Dear Editor-in-Chief
Fluoride (F), a powerful oxidizing agent, is used in a variety of industries in China.
Health problems among industrial workers due to F poisoning are on the rise. Long-term
F exposure, together with varieties of relevant factors, leads to high F burden [blood
fluoride (BF), urinary fluoride (UF)], which can finally result in F bone injury (1).
As F burden is the major cause of F bone injury, to prevent the F bone injury, we
have to control the F burden to a moderate level. The purpose of the present study
was to examine the F burden and relevant factors of aluminum plant workers, and provide
the basis for the early prevention of F bone injury.
Overall, 300 subjects, 20 to 50 of age, were randomly selected from workshops of an
aluminum plant, who have been working in their present position for 5 years or longer.
We conducted a face-to-face questionnaire for the 300 subjects. After finishing the
questionnaire, only 279 subjects were included in our study. The participating subjects
signed informed consent forms. Blood samples were collected from a brachial vein within
a few minutes after the end of the shift. Urine samples were collected as follows:
just before the afternoon half-shift, the workers were asked to empty their bladders;
then a sample of urine was collected at the end of the shift, just after blood drawing.
Blood and urine samples were kept refrigerated until analysis. Air samples were collected
from 6 different points in each workshop 16 times per day, for two consecutive days.
The levels of BF and UF were determined by fluoride ion-selective electrode method.
Levels of AF were determined by filter sampling and fluoride ion-selective electrode
method (2, 3).
This study was approved by the Institutional Ethical Boards of Tongji Medical College,
Wuhan China, and had been performed in accordance with the ethical standards laid
down in the 1964 Declaration of Helsinki and its later amendments. Statistical analyses
were performed using SPSS 16.0 statistical software.
The highest AF was observed in aluminum electrolytic workshop (2.31±1.01mg/m3), followed
by aluminum pole workshop (0.36±0.10mg/m3), the lowest observed in the office area
(0.11±0.09mg/m3). The differences among the three workshops were significant (P<0.01).Means
and standard deviations of BF and UF levels are presented in Table 1, for workers
classified by different factors. Results showed that BF of aluminum electrolytic workers
were significantly higher than that of aluminum pole workers and that of office workers
(P<0.01); BF of aluminum pole workers were significantly higher than that of office
workers (P<0.01). UF of aluminum electrolytic workers were significantly higher than
that of aluminum pole workers and that of office workers (P<0.01); UF of aluminum
pole workers were significantly higher than that of office workers (P<0.01). Age,
Working history, smoking and alcohol consumption did not significantly affect the
BF and UF levels (P>0.05).
Table 1:
BF and UF levels (mean ± SD, mg/L) in relation to different factors
Factors
n
BFa(mean ± SD)
UFa(mean ± SD)
All subjects
279
0.20±0.06
4.49±4.49
Work category
1. Office workers (af: 0.11±0.09mg/m3)
94
0.06±0.02
1.32±0.87
2. Aluminum pole workers (af: 0.36±0.10mg/m3)
90
0.12±0.03 b
2.85±1.94 b
3. Aluminum electrolytic workers (af: 2. 31±1.01mg/m3)
95
0.21±0.06b
c
7.13±5.72b
c
Age(yr)
1. <30
89
0.20±0.05
6.92±5.62
2. 30∼40
102
0.19±0.05
5.92±4.68
3. >40
88
0.22±0.07
5.82±5.52
Working history(yr)
1. <10
92
0.21±0.06
5.78±5.28
2. 10∼20
113
0.19±0.05
4.20±4.18
3. >20
74
0.22±0.07
4.65±4.04
Smoking
1. Never smoker
99
0.20±0.05
4.61±4.80
2. Non-daily smoker
69
0.19±0.06
3.17±1.99
3. Daily smoker
111
0.20±0.06
4.61±4.49
Alcohol consumption
1. Never consumer
62
0.20±0.06
4.55±4.92
2. Non-daily consumer
101
0.20±0.06
4.25±4.24
3. Daily consumer
116
0.20±0.05
5.06±4.66
a:
BF, blood fluoride level; UF, urinary fluoride level;
b:
compare with work category 1, P<0.01 by ANOVA;
c:
compare with work category 2, P<0.01 by ANOVA
BF and UF levels of aluminum electrolytic and aluminum pole workshop workers were
significantly higher (P<0.01), which were due to higher level of AF in the workshop.
Since the large-scale use of cryolite, which is rich in F and could emit a lot of
F into the air (4), the levels of AF in the aluminum electrolytic and aluminum pole
workshop were significantly higher than the office area, (P<0.01). As the AF level
increased, the BF and UF levels increased too. Related studies have shown that F bone
injury is mainly caused by high F burden (5), so reduce the AF of the workplace contribute
to the prevention of F bone injury. Meanwhile enhancing the operations of the personal
protection of workers, workshop monitoring and occupational health care of the workers
are still necessary. To sum up, our study found that due to AF, the work category
could affect the F burden indirectly. Some appropriate measures were presented to
reduce AF and prevent F bone injury. However, the relevant factors of F burden in
our study are not comprehensive enough, and thus, our survey need further in-depth
study.