Dipotassium tetraborate

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-2017

Reliability:

other: not applicable

Data source

Reference

Reference Type:

publication

Title:

Evaluation of the DNA damage in lymphocytes, sperm and buccal cells of workers under environmental and occupational boron exposure conditions

Author:

Basaran N, Duydu Y, Üstündag A, Taner G, Aydin S, Anlar HG, Yalcin CÖ, Baganli M, Aydos K, Atabekoglu CS, Golka K, Ickstadt K, Schwerdtle T, Werner M, Meyer S, Bolt HM

Year:

2019

Bibliographic source:

Mutat Res. 843:33-39

Materials and methods

Study type:

cohort study (retrospective)

Endpoint addressed:

genetic toxicity

toxicity to reproduction / fertility

Test guideline

Qualifier:

no guideline required

Principles of method if other than guideline:

102 male workers who were occupationally exposed to boron from Bandırma and 110 workers who were occupationally and environmentally exposed to boron from Bigadic participated to this study. DNA damage in the sperm, blood and buccal cells of 212 males was evaluated by comet and micronucleus assays.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Boron

Cas Number:

7440-42-8

Molecular formula:

B

IUPAC Name:

Boron

Method

Type of population:

occupational

Ethical approval:

confirmed and informed consent free of coercion received

Details on study design:

HYPOTHESIS TESTED (if cohort or case control study):
The main aim of the present study was to assess the DNA damage in the blood, sperm and buccal samples of male residents living in boron rich areas.

METHOD OF DATA COLLECTION
- Type: Questionnaire
- Details: The aim of the questionnaire survey was to gather demographic information. Information on some possible confounders (alcohol, smoking, pesticide application) was also obtained. After completing the questionnaire, blood and buccal cell and sperm samples were taken.

STUDY PERIOD:

SETTING: The study was conducted in two districts of Balıkesir; Bandırma (40° 21′ 13.3416′' North and 27° 58′ 17.0580′' East) and Bigadic (39° 23´ 47.0832″ North and 28° 7´ 47.6616″ East), which geographically belong to the Marmara Region of Turkey. Bandırma, distant from the boron deposits and mining areas (about 130 km away), is the production and exportation zone for the produced boric acid and some borates.

STUDY POPULATION
- Total population (Total no. of persons in cohort from which the subjects were drawn): 212
- Total number of subjects participating in study: 212
- Sex/age/race: male/35.25 (Bandirma), 35.67 (Bigadic)
- Smoker/nonsmoker: 57/45 (Bandirma), 70/40 (Bigadic)
- Total number of subjects at end of study: 212

OTHER DESCRIPTIVE INFORMATION ABOUT STUDY:

Exposure assessment:

measured

Remarks:

Blood boron concentration

Details on exposure:

TYPE OF EXPOSURE: The majority of males participating from Bandırma constitute very low or low (occupationally) exposed groups in the study, while the majority of males from Bigadic constitute medium, high or higher (occupationally and environmentally) exposed groups, samples of male residents living in boron rich areas.

TYPE OF EXPOSURE MEASUREMENT: Biomonitoring blood

EXPOSURE PERIOD: continuously

DESCRIPTION / DELINEATION OF EXPOSURE GROUPS / CATEGORIES:
Volunteers participating in the study are grouped according to their blood boron concentrations as follows:
Very low group (n=12): blood B concentrations<100 ng B/g blood
Low exposure group (n=17): blood B concentrations of 101–150 ng B/g blood
Medium exposure group (n=108): blood B concentrations of 151–450 ng B/g blood
High exposure group (n=50): blood B concentrations of 451–600 ng B/g blood
Overexposure group (n=25): blood B concentrations>651 ng B/g blood

Statistical methods:

All results were presented using mean, standard deviation and minimum-maximum values and statistics were made using the "IBM SPSS Statistics, version 23.0″ program. All data were tested for normal distribution according to the Komolgorov-Smirnow normality test. The significance of the difference between the mean values for the data with normal distribution was checked by ANOVA or t test. If ANOVA test results were found to be statistically significant, Tukey HSD test was applied from Post Hoc tests following ANOVA test. Correlation between normal distribution data made by Pearson correlation test and the correlation between non-normal distribution data was also made by Spearman rank test. The χ2 test was used to check the significance of the differences between the categorical variables. P values of less than 0.05 were considered as statistically significant.

Results and discussion

Results:

No statistically significant differences were found (p=0.861) between the groups for both alkaline and neutral Comet assay in the sperm cells. No correlation was seen between blood boron levels and tail intensity values of the sperm samples (Pearson correlation coefficient was 0.028).
No significant difference was observed in the lymphocytes between the B exposed groups of male volunteers (p=0.116). No correlation was seen between blood boron levels and tail intensity values of the lymphocyte samples (Pearson correlation coefficient was -0.024). No significant difference was found in the MN frequencies between the low, medium, high and overexposure groups. Buccal MN frequency observed in the very low exposure group was significantly lower than the all exposed groups (p=0.042) but the sample size of the very low exposure group was very small. In the majority of the men in low, medium, high and overexposure groups (n=200), no significant difference in MN frequency was noted. On the other hand, when evaluating the abnormal cells (binucleated (BN), condensed chromatin (CC), karyorrhectic (KHC), karyolitic (KYL), pyknotic (PYC), nuclear bud (NBUD)) other than MN in buccal mucosa cells, no statistically difference between the groups was found (BN, p=0.955; CC, p=1.486; KHC, p=0.455; KYL, p=0.541; PYC, p=1.057; NBUD, p=0.331). No correlation was seen between blood boron levels and frequencies of MN, BN, KHC, KYL, PYC and NBUD in the buccal cell samples (Pearson correlation coefficients were 0.023, -0.052, 0.047, -0,045, 0058 and 0.023, respectively). A negative correlation was found between blood boron levels and frequencies of CC (Pearson correlation coefficient was -0.156).

Any other information on results incl. tables

Table 1: Comet test results in the sperm samples according to blood boron concentration of all male volunteers.*

	Very Low Exposure Group (n = 12) < 100 ng B/g blood	Low Exposure Group (n = 17) 101- < 150 ng B/g blood	Medium Exposure Group (n = 108) 151- < 450 ng B/g blood	High Exposure Group (n = 50) 451- < 650 ng B/g blood	Overexposure Group (n = 25) > 651 ng B/g blood
% Tail Intensity	5.37 ± 1.63	5.61 ± 1.2	6.03 ± 4.83	5.55 ± 1.88	5.36 ± 1.88
(Alkaline Comet Assay)	(3.1 - 8.42)	(3.97 - 8,96)	(2.6 - 49.71)	(2.81 - 13.73)	(3.04 - 12.32)
% Tail Intensity	6.31 ± 1.16	6.09 ± 1.1	6.23 ± 1.36	6.16 ± 1.26	5.71 ± 0.97
(Neutral Comet Assay)	(5.13 - 8.49)	(4.22 - 7.81)	(3.95 - 13.68)	(4.12 - 9.66)	(4.24 - 8.4)

* The results are given as mean ± standard deviation (minimum-maximum) (p=0.861).

 

Table 2: Comet test results in the lymphocytes according to blood boron concentration of all male volunteers.*

	VeryLow Exposure Group < 100 ng B/gblood	Low Exposure Group 100- < 150 ng B/gblood	Medium Exposure Group 151- < 450 ng B/gblood	High Exposure Group 451- < 650 ng B/gblood	Overexposure Group> 651 ng B/gblood
Bandirma +Bigadicn = 212	6.0 ± 2.69 (2.82 - 11.95) n=12	7.79 ± 5.18 (1.85 - 24.5) n=17	7.5 ± 5.34 (1.64 - 27.47) n = 108	8.7 ± 7.94 (1.38 - 36.0) n=50	5.04 ± 2.26 (0.65 - 10.08) n=25

* The results are given as mean ± standard deviation (minimum-maximum) (p=0.116).

 

Table 3: Micronucleus frequencies in the buccal cells according to blood boron concentrations of all male volunteers.*

	Very Low Exposure Group < 100 ng B/g blood	Low Exposure Group 100- < 150 ng B/gblood	Medium Exposure Group151- < 450 ng B/gblood	High Exposure Group451- < 650 ng B/gblood	Overexposure Group > 651 ng B/g blood
Bandirma + Bigadic n = 212	3.54 ± 2.73^a(1 - 9) n=12	5.13 ± 4.69 (0 - 19) n=17	4.32 ± 3.82 (0 - 19) n = 108	4.56 ± 3.61 (0 - 16) n=50	4.06 ± 2.93^a(0 - 10) n=25

* The results are given as mean ± standard deviation (minimum-maximum).

a Statistically difference between groups (p=0.042).

 

Table 4: Abnormal cell frequencies other than MN in buccal cells.*

	Bandirma + Bigadic (n = 212)
	VLEG	LEG	MEG	HEG	OEG
BN	18.18 ± 8.20 (2 - 30)	19.73 ± 8.42 (10 - 35)	16.57 ± 6.17 (5 - 32)	16.81 ± 6.75 (0 - 31)	16.35 ± 8.09 (3 - 36)
CC	20.55 ± 12.77 (2 - 40)	22.33 ± 21.74 (0 - 90)	17.44 ± 14.86 (0 - 77)	14.13 ± 11.87 (0 - 93)	13.52 ± 10.62 (3 - 41)
KHC	4.00 ± 3.00 (0 - 10)	3.27 ± 3.20 (0 - 9)	3.67 ± 5.01 (0 - 22)	4.75 ± 7.35 (0 - 29)	4.43 ± 9.58 (0 - 43)
KYL	17.45 ± 19.38 (1 - 53)	17.60 ± 33.88 (0 - 135)	12.63 ± 13.28 (0 - 71)	13.35 ± 13.60 (0 - 82)	10.91 ± 12.35 (0 - 74)
PYC	5.1 ± 3.70 (0 - 14)	6.73 ± 3.63 (1 - 16)	9.40 ± 10.64 (0 - 90)	7.38 ± 5.00 (0 - 24)	6.74 ± 4.90 (1 - 23)
NBUD	0.73 ± 1.56 (0 - 5)	0.60 ± 0.51 (0 - 1)	0.82 ± 1.27 (0 - 8)	0.69 ± 0.98 (0 - 4)	0.74 ± 1.25 (0 - 4)

VLEG, very low exposure group; LEG, low exposure group; MEG, medium exposure group; HEG; high exposure group; OEG, overexposure group; BN, binucleated; CC, condensed chromatin; KHC, karyorrhectic; KYL, karyolytic; PYC, pyknotic; NBUD, nuclear bud.

* The results are given as mean ± standard deviation (minimum-maximum) (BN, p=0.955; CC, p=0.148; KHC, p=0.455; KYL, p=0.541; PYC, p=0.157; NBUD, p=0.331).

Applicant's summary and conclusion

Conclusions:

The study showed that even in extreme exposures of environmentally and occupationally B exposed workers no significant DNA damage was observed in the sperm, blood and buccal cells of workers. Under conditions of normal handling and use of boron compounds. It is very unlikely that adverse fertility effects can occur. Even in the highly exposed workers, it seems not possible to reach the experimental exposures that had led to reproductive toxicity in animals.

Executive summary:

Industrial production and use of boron compounds have increased during the last decades, especially for the manufacture of borosilicate glass, fiberglass, metal alloys and flame retardants. This study was conducted in two districts of Balıkesir; Bandırma and Bigadic, which geographically belong to the Marmara Region of Turkey. Bandırma is the production and exportation zone for the produced boric acid and some borates and Bigadic has the largest B deposits in Turkey. 102 male workers who were occupationally exposed to boron from Bandırma and 110 workers who were occupationally and environmentally exposed to boron from Bigadic participated to our study. In this study the DNA damage in the sperm, blood and buccal cells of 212 males was evaluated by comet and micronucleus assays. No significant increase in the DNA damage in blood, sperm and buccal cells was observed in the residents exposed to boron both occupationally and environmentally (p=0.861) for Comet test in the sperm samples, p=0.116 for Comet test in the lymphocyte samples, p=0.042 for micronucleus (MN) test, p=0.955 for binucleated cells (BN), p=1.486 for condensed chromatin (CC), p=0.455 for karyorrhectic cells (KHC), p=0.541 for karyolitic cells (KLY), p=1.057 for pyknotic cells (PHC), p=0.331 for nuclear bud (NBUD)). No correlations were seen between blood boron levels and tail intensity values of the sperm samples, lymphocyte samples, frequencies of MN, BN, KHC, KYL, PHC and NBUD. The results of this study came to the same conclusions of the previous studies that boron does not induce DNA damage even under extreme exposure conditions.