Chemistry Reference
In-Depth Information
In lead workers, ALA increases earlier in plasma
(but not in red cells) than in urine; there is an exponen-
tial increase of plasma ALA with rising B-Pb (Morita
et al
., 1994; Sakai and Morita, 1996; Sakai
et al
., 1998).
Plasma lead is associated with ALA concentrations in
plasma and urine and coproporphyrin in urine; it dis-
plays closer correlations than B-Pb (Hirata
et al
., 1995;
Sakai
et al
., 1998).
In Japanese workers with B-Pb <400
for ALA in plasma, and 88
g/L for ALA in urine
(Murata
et al
., 2003). Probably, effects on the enzymes
ALAD in red cells are proportional to the B-Pb, right
down to the B-Pb in subjects without particular lead
exposure, even at the low B-Pb seen in many geograph-
ical regions (mean B-Pb approximately 0.10
µ
mol/L;
Table 3; Skerfving, 2005). Disturbance of heme metabo-
lism is more pronounced in women than in men, and
more in children than in adults.
Lead exposure causes accumulation of free eryth-
roporphyrin/zinc (FEP) protoporphyrin (ZPP) in
µ
g/L, the
“benchmark dose” (excess risk 5%) was calculated to
B-Pb of 27
µ
µ
g/L for erythrocyte ALAD activity, 33
µ
g/L
TABLE 3
Overall Summary of Information on at Which Lowest Blood Concentrations (average in studied populations;
mol/L
1
) Various Adverse, Slight Effects of Lead Have Been Reported with Some Consistency
.
Population
General
Organ
Effect
Occupational
Adults
Children
Nervous system
Encephalopathia
2
Central
>4.0
>4.0
>4.0
Slight symptoms
1.5-2.0
−
−
<0.5
3
Neurobehavioural
1.5-2.0
−
Peripheral
Symptoms
1.5
−
−
Neurophysiological
1.5
−
−
Complex effects
Evoked potentials
1.5
−
−
Posture
1.5
−
−
Hearing
−
−
0.5
Autonomous
Heart rate variability
1.5
−
−
Anemia
2
Blood
>3.0
>3.0
>3.0
Hemoglobin concentration
2.0-2.5
−
−
Heme metabolism
0.1-0.3
−
−
Nucleotide metabolism
≈
0.3
−
−
Kidneys
Tubular
1.5
−
0.5?
Glomerular
2.0?
0.5?
0.5?
Cardiovascular
Blood pressure
1.5-2.0?
0.4
1.8?
Heart rate variability
1.5
−
−
Endocrine system
4
Hypothalamus/pituitary/thyroid/adrenal axes
1.5-2.0
−
−
Immune system
Immunosuppression
2.0
−
−
Mutagenicity
Chromosome aberrations, micronuclei, SCEs
1.5-2.0
−
−
Kidney, lung
5
Cancer
?
−
−
Reproduction
?
6
Female
Abortion
0.5?
−
Fetal growth
−
0.1?
−
<0.5
3
Neurobehavioural
−
−
Male
Endocrine function
1.5
−
−
Sperm quality
2.0
−
−
Fertility
2.0?
−
−
Gastro-intestinal tract
2
Constipation, abdominal pain
>3.0
>3.0
>3.0
?=Limited data, inconsistent results and/or possible/probable confounding
-= Not relevant or not suffi ciently studied. From Skerfving (2005)
1
1
µ
mol/L = 207
µ
g/L. 100
µ
g/L= 0.48
µ
mol/L.
2
See Skerfving, 1993.
3
Unceratinty whether effects are mainly due to exposure
in utero
or after birth.
4
Except for reproduction.
5
Uncertain.
6
Levels not clear, probably high.
