Methylmercury and elemental mercury differentially associate with blood pressure among dental professionals

Abstract

Methylmercury-associated effects on the cardiovascular system have been documented though discrepancies exist, and most studied populations experience elevated methylmercury exposures. No paper has investigated the impact of low-level elemental (inorganic) mercury exposure on cardiovascular risk in humans. The purpose of this study was to increase understanding of the association between mercury exposure (methylmercury and elemental mercury) and blood pressure measures in a cohort of dental professionals that experience background exposures to both mercury forms. Dental professionals were recruited during the 2010 Michigan Dental Association Annual Convention. Mercury levels in hair and urine samples were analyzed as biomarkers of methylmercury and elemental mercury exposure, respectively. Blood pressure (systolic, diastolic) was measured using an automated device. Distribution of mercury in hair (mean, range: 0.45, 0.02–5.18 μg/g) and urine (0.94, 0.03–5.54 μg/L) correspond well with the US National Health and Nutrition Examination Survey. Linear regression models revealed significant associations between diastolic blood pressure (adjusted for blood pressure medication use) and hair mercury (n = 262, p = 0.02). Urine mercury results opposed hair mercury in many ways. Notably, elemental mercury exposure was associated with a significant systolic blood pressure decrease (n = 262, p = 0.04) that was driven by the male population. Associations between blood pressure and two forms of mercury were found at exposure levels relevant to the general population, and associations varied according to type of mercury exposure and gender.

Associations of blood and urinary mercury with hypertension in U.S. Adults: The NHANES 2003–2006

“…To the best of our knowledge, only one study has examined this association, which also observed an inverse association between urinary mercury and SBP but in a convenience sample of male dental professions (Goodrich, 2012). This inverse association is striking but not unrealistic since several laboratory studies have shown that inorganic mercury can decrease blood pressure (Massaroni et al, 1995; Rhee and Choi, 1989; Rossoni et al, 1999).…”

“…Cardiovascular health effects of inorganic mercury are poorly understood, and there is no epidemiologic study that has examined the association between inorganic mercury exposure and hypertension, except for one recent pilot study by us which documented reduced SBP among male dental professionals in association with inorganic mercury exposure (Goodrich, 2012). Such an association is plausible given that several laboratory rodent studies have reported that unlike methylmercury, inorganic mercury exposure causes depressed arterial systolic pressure (Massaroni et al, 1995; Rhee and Choi, 1989; Rossoni et al, 1999).…”

Mercury biomarkers and DNA methylation among michigan dental professionals

“…While several studies investigated chronic low dose Hg exposure and its association with subclinical effects on nervous, cardiovascular and immune systems, the true impact of chronic exposure to relevant and low doses of Hg remains uncertain and conflicted [Franzblau et al, 2012; Goodrich et al, 2012; Karagas et al, 2012; Roman et al, 2011]. While recent animal and in vitro studies suggest MeHg and I-Hg exposure may modify the epigenome, epidemiological evidence is limited to one cohort of women with blood Hg measurements [Hanna et al, 2012].…”

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

“…Urinary mercury concentrations, reflecting exposure to IHg, have been associated with a lower SBP among United States adults in the 2003-2006 NHANES (Park et al, 2013) and dental professionals (Goodrich et al, 2013); the latter study notes this was driven by associations among males. This is consistent with our observations that inorganic mercury was associated with a lower in PP.…”