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Table 3 Diagnosis of chronic mercury intoxication (adapted from[32])

From: The burden of chronic mercury intoxication in artisanal small-scale gold mining in Zimbabwe: data availability and preliminary estimates

[a] Diagnostic algorithm

Exposure limit values [b]

Medical score sum [c]: Low (0-4)

Medical score sum [c]: Mediun (5-9)

Medical score sum [c]: High (10-21)


Hg in all biomonitors <HBM I

no intoxication

no intoxication

no intoxication


Hg in at least one biomonitor >HBM I and <HMB II

no intoxication

no intoxication



Hg in at least one biomonitor >HBM II and <BAT

no intoxication




Hg in at least one biomonitor >BAT




[b] Exposure limit values* for mercury in human biomonitoring samples

Exposure limit values

Hg in blood (μg/l)

Hg in urine (μg/l)

Hg in urine (μg/g crea.)

Hg in hair (μg/g)








>HBM I and <HBM II






>HBM II and < BAT











c] Indicators of the medical score sum


Clinical examination

Neuropsychological tests

(0/1): 0= negative; 1= positive; (0/1/2): 0= good, 1= restricted, 2= poor performance; maximum medical score sum: 21 points

Metallic taste (0/1)

Bluish coloring of the gingiva (0/1)

Frostig test1 (0/1/2)


Excessive salivation (0/1)

Ataxia of gait (0/1)

Matchboxtest2 (0/1/2)


Tremor at work (0/1)

Finger-to-nose tremor (0/1)

Memory test3 (0/1/2)


Sleeping problems at night (0/1)

Dysdiadochokinesia (0/1)

Pencil tapping test4 (0/1/2)


Health problems worsened since

Heel-to-knee ataxia (0/1)


having been exposed to

Heel-to-knee tremor (0/1)


mercury (0/1)

Mento-labialreflex (0/1)


Proteinuria (0/1)

  1. *HBM I and II for blood and urine [3436]; BAT for blood and urine [37]. HBM I for hair derived by Drasch et al. [32] from the U.S. EPA [38] benchmark limit. HBM II for hair derived by Drasch et al. [32] from the HBM II value for blood [3436] in combination with results from the Seychelles study [39].
  2. 1Frostig test for examining tremor and visual-motor capacity: The test person must draw a straight line from one symbol to another across a narrow gap without touching the surrounding areas or breaking the line. This is a subtest of a more detailed test by Lockowandt [40].
  3. 2Matchbox test for examining coordination, intentional tremor and concentration: The test person must collect matches and put them in the matchbox as quickly as possible while alternating hand. The matchbox test is part of the MOT (Motoriktest) test battery developed by Zimmer and Volkamer [41].
  4. 3Memory test for short-term memory: The test subject must repeat numbers shown in columns in the correct order. This test was developed by Masur [42].
  5. 4Pencil tapping test for examining intentional tremor and coordination: The test person must make as many dots as possible in 10 seconds by repeatedly tapping a pencil on a piece of paper. This test is also part of the MOT battery [41].
  6. BAT: Biologischer Arbeitsplatztoleranzwert, the maximum acceptable concentration at the workplace; crea.: creatinine; HBM I and II: Human Biomonitoring values from the Human Biomonitoring Commission of the Federal Environmental Agency; Hg: mercury.