**1. Introduction**

Obesity is a major risk factor for several chronic diseases, including hypertension, diabetes, and hyperlipidemia, and is a growing concern worldwide. The prevalence of metabolic syndromes in Korea is approximately 30% due to increasing obesity [1]. A Westernized diet, lifestyle patterns, and exposure to environmental pollutants are involved in the development of obesity. Endocrine-disrupting chemicals such as phthalates, phenols, polychlorinated biphenyl (PCBs), and polybrominated diphenyl ether (PBDEs) are well-known obesogens [2], and several studies have reported that mercury (Hg) is also associated with metabolic syndromes [3,4].

According to the first cycle of the Korean National Environmental Health Survey [5], the geometric mean (GM) of blood Hg among Koreans was 3.08 μg/L, which is high compared to the US (mean: 0.68 μg/L) [6] and Canada (mean: 0.59 μg/L) [7]. Blood Hg levels in Korea have been decreasing for the

last ten years, but approximately 25% of the Korean population still has high levels over 5.00 μg/L, which represents the control value for blood Hg (HBM-I) [8].

The main reason for high blood Hg levels in the Korean population is frequent seafood consumption, due to the country's geographical characteristics [9]. A previous study reported that methyl mercury (MeHg) exposure is approaching the reference dose within the Korean population, which is the allowable daily intake [10].

Exposure to Hg induces oxidative stress, lipid peroxidation, and mitochondrial dysfunction [11,12], and γ-glutamyltransferase (GGT), a well-known biological marker of oxidative stress, is significantly associated with blood Hg [13]. Interestingly, GGT levels may reflect insulin resistance [14] and cardiovascular risk because of the relationship with lipoprotein cholesterol oxidation [15]. In a cohort study from Japan, the risk of metabolic syndrome and diabetes increased with the levels of hepatic enzymes, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and GGT, among the metabolic syndrome–free participants [16]. Thus, the hepatic enzymes may serve as surrogate markers of obesity.

Several studies have investigated the associations between Hg and health, but the population-level health e ffects of Hg exposure remain unclear. Therefore, we hypothesized that Hg exposure induces obesity-related outcomes and investigated the relationships between blood Hg and hyperlipidemia and elevated liver enzymes. We used national biomonitoring data to identify the variables that influence blood Hg and analyzed the relationships between blood Hg and the lipid profiles and hepatic enzymes. Finally, we assessed the e ffects of Hg on hyperlipidemia and elevated liver enzymes.

#### **2. Material and Methods**
