Diammonium decaborate

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2014-2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Evaluation of FSH, LH, testosterone levels and semen parameters in male boron workers under extreme exposure conditions

Author:

Duydu, Y., Basaran, N., Aydin, S., Üstündag, A., Özgür Yalcin, C., Gül Anlar, H., Bacanli, M., Aydos, K., Somer Atabekoglu, C., Golka, K., Ickstadt, K., Schwerdtle, T., Werner, M., Meyer, S., Bolt, H.M.

Year:

2018

Bibliographic source:

Arch Toxicol. 92(10):3051-3059

Materials and methods

Study type:

cohort study (retrospective)

Endpoint addressed:

basic toxicokinetics

toxicity to reproduction / fertility

Test guideline

Qualifier:

no guideline required

Principles of method if other than guideline:

Investigation of possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions. The mean daily boron exposure (DBE) and blood boron concentration of workers in the extreme exposure group (n = 98) were 47.17 ± 17.47 (7.95–106.8) mg B/day and 570.6 ± 160.1 (402.6–1100) ng B/g blood, respectively. Boron-associated adverse effects were investigated on semen parameters, as well as on FSH, LH and total testosterone levels.

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

other: and non-occupational

Ethical approval:

confirmed and informed consent free of coercion received

Remarks:

The study was approved by the Ethics committee of the Ankara University School of Medicine. All participants gave their informed consent prior to participation.

Details on study design:

HYPOTHESIS TESTED (if cohort or case control study): Investigation of possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions.

METHOD OF DATA COLLECTION
- Type: Questionnaire / other: sampling
- Details: Bandirma: Workers employed in the boric acid production zone were working for 8 h per day, in three work shifts. The participants of the study came to the infirmary on pre-scheduled days and brought actual meal and drinking water samples from their homes. The infirmary is located within the boric acid production zone. The volunteers were previously informed how to obtain drinking water samples and meal samples. Appropriate containers for the food and water samples were provided. The biological sampling (blood, urine and semen) was performed at the day at which the workers completed their work shift periods. A questionnaire survey was carried out to gather information on demographic data and possible confounding variables (age, duration of employment, pesticide application, smoking and alcohol consumption). As lunch was regularly provided for all employees in the central cafeteria, which was located within the boric acid production zone, drinking water and meal samples were taken also from there.
Bigadic: Personal air sampling was performed for workers working in high exposure areas (packaging workers), and static air sampling was performed for the rest of the workers. Biological samples (blood, urine and semen) were obtained immediately after work shift in the infirmary located within the “Bigadic Boron Works”. Drinking water and meal samples were obtained from the workers. The questionnaire survey was carried out at this occasion.

STUDY PERIOD: 2014-2017

SETTING: The study was conducted in Bandirma (boric acid production zone) and Bigadic (Bigadic Boron Works) districts of Balikesir in Turkey.

STUDY POPULATION
- Total population (Total no. of persons in cohort from which the subjects were drawn): Badirma: In the current (second) project, 102 workers participated from sulfuric acid production facilities, steam power plant, mechanical workshop, garage, steelyard, demineralized water production unit, construction units and central cafeteria (cooks), but not from the boric acid production facilities. In total, 110 workers participated in the study, employed at the Bigadic Boron Works and residing in Iskele or Osmanca
- Selection criteria: occupationally and not occupationally exposed
- Total number of subjects participating in study: 212
- Sex/age/race: male/ age: 24-46 low exposure group, 27-48 medium exposure group, 22-49 high exposure group, 23-50 extreme exposure group
- Total number of subjects at end of study: 212
- Other: Workers with blood boron concentrations lower than 100 ng B/g blood were classified having “low exposure” (n = 12). Blood boron concentrations of 17 workers between 100 and less than 150 ng B/g blood were classified as “medium exposure”. The blood boron concentrations of the majority of the workers (n = 183) were in excess of 150 ng B/g blood. Therefore, we decided to classify 85 workers with blood boron concentration between 150 and less than 400 ng B/g blood as having “high exposure”. The rest of the workers with blood boron concentrations of 400 ng B/g blood and higher were classified as having “extreme exposure” (n = 98).

COMPARISON POPULATION
- Type: Other comparison group: low exposure group

Exposure assessment:

estimated

Details on exposure:

TYPE OF EXPOSURE: occupational and environmental

TYPE OF EXPOSURE MEASUREMENT: Area air sampling / Personal sampling
Personal air sampling was performed for workers working in high exposure areas (packaging workers), and static air sampling was performed for the rest of the workers. Static air sampling was performed at 5 different stations (central cafeteria/garage, mechanical workshop, steam power plant, infirmary and sulfuric acid production plant) representing the whole sampling area. Static air sampling was also performed at one air sampling station in downtown Bandirma.
Bandirma
Boron concentrations in air samples were < LOQ. The major sources of boron exposure for the workers were drinking water and food. For estimation of boron exposure via drinking water, the drinking water consumption was assumed to be 2 L/day. The daily boron exposure via food (both lunch and dinner) was estimated using the “double plate method”.
Bigadic
A number of the workers were highly exposed to boron via inhalation at work. In contrast, boron concentrations in environmental air samples from the residential areas of Osmanca and Iskele were < LOQ.
Major sources of boron exposure were drinking water, food and the workplace. The workers had lunch at the enterprise’s dining hall, located within the premises. A special condition was observed in the dining hall: the boron concentration in table water samples taken from the dining hall was very low (0.017 mg B/L), due to consummation of bottled water. However, the boron concentration in the tap water of the dining hall that was used for cooking was very high (18.04 mg B/L). Therefore, the major source of boron exposure in the dining hall was the meal. Drinking water and meal samples were taken

EXPOSURE LEVELS: The daily boron exposure (DBE) was estimated for Banırma and Bigadic workers by the below mentioned formulas:
Bandirma ∶ DBE (mg B∕day) = [BWw + BWh]+ [BFw + BFh]
Bigadic ∶ DBE (mg B∕day) = [BWw + BWh] + [BFw + BFh] + [BIw]

BWw, B exposure via drinking water at work; BWh, B exposure via drinking water at home; BFw, B exposure via food at work; BFh, B exposure via food at home; BIw, B exposure via inhalation at work.

EXPOSURE PERIOD: continuously

DESCRIPTION / DELINEATION OF EXPOSURE GROUPS / CATEGORIES:

Statistical methods:

Box plots, Pearson’s correlation coefficient and linear regression (Figs. 1, 2) display the empirical distribution and possible linear dependencies. To investigate the global hypothesis that the means of the five groups are equal, a Kruskal–Wallis test was used for all variables in Tables 2, 3, 4 and 5. If the resulting p value was significant (p < 0.05), i.e., if the hypothesis of equal group means was rejected, the two-sided Wilcoxon–Mann–Whitney test as a post hoc test was applied to find distinct differences between each of the pairs of groups. The corresponding ten p values were adjusted with the Bonferroni–Holm method for each variable to account for the problem of multiple testing. These nonparametric tests were deliberately employed as some of the variables showed outliers. All statistical tests were performed with R, version 3.4.1 (R Core Team 2017). The local as well as multiple significance levels of the tests were set at 0.05. For theoretical details of the nonparametric Kruskal–Wallis as well as Wilcoxon–Mann–Whitney tests.

Results and discussion

Results:

In general, the boron concentrations in the biological fluids were very much paralleled by the levels of calculated daily boron exposure (DBE). The correlations between blood boron- DBE, blood boron-urine boron and blood boron-semen boron levels were all statistically significant (p < 0.01). The mean semen boron concentrations of the workers were 6.4, 8.0, 4.3 and 3.1 times higher than the mean blood boron concentrations of workers classified in low, medium, high and extreme exposure groups. These ratios confirm an accumulation of boron in human semen over blood concentrations, as already reported previously. Sperm quality parameters and reproductive hormone levels were compared between the differently exposed groups of workers to identify possible reproductive effects attributable to boron exposure. When specifically looking at the “sperm concentration” and “total sperm number” of each exposure groups, all mean values of these parameters were well above these reference values. The mean values of total motility, progressive motility, non-progressive motility, immotility, velocity, and sperm motility index were compared between the low, medium, high and extreme exposure groups, and again a statistically significant difference was not observed (p > 0.05) in pairwise comparisons of the exposure groups. Statistically significant differences between exposure groups were not observed also for the sperm motility parameters. FSH, LH and total (free and protein-bound) testosterone concentrations were determined in the blood samples. Statistically significant differences of mean FSH, LH and total testosterone concentrations between the low, medium, high and extreme exposure groups were not found (p > 0.05). The median values and the distributions of FSH, LH and total testosterone do not point to an influence of boron exposure. Statistically significant correlations between blood boron-FSH, blood boron-LH and blood boron-total testosterone concentrations were not apparent (p > 0.05).

The mean DBE level of the high exposure group was 14.45 mg B/ day, and boron-associated adverse effects on sperm quality parameters and reproductive hormone levels (FSH, LH and testosterone) were again not visible under these conditions the mean levels of sperm concentration, sperm morphology and sperm motility parameters in the low, medium, high and extreme exposure groups were statistically not different between the
exposure groups (p > 0.05). This indicates that even extreme levels of boron exposure, as defined in this study, do not adversely affect semen parameters. Hence, the results of our study strongly corroborate a lack of boron-mediated male effects on human reproduction.

Confounding factors:

Associations between the independent variables (blood boron concentration, age, duration of employment, pesticide application, alcohol consumption and smoking) and the dependent variables of sperm concentration, motile sperm concentration, total morphologically normal sperm, FSH, LH and testosterone concentrations were also analyzed, using multiple linear regression models. Statistically significant associations were observed between “pesticide application” vs. sperm concentration (p = 0.04), “pesticide application” vs. motile sperm concentration (p = 0.02) and “pesticide application” vs. total morphologically normal sperm (p = 0.01). The remaining associations were statistically not significant.

Any other information on results incl. tables

Table 1: Boron concentrations in biological fluids and DBE levels in low, medium, high and extreme exposure groups

Parameters	Exposure groups				p value
	Low exposure, <100 ng B/g blood (n = 12)	Medium exposure, 100-150 ng B/g blood (n = 17)	High exposure, 150-400 ng B/g blood(n= 85)	Extreme exposure, >400 ng B/g blood(n= 98)
Age	33.75 ± 7.85 (24-46)	35.71 ± 6.75 (27-48)	34.24 ± 6.20 (22-49)	36.69 ± 6.52 (23-50)	> 0.05
Duration of employment, year	4.79 ± 2.37 (2.5-11,0)	9.06 ± 7.31 (1-22)	6.33 ± 2.98 (1-15)	6.28 ± 4.76 (1-27)	> 0.05
Blood boron, ng B/g blood	74.03 ± 28.16 (23.8099.37)	126.6 ± 14.41 (102149.8)	269.2 ± 73.81 (151391.9)	570.6 ± 160.1 (402.51100)	< 0.05*
Urine boron, mg B/g creat	7.54 ± 17.68 (0.7963.46)	7.01 ± 6.13 (1.7927.12)	5.63 ± 3.09 (1.1319.09)	14.20 ± 7.91 (1.0643.09)	< 0.05**
Semen boron, ng B/g semen	475.9 ± 639.4 (110.62455)	1019 ± 1082 (346.73863)	1158 ± 1449 (179.410543)	1772 ± 1791 (188.718072)	< 0.05**
DBE, mg B/day	15.07 ± 10.50 (3.6135.61)	19.85 ± 15.06 (4.1047.18)	26.84 ± 15.03 (3.8455.10)	47.17 ± 17.47 (7.95106.8)	< 0.05***

Mean ± SD (range)

DBE daily boron exposure, Kruskal–Wallis for global hypothesis, Wilcoxon–Mann–Whitney as post hoc test with Bonferroni–Holm correction

*All pairwise

**L-M, L-H, L-E, M-E, H-E

***L-H, L-E, M-E, H-E

Table 2: Sperm parameters, as determined by SQA-V gold sperm quality analyzer

Parameters	Low exposure (n= 12)	Medium exposure (n= 17)	High exposure (n= 85)	Extreme exposure(n= 98)	pvalue
Sperm concentration, M/ mL. RV> 15	81.51±67.23(14.8234.5)	79.36 ± 58.6 (4.6-195.3)	89.69±59.74(8.0276.3)	82.44±62.85(4.9260.3)	> 0.05
Motile sperm conc., M/ mL	39.43 ± 29.53 (7.8108.1)	38.15±28.42(2.1101.1)	43.45±31.13 (0.4-143)	38.77 ± 30.33 (0.4140.7)	> 0.05
Progressively motile sperm conc., M/mL	32.05±26.22 (5.7-93.2)	31.35±25.05 (0-86)	35.83±27.94 (0-129.3)	31.87±27.37 (0-127.1)	> 0.05
Functional sperm conc., M/mL	8.35±8.11 (1-24.4)	8.79 ± 8.44 (0-27.6)	10.37±9.83 (0-46)	9.1 ± 9.68 (0-44.3)	> 0.05
Total sperm number, M/ ejac., RV:> 39	215.4±193.8(24.5583.7)	254.7 ± 244.4 (11.5825.6)	263.4±241.9(161253.4)	276.8 ± 323.8 (8.51973.7)	> 0.05
Total motile sperm, M/ ejac	100.2±79.46(14.50258.7)	120.9 ± 110.2 (5.3404.4)	129.7±132.4 (1.8-679)	127.8 ± 134.8 (1.2-566)	> 0.05
Total progressive motile sperm, M/ejac.	79.88±67.09(10.3213.9)	98.41 ± 93.64 (0-344)	108±115.9 (0-592.3)	104.8±114.9 (0-486.5)	> 0.05
Total functional sperm, M/ejac	19.25±18.45 (2-56.8)	26.46 ± 27.21 (0-110.4)	32.45±41.41 (0-207)	27.94±33.15 (0-147)	> 0.05
Total morphologically normal sperm, M/ejac	21.82±20.28 (2.3-57.5)	29.24 ± 30.23 (0.3-120)	33.95±41.29(0.5207.8)	32.19±37.26(0.3160.3)	> 0.05
Morph. normal forms, RV> 4%	11.33±5.26 (6-23)	10.31±4.85 (3-21)	11.13±5.05 (3-30)	10.53±5.42 (3-24)	> 0.05

Mean ± SD (range)

M million, RV reference value, ejac. ejaculate, Kruskal–Wallis for global hypothesis, Wilcoxon–Mann–Whitney as post hoc test with Bonferroni–

Holm correction

Table 3: Sperm motility parameters determined by SQA-V gold sperm quality analyzer

Parameters	Low exposure (n= 12)	Medium exposure (n= 17)	High exposure(n= 85)	Extreme exposure (n= 98)	pvalue
Total motility (PR+NP), RV> 40%	52.08±10.32 (38-75)	48.53±11.17 (28-74)	48.25±15.07 (0-97)	46.85±15.68 (2-83)	> 0.05
Progressive motility (PR), RV> 32%	40.92 ± 9.89 (28-57)	35.71±16.36 (0-60)	37.93 ± 15.01 (0-88)	35.96±15.86 (0-67)	> 0.05
Non-progressive motility (NP), %	11.33±4.72 (5-21)	12.82±10.22 (6-44)	10.32 ± 4.49 (0-28)	10.90±5.37 (2-32)	> 0.05
Immotility,%	47.25±10.27 (25-62)	51.47±11.17 (26-72)	51.75±15.07 (3-100)	53.15±15.68 (17-98)	> 0.05
Velocity, mic./s	11.75±3.19 (8-18)	11.12±4.44 (1-18)	11.31±3.80 (1-18)	10.83 ± 4.08 (1-18)	> 0.05
Sperm motility index	176.5±166.3 (32-580)	163.2±139.5 (0-540)	178.8±137.4 (0-556)	167.7±147.2 (0-593)	> 0.05

Mean ± SD (range)

mic./sec. micron/second, Kruskal–Wallis for global hypothesis, Wilcoxon–Mann–Whitney as post hoc test with Bonferroni–Holm correction

Table 4: FSH, LH and total testosterone levels in low, medium, high and extreme exposure groups

Parameters	Low exposure (n= 12)	Medium exposure (n= 17)	High exposure(n= 85)	Extreme exposure(n= 98)	pvalue
FSH,mlU/mL	4.15±1.95 (1.6-7.69)	3.91 ± 2.88 (1.17-9.95)	4.04 ± 3.40 (1.02-26.56)	4.21 ± 2.63 (0.42-16.65)	> 0.05
LH,mlU/mL	3.71±1.1 (1.80-5.13)	4.01 ± 1.63 (1.33-7.09)	3.82 ± 1.68 (0.83-9.18)	3.72±1.70 (1.18-8.66)	> 0.05
Total testosterone, ng/dL	323.8 ± 135.8 (162.3615.6)	373±183.7(172.8922.4)	354±152.9 (44.3-899.7)	332.5±129(120.9731.2)	> 0.05

Mean ± SD (range), Kruskal–Wallis for global hypothesis, Wilcoxon–Mann–Whitney as post hoc test with Bonferroni–Holm correction

Table 5: p values obtained from multiple linear regression analysis for the total study group (n = 212)

y=βo+βlxl+ …+ β6x6+ε	Dependent variables (y)
	Sperm concentration (M/ mL)	Motile sperm concentration (M/ mL)	Total morphologically normal sperm (M/ejacu- late)	FSH(mlU/mL)	LH(mlU/mL)	Testosterone (ng/dL)
Independent variables (x)	p value	pvalue	pvalue	pvalue	pvalue	p value
Intercept (β0)	0.05	0.30	0.22	0.13	4.67e-07	2.86e-04
Age (β1)	0.56	0.58	0.97	0.22	0.56	0.13
Duration of employment (β2)	0.07	0.16	0.09	0.38	0.67	0.57
Blood boron conc. (β3)	0.93	0.95	0.91	0.43	0.99	0.08
Pesticide application (β4)	0.04	0.02	0.01	0.65	0.17	0.14
Alcohol consumption (β5)	0.23	0.28	0.16	0.51	0.50	0.52
Smoking (β6)	0.89	0.63	0.52	0.54	0.88	0.63

M million

Applicant's summary and conclusion

Conclusions:

Boron-mediated adverse effects on semen parameters and reproductive hormone levels in males have not been observed under extreme exposure conditions. The results of the present study corroborate those of earlier studies conducted in China and Turkey. Therefore, it has to be concluded that male reproductive effects are not relevant to humans under any feasible and realistic conditions of exposure to inorganic boron compounds.

Executive summary:

Boric acid and sodium borates are currently classified in the EU-CLP regulation as “toxic to reproduction” under “Category 1B”, with hazard statement of H360FD. However, so far field studies on male reproduction in China and in Turkey could not confirm such boron-associated toxic effects. As validation by another independent study is still required, the present study has investigated possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions. The mean daily boron exposure (DBE) and blood boron concentration of workers in the extreme exposure group (n = 98) were 47.17 ± 17.47 (7.95–106.8) mg B/day and 570.6 ± 160.1 (402.6–1100) ng B/g blood, respectively. Nevertheless, boron-associated adverse effects on semen parameters, as well as on FSH, LH and total testosterone levels were not seen, even within the extreme exposure group. With this study, a total body of evidence has accumulated that allows to conclude that male reproductive effects are not relevant to humans, under any feasible and realistic conditions of exposure to inorganic boron compounds.