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Unit Code 82385:
Heavy Metals Screen Occupational Exposure, Urine

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Useful For

Screening potentially exposed workers for heavy metal toxicity

in settings where a 24-hour collection is problematic

Clinical Information

Arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) are

well-known toxins and toxic exposures are characterized by

increased urinary excretion of these metals.

 

Arsenic exists in a number of different forms; some are toxic while others

are not. Toxic forms, which are typically encountered as a result of

an industrial exposure, are the inorganic species As ( 3) (As-III) and

As ( 5) (As-V) and the partially detoxified metabolites,

monomethylarsine (MMA) and dimethylarsine (DMA). The 2 most

common nontoxic forms are arsenobetaine and arsenocholine.

Arsenic toxicity affects a number of organ systems.

 

Lead toxicity primarily affects the gastrointestinal, neurologic, and

hematopoietic systems.

 

Chronic exposure to Cd causes accumulated renal damage.

 

Mercury is essentially nontoxic in its elemental form. However, once

it is chemically modified to the ionized, inorganic species, Hg( ),

it becomes toxic. Further bioconversion to an alkyl Hg, such as

methyl Hg (CH[3]Hg[ ]), yields a species of Hg that is highly

selective for lipid-rich tissue, such as the myelin sheath, and is

very toxic.

Reference Values

ARSENIC

  <50 ug/g creatinine

MERCURY

  <35 ug/g creatinine

CADMIUM

  <3.0 ug/g creatinine

LEAD

  <150 ug/g creatinine

Interpretation

The reference intervals for this test are Occupational Safety and

Health Adminstration (OSHA) thresholds.

 

The ordering physician will be contacted regarding any result

exceeding OSHA thresholds to determine the level of workplace

exposure and follow-up action.

 

Arsenic results exceeding the OSHA threshold will be fractionated to

confirm the presence of toxic forms.

 

Measurement of urine excretion rates either before or after chelation

therapy has been used as an indicator of Pb exposure. However,

blood Pb analysis has the strongest correlation with toxicity.

 

Normally, the excretion of Cd is proportional to creatinine.

When renal damage has occurred, Cd excretion increases

relative to creatinine.

 

The correlation between the levels of Hg in the urine and clinical

symptoms is poor, but urinary Hg is the most reliable way to

assess exposure to inorganic Hg.

Cautions

Nitric acid cannot be added to either the collection or aliquot

container. Nitrate interferes with the extraction procedure that

would need to take place in the event of a positive As result.

 

High concentrations of gadolinium and iodide are known to

interfere with most metals tests. If either gadolinium or iodide-

containing contrast media has been administered a specimen

can not be collected for 48 hours.

 

This test is intended for use as a screening tool for occupational

monitoring. It is not a replacement of #8633 "Heavy Metals Screen,

Urine".

Special Instructions and Forms

• Metals Analysis - Collection and Transport 

Clinical Reference

Handbook on Metals in Clinical and Analytical Chemistry, Edited

by HG Seiler, A Sigel, H Sigel. Marcel Dekker, Inc., New York, 1994

Key