Evaluation of Urinary Lead Excretion Following EDTA Administration in
Occupational Lead Exposure
A. Hudák, T. Kákosy, M. Lászlóffy, K. Szabó,
and M. Náray
National Institute of Occupational Health, Budapest, Hungary
CEJOEM 1997, Vol.3. No.4.:338
The occurrence of increased lead exposure and/or lead poisoning of occupational
origin is still rather frequent. The treatment of these cases involves
the mobilisation of lead into the urine by chelating agents, such as CaNa2EDTA
(EDTA). These, however, may have unfavourable side effects and because
of this it is important to administer them only when it is justified. Evaluation
of the cases is based on the amount of lead excreted in the urine collected
during 24 hours after the administration of a pilot dose of EDTA. In Hungary
it is recommended that a value, higher than 3.12 µmol/l indicates
the justification of chelation therapy (Timár, 1990).
In out-patient setting, however, 24-hour urine collection
is inconvenient and sometimes impossible. Therefore, in general practice
the urine is collected for 4 hours afterwards and the lead concentration
of the sample is determined. This value is greatly influenced by the concentration
of the urine, and cannot be compared to the 24-hour value, because excretion
of lead has a peak 1–2 hours after the administration of EDTA (Aono and
Araki, 1984).
The aim of the study was:
-
to establish relationship between blood lead concentration (Pb-B) before
the initiation of EDTA therapy and the urinary parameters characterising
the amount of lead mobilised into the urine during 4 hours after the i.v.
dose of 1 g EDTA;
-
to select the best parameter to recommend for use in everyday practice;
-
to establish a value of the selected parameter, that could be recommended
for orientation regarding the justification of EDTA treatment.
Altogether 51 samples of 24 male and 17 samples of 10
female consecutive patients were analysed. Pb-B, urine lead concentration
(Pb-U), urine creatinine concentration (cr.) and urinary volume (V) were
measured, Pb-U/cr., Pb-U/log. cr. ratios and 4-hour lead excretion were
calculated.
The Pb-B values ranged from 0.77 to 5.21 for males
and from 0.44 to 1.77 for females. The cr. and V values varied widely.
The best correlation was found between Pb-B and
Pb-U/log.cr. after EDTA (r = 0.81, in males; r = 0.74 in females).
A preliminary limit value of 3.0 µmol/log.
mmol cr. in 4-hour after EDTA urine sample is recommended. The establishment
of a final value, however, requires the accumulation of more data.
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