Further adjusting for second trimester maternal fish consumption, as well as docosahexaenoic acid and eicosapentaenoic acid consumption, did not substantially change the estimates. Conclusions The results of this study demonstrate an absence of association between childhood blood pressure and low-level mercury exposure typical of the general US population.

“…PP has been found to be an independent predictor of future cardiovascular risk (Safar et al, 2003). PP is widely used in the literature, including several recent studies on whole blood total mercury (Valera et al, 2011a; Valera et al, 2011b) toenail mercury (Mordukhovich et al, 2012), or hair mercury (Valera et al, 2011a; Virtanen et al, 2012b); however, only one reported an association of PP with mercury, and this was only observed in unadjusted analyses (Valera et al, 2011a). …”

Section: Discussionmentioning

confidence: 99%

“…Several studies report no association of SBP or DBP with THg in blood among women (Nielsen et al, 2012), in both sexes (Bautista et al, 2009; Valera et al, 2011b), or among fish consumers (Vupputuri et al, 2005); with THg in hair (Bautista et al, 2009; Virtanen et al, 2012b); or with toenail mercury (Mordukhovich et al, 2012). While Valera et al observed a crude association of blood mercury with both SBP and DBP in a population of Canadian Cree, this did not persist after adjustment for confounders, including serum n-3 PUFAs and selenium (Valera et al, 2011a).…”

Section: Discussionmentioning

confidence: 99%

Methyl mercury, but not inorganic mercury, associated with higher blood pressure during pregnancy

Wells

Herbstman

Lin

et al. 2017

Prior studies addressing associations between mercury and blood pressure have produced inconsistent findings; some of this may result from measuring total instead of speciated mercury. This cross-sectional study of 263 pregnant women assessed total mercury, speciated mercury, selenium, and n-3 polyunsaturated fatty acids in umbilical cord blood and blood pressure during labor and delivery. Models with a) total mercury or b) methyl and inorganic mercury were evaluated. Regression models adjusted for maternal age, race/ethnicity, prepregnancy body mass index, neighborhood income, parity, smoking, n-3 fatty acids and selenium. Geometric mean total, methyl, and inorganic mercury concentrations were 1.40 μg/L (95% confidence interval: 1.29, 1.52); 0.95 μg/L (0.84, 1.07); and 0.13 μg/L (0.10, 0.17), respectively. Elevated systolic BP, diastolic BP, and pulse pressure were found, respectively, in 11.4, 6.8, and 19.8% of mothers. In adjusted multivariable models, a one-tertile increase of methyl mercury was associated with 2.83 mmHg (0.17, 5.50) higher systolic blood pressure and 2.99 mmHg (0.91, 5.08) higher pulse pressure. In the same models, an increase of one tertile of inorganic mercury was associated with a -1.18 mmHg (-3.72, 1.35) lower systolic blood pressure and -2.51 mmHg (-4.49, -0.53) lower pulse pressure. No associations were observed with diastolic pressure. There was a non-significant trend of higher total mercury with higher systolic blood pressure. We observed a significant association of higher methyl mercury with higher systolic and pulse pressure, yet higher inorganic mercury was significantly associated with lower pulse pressure. These results should be confirmed with larger, longitudinal studies.