272
A. Kobal et al.
2
Study Design, Subject and Methods
Thirty two miners (16 mercury miners and 16 assistant miners) were observed
before and immediately after exposure in the mine. Where native mercury was
mined, the workers were exposed to Hgo (Hg vapour and Hg liquid aerosols).
Before our observations the miners and their assistants were not exposed to HgO for
a period of 2 months (the half-life ofU-Hg). The physical activity of the miners and
their assistants was practically the same, and their loads varied from 5-9 Kcal per
minute. During their work, all the miners regularly used air-purifying helmets with
mercury-absorbing filters and anti-dust filters (AH6 Airstream Racal safety
helmets with AS60502 filter). Because the workers made use of respiratory
protection, the degree of current external exposure cannot be evaluated on the
basis ofHgO measurements in the working areas. In 15 miners the residual external
exposure was assessed with a personal sampler positioned inside the helmet.
Breathing zone air was continuously aspirated through a glass tube containing a
gold trap where Hgo was amalgamated and later analyzed by double amalgamation
cold vapour atomic absorption spectrometry (CVAAS) (Horvat 1989). The HgO
concentration in the air of working places was measured by means of the instant
reading method (Mercury Vapour Indicator, MVI Shawcity, range 0.00-2.00 mg/
m 3 , sensitivity 1 ~lg/m3, repeatability ±5%). Blood and urine samples of all
examined miners were taken before and after exposure for analysis of total Hg.
Blood postexposure samples were taken 1 hour postshift, urine postshift samples
were collected in the first 2 h after the shift. Total Hg was determined in blood,
plasma, erythrocytes and also in the 18-h urine samples of 20 miners. The 18-h urine
samples included postshift urine (12:00-14:00 h), afternoon urine (14:00-22:00 h)
and morning urine (10:00-18:00 h). The mercury concentration in all urine
postshift samples was corrected to a urinary specific gravity (SG) of 1.024 [Barber
and Wallis 1986; SG corrected concentration: (C)lIg *(SGO-l)/(SG-l); (C)lIg = measured concentration, SG = 1024, SG = measured]. The mercury concentration
in the postexposure 18-h urine samples of 20 workers was corrected to a urine
volume (UV) of! ml/min (Araki et al. 1986; UV-corrected concentration: Ui*Vib,
Ui = non-adjusted concentration, Vi = urinary flow rate (mllmin), b = the
value specific for U-Hg equal to 1). U-Hg was analyzed on the day of sampling.
Mercury in the blood and urine was determined by reduction-amalgamation
CV AAS and by neutron activation analysis (NAA). The limit of B-Hg detection
by CVAAS was 0.1 ngHg/g in a 0.2 g sample, with a coefficient of variability (CV)
from 3 to 10%. The limit of U-Hg detection was 0.1 ng/g in a 0.5 g sample, CV
varied (depending on the concentration) from 5 to 10%. The limit of B-Hg
detection by NAA was 0.1 ng/g, with CV dependent on the Hg concentration in
the sample, generally about 5% (Kosta and Byrne 1969). The quality control
program for analysis of total Hg included the certified reference materials,
comparison with NAA results and the results of other laboratories. The statistical
evaluation of data was performed using a paired t-test, Pearson's correlation
coefficient and linear regression analysis.
A. Kobal et al.
2
Study Design, Subject and Methods
Thirty two miners (16 mercury miners and 16 assistant miners) were observed
before and immediately after exposure in the mine. Where native mercury was
mined, the workers were exposed to Hgo (Hg vapour and Hg liquid aerosols).
Before our observations the miners and their assistants were not exposed to HgO for
a period of 2 months (the half-life ofU-Hg). The physical activity of the miners and
their assistants was practically the same, and their loads varied from 5-9 Kcal per
minute. During their work, all the miners regularly used air-purifying helmets with
mercury-absorbing filters and anti-dust filters (AH6 Airstream Racal safety
helmets with AS60502 filter). Because the workers made use of respiratory
protection, the degree of current external exposure cannot be evaluated on the
basis ofHgO measurements in the working areas. In 15 miners the residual external
exposure was assessed with a personal sampler positioned inside the helmet.
Breathing zone air was continuously aspirated through a glass tube containing a
gold trap where Hgo was amalgamated and later analyzed by double amalgamation
cold vapour atomic absorption spectrometry (CVAAS) (Horvat 1989). The HgO
concentration in the air of working places was measured by means of the instant
reading method (Mercury Vapour Indicator, MVI Shawcity, range 0.00-2.00 mg/
m 3 , sensitivity 1 ~lg/m3, repeatability ±5%). Blood and urine samples of all
examined miners were taken before and after exposure for analysis of total Hg.
Blood postexposure samples were taken 1 hour postshift, urine postshift samples
were collected in the first 2 h after the shift. Total Hg was determined in blood,
plasma, erythrocytes and also in the 18-h urine samples of 20 miners. The 18-h urine
samples included postshift urine (12:00-14:00 h), afternoon urine (14:00-22:00 h)
and morning urine (10:00-18:00 h). The mercury concentration in all urine
postshift samples was corrected to a urinary specific gravity (SG) of 1.024 [Barber
and Wallis 1986; SG corrected concentration: (C)lIg *(SGO-l)/(SG-l); (C)lIg = measured concentration, SG = 1024, SG = measured]. The mercury concentration
in the postexposure 18-h urine samples of 20 workers was corrected to a urine
volume (UV) of! ml/min (Araki et al. 1986; UV-corrected concentration: Ui*Vib,
Ui = non-adjusted concentration, Vi = urinary flow rate (mllmin), b = the
value specific for U-Hg equal to 1). U-Hg was analyzed on the day of sampling.
Mercury in the blood and urine was determined by reduction-amalgamation
CV AAS and by neutron activation analysis (NAA). The limit of B-Hg detection
by CVAAS was 0.1 ngHg/g in a 0.2 g sample, with a coefficient of variability (CV)
from 3 to 10%. The limit of U-Hg detection was 0.1 ng/g in a 0.5 g sample, CV
varied (depending on the concentration) from 5 to 10%. The limit of B-Hg
detection by NAA was 0.1 ng/g, with CV dependent on the Hg concentration in
the sample, generally about 5% (Kosta and Byrne 1969). The quality control
program for analysis of total Hg included the certified reference materials,
comparison with NAA results and the results of other laboratories. The statistical
evaluation of data was performed using a paired t-test, Pearson's correlation
coefficient and linear regression analysis.