Methylmercury exposure and adverse cardiovascular effects in Faroese whaling men

Abstract

Background: Methylmercury (MeHg), a worldwide contaminant found in fish and seafood, has been linked to an increased risk of cardiovascular mortality.

Objective: We examined 42 Faroese whaling men (30-70 years of age) to assess possible adverse effects within a wide range of MeHg exposures from consumption of pilot whale meat.

Methods: We assessed exposure levels from mercury analysis of toenails and whole blood (obtained at the time of clinical examination), and a hair sample collected 7 years previously. Outcome measures included heart rate variability (HRV), blood pressure (BP), common carotid intima-media thickness (IMT), and brainstem auditory evoked potentials (BAEP). We carried out multiple regression and structural equation model (SEM) analyses to determine the confounder-adjusted effect of mercury exposure. Taking into account correlations among related measures, we categorized exposure and outcomes in groups to derive latent exposure and response variables in SEMs. We used multiple regression analysis to compare the predictive validity of individual exposure biomarkers and the latent exposure variable on individual and latent outcomes.

Results: The toenail mercury concentrations varied widely and had a geometric mean of 2.0 microg/g; hair concentrations averaged about 3-fold higher. Mercury exposure was significantly associated with increased BP and IMT. This effect was reflected by SEMs, but mercury in toenails tended to be the best effect predictor.

Conclusions: The results support the notion that increased MeHg exposure promotes the development of cardiovascular disease.

Keywords: cardiovascular physiology; evoked potentials; food contamination; methylmercury; neurotoxicity; pilot whale; seafood.

Figure 1

Path diagram for an SEM linking mercury exposure to adverse effects, with adjustment for confounders. The estimated true exposure (Hg) is modeled as a latent parameter based on mercury concentrations in toenail (N-Hg), blood (B-Hg), and hair sample taken 7 years ago (H-Hg7). Three latent effect parameters, HRV, CVF, and latencies of BAEP, are expressed by a series of heart variability, cardiovascular, and BAEP (peaks III and V at both 20 and 40 Hz) test results, respectively. HRV, CVF, and BAEP may be correlated (indicated by double-headed arrows), and potential confounders are allowed to be associated with both the latent exposure variables and the latent effect variables.