Abstract
There is increasing concern about the cardiovascular effects of mercury (Hg) exposure, and that organic methylmercury and inorganic Hg2+ may affect the cardiovascular system and blood pressure differentially. In small-scale gold mining communities where inorganic, elemental Hg exposures are high, little is known about the effects of Hg on blood pressure. In 2011, we assessed the relationship between Hg exposure and blood pressure (BP) in a cross-sectional study of adults from a small-scale gold mining community, Kejetia, and subsistence farming community, Gorogo, in Ghana’s Upper East Region. Participants’ resting heart rate and BP were measured, and hair and urine samples were provided to serve as biomarkers of organic and inorganic Hg exposure, respectively. Participants included 70 miners and 26 non-miners from Kejetia and 75 non-miners from Gorogo. Total specific gravity-adjusted urinary and hair Hg was higher among Kejetia miners than Kejetia non-miners and Gorogo participants (median urinary Hg: 5.17, 1.18, and 0.154 µg/L, respectively; hair Hg: 0.945, 0.419, and 0.181 µg/g, respectively). Hypertension was prevalent in 17.7% of Kejetia and 21.3% of Gorogo participants. Urinary and hair Hg were not significantly associated with systolic or diastolic BP for Kejetia or Gorogo participants while adjusting for sex, age, and smoking status. Although our results follow trends seen in other studies, the associations were not of statistical significance. Given the unique study population and high exposures to inorganic Hg, the work contained here will help increase our understanding of the cardiovascular effects of Hg.
Highlights
Mercury is an established pollutant of global concern given the body of evidence concerning its neurological impacts [1,2]
While the majority of the research shows Hg to increase oxidative stress, endothelial dysfunction, and subsequently blood pressure (BP), Rhee and Choi [10] found that inorganic Hg can cause a decrease in renal blood flow while renal activity remains constant, as inorganic Hg may inhibit sodium and chloride reabsorption in the kidneys [11]
The majority of participants in Kejetia and Gorogo had a normal body mass index (BMI) (18.5 to 24.9), but women in Kejetia and Gorogo had a higher prevalence of overweight BMI (25.0 to 29.9)
Summary
Mercury is an established pollutant of global concern given the body of evidence concerning its neurological impacts [1,2]. In recent years there has been increasing concern over the impact of mercury (Hg) on the cardiovascular system, though studies have been limited with variable results. Organic Hg, has been associated with increases in carotid intima-media thickness and obstruction, coronary heart disease, myocardial infarctions, cerebrovascular accidents, cardiac arrhythmias, heart rate variability, atherosclerosis, carotid artery disease, and renal dysfunction [2,3]. The mechanisms through which Hg affects blood pressure (BP) are not well defined, but point toward oxidative stress as being key [4,5]. Increases in oxidative stress from lipid peroxidation and reduced antioxidant capacity can promote endothelial and renal dysfunction, which can increase the risk of hypertension and atherosclerosis, and result in the elevation of pulse pressure [3,6,7,8,9]. While the majority of the research shows Hg to increase oxidative stress, endothelial dysfunction, and subsequently BP, Rhee and Choi [10] found that inorganic Hg can cause a decrease in renal blood flow while renal activity remains constant, as inorganic Hg may inhibit sodium and chloride reabsorption in the kidneys [11]
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