Lake Melville

6. METHYLMERCURY
Amina Schartup, Ryan Calder, Miling Li, Prentiss Balcom, Amelia Valberg, Jessica Ewald and Elsie Sunderland
Harvard John A. Paulson School of Engineering and Applied Science
Harvard T.H. Chan School of Public Health
6.1. Introduction
Methylmercury is a potent neurotoxin that has been associated
with a variety of adverse health effects on humans. At high levels
of exposure it is a central nervous system toxin causing kidney
and liver failure. Early signs of acute methylmercury poisoning
include tremors, dizziness, memory loss, hair loss, blurred vision
and tingling at the extremities (Clarkson et al., 2003). Chronic low
levels of exposure are typically observed among frequent seafood
consumers. Long-term dietary exposure to methylmercury has
been associated with neurocognitive delays in children including
long-term IQ deficits, attention deficit behavior and reductions in
verbal function and memory. For example, prenatal methylmercury
exposure has been linked to attention deficit symptoms in schoolage
Inuit children in Nunavik, Canada (Boucher et al., 2012). The
developing brain during the third trimester of pregnancy is most
vulnerable to impacts of methylmercury exposure, in part because
it can readily cross the blood-brain barrier and accumulates in fetal
umbilical blood (Mahaffey et al., 2011). Recent research provides new
evidence for impacts of methylmercury on cardiovascular health
of adults (reviewed by Karagas et al., 2012). For example, Roman et
al. (2011) synthesized the epidemiological literature and noted that
there was sufficient information to use this outcome in regulatory
assessments. New information is also emerging about potential
impacts of methylmercury on immune health and as an endocrine
disruptor (Tan et al., 2009).
Managing and reducing methylmercury exposures in Inuit
populations to avoid adverse health effects is extremely
complex. Country foods provide essential nutrition (protein and
micronutrients) that are not generally replaced when individuals
switch away from their traditional diet. Country foods are also
important to Inuit for social, cultural, psychological, and spiritual
reasons (Donaldson et al., 2010). For these reasons, the benefits
of country foods are difficult to replace and must therefore be
protected as a nutritional source.
Methylmercury is formed from inorganic mercury naturally
present in ecosystems. Levels of inorganic mercury in the global
environment, including the Arctic, have been substantially enriched
by human activities such as coal combustion and mining (Amos et
al., 2013; 2014). Methylmercury is formed when bacteria that require
very specific geochemical conditions that are typically associated
with low oxygen environments, convert inorganic mercury to
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