Pathology Handbook




Clinical Indications

Suspected toxicity. Metallic mercury vapour is toxic and inhalation of high concentrations may give rise to pneumonitis and pulmonary oedema. Chronic exposure to lower concentrations causes gingivitis and stomatitis with excessive salivation, headaches and CNS effects.
Ingestion of inorganic mercury salts produces abodominal pain, vomiting and corrosion of mucosal membranes and following absorption, renal tubular necrosis.
There is little evidence of long term hazard to patients from use of mercury in dental amalgam (mixture of metallic mercury and a silver-tin alloy).  However, preparation of such amalgams can be hazardous to dental personnel if insufficient precautions are not taken.  Symptoms of long-term exposure may be vague in the form of headaches and irritability.

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Analysed by referral laboratory if specific criteria met.

Specific Criteria

If agreed with Consultant Biochemist

Turnaround Time

One month

Sample type

Urine mercury determination is preferred for exposure to mercury vapour or inorganic mercury salts e.g. amalgam fillings

Blood mercury determination is preferred for exposure to organic mercury derivatives e.g. industrial exposure

Confirmatory 24 hour urine If screening test is positive a 24 hour urine mercury level should be measured. Urine should be collected into a nitric acid washed 24 hour urine bottle. To prepare the bottle fill with 10% nitric acid. Stand for at least 24 hours. Discard the acid but do not rinse the bottle before giving to the patient.


Urine is normally used for the initial screening test


Urine bottle white top

Early-morning urine sample (for screening test)

Vacutainer lemon top

Biochemistry EDTA sample for blood mercury

Lab Handling

Sent to referral laboratory (Royal Surrey County Hospital)

Causes for Rejection

Unlabelled or incorrectly labelled sample; sample in wrong container; not meeting specific criteria for analysis 

Reference range:

 1. Blood
Normal population  - <20 nmol/L (< 4 μg/L)
Industrial exposure - <76 nmol/L (<15μg/L)

2. Urine
Less than 50 nmol/24h (< 10 μg/24h)
Less than 5.5 nmol/mmol creat in early morning samples (<10μg/g creat)