Mercury Exposure and Health Effects Quiz

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Questions and Answers

What is the primary route of mercury exposure for humans?

Inhalation of mercury vapors

Exposure to contaminated water sources

Consumption of fish (correct)

Direct contact with mercury surfaces

What natural events can release mercury into the environment?

Agricultural runoff

Forest fires and volcanic eruptions (correct)

Industrial waste disposal

Landfill decomposition

What form of mercury is most toxic and accumulates in living organisms?

Methylmercury (correct)

Mercury vapor

Inorganic mercury

Elemental mercury

What percentage of fish advisories in Canada are related to mercury?

90% Signup and view all the answers

What potential health effects can result from elevated mercury exposure?

Neurological, immune, and reproductive system effects Signup and view all the answers

How should the concentration of mercury in fish be expressed for the molar correction?

µmol/kg Signup and view all the answers

What is the conversion factor used to determine the concentration of mercury from µg/kg to µmol/kg?

200.59 g/mol Signup and view all the answers

What crucial aspect must be considered in calculating the Health Benefit Value of selenium?

Perform a molar adjustment to the concentration Signup and view all the answers

What is a primary risk associated with consuming fish highlighted in the content?

Excessive mercury intake leading to selenosis Signup and view all the answers

What long-term solution is proposed for addressing mercury emissions globally?

Decrease global emissions via the Minamata Convention Signup and view all the answers

Which fish species were identified as having extremely high levels of MeHg?

Walleye and northern pike Signup and view all the answers

What was one of the significant health impacts observed in the Grassy Narrows community?

High rates of depression and anxiety Signup and view all the answers

What disease were individuals diagnosed with due to MeHg exposure?

Minamata disease Signup and view all the answers

What role does selenium play in relation to mercury exposure?

It acts as a protective sequestration mechanism Signup and view all the answers

Which group is suggested to have experienced unrecognized diagnoses of MeHg-related conditions?

Mercury Disability Board Signup and view all the answers

What is the primary economic activity for the Faroes Islands?

Fishing and fish farming Signup and view all the answers

What is a controversial aspect concerning low doses of MeHg exposure?

They have unclear implications due to contrasting studies. Signup and view all the answers

What has been a significant psychosocial effect in the community affected by MeHg exposure?

High percentage of deaths from drugs and alcohol Signup and view all the answers

What was the primary cause of Minamata Disease in Japan?

Methylmercury dumping by Chisso Corporation Signup and view all the answers

How many people were officially recognized as being affected by Minamata Disease?

2200 Signup and view all the answers

Which demographic was particularly impacted by congenital effects of mercury poisoning in Minamata?

Newborns and infants Signup and view all the answers

What legal action was taken by victims of mercury poisoning in the Minamata case?

Victims received compensatory payments from the Chisso Corporation. Signup and view all the answers

What long-term impact was observed at the Grassy Narrows and White Dog First Nations Reserves?

Enduring effects of mercury poisoning on community health Signup and view all the answers

What was the total estimated amount of neurotoxicants dumped by the Dryden Chemical Company between 1962 and 1970?

10 tonnes Signup and view all the answers

How did the Government of Japan approach the criteria for methylmercury poisoning as of 2006?

They maintained a strict standard established in 1977. Signup and view all the answers

What type of effects were observed in the local cat population due to mercury exposure in Minamata?

Neurotoxic effects Signup and view all the answers

What is the implication of a Selenium Health Benefit Value (SeHBV) less than 0?

Increased mercury and decreased selenium indicate net risk. Signup and view all the answers

How is the Se:Hg ratio calculated?

Total selenium concentration divided by total mercury concentration. Signup and view all the answers

What is the first step in determining the selenium concentration in Northern Pike?

Looking up the selenium value from Health Canada. Signup and view all the answers

Based on the provided information, what is the molar conversion for 500 µg/kg of selenium?

6.33 µmol/kg Signup and view all the answers

What is the calculated ratio of mercury to selenium (Hg:Se) if [Hg] = 1.25 µmol/kg and [Se] = 6.33 µmol/kg?

0.20 Signup and view all the answers

Which molecular weight is used for calculating the concentration of mercury in µmol/kg?

200.59 g/mol Signup and view all the answers

What happens when the SeHBV is equal to or greater than 0?

Selenium intake is considered safe. Signup and view all the answers

Why is the ratio of [Se]:[Hg] essential in assessing health benefits?

It determines the net risk associated with mercury levels. Signup and view all the answers

Which is the correct formula to express Selenium Health Benefit Value (SeHBV)?

Se μmol/kg × (Se μmol/kg - Hg μmol/kg) Signup and view all the answers

What does an increased Se:Hg ratio signify regarding fish consumption?

Higher selenium results in lower health risks. Signup and view all the answers

What is the unit for measuring selenium concentration in the given equations?

µmol/kg Signup and view all the answers

Which formula correctly represents the Selenium Health Benefit Value (Se HBV)?

Se HBV = [Se] µmol × (Se kg) - [Hg] µmol × (µmol Hg kg) Signup and view all the answers

If the mercury content of the pike increases to 2.8 mg/kg, what is the expected impact on Se HBV?

Se HBV will likely decrease. Signup and view all the answers

What conversion is necessary when calculating selenium concentration from a given value in µg/kg?

Divide by 78.96 g/mol Signup and view all the answers

What is the selenium level [Se] in the example provided?

6.33 µmol/kg Signup and view all the answers

In the selenium-health benefit value formula, which component negatively affects the Se HBV?

[Hg] µmol Signup and view all the answers

What is the maximum selenium concentration related to health benefits based on the example?

500 µg/kg Signup and view all the answers

Which of the following values represents mercury content [Hg] in the provided data?

5.08 Signup and view all the answers

Study Notes

Environmental Exposures to Mercury

Mercury is a metal released into the ecosystem naturally (forest fires, volcanic eruptions) and through human activities (coal burning, metal smelting).
In its elemental form, mercury is stable in the air and travels far from its source.
When deposited, mercury transforms into methylmercury, an organic and toxic form.
Methylmercury accumulates in living organisms (plants, animals, humans) reaching levels posing health risks.
The primary route of mercury exposure for humans is through consuming fish and specific wildlife.
Over 90% of fish advisories in Canada relate to mercury contamination, affecting various fish and wildlife.
Arctic wildlife faces higher mercury levels, posing health risks to northern Canadians due to traditional food consumption.
Metallic mercury (Hg⁰) is a liquid metal at room temperature.

Sources of Exposure to Mercury and Methylmercury

Individual exposures arise from dental amalgams, religious practices, thermometers, and barometers.
Community exposures result from mining, fossil fuel combustion, waste incineration, and industrial processes impacting aquatic environments.
Mercury exposure pathways include air, water, and through food.
Consequently, mercury is deposited in water and transformed through bio-accumulation to methylmercury in food and subsequently to human tissue.

The Mercury Cycle

Mercury is emitted into the atmosphere.
Mercury is deposited in rain, snow, and as gases/particles.
Methylmercury bioaccumulates in food webs.
Mercury is transported through watersheds and converts into methylmercury.
Mercury accumulates in lakes, reservoirs, and forests.

Movement of Mercury in the Environment

Mercury vapor (Hg⁰), a stable gas, evaporates from the Earth's surface (soil and water) and is emitted by volcanoes.
Anthropogenic sources include coal-burning power stations, municipal incinerators.
Mercury vapor transforms to its soluble form (Hg²⁺) and is returned to Earth by rainwater, converting back to vapor by microorganisms, recirculating for extended periods.
Mercury attached to sediments undergoes microbial conversions to methylmercury, building up in aquatic organisms—plankton, herbivorous fish, and carnivorous fish and mammals.
Human exposure is through consuming fish, specifically concerning the developing fetus.

Fish Mercury Regulatory Values

Canadian Food Inspection Agency has a 0.5 ppm limit on retail-purchased fish (excluding shark, swordfish, fresh/frozen tuna).
Consumer advisory (2002) provides dietary advice for consuming exempted fish: general adult population (1 meal/week), women of child-bearing age (1 meal/month), and young children (1 meal/month).
A non-enforceable guideline of 0.2 ppm is used for risk assessments involving frequent fish consumers.

Advice on Sport Fishing in Ontario

Ontario's guide provides information on safe fish consumption amounts and sizes, fish selection with the lowest contaminant levels, advice for children and pregnant women, and preparing fish to reduce contaminants.

Mercury Tolerable Daily Intake

Total Mercury for the General Population (BCS 2007): 0.71 µg/kg/d
Methylmercury for the General Population (BCS 2007): 0.47 µg/kg/d
Methylmercury for Sensitive Sub-populations (BCS 2007): 0.20 µg/kg/d
WHO 2003: 0.23 µg/kg/d

Sport Fish Consumption Advisories

Regional variations exist concerning the percentages of restricted fish, PCB, mercury, and dioxin/furan contamination, affecting consumption advisory levels.

Organic Mercury Compounds

Organic mercury compounds include methylmercury (MeHg), ethylmercury (EtHg), dimethylmercury, and thiomersal.

Molecular Mimicry: Methylmercury

Methylmercury (MeHg) mimics the methyl sulfur group in the amino acid methionine.

Transport of Methylmercury

Methylmercury and possibly ethylmercury (EtHg) are transported across the blood-brain barrier via the amino acid transporter LAT1, possibly mimicking methionine.

Evaluation of Cardiovascular Effects of Methylmercury

Research data suggests a dose-response correlation between methylmercury exposure (hair Hg concentration) and increased cardiovascular disease risk.

Myocardial Infarction and Risk-benefit Analysis

Mercury and fatty acids from fish consumption can impact cardiovascular health.
Risk-benefit analysis based on pooled Finnish and Swedish data indicates a potential adverse increase in myocardial infarction cases related to Hg concentration, with protective role from S-PUFA (saturated polyunsaturated fatty acids).

Mercury Emissions

Global issue with major contributions coming from outside Canada.
China accounts for a significant portion of global mercury emissions across various industrial sectors.

Minamata Convention on Mercury

A global treaty protecting human health and the environment from mercury's adverse effects.
Agreement established in Geneva in January 2013.
First signatory and ratification in June 2013 by the US, and signature in October 2013 by Canada and 85 other countries.
Controls focus on coal-fired power plants, small-scale artisanal gold mines, and banning new mercury mines.

Production, Import and Export of Certain Mercury-containing Items

Some mercury-containing items, such as batteries (with exception of implantable medical device button cells), compact fluorescent lamps, switches, relays, soaps, and cosmetics, thermometers, and blood pressure devices, are targeted for banning by 2020.

Minamata Disease

Neurological and neurotoxic effects in adults, and congenital neurodevelopmental effects.
Minamata Bay, Japan case study illustrating severe methylmercury poisoning from industrial contamination impacts human health and the environment.
Japan's investigations helped raise awareness of this disease

The Grassy Narrows and the White Dog Reserves

Mercury poisoning affected two First Nations communities, Grassy Narrows, and White Dog, near Dryden, Ontario, Canada.
Local paper mill dumped large amounts of methylmercury into the English-Wabigoon River, leading to contamination in lakes and rivers.
Significant neurotoxic effects.
Cases of contamination exceed those of Minamata disease from the outset.
Health and socio-economic effects.

Molecular Sequestration: Selenium

Selenium (Se) is a metalloid displaying a high affinity for mercury in both inorganic and organic forms within tissues.
Selenium has a significantly higher affinity for mercury than sulfur. Selenium binds to mercury sequestering it for extended periods.
Se is thought to provide a protective mechanism for mercury sequestering in organs. The role of selenium binding on brain tissue is still debated.

MeHg Neurotoxicity and Selenium

Adverse effects from high MeHg doses in humans and animals.
Low MeHg dose implications remain debated in epidemiology due to varying results.
Relevant case studies explored using epidemiologic data from Seychelles and Faroe Islands, with contrasting implications based on specific dietary composition including Selenium.
High selenium intake protects against MeHg toxicity in humans and animals.
MeHg impacts selenium enzyme activity.
Selenium sequestration is a primary mechanism for MeHg toxicity.

Selenium Health Benefit Value

A method developed to calculate a relative ratio of selenium to mercury in seafood, indicating whether or not a food provides selenium in a ratio high enough to offset the risk of mercury exposure.

Relationship Between Selenium and Mercury

The relationship between selenium and mercury in food (like fish) needs to be considered; exposures must assess both elements due to the protective role of Se.
Selenium's impact on health benefits in different seafoods can vary; Selenium Health Benefit Value (SeHBV) measures not only mercury contamination but also the selenium content for relative risk assessment.
Mercury and selenium molar ratios and amounts can indicate potential MeHg risk.
SeHBV calculation involves dividing the selenium content by the mercury content. A positive SeHBV indicates a positive benefit from selenium in offsetting mercury risk.

Toxic Xenobiotics in Breast Milk

Many toxic xenobiotics accumulate in adipose tissues, including organochlorine pesticides (aldrin, chlordane, DDT), polychlorinated biphenyls (PCBs), dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and metals like lead, are secreted into breast milk.
Breast milk has a slightly acidic pH allowing concentration of specific compounds.
Compounds diffuse into breast milk, primarily through simple diffusion or mammary gland transporters.

BCRP as a Mechanism of Infant Exposure from Breast Milk

The transporter BCRP (ABCG2) actively secretes toxicants from the mammary glands into breast milk.
It handles a diverse array of compounds including pharmaceuticals (Cimetidine, Nitrofurantoin, Acyclovir, and Topotecan).
BCRP activity influences exposure to foodborne carcinogens such as heterocyclic amines (PhIP, IQ) and toxins like aflatoxin B1.

Elimination Kinetics of Organochlorine Compounds

Organochlorine compounds elimination kinetics are assessed in breast-feeding women (day 2 to 10 postpartum).
Plasma lipid content plays a significant role in organochlorine concentration changes during this period, impacting the observed levels.

Toxicant Breast Milk to Material Plasma Ratio

Toxicant concentrations in breast milk compared to maternal plasma vary, and some like lead have a higher ratio than PCBs, DDT, alcohol, nicotine, and caffeine.

Pros and Cons of Breast Milk in Biomonitoring

Pros: non-invasive, rich in lipids, integrates mother/infant historical/current exposures, and provides exposure assessment for children and women.
Cons: sample collection only from lactating women, burden during initial postpartum period, and may mislead consumer attitudes concerning exposure and safety.

Organochlorines in Breast Milk

Levels of organochlorines (e.g., dioxins) in breast milk are decreasing over time, and different countries show different levels.

Brominated Contaminants in Breast Milk

Trends in concentrations of brominated contaminants in Swedish breast milk, specifically PCBs and PBDEs.

Polybrominated Diphenyl Ethers (PBDEs)

A group of 209 organobromine compounds.
They are used commercially as flame retardants and are present in many consumer products, such as electronic equipment, furnishings, building materials, motor vehicles, and textiles.

Why Are We Concerned About PBDEs

PBDEs bioaccumulate, like PCBs and dioxins/furans, in body tissues and fluids, including blood, breast milk, and fatty tissues.
They have a long environmental half-life, and bioaccumulate in wildlife.
Exposure is present in common household items and common food sources (beef, fish, butter, cheese).
Increased PBDE concentrations in indoor dust suggest significant exposures.

What Have We Done About PBDEs

In 2009, the chemical constituents penta-BDE and octa-BDE were added to the Stockholm Convention as Persistent Organic Pollutants (POPs);
In 2008, penta-BDE and octa-BDE were declared “CEPA-toxic” and slated for near elimination by the Canadian Environmental Protection Act (CEPA);
Subsequent studies and further management plans implemented to restrict PBDE use.

Flame Retardants in Furniture

Brominated flame retardants (BFRs) were added to furniture to comply with various flammability standards, originally in California in 1975.
Key chemicals include PentaBDE, TDCPP, TB117-2013 standard, and various other components now under different standards.

Fire Safety Evaluation

The use of flame retardants (i.e., TB117) for preventing ignition from small flames is ineffective according to various studies.
Flame retardants (TB117) negatively impact fire severity by producing significant amounts of smoke, soot, and carbon monoxide (potentially causing fatal health outcomes).

Human Health Evaluation

PentaBDE levels are high in the United States and Canada.
Young children have higher levels than parents in many studies.
PentaBDE is found in blood, fat, cord blood, breast milk globally, and pentaBDE levels in dust correlate significantly.
Breast milk pentaBDE levels are associated with undescended testis.
A relationship exists between hormone alterations and pentaBDE levels in house dust.
PentaBDE is associated with increased gestation time in exposed women.
20% of women with the highest pentaBDE levels exhibit lower IQ scores (5-8 points).
TPP and TDCPP correlate with lower sperm counts
Exposure to high pentaBDE levels prenatally is associated with negative motor, cognitive, and behavioural outcomes.
TB117 needs re-evaluation to protect human health.

Update on TB117

The old TB117 standard was implemented in 1975 in California.
It required particular characteristics of polyurethane foam materials to withstand specific fire conditions, requiring particular chemical additives.
The new 2013 standard adopted a performance based method; this new standard does not require flame retardant chemicals to meet flammability standards, unlike the previous standard.

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Description

Test your knowledge on mercury exposure routes, environmental impacts, and health risks associated with mercury. This quiz covers key concepts regarding the toxicity of mercury, its presence in fish, and the implications for public health, with a focus on Canadian fish advisories. Explore the solutions for addressing mercury emissions globally.