Disodium octaborate

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:

Unnamed

Year:

2018

Materials and methods

Study type:

cohort study (retrospective)

Endpoint addressed:

basic toxicokinetics

developmental toxicity / teratogenicity

Test guideline

Qualifier:

no guideline required

Principles of method if other than guideline:

- Principle of test: The study covers 199 voluntarily participating females with 326 children (162 girls and 164 boys), living in the South Marmara region of Turkey. The specific sampling areas of this study were Bandirma and Bigadic (Iskele) in the Balikesir district. The study aimed at assessing possible developmental effects mediated by environmental boron exposure in a population that included high environmental exposures to B in drinking water and food.
- Short description of test conditions: Boron content of drinking water and food, as well as blood boron content were sampled. Demographic information and information on pregnancy outcomes were obtained by a questionnaire survey. Included items were age, duration of marriage, preterm birth, numbers of children, birth weights of newborns, congenital anomalies, abortions, miscarriage, stillbirth, early neonatal death, neonatal death and infant death. Information on possible confounders (alcohol consumption, smoking, pesticide application) was also obtained. There is a time gap between the time of sampling ans the time of birth However, it was anticipated that the females were chronically exposed to an area-specific level of boron, at least since water monitoring started in this region about 20 years ago.
- Parameters analysed / observed: blood boron content, reproductive outcomes, birth weights and reproductive characteristics of females

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:

general

Ethical approval:

confirmed and informed consent free of coercion received

Remarks:

This study was approved by the Ethics committee of the Ankara University School of Medicine (no. 20-853-14, dated 08/12/2014). All participants gave their informed written consent prior to participation in the project.

Details on study design:

HYPOTHESIS TESTED (if cohort or case control study): The mean developmental parameters of the three groups (low, medium and high Boron exposure) are equal.

METHOD OF DATA COLLECTION
- Type: Questionnaire
- Details: Demographic information and information on pregnancy outcomes were obtained by a questionnaire survey. Included items were age, duration of marriage, preterm birth, numbers of children, birth weights of newborns, congenital anomalies, abortions, miscarriage, stillbirth, early neonatal death, neonatal death and infant death. Information on possible confounders (alcohol consumption, smoking, pesticide application) was also obtained.

STUDY PERIOD: 2014 - 2017

SETTING: Bandirma and Bigadic (Turkey)

STUDY POPULATION
- Total number of subjects participating in study: The study covers 199 voluntarily participating females with 326 children (162 girls and 164 boys),

Exposure assessment:

estimated

Details on exposure:

TYPE OF EXPOSURE: environmental exposure

TYPE OF EXPOSURE MEASUREMENT: Area air sampling, Personal sampling (food, drinking water), Biomonitoring (urine, blood)

EXPOSURE LEVELS: 3.28 - 975.66 ng B/g blood

DESCRIPTION / DELINEATION OF EXPOSURE GROUPS / CATEGORIES: The study participants were classified into low, medium and high exposure groups, according to their blood boron concentrations. Females with blood boron concentrations lower than 100 ng B/g blood were classified as “low exposure group” (n = 143). Blood boron concentrations of 29 females ranged between 100 and 150 ng B/g blood; these were classified as “medium exposure group”. Females (n = 27) with concentrations higher than 150 ng B/g blood were classified as “high exposure group”.

Statistical methods:

The different exposure groups were characterised by the mean, the empirical standard deviation, the range and the 5th and 95th quantile of B in blood. Moreover, boxplots, Pearson’s correlation coefficient, linear regression and spline regression display the empirical distribution and possible linear dependencies. Spline regression is a piecewise regression method, which is more flexible than linear regression and particularly suited to show within class effects, i.e. the effects in our three exposure groups. To investigate the global hypothesis that the means of the three groups are equal, a Kruskal–Wallis test is used. 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 three p values were adjusted with the Bonferroni–Holm method for each variable to a count for the problem of multiple testing (Holm 1979). For the comparison of the reproductive outcomes the χ2 test was used. 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.

Results and discussion

Results:

Nevertheless, the spontaneous and induced abortion rates were lower in our study cohort than the average rates of the country and the average rates of the West Marmara region. A statistically significant boron-mediated increase in spontaneous and induced abortion rates between low, medium and high exposure groups was not visible (p > 0.05, χ2 test) as shown in Table 3.
In Turkey, according to the records in TDHS-2013, there were 0.9 stillbirths per 100 pregnancies. The percentage of stillbirth in our cohort was determined as 0.61 per 100 pregnancies (live births + stillbirths) and there was no significant (p > 0.05, χ2 test) boron-associated increase in stillbirth rates between the low, medium and high exposure groups (Table 3).
The infant mortality rate in Turkey was 13 deaths per 1000 live births, and the neonatal mortality rate was seven deaths per 1000 live births (TDHS-2013). Any early neonatal death or neonatal death was not observed in our study cohort (probably due to the low sample size), while the infant death rate was 1.2 per 100 live births (Table 3). The infant mortality rate of our cohort was lower than the average rate of Turkey, and a boron-associated statistically significant (p > 0.05, χ2 test) increase with exposure was not visible.
According to the UN World Health Statistics-(2014), the preterm birth rate per 100 live births in Turkey was 12. The preterm birth rate in our study cohort was 5.2 per 100 live births (Table 3) and a boron-associated statistically significant (p > 0.05, χ2 test) increase with exposure groups was not visible.
The prevalence of major congenital anomalies in Europe has been reported as 23.9 per 1000 births for 2003–2007 (Dolk et al. 2010). Unfortunately, figures on congenital anomalies covering all regions of Turkey are not available. However, the rate of congenital anomalies recorded for our study area (2.4 per 100 birth) was in line with the results of Europe, and boron-mediated statistically significant differences (p > 0.05, χ2 test) between low, medium and high exposure groups were not apparent (Table 3).
According to the report of Turkey Demographics Profile (2017), the sex ratio at birth in Turkey is 1.05 males/female. Within our study population, the mothers had 326 children, and 164 being male. Accordingly, the male/female sex ratio of 1.01 in our study population is in line with the report of Turkey Demographics Profile. The sex ratio in the high exposure group was 1.25. This ratio does not support a tendency in sex ratio at birth towards females, as claimed in earlier studies for a similarly boron-exposed population in China.
The prevalence of LBW and VLBW was 34 and 4, respectively, in our cohort and a statistically significant boron-associated adverse effect on these parameters could not be seen, even in the high exposure group (Table 3). The birth weights were also assessed as continuous variables, and the mean birth weights of infants (girls, boys and girls + boys) were compared between the exposure groups as shown in Table 4. The mean birth weights of newborns were statistically not different (p > 0.05) between the exposure groups. Possible boron-mediated effects on the birth weights of newborns were also analysed using linear spline regression models with two knots at 100 and 150 ng B/g blood. The association between birth weights and blood boron concentrations was negative between blood boron concentrations of 100 and 150 ng/g. An increase of 1 ng B/g blood was associated with a reduction in birth weight of 4.1 g between these blood boron concentrations. However, this association was statistically not significant, as shown in Table 5.

Any other information on results incl. tables

Table 1 Boron concentrations in blood/urine samples and the estimated DBE levels of the voluntary females
Boron exposure groups (ng B/g blood)	Blood (ng B/g blood)		DBE (mg B/day)
	Mean ± SD (min-max)	5th-95th percentile	Mean ± SD (min-max)	5th-95th percentile
Low (L), < 100, n = 143	39.74 ± 27.60 (3.28-99.28)	3.62-93.40	9.73 ± 5.29* (2.26-38.27)	2.30-17.37
Medium (M), 100-150, n = 29	124.19 ± 13.10 (100.35-146.74)	105.35-143.43	21.62 ± 7.87* (8.08-39.71)	10.14-34.80
High (H), > 150, n = 27	274.58 ± 213.00 (151.81-975.66)	152.92-762.89	24.67 ± 11.39* (10.47-57.86)	11.29-49.14
DBE daily boron exposure, SD standard deviation *The means are signiicantly diferent, p < 0.05, (L-M, L-H). Kruskal-Wallis test for global comparison. Wilcoxon-Mann-Whitney test with Bonferroni-Holm correction as post hoc test

Table 2 Mean boron concentrations in water and food samples from the Bigadic area
Samples	Low exposure group	Medium exposure group	High exposure group
	Mean ± SD (min-max)	Mean ± SD (min-max)	Mean ± SD (min-max)
Boron concentrations in drinking water samples taken from the residents, mg B/L	0.74 ± 1.03 (LOQ-3.86)	2.35 ± 0.95 (0.67-5.00)	3.99 ± 2.44 (1.69-12.20)
Boron concentrations in meal samples taken from lunch, mg B/ food*	1.18 ± 1.22 (0.02-5.90)	2.92 ± 3.32 (0.02-8.20)	3.37 ± 3.52 (0.02-12.09)
Boron concentrations in meal samples taken from dinner, mg B/ food*	1.57 ± 1.87 (0.02-6.10)	2.29 ± 2.92 (0.06-7.72)	2.76 ± 3.67 (0.02-22.14)
*Mean boron concentrations in the equal amount of meal samples consumed by the females in the lunch and dinner menus. A menu includes three dishes served together in both lunch and dinner

Table 3 Reproductive outcomes
Parameters	(T) Total population (n = 199)	(L) Low exposure (n=143)	(M) Medium exposure (n = 29)	(H) High exposure (n= 27)	p value*
	Sum	Sum	Sum	Sum
Number of children	326	215	57	54	> 0.05
Number of girls	162	105	33	24	> 0.05
Number of boys	164	110	24	30	> 0.05
Sex ratio, male/female	1.01	1.05	0.72	1.25	> 0.05
Low body weight (LBW), < 2500 g	34	21	6	7	> 0.05
Very low body weight (VLBW), < 1500	4	2	1	1	> 0.05
Number of childless women	15	14	1	0	> 0.05
Number of pregnant women	6	6	0	0	> 0.05
Preterm birth	17	12	1	4	> 0.05
Congenital anomalies	8	6	1	1	> 0.05
Induced abortion	23	18	4	1	> 0.05
Spontaneous abortion (miscarriage)	33	21	6	6	> 0.05
Stillbirth	2	0	1	1	> 0.05
Early neonatal death	0	0	0	0	-
Neonatal death	0	0	0	0	-
Infant death	4	2	2	0	> 0.05
*Statistical comparisons were performed between the low, medium and high exposure groups; x^2tests were used to determine the statistical significance between the groups

Table 4 Birth weights and reproductive characteristics of females
Parameters	(L) Low exposure (n = 143)		(M) Medium exposure(n= 29)		(H) High exposure(n= 27)		p value
	Mean ± SD (min-max)	5th-95th per-centile	Mean ± SD (min-max)	5th-95th per- centile	Mean ± SD (min-max)	5th-95th per- centile
Age of mothers	32.31 ± 6.77 (17-49)	23.00-44.90	36.28 ± 6.95 (23-49)	24.40-46.60	34.56 ± 6.10 (24-46)	26.00-44.70	< 0.05 (L-M)
Duration of marriage, year	11.17 ± 7.02 (0.66-29)	2.00-25.00	16.61 ± 7.73 (0.58-29)	3.20-28.60	14.81 ± 8.64 (3-42)	5.30-28.10	< 0.05 (L-M)
Birth weight of newborns, g	3213 ± 561 (1140-5000)	2200-4000	3083 ± 563 (1400-4200)	1950-3820	3112 ± 709 (1200-4750)	2000-4000	> 0.05
Birth weight of newborns, girls, g	3154 ± 536 (1140-4250)	2600-3919	2991 ± 615 (1400-4000)	1690-3840	3057 ± 674 (2000-4000)	2015-4000	> 0.05
Birth weight of newborns, boys, g	3269±580 (1400-5000)	2250-4000	3209 ± 464 (2000-4200)	2703-3800	3142 ± 745 (1200-4750)	1725-4055	> 0.05
*Kruskal-Wallis test for global comparison. Wilcoxon-Mann-Whitney test with Bonferroni-Holm correction as post hoc test

Table 5 Linear spline regression analysis between blood boron concentrations and birth weights of newborns
	Birth weights of newborns
	Estimate	Std. error	t	Slope	pvalue
Intercept	3192.09	64.77	49.28		< 2e-16
Low exposure	40.65	120.34	0.34	0.4203	0.74
Medium exposure	- 166.88	98.34	- 1.70	- 4.0693	0.09
High exposure	207.03	281.08	0.74	0.4534	0.46

Table 6 Linear regression analysis for the birth weight of newborns
	Total study group
	Estimate	Std. error	t	p value
Intercept, (β0)	3517.58	194.36	18.10	< 2e-16
Blood boron conc., (β1)	0.01	0.27	0.02	0.98
Alcohol consumption, (β2)	- 138.49	74.02	- 1.87	0.06
Age,(β3)	- 7.94	5.45	- 1.46	0.147
Smoking during pregnancy, (β4)	- 279.77	139.60	- 2.01	0.04
Smoking,(β5)	12.28	93.87	0.13	0.89
Pesticide application,(β6)	145.07	88.37	1.64	0.10

Applicant's summary and conclusion

Conclusions:

In spite of the high level of daily boron exposure, boron-mediated adverse effects on induced abortion, spontaneous abortion (miscarriage), stillbirth, infant death, neonatal death, early neonatal death, preterm birth, congenital anomalies, sex ratio and birth weight of newborns were not observed.

Executive summary:

Boric acid and sodium borates are currently classified as being toxic to reproduction under “Category 1B” with the hazard statement of “H360 FD” in the European CLP regulation. This has prompted studies on boron-mediated reprotoxic effects in male workers in boron mining areas and boric acid production plants. By contrast, studies on boron-mediated developmental effects in females are scarce. The present study was designed to fill this gap. Hundred and ninety nine females residing in Bandirma and Bigadic participated in this study investigating pregnancy outcomes. The participants constituted a study group covering blood boron from low (< 100 ng B/g blood, n = 143) to high (> 150 ng B/g blood, n = 27) concentrations. The mean blood boron concentration and the mean estimated daily boron exposure of the high exposure group was 274.58 (151.81–975.66) ng B/g blood and 24.67 (10.47–57.86) mg B/day, respectively. In spite of the high level of daily boron exposure, boron-mediated adverse effects on induced abortion, spontaneous abortion (miscarriage), stillbirth, infant death, neonatal death, early neonatal death, preterm birth, congenital anomalies, sex ratio and birth weight of newborns were not observed.