Dried Urine ICPMS Toxic and Essential Elements

Mercury exists in multiple forms — elemental, inorganic, and organic (methylmercury). Urinary excretion predominantly reflects inorganic and elemental exposure (dental amalgam, occupational vapour), whereas organic mercury from fish is largely excreted in faeces. Renal proximal-tubule transport actively secretes inorganic mercury into urine, making it a useful marker of recent exposure.

Elevated urinary mercury may indicate amalgam burden, occupational exposure, or recent chelation. It does not reliably reflect methylmercury body burden from dietary sources, which requires blood or hair analysis. Practitioners use urine mercury to screen patients with suspected inorganic exposure or to monitor post-amalgam-removal excretion.

Lead accumulates in bone over decades and is slowly released into blood; urinary lead reflects recent exposure and the exchangeable pool. After acute exposure or provocation with a chelator, urinary lead rises sharply. Baseline (unprovoked) urine lead correlates only loosely with total body burden.

Urinary lead is used to screen for ongoing exposure (paint, water, occupation) and to quantify excretion during chelation. Blood lead remains the standard for diagnosis and surveillance, while urine lead adds information about renal excretion and chelation response.

Cadmium is absorbed from tobacco smoke and contaminated food (rice, leafy greens grown in polluted soil) and accumulates in the kidneys, where it has a half-life measured in decades. Urinary cadmium reflects cumulative body burden rather than recent exposure, because renal tubular cells damaged by cadmium leak it into urine.

Elevated urinary cadmium indicates significant body burden and is a marker of chronic exposure, most commonly from smoking. It is associated with renal tubular dysfunction, bone demineralisation, and increased cardiovascular risk at higher levels. Practitioners order it to assess exposure history in smokers and to investigate possible toxic nephropathy.

Arsenic appears in water (well water in endemic regions), rice, and seafood. Inorganic arsenic and its methylated metabolites (monomethylarsonic and dimethylarsinic acids) are toxic; organic arsenobetaine from seafood is rapidly excreted and non-toxic. Total urinary arsenic without speciation can be misleading after a seafood meal.

Urinary arsenic is the screening test for recent inorganic exposure. Speciation distinguishes toxic inorganic forms from benign seafood arsenic. Chronic inorganic arsenic is a carcinogen (skin, bladder, lung) and raises cardiovascular risk; acute high-level exposure causes gastrointestinal and neurological toxicity.

Aluminium is ubiquitous in soil, water, food, and consumer products; normal gastrointestinal absorption is low. In renal failure, retention can occur, historically causing dialysis encephalopathy and bone disease. In healthy kidneys, absorbed aluminium is efficiently excreted in urine.

Elevated urinary aluminium in individuals with normal renal function may reflect high exposure (occupational, contaminated water, or certain antacids) but is rarely linked to clinical toxicity outside the setting of renal impairment. Its significance in functional-medicine testing is debated.

Zinc is an essential trace element, cofactor for hundreds of enzymes, and critical for immune function, wound healing, and protein synthesis. Serum and red-cell zinc are more commonly used to assess status; urinary zinc reflects recent intake and renal handling but is less informative about total-body stores.

Urinary zinc is sometimes included in multi-element panels but has limited standalone clinical utility. High urinary loss can occur with renal tubular disease or high-dose supplementation; interpretation requires correlation with serum zinc and clinical context.

Copper is an essential trace element bound to caeruloplasmin in serum. Urinary copper reflects free, non-caeruloplasmin-bound copper and is low in healthy individuals. Elevated urinary copper is the hallmark of Wilson disease, where impaired biliary excretion leads to toxic accumulation and increased renal loss.

Urinary copper is critical in the diagnosis and monitoring of Wilson disease (typically >100 μg/24 h, or proportionally in spot samples). In other contexts, elevated urinary copper may be seen with hepatocellular necrosis releasing stored copper or with high-dose supplementation. Low urinary copper has no established clinical significance.

Selenium is an essential trace element, component of selenoproteins (glutathione peroxidases, thioredoxin reductases) with antioxidant and thyroid-hormone-metabolism roles. Urinary selenium reflects recent dietary intake and is influenced by supplementation; plasma selenium is a better marker of status over weeks to months.

Urinary selenium is included in comprehensive element panels but is rarely used in isolation. Deficiency is uncommon outside areas with selenium-poor soil; excess intake (chronic selenosis) causes hair and nail brittleness and neurological symptoms. Serum selenium is the preferred clinical marker.

Copper and zinc interact at the level of absorption (competition via metallothionein) and cellular metabolism. The serum copper-to-zinc ratio is used in some clinical contexts (inflammation, oestrogen states); the urinary ratio is less well characterised and reflects renal handling more than systemic status.

Elevated urinary copper-to-zinc ratios have been explored in functional medicine as markers of oxidative stress or zinc deficiency, but evidence is limited. Serum or red-cell measurements of both elements are more established tools for assessing balance.