17 environmental tox of mercury Flashcards
what is the outline of this lecture?
-history of mass Hg poisoning in humans
-environmental source and cycling of Hg
-Hg toxicity and human exposure
-Hg transport and biomagnification in the arctic
what is the historical perspective of mercury?
-mercury is thought to be one of the first metals used by humans
-commonly used by ancient Egyptian and Chinese civilizations
-mercury found in an egyptian tomb dating from 1500 BC, and in the writing of a chinese alchemist around 4500 BC
what are examples of mass mercury poisoning in humans?
what are the sources of mercury?
- natural (e.g. volcanic eruption)
- anthropogenic
-industrial: mining, burning of fossil fuel (coal)
applications
-in old times: batteries, dentistry, paints
-modern: notebook computers, modern telephones, new lighting technologies etc
what is a major source of Hg found in canada?
a major source (reservoirs created for hydroelectric power plants) of Hg pollution was identified in canada in the late 1970s, in many parts of canada, notably manitoba, ontario, quebec, labrador, and newfoundland
-natural mercury found in the underlying rock and soil was being released by the increased bacterial activity associated with the decomposition of the plant life in the flooded areas
-important water chemistry parameters that influence Hg conc. in the aquatic ecosystems: NOM and pH
what is the historical record of mercury from ice core data?
what are the sources of Hg contamination in Canada?
what is the table of total mercury emissions from provinces and territories?
what is the biogeochemistry of Hg?
speciation:
-Hg (0), Hg (I), Hg (II)
-organic mercury (methylmercury)
methylmercury (MeHg):
-highly lipophilicity and toxicity
-biomagnified along the food chain
-in fish muscle, >90% is methylmercury
what is toxicology of mercury?
-methyl and methylmercury: nerve toxicants or neurotoxicants
-ingesting or inhaling mercury vapors can cause serious injury or death
-main target organs: brain, kidney
-methylmercury can pass through the blood brain barrier (BBB)
high risk for people who:
-regularly eat fish that are high in methylmercury
-pregnant woman and children
what is the chronic toxicity of mercury?
-permanent brain damage
-central nervous system disorders (e.g. memory loss)
-loss of vision
-kidney damage
-damage of reproductive health in adults, and development and growth of fetuses and infants
where does most of our mercury exposure come from?
-methylmercury can accumulate to extremely high levels in the tissue of fish
-most of the mercury present in humans originates from fish in the food supply
what does canned tuna do?
what are the Hg levels in wild fish in canada?
what happened in grassy narrows?
why is mercury considered?
what is the graph of transport of Hg to arctic?
what is mercury in the atmosphere?
what is the Hg depletion event in the arctic?
what is the frequency of atmospheric mercury depletion (AMD) events in canadian arctic?
what is the biomagnification of Hg in arctic food web?
what do mercury levels in the arctic put at risk?
what are the toxicological effects of mercury in arctic biota?
effects on polar bears?
