Clinical Information

The correlation between the levels of mercury (Hg) excretion in the urine and the clinical symptoms is considered poor.

Previous thought indicated urine as a more appropriate marker of inorganic mercury because organic mercury represented only a small fraction of urinary mercury. Based on possible demethylation of methylmercury within the body, urine may represent a mixture of dietary methylmercury and inorganic mercury. Seafood consumption can contribute to urinary mercury levels (up to 30%),(1) which is consistent with the suggestion that due to demethylation processes in the human body, a certain proportion of urinary mercury can originate from dietary consumption of fish/seafood.(2)

Small amounts of mercury are often present in urine, often stemming from environmental exposure or from dental amalgam. The amount of mercury in urine depends upon the form of mercury, the level and duration of mercury exposure, and the elapsed time between exposure and urine sample collection.

For potential mercury vapor exposure: urine mercury levels are unlikely to be useful for assessing potential health effects from short-term, low-level exposures to mercury vapor because such exposures are unlikely to result in mercury urine levels elevated above typical values. High level mercury vapor exposure or long-term, low-level vapor exposures may result in elevated urine mercury levels, which can indicate potential for health effects. Random urine mercury level is adjusted to concentration of creatinine.

Urine mercury concentrations in unexposed individuals are typically less than 10 mcg/L (50 nmol/L) or 2 mcg/g creatinine. Twenty-four-hour urine concentrations of 30 mcg/L to 100 mcg/L (150-499 nmol/L) may be associated with subclinical neuropsychiatric symptoms and tremor, while concentrations greater than 100 mcg/L (499 nmol/L) can be associated with overt neuropsychiatric disturbances and tremors.(4)

Mercury concentrations of greater than 10 mcg/g creatinine may associate with subtle effects on visual memory, attention, manual coordination, mood, increased levels of fatigue and confusion. Higher level of urine mercury is associated with increasing frequent and severe nervous system changes in personality, cognition, and coordination.(3)

Mercury concentrations of 20 mcg/g to 35 mcg/g creatinine may be associated with hand tremors and potential kidney damage.(3)