A comparative assessment of some biochemical markers in occupational lead exposure.

2. Introduction  Lead, an industrially  useful metal with
wide applications.
  Industrialization  use ………… 
Pollution.
 Biologically Pb has no role, useless,
unwanted mineral for living organisms.
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3.  Occupations such as Lead
battery manufacturing, silver
Industrial use of LEAD jewelry making, painting have
inherent dangers of lead
toxicity.
 Occupational exposure at
small scale units in developing
countries unregulated.
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4. Lead is used as alloy in making
LEAD
Silver Jewelry
all types of Silver Jewelry. And
for marking designs on silver
rings.
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6. Lead (Pb)  Lead toxicity   most organ systems.
Major Hematological, Nervous etc
 Moderate to clinically significant toxicity is
very common in small scale industrial units.
Metarubricytosis and slight
basophilic stippling of
erythrocytes in lead
toxicosis. The remaining
erythrocytes appear
hypochromic because lead
inhibits the synthesis of
hemoglobin (Wright-
Leishman stain).
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7. Lead lines
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8. 8
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9. Enzyme inhibition by Lead
Lead inhibits 3 enzymes in Hb
biosynthesis
1. δ-Amino Levulinic acid
dehydratase (ALAD) (Step 2)
2. Coproporpyrinogen oxidase.
(Step 6)
3. Ferrochelatase (step 8)
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10. Erythropiesis and lead
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11. Aims & Objectives
Purpose of the study:
To assess the lead toxicity in
SSI workers and to evaluate
biochemical markers suitable
for screening occupational
exposure in developing
country like India.
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12.  Setting & Design:
Industrial, Rural, Case control study.
 Subjects:
Employees of SSI units of,
Material and Methods
› Battery manufacturing & recycling.
› Silver jewelry making.
› Spray painting.
Size & selection: 30 from each category,
Random, non-stratified.
 Controls:
30 healthy subjects from rural areas,
clinically normal, age matched (non-exposed)
 Samples:
Random blood, urine samples with proper
preservatives. Processing (Pre analytical treatment)
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13.  Lead (Pb) by Atomic absorption
spectrophotometry (Perkin Elmer A300; Abs λ 283.3 nm).
Methods of sample analysis
 Zinc Protoporphyrin (ZPP): by Hematoflurometry
(Wayne NA NSSLS – C42A; 1996). Ex 415 nm, Em 595 nm)
 δ-amino levulinic acid (ALA) by colorimetric
method (Wada et al Br J Industr Med 1969; 26: 240-43).
 Porphobilinogen (PBG) by colorimetric method,
Ehrlich’s reaction (Mauzeroall & Granick, JBC 1956; 435-46).
 Cost-Effective index:
Cost-Benefit analysis
Statistical methods: Mean, SD, Student t test.
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14. Scheme of ALA analysis
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15. Table I
Biochemical markers in the occupation groups.
Marker BMW SJM SP NEC
(units) n=30 n=30 n=30 n =35
BPb 53.65 ± 16.98 48.56 7.39* 22.32 8.87* 12.52 ± 4.08
1
(μg/dl) (25.8 – 78.0) (30.2 - 64.7) (7.5 - 45.7) (2.8 – 22.0)
UPb 20.04 ± 15.20 9.39 6.52 11.22 7.15** 6.97 ± 3.59
2
(μg/dl) (5.2 – 62.8) (2.0 - 30.7) (1.5 - 30.2) (1 – 13.2)
ZPP 122.6 ± 201.5 9.55 3.21 15.67 4.24* 8.25 ± 7.79
3
(μg/dl) (10 – 972) (1.0 - 11) (8.12 - 23.12) (1 – 35)
ALA 38.10 ± 17.52 25.13 9.52* 11.82 3.53*** 9.62 ± 5.45
4
(mg/dl) (9.3 – 74.9) (9.38- 50) (7.05 - 21.17) (2.5 – 17.5)
PBG 13.95 ± 5.23 12.06 4.81*** 10.45 3.33 10.10 ± 2.87
5
(mg/dl) (7.0 - 24.7) (7.05 - 24.7) (1.0 - 57) (3.5 – 15.8)
(Figures are mean + SD. Those in parenthesis are range of values).
BMW = Battery Manufacture workers; SJM = Silver Jewelry makers; SP = Spray
painters; NEC = Non exposed controls, BPb = Blood lead; UPb = Urine lead; ZPP =
Erythrocyte zinc protoporphyrin; ALA = Urinary δ-Amino levulinic acid; PBG =
Urinary porphobilinogen.
Figures in red are highest values & those in blue are the lowest one.
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16. Biochemical markers in lead exposure
140
BMW SJM SP NEC
120
100
80
values
60
40
20
0
BPb UPb eZPP uALA uPBG
Markers
BMW = Battery workers, SJM = Silver Jewelry makers, SP = Spray painters, NEC = Controls.
BPb = Blood lead, UPb =Urinary lead, eZPP = Erythrocyte zinc protoporphyrin,
uALA = Urinary δ-amino levulinic acid, uPBG = Urinary Porphobilinogen.
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17. Lead levels in Subjects
UPb, 6.97
NEC
BPb, 12.52
UPb, 11.22
SP BPb, 22.32
UPb, 9.39
SJM
BPb, 48.56
UPb, 20.04 BPb, 53.63
BMW
0 10 20 30 40 50 60 70 80
Microgram /dl
BMW = Battery workers, SJM = Silver Jewelry makers, SP = Spray painters, NEC = Controls.
BPb = Blood lead, UPb =Urinary lead, eZPP = Erythrocyte zinc protoporphyrin,
uALA = Urinary δ-amino levulinic acid, uPBG = Urinary Porphobilinogen.
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18. Table II
Comparison of biochemical markers for screening
occupational Pb exposure.
ZPP PBG ALA
Precision (%) CV
Intra assay 4.9 4.2 2.8
Inter assay 2.3 3.2 1.5
Sensitivity Non-linear Poor Linear ~40 mg/L
Poor Moderate High
Specificity ( Chr Fe defy anemia, ( Porphyria) (Amino acetone ns)
Porphyria, febrile state)
Correlation vs PbB 0.3789 0.1648 0.5798
Normal Range 1–16 μg/dl 7–13 mg/L 4–15 mg/L
95% CI 5.5 - 11.0 9.1 - 11.1 7.7 - 11.5
Level at PbB = 20 μg/dl 21.32 10.97 14.67
Level at PbB = 50 μg/dl 132.6 12.58 34.19
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19. Table III
Comparison of biochemical markers for screening
occupational Pb exposure.
ZPP PBG ALA
Assay design (steps) Simplest (1) Simple (4) Multi step (8)
Time/test < 3 mins ~ 8 mins ~ 20 mins
Samples used WB (R) Urine (R) Urine (R)
pH 8-9, dark, pH 3-4, dark,
Storage, Stability <4.°C, 5 w
<4°C, 2w <4°C, 2 w
Interference Bilirubin, Riboflavin, Ehrlich’ +ve Amino acetone
in assay several drugs >5 substances (NR 0 – 1 mg/L)
Specificity Poor Moderate High
Test type Invasive Non-Invasive Non-Invasive
Cost/test (2004) 35.11 16.98 35.53
Cost effective index 3.3 2.4 7.1
Rating for screening *** ** *****
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20. Conclusion
ZPP is not a suitable marker for
screening of occupational lead exposure
due to poor specificity which makes it
unfit for screening low level toxicity at
earlier stages. Urinary ALA is ideal &
convenient marker as it has higher
sensitivity & specificity apart from
being an cost effective non-invasive
investigation.
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