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Administrative data

Endpoint:
health surveillance data
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
other: Any kind of reliability rating is not considered to be applicable, since human health surveillance studies, epidemiological studies, field studies and case reports are not conducted/reported according to standardised guidelines
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This publication has a low relevance for human risk assessment, since exposure conditions were not determined. It is unknown to which substances the jewellery workers were expose to and the duration and concentration of exposure is not known. Furthermore, confounding factors were not considered at all, such as sex, smoking habits, alcohol consumption, recreational behaviour, medication. No significant correlation between (assumed) silver exposure and presence of DNA damage could be shown by the authors.

Data source

Reference
Reference Type:
publication
Title:
Increased DNA damage and oxidative stress among silver jewelry workers
Author:
Aktepe, N. et al.
Year:
2015
Bibliographic source:
Biol. Trace Elem. Res. DOI 10.1007/s12011-014-0224-0

Materials and methods

Study type:
medical screening
Endpoint addressed:
genetic toxicity
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
In this study the genotoxic effect of silver particle exposure among silver jewellery workers was investigated. The silver jewellery workers were exposed to the silver particles by inhalation. DNA damage in peripheral mononuclear leukocytes was measured by using the alkaline comet assay.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: particles
Details on test material:
- Name of test material (as cited in study report): silver particles

Method

Type of population:
general
occupational
Ethical approval:
confirmed and informed consent free of coercion received
Details on study design:
SETTING: Mardin-Turkey

STUDY POPULATION:
- Total number of subjects participating in study: 35 silver workers
- age: 17 - 48 years old (mean age: 31.7 ± 8.4 years)
- smokers: 15 silver workers (no alcohol consume)
- body index: 24.95 ± 3.03 kg/m²
- silver workers were without any chronic and infectious diseases.
- silver jewelry workers were working at least 4 hours daily.
- silver workers were exposed to silver particles by inhalation during work.

COMPARISON POPULATION:
The control group was selected from the same area and for similar living conditions as the study group.
- Total number of subjects participating in study: 41 volunteers
- age: 17 - 45 years old (mean age: 29.42 ± 7.4 years)
- smokers: 16 silver volunteers (no alcohol consume)
- body index: 23.27 ± 3.22 kg/m²
- volunteers were without any chronic and infectious diseases
- socioeconomic statuses of control subjects were similar to those of silver workers.

There were no significant differences between the control and the study groups with respect to age and body index.

METHOD OF SAMPLING (blood):
After an overnight fasting, venous blood was withdrawn into heparinized tubes. One milliliter of heparinized blood was pipette into another tube immediately to measure mononuclear leukocyte DNA damage. Remaining blood was centrifuged to separate plasma for analysis of total antioxidant status, total oxidant status, total thiol, and ceruloplasmin.
For peripheral mononuclear leukocyte separation, an amount of 1 mL heparinized blood was carefully layered over 1 mL Histopaque 1077 (Sigma) and centrifuged at 25 °C. The interface band containing lymphocyte was washed with phosphate buffered saline and then collected by centrifugation. The resulting pellets were resuspended in phosphate buffered saline. Membrane integrity was assessed by means of Trypan Blue exclusion method.

ALKALINE COMET ASSAY:
Endogenous mononuclear leukocyte DNA damage was analyzed by alkaline comet assay according to Singh et al. (1988)* with minor modifications. Fresh peripheral mononuclear leukocyte cell suspension (around 20,000 cells) was mixed with 0.7 % low-melting-point agarose in PBS at 37 °C. Subsequently, this mixture was layered onto slides that had previously been coated with 1.0 % hot (60 °C) normal melting point agarose and covered with a coverslip at 4 °C to allow the agarose to solidify. After removing the coverslips, the slides were submersed in freshly prepared cold (4 °C) lysing solution (NaCl, EDTA-2Na; Tris–HCl, pH 10–10.5; Triton X-100; and DMSO added just before use) for at least 1 hour. Slides were then immersed in freshly prepared alkaline electrophoresis buffer (NaOH and Na2ETDA, pH >13) at 4 °C for unwinding (40 minutes) and then was subjected to electrophoresis (25 V/300 mA, 25 min). All of the above steps were conducted under red light or without direct light in order to prevent additional DNA damage. After electrophoresis, the slides were stained with ethidium bromide (in distilled; 70 μl/slide), covered with a coverslip and analysed using a fluorescence microscope vied with epiflourescence and equipped with rhodamine filter (excitation wavelength, 546 nm; barrier filter, 580 nm). The images of 100 randomly chosen nuclei (50 cells from each of two replicate slides) were analysed visually from each subject, as described by Cortés-Gutierrez et al. (2011)*. Each image was classified according to the intensity of the fluorescence in the comet tail and was given a value of either of 0, 1, 2, 3, or 4 (from undamaged class 0 to maximally damaged class 4), so that the total scores of slide could be between 0 and 400 arbitrary units.

MEASUREMENTS OF OXIDATIVE EFFECTS:
Serum total antioxidative status, total oxidative status, total thiol contents, and ceruloplasmin levels were measured by using colorimetric methods among silver jewelry workers. Moreover, oxidative stress index was calculated.

STATISTICS:
Differences in DNA damage between study and control groups were analysed by Student’s t test. The data were expressed as mean ± standard deviation, and differences were considered statistically significant at p<0.001. Statistical analyses were performed using SPSS for Windows Release 11.5 (SPSS Inc., Chicago, IL, U.S.)

*References:
- Singh NP, McCoy MT, Tice RR, Schneider EL (1988) A simple technique for quantitation of low levels of DNA damage in individual cells. Exp Cell Res 175: 184–191.
- Cortés-Gutiérrez EI, Dávila-Rodríguez MI, Fernández JL, López-Fernández C, Gosálbez A et al (2011) New application of the comet assay: chromosome-comet assay. J Histochem Cytochem 59: 655 – 660.

Results and discussion

Results:
ALKALINE COMET ASSAY:
DNA damage scores were 10.71 ± 3.37 in the control group and 12.91 ± 3.64 in the silver jewelry workers group. The mean values of mononuclear leukocyte DNA damage were higher than control subjects and it was statistically significant (study group: 15.37 ± 6.07; control group: 7.48 ± 5.46; p < 0.001).

MEASUREMENTS OF OXIDATIVE EFFECTS:
Plasma total oxidant status, oxidative stress index, and ceruloplasmin levels were found significantly higher in silver exposed group than those of non-exposed group (p<0.001, p<0.001, p<0.01, respectively). However, serum total antioxidant status levels and total thiol contents of silver exposed group were found significantly lower (p<0.05, p<0.001 respectively).

Applicant's summary and conclusion

Conclusions:
According to the authors, exposure to silver particles by inhalation caused significant genotoxicity in mononuclear leukocytes in silver jewellery workers. However, this publication has a low relevance for human risk assessment, since exposure conditions were not determined. It is unknown to which substances the jewellery workers were expose to and the duration and concentration of exposure is not known. Furthermore, confounding factors were not considered at all, such as sex, smoking habits, alcohol consumption, recreational behaviour, medication. No significant correlation between (assumed) silver exposure and presence of DNA damage could be shown by the authors.