Mercury

Mercury can be absorbed by the human body through several pathways, depending on its form (elemental, inorganic, or organic):

Absorbtion

• Inhalation (breathing in): Elemental mercury vapor is readily absorbed through the lungs when inhaled and quickly enters the bloodstream, distributing to organs including the brain and kidneys

• .
• Ingestion (eating):

• Inorganic mercury compounds: About 7–15% is absorbed through the gastrointestinal tract after ingestion

• Organic mercury (methylmercury): Almost completely absorbed (over 90%) when ingested, especially from fish and seafood

• Elemental mercury: If swallowed, less than 0.01% is absorbed through the gut due to its poor solubility

• Skin contact:

• Elemental mercury: Very little is absorbed through intact skin

• Inorganic mercury compounds: Can be absorbed through the skin, especially when used in products like skin-lightening creams

Mercury is primarily found in seafood, but trace amounts can also be present in other foods depending on environmental contamination:

Nearly all fish and shellfish contain some mercury, especially as methylmercury, which is the most toxic form- .

Mercury can accumulate in rice grown in contaminated soil or water, particularly in areas near industrial or mining activities- .

Leafy and root vegetables can absorb mercury from contaminated soil, water, or air, but generally at much lower levels than seafood- .

: Wine and cereals may contain trace amounts if grown or processed in contaminated areas, but these are minor sources compared to seafood

• .

Toxicity and Accumulation

• Toxicity: Mercury is highly toxic to the nervous, digestive, and immune systems, as well as to the lungs, kidneys, skin, and eyes. It can interfere with enzyme function by binding to sulfhydryl (SH) groups, leading to tissue damage and disrupted metabolic processes

• .
• Accumulation: Mercury accumulates in the body, particularly in the kidneys (for inorganic mercury) and brain (for elemental mercury vapor)

. Methylmercury accumulates in tissues and is especially concerning for fetuses and infants, as it can cross the placenta and be passed through breast milk

• .

Diseases and Health Effects

• Neurological effects: Tremors, memory loss, irritability, vision and hearing disturbances, muscle weakness, and lack of coordination. Severe cases can lead to permanent brain damage

• .
• Kidney damage: Inorganic mercury targets the kidneys, leading to kidney failure in severe cases
• .
• Digestive issues: Nausea, vomiting, diarrhea, and abdominal pain
• .
• Developmental effects: Exposure in utero or in early childhood can impair brain development, resulting in learning disabilities and developmental delays
• .
• Other effects: Lung damage (from inhalation of vapor), skin rashes, and immune system impairment

• .

Safe Levels

• General population: Safe exposure levels are set by regulatory agencies such as the EPA and WHO. For example, the WHO sets a provisional tolerable weekly intake (PTWI) for methylmercury at 1.6 μg/kg body weight per week for adults

• .
• Occupational exposure: Lower limits are set for workplace exposure to mercury vapor and other forms.
• Blood and urine levels: Blood mercury is a biomarker for recent or high-level exposure, while urine mercury is used for long-term exposure assessment

• .

Summary Table

Mercury exposure is a significant public health concern, and even low levels can be harmful, especially to vulnerable populations such as pregnant women and children

.