What Raises Mercury Levels in People and the Environment?

Human activities have increased atmospheric mercury concentrations by nearly seven times above natural levels. These elevated levels of mercury, a neurotoxin, can pose significant health risks when it enters the food chain and is absorbed by the body. Understanding what raises mercury levels is crucial for protecting human health and the environment.

Quick Summary

Mercury levels increase in people and the environment primarily due to human activities like industrial emissions, mining, and waste incineration. The highly toxic form, methylmercury, accumulates in fish and shellfish, posing the greatest threat to human health through diet. Other sources include dental amalgam and certain consumer products.

Key Points

• Human Activities Dominate Pollution: Industrial practices like burning coal and gold mining release large quantities of mercury.

• Dietary Intake is the Main Risk for Humans: The greatest exposure occurs through eating contaminated fish and shellfish.

• Bioaccumulation Drives Fish Contamination: Mercury levels are highest in large, predatory fish due to biomagnification.

• Vulnerable Populations Face Higher Risks: Fetuses, young children, and people with high fish consumption are most susceptible.

• Household Products Pose a Threat: Items like fluorescent bulbs and old thermometers contain mercury.

• Global Action is Underway: The Minamata Convention aims to regulate and reduce mercury emissions.

Human Activity: The Primary Driver of Mercury Pollution

Human activities are overwhelmingly responsible for elevated mercury levels globally. Anthropogenic sources account for a significant majority of annual mercury emissions.

Key Anthropogenic Sources:

• Coal-Fired Power Plants: Burning coal releases mercury into the atmosphere.
• Artisanal and Small-Scale Gold Mining (ASGM): This practice uses elemental mercury, releasing it into the air and waterways.
• Industrial Processes: Manufacturing and waste incineration contribute to mercury releases. Improper disposal of mercury-containing products like batteries and light bulbs also contributes.
• Dental Amalgam: These fillings contain elemental mercury.
• Certain Skin-Lightening Creams: Some illegal cosmetics contain mercury compounds.

Bioaccumulation in the Food Chain

Mercury deposited in soil and water is converted to methylmercury by microorganisms. Methylmercury bioaccumulates in the food chain, posing a threat to human health through consumption.

The Process of Biomagnification:

1. Small organisms absorb methylmercury from water.
2. Larger fish eat smaller organisms, accumulating higher concentrations.
3. Predatory fish amass the highest levels.

Natural Contributions to Mercury Levels

Natural events like volcanic eruptions, geothermal activity, and forest fires release mercury, but human activity's impact is significantly larger.

Comparison of Major Mercury Sources

Source Category	Primary Form of Mercury Released	Route of Exposure to Humans	Relative Contribution to Global Emissions
Artisanal Gold Mining	Elemental mercury vapor	Inhalation, environmental contamination	Very high.
Coal Combustion	Elemental mercury vapor	Inhalation, bioaccumulation via water	High.
Fish Consumption	Methylmercury	Ingestion	Most common dietary cause.
Dental Amalgam	Elemental mercury vapor	Inhalation	Low-level chronic exposure for individuals.
Volcanic Activity	Elemental mercury vapor	Inhalation, environmental contamination	Significant natural source, but less than human activity.
Industrial Waste	Various forms	Environmental contamination, inhalation	Varies by industry and waste type.

Conclusion

Elevated mercury levels in the human body are primarily caused by environmental pollution from human industrial and mining activities. Consuming large, predatory fish contaminated with methylmercury is the most common route of high-level exposure for the general population. Global efforts and informed dietary choices are essential to reduce mercury levels and exposure.

Lists of Mercury-Containing Items and High-Mercury Fish

Common Household Items Containing Mercury

• Batteries: Some older types.
• Fluorescent Light Bulbs: Both linear and compact types.
• Thermostats and Thermometers: Older models.
• Electrical Switches: In appliances and automotive systems.
• Some Cosmetics: Illegally imported skin-lightening creams.

Fish Species with Higher Mercury Levels

• Shark
• Swordfish
• King Mackerel
• Tilefish
• Bigeye Tuna
• Marlin
• Orange Roughy

Ways to Reduce Mercury Exposure

To reduce mercury exposure, consider these actions:

• Check Local Fish Advisories: Consult local guidelines if catching your own fish.
• Switch to Lower-Mercury Fish: Choose species like salmon and sardines.
• Handle Spills Safely: Follow EPA guidelines for cleaning broken mercury items.
• Inquire About Dental Fillings: Discuss non-amalgam options with your dentist if pregnant or planning pregnancy.
• Dispose of Products Properly: Dispose of mercury-containing products as hazardous waste.

For more information on mercury and health, see the World Health Organization (WHO): World Health Organization - Mercury and health.

Individual Risk Factors for Elevated Mercury Levels

Populations such as developing fetuses, young children, individuals with high fish consumption, and workers in certain industries are more susceptible to high mercury levels and their effects.

The Global Response to Mercury

The Minamata Convention on Mercury is a global treaty to protect human health and the environment by addressing emissions, reducing mercury use in products, and minimizing releases. Challenges remain, particularly from small-scale gold mining.

In-utero and Childhood Exposure Risks

Methylmercury can cross the placenta, potentially impacting fetal nervous system development. Studies suggest a link between prenatal exposure and developmental delays. Children can also be exposed through breast milk or contaminated soil.

Frequently Asked Questions

What is the most common cause of high mercury levels in humans?

The most common cause is consuming fish and shellfish contaminated with methylmercury. This form accumulates in aquatic life through bioaccumulation.

Which types of fish are highest in mercury?

Large, predatory, long-lived fish have the highest mercury levels. Examples include shark, swordfish, and king mackerel.

How does human activity contribute to mercury pollution?

Human activities like burning coal, gold mining, and industrial manufacturing are primary causes.

Are dental fillings a source of mercury exposure?

Amalgam fillings contain elemental mercury. Inhalation exposure is possible, especially during placement or removal.

What are natural sources of mercury in the environment?

Natural sources include volcanic eruptions and forest fires, but human emissions are significantly larger.

Who is most at risk from mercury exposure?

Fetuses, young children, those who eat a lot of high-mercury fish, and workers in certain industries are most vulnerable.

How can I reduce my dietary mercury intake?

Limit large predatory fish and choose lower-mercury options like salmon and sardines. Check local advisories.