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Toxicological information

Toxicity to reproduction

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Administrative data

Endpoint:
screening for reproductive / developmental toxicity
Remarks:
based on test type (migrated information)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Justification for type of information:
Green liquor (GL) is a complex mixture of inorganic salts in highly alkaline water solution (ca. 80% water). The composition of Green liquor is well known even if it is registered as an UVCB. All anionic and cationic groups present in green liquor is known, even if the speciation and ratio between the ionic constituents may vary in some extent. The variety in ratio/speciation makes the composition of the mixture complex. However, since all groups of the GL constituents are known and in order to avoid unnecessary animal testing, the non-testing read-across method can be performed by applying available hazard/study data from the mono-constituent pure inorganic salts (ie. those salts known to be dissolved in GL).
The referred Key study is part of effects on fertility read-across data evaluation from the green liquor constituent hydrogen sulfide. The read-across can be performed since hydrogen sulfide (H2S) and sulfides in general are expected to be the toxicologically most hazardous/potent classified group of GL constituents. The analogue approach apply to H2S even if free sulfides in Green liquor are mainly in the form of HS/S2-- anions. Unrestricted read-across between the substances sodium sulfide, sodium hydrogensulfide and dihydrogen sulfide is considered feasible, in view of the potential systemic toxicity being driven by the pH dependent equilibria between the H2S and S2-/HS- sulfide ions under physiological conditions.
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2000

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)
Deviations:
yes
Remarks:
Beyond the 421 Guideline study, additional goal of the investigation was to determine whether repeated exposure to H2S during the perinatal period of development resulted in neurotoxicity in the offspring.
Principles of method if other than guideline:
The purpose of this study was to evaluate whether repeated 6-h daily exposure of male and female CD rats (n 12 rats/sex/concentration) to H2S atmospheres of 0, 10, 30, or 80 ppm resulted in reproductive or developmental toxicity. This portion of the study was performed, to the extent possible, in compliance with the (OECD 421) screening test guideline for reproductive and developmental toxicity.

Another goal of the present investigation was to determine whether repeated exposure to H2S during the perinatal period of development resulted neurotoxicity in the offspring. Developmental neurotoxicity in pups was assessed by evaluating the ontogeny of a number of developmental milestones, use of a blinded functional observational battery (FOB), an assessment of spontaneous motor activity, and an evaluation of acoustic startle and passive avoidance behaviors.
GLP compliance:
yes
Remarks:
(40 CFR 792).

Test material

Constituent 1
Reference substance name:
7783-06-4 hydrogen sulfide
IUPAC Name:
7783-06-4 hydrogen sulfide
Test material form:
gas
Details on test material:
Gas cylinders containing 5% (50,000 ppm) H2S (hydrogen sulfide) in nitrogen were purchased from Holox Gases (Cary, NC, USA).

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
Eight-week-old male and female CD rats (80 rats per sex) were obtained from Charles River Laboratories, Inc. (Raleigh, NC). On the day of animal receipt, three rats per sex were randomly chosen and euthanized by CO2 inhalation, and blood was collected for assessment of viral antibody status (Microbiological Associates, Bethesda, MD). The remaining animals were acclimated for approximately 2 weeks in a HEPA-filtered, mass air-displacement room maintained at 18.5–21.5 °C and 40–70% relative humidity. During the acclimation period, rats were individually housed in suspended stainless steel cages with an automatic watering system. Animals were randomly assigned to the different groups (12 rats/sex/group) at the end of the acclimation period by means of their prestudy body weight. Rats selected for the study were then singly housed (except during mating when they were housed 1:1) in polycarbonate cages with stainless steel lids (Laboratory Products, Inc., Rochelle Park, NJ) with Alpha-Dri ™ cellulose-fiber chip bedding (Shepard Specialty Papers, Kalamazoo, MI). For each daily exposure, F0 male rats were transferred from their home polycarbonate cages into individual stainless steel inhalation cage units. A similar procedure was used for F0 females until GD 19. The dams with litters were exposed on PND 5–18 using individual glass exposure cylinders [26] that contained approximately 60 g of ALPHA-Dri bedding.
A 1-h experiment using 10 ppm H2S through the exposure cylinder and bedding in the absence of animals confirmed that adsorption of H2S to the bedding material did not occur.

In addition, approximately 25 g of Transgel © (Charles River Laboratories, Inc. Raleigh, NC) was placed into each exposure cylinder as a water source for the lactating females. Deionized, filtered tap water was otherwise available ad lib. Following each daily exposure, all animals were transferred back to their home cages for residence and access to feed overnight. Rats were fed NIH-07 rodent chow (Zeigler Bros., Gardners, PA) ad lib, except during the 6-h exposure periods. Fluorescent lighting was kept on a 12-h light–dark cycle (lights on 0700–1900 h).

Administration / exposure

Route of administration:
inhalation: gas
Type of inhalation exposure (if applicable):
whole body
Vehicle:
air
Details on exposure:
Adult (F0) male and female rats were exposed in four Hazelton H1000 stainless steel and glass inhalation 1-m3 exposure chambers (Lab Products, Maywood, NJ) contained within permanent 8-m3 Hinners-style stainless steel and glass inhalation exposure chambers. The air flow through each 1-m3 chamber was maintained at approximately 200–250 l/min to provide 12–15 air changes per hour during the exposures. Hydrogen sulfide was metered through mass flow controllers (MKS Instruments, Andover, MA) and mixed with the chamber air supply to provide the desired target H2S concentrations.

For the whole-body exposure of dams and pups, 4.9-liter glass exposure cylinders sealed with two anodized aluminum end plates with neoprene gaskets and an aluminum outer face [CH Technologies (USA), Inc., Westwood, NJ] were used. Once the end plates are in place, the internal volume of the cylinder is 4.3 liters. Airflow through the individual glass exposure cylinders was controlled by an adjustable stainless steel metering valve (Raleigh Valve and Fitting, Raleigh, NC). Airflow through the exposure cylinders was maintained at 2.8–4.1 l/min during the exposures to provide approximately 35 to 50 air changes per hour. The temperature and humidity in one exposure cylinder per concentration group were measured every 30 min using a thermistor (PreCon, Memphis, TN) and a humidity probe (OMEGA Engineering, Inc., Stamford, CT) located in the outlet end of the glass chamber. Chamber and cylinder exposure atmospheres were measured with a calibrated gas chromatograph (Hewlett Pac ard Model 6890, Hewlett Packard Co., Palo Alto, CA) equipped with a flame photometric detector and a GS-Q (30-m × 53µm) column (Alltech, Deerfield, IL).
Details on mating procedure:
The animals were mated (1:1) with no change in mating partners. Each female was placed into the male’s home cage in the afternoon after each daily H2S exposure and then removed the next morning prior to the start of exposure. Females were examined daily during the cohabitation period for
the presence of sperm or copulation plugs in the vaginal tract. The observation of a copulation plug or sperm in vaginal lavage fluid was considered evidence of successful mating. The day that vaginal sperm or plug was observed was designated as GD 0.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Prior to animals being placed in the 1-m3 chambers, each chamber was checked for uniformity of distribution of the test article H2S by measuring
its concentration at nine positions within the chamber. The generation system was operated by the Andover Infinity control system (Andover
Controls Corporation, Andover, MA).
- Analytical method: Chamber and cylinder exposure atmospheres were measured with a calibrated gas chromatograph equipped with a flame photometric detector and a GS-Q (30-m X 0.53-µm) column
- Samples taken from breathing zone: yes
Duration of treatment / exposure:
Ten-week-old parental (F0) rats were exposed to H2S vapor for a 2-week prebreed exposure period followed by a 2-week mating period.
Presumed pregnant F0 rats were exposed to H2S from GD 0 (gestation day)until GD 19. No exposures occurred through the remainder of
gestation and during the period of parturition (GD 20 through PND 4). The date of parturition was designated as PND 0 (postnatal day).
The dams and their pups were then concurrently exposed to H2S starting on PND 5 with daily exposures continuing through PND 18.
No further H2S exposures to the dam or pups occurred beyond PND 18.

Each litter was weaned on PND 21. Adult (F0) females without positive evidence of insemination were exposed to H2S until 23–24 days
after the end of the breeding period.

Daily exposure of the F0 males continued until they were exposed for at least 70 consecutive days.
Frequency of treatment:
One daily 6 h exposure, 7 days/week
Doses / concentrationsopen allclose all
Dose / conc.:
0 ppm (analytical)
Remarks:
All Doses / Concentrations ppm of H2S. Basis: analytical conc. 0-80 ppm
(0 - 111 mg/m3)
Dose / conc.:
10 ppm (analytical)
Remarks:
14 mg/m3
Dose / conc.:
30 ppm (analytical)
Remarks:
42 mg/m3
Dose / conc.:
80 ppm (analytical)
Remarks:
111 mg/m3
No. of animals per sex per dose:
The study began with 12 male and 12 female rats/group to yield at least eight pregnant females/group. Litters were randomly reduced to four animals per sex whereever possible.
Control animals:
yes
Details on study design:
The pups were tested for motor acitivity, passive avoidance, and acoustice statle, and a functional observation battery was also performed on them..

Motor activity was measured using an automated cage rack photobeam activity system.

Passive avoidance with a step-through to darkness paradigm including one training and one retention trial was used to assess short-term
learning and memory.

Acoustic startle was assessed using a microcomputercontrolled test system. The peak amplitude of each startle response and the interval between the acoustic stimulus and peak amplitude were analysed.

The functional observation battery was performed on the test animals on PND 60 ± 2.

Examinations

Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: before and after each daily H2S exposure

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
The body weights of the Fo male rats were determined weekly throughout the study. The body weights of the F0 female rats were recorded in the same manner until confirmation of mating. Presumed pregnant females were weighed on GD 0, 7, 14, and 20. Dams producing litters and their pups were weighed individually on PND 0, 4, 7, 14, and 21. After weaning on PND 21, pup body weights were collected twice weekly throughout the remainder of the study.

FOOD CONSUMPTION :
Feed consumption for F0 males was recorded weekly throughout the study except during the period of cohabitation. Feed consumption measurements were made weekly for ail F0 female rats throughout the prehreed treatment periods. During pregnancy, feed consumption of F0 females was recorded for GD 0-7, 7-14, and 14-20. Maternal feed consomption was also measured for PND 0-4, 4-7, 7-14, and 14-21.

WATER CONSUMPTION : No
Oestrous cyclicity (parental animals):
Not recorded.
Sperm parameters (parental animals):
Daily sperm production was calculated for all F0 male rats assuming a 6.1-day spermatid cycle. The results are reported in table 1.


Litter observations:
ASSESSMENT OF DEVELOPMENTAL EFFECTS: All pups were counted, sexed, examined for external anomalitie, and individually weighed on PND0. Each pup was monitored for the appearance of
pinnae detachmend (PND1), surface rightning (PND4), incisor eruption and negative geotaxis (PND7), and eyelid separation (PND12).

BEHAVIORAT TESTING
Motoric activity:
Motoric activity was measured in the same animal (one male and one female from each litter) before the 6-h H2S exposure on PND 13 and 17 and on PND 21 and 60 ± 2. Spontaneous motor activity was measured during ten 6-min intervals for a total of 60 min using an automated cage rack photobeam activity system.
Passive avoidance:
Passive avoidance with a step-through to darkness para¬digm including one training and one retention trial was used to assess short-term learning and memory [271. Passive avoidance was evaluated for one male and female from each litter on PND 22 - 1 and on PND 62 ± 3. Naive animals were tested on PND 21, whereas the PND 62 ± 3 animals had been previously tested for FOB.
Functional observation battery (FOB):
An FOB was performed on one male and one female from each litter on PND 60 ±: 2 using methods described by Moser et al. (1988)..
Acoustic startle:
Acoustic startle was assessed using a microcomputer-controlled automated test system. Acoustic startle was assessed for one male and one female from each litter on PND 21 and 62 ± 3.

Postmortem examinations (parental animals):
SACRIFICE
At the end of the exposure regimen, adult F0 rats were weighed, euthanised with CO, and exsanguinated.
The nulliparous adult females (n = 11) and adult males (n = 48) were necropsied the day after their last day of exposure. The post-parturient adult females (n = 37) were necropsied the day of or the day after their pups were weaned.

GROSS NECROPSY
A complete necropsy was then performed with special emphasis on the reproductive and accessory sex organs.

ORGAN WEIGHT
Brain, liver, kidney, adrenal gland, spleen, ovaries with oviducts, uterus, cervix, vagina, seminal vesicles with coagulating gland, prostate, testis and the head, body, and cauda of the left epididymis.

HISTOPATHOLOGY / ORGAN WEIGHTS
Ovaries with oviducts, uterus, cervix, vagina, seminal vesicles with coagulating gland, prostate, testis and the head, body, and cauda of the left epididymis, major structures and mucosae (squamous, respiratory, transitional, and olfactory) of the nasal cavity.
Postmortem examinations (offspring):
NEUROPATHOLOGY: Neuropathology in F1 rats was evaluated (one rat/sex/litter) in weanling (PND 23 ± 2) rats tested for passive avoidancc and in adult offspring (PND 61 ± 2) rats tested for motor activity.

The brain, spinal cord, and sciatic nerve with its main branches were exposed, grossly examined, and immersed in perfusion fixative at 4°C for at least 24 h. Brains were then removed, weighed, and measured. Cross-sections of the brain were collected for neuroanatomic pathology at the following sites: forebrain, caudate nucleus, center of the cerebrum, center of the midbrain, cer¬ebellum and pons, and medulla oblongata.

GROSS NECROPSY: The remaining F1 rat pups (n = 144) were weighed on PND 63 ± 3, euthanized with CO2, and exsanguinated and had a complete necropsy performed. The following organs were weighed: adrenal glands, brain, heart, kidneys, liver, lungs, ovaries with oviducts, spleen, and testes.
Statistics:
The unit of comparison was the male, the female, the pregnant female, or the litter, as appropriate. Following an assessment for homogeneity of
variance (Levene’s test), the data for quantitative, continuous variables (e.g., parental and pup body weights, organ weights, feed consumption)
were intercompared for the exposure and control groups by tests for two-way fixed effects (dose and sex) analysis of variance (ANOVA) and
Dunnett’s multiple comparison procedure for significant ANOVAs (F-tests). The F1 generation data were analyzed jointly for both male and female
offspring unless a statistical difference between male and female values within each treatment group was observed. A natural log (ln)
transformation of the data was used when the Levene’s test for homogeneity (p < 0.01) indicated the data to be nonhomogenous. When the
ANOVA indicated statistical significance among experimental groups, the Dunnett’s test was used to delineate which groups differed from the
control group. When the assumptions for a parametric ANOVA were not met, nonparametric procedures (Kruskal–Wallis test and Wilcoxon
2-sample rank-sum test) were used. A nested analysis of total motor activity data was performed using a repeated-measures analysis MANOVA)
with exposure as a grouping factor and test period as within- subject factors. For developmental landmarks (e.g., vaginal patency and
preputial separation), each treatment percentage or mean was compared to the control percentage or mean by the Kruskal–Wallis test. Incidence
data were compared using the Fisher’s Exact Test. Categorical FOB data were analyzed using a log-linear model. Statistical analyses were
performed using SAS Statistical Software. The significance level for any given statistical test was set at p < 0.05.
Reproductive indices:
The following reproductive indices were reported for H2S exposure:
- mating index (%)
- fertility index (%)
- postimplantation loss per litter(%)
- late resorption or stillbirth (%)
- number of live births
- abnormal sperm (%)
- motile sperm (%)
- Cauda sperm count
- daily sperm production

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:
no effects observed
Description (incidence and severity):
There were no deaths and no adverse physical signs observed in F0 male or female rats during the study.
Dermal irritation (if dermal study):
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
A statistically significant decrease in feed consumption was observed in F0 male rats from the 80-ppm H2S exposure group during the first week of exposure.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
A statistically significant decrease in feed consumption was observed in F0 male rats from the 80-ppm H2S exposure group during the first week of exposure.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
One case each of epididymal sprem granuloma and unilateral necrosis of the cauda in the high exposure group. Ovarian cysts in two rats (10 ppm and 30 exposure).
Histopathological findings: neoplastic:
no effects observed
Other effects:
no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
no effects observed
Description (incidence and severity):
No effects on sperm production or morphology. A large % of abnormal sperm was observed in two F0 rats, one from 30 ppm and one from the 80 ppm exposure group.
Reproductive performance:
no effects observed
Description (incidence and severity):
No statistically significant effects on mating index, fertility index, postimplantation loss per litter, or number of late resorptions or still births.

Details on results (P0)

The reproductive and developmental toxicity indeces are reported in Table 1.

The only statistically significant difference from control in either absolute or relative F0 rat organ weights was a decrease in the absolute and
relative weight of the adrenal glands of male F0 rats from the 10 and 80 ppm H2S exposure groups and a decrease in the relative weight of the
ovaries from female rats exposed to 10 ppm H2S. Subchronic exposure of male F0 rats to H2S was associated with mild to marked sensory neuron
loss and basal cell hyperplasia in the olfactory mucosa lining the dorsal medial meatus and the dorsal medial region of the ethmoid recess. Due to
the lack of toxicologically relevant lesions in other body systems, microscopic examination of F0 male rats was limited to the reproductive tracts
in the control and high exposure groups.

In addition, F0 males in the 10- and 30-ppm exposure groups that were not reproductively successful or that had gross observations made in the
reproductive tract were also evaluated histologically. Statistical comparison of the control and high-exposure groups showed no significant
difference from control in the incidences of the histologic diagnoses found. However, there were a few histologic diagnoses with a higher incidence
in the 80-ppm treatment group when compared to control rats. Most of these diagnoses were related to seminiferous tubular degeneration
(including intratubular sperm stasis, tubular mineralization, sperm granulomas, and multinucleated giant cells), and associated changes in the
epididymis (degenerate sperm forms in lumen, aspermia, and oligospermia). One case each of epididymal sperm granulomas and unilateral
necrosis of the cauda were detected only in the high exposure group (n=12 rats).

Although not statistically significant, lymphoid interstitial infiltrate in the ventral prostate was observed more frequently in the 80ppm treatment
group (5 of 12) when compared to control animals (3 of 12). Statistical comparison of the control and high-exposure groups showed no
significant difference from control in the incidences of histologic diagnoses found. However, there were a few possibly relevant histologic
lesions that occurred in exposed groups but not in unexposed rats. One rat each in both the 10-ppm and the 30ppm exposure groups had
ovarian cysts. Ovaries of one rat in the 80-ppm group contained only a few corpora lutea, which were regressing, and a relatively large number
of tertiary follicles. This rat, as well as one other in the 30-ppm exposure group, also had squamous metaplasia of the endometrium localized to
the uterus.

Effect levels (P0)

open allclose all
Dose descriptor:
NOAEL
Remarks:
nasal olfactory lesions
Effect level:
ca. 10 ppm
Based on:
test mat.
Sex:
male
Basis for effect level:
clinical signs
Key result
Dose descriptor:
NOAEC
Effect level:
> 80 ppm (analytical)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
mortality
neuropathology
reproductive function (sperm measures)
reproductive performance

Results: F1 generation

General toxicity (F1)

Clinical signs:
no effects observed
Dermal irritation (if dermal study):
not examined
Mortality / viability:
no mortality observed
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No treatment-related effects in pups were noted in growth.
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Sexual maturation:
not examined
Anogenital distance (AGD):
no effects observed
Nipple retention in male pups:
no effects observed
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
No treatment-related effects in pups were noted in growth or organ/body weight ratios.
Gross pathological findings:
no effects observed
Histopathological findings:
no effects observed
Other effects:
no effects observed

Developmental neurotoxicity (F1)

Behaviour (functional findings):
no effects observed
Description (incidence and severity):
No treatment-related effects in pups were noted in development or behavioral tests. The NOAEC for the developmental toxicity was 80 ppm (111 mg/m3).

Developmental immunotoxicity (F1)

Developmental immunotoxicity:
no effects observed

Details on results (F1)

The pups (F1 generation): The results of the study suggest that H2S at any studied exposure concentrations is not a behavioral or developmental neurotoxicant in rats.

Effect levels (F1)

Key result
Dose descriptor:
NOAEC
Generation:
F1
Effect level:
> 80 ppm (analytical)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
viability
clinical signs
mortality
body weight and weight gain
organ weights and organ / body weight ratios
neuropathology
histopathology: non-neoplastic
developmental neurotoxicity

Overall reproductive toxicity

Key result
Reproductive effects observed:
no
Lowest effective dose / conc.:
80 ppm (analytical)

Any other information on results incl. tables

 

Table 1. Reproductive and developmental toxicity indices following H2S exposure

 

Endpoint

Exp. group

Mating index

(%)

Fertility index

(%)

Post-implanta-tion loss per litter (%)

Late resorption or stillbirth

Number of

live birthsa

 

Abnormal

sperm (%)

 

Motile

sperm (%)

 

Cauda sperm

countb

 

Daily sperm

productionc

 

0

92 (11/12)

82 (9/11)

2.5

1 (1)

16.3 ± 1.6

0.33 ± 0.44

81.6 ± 6.2

1.02 ± 0.15

17.9 ± 2.2

10

92 (11/12)

100 (11/11)

11.0

3 (3)

14.6 ± 2.6

1.46 ± 1.89

74.9 ± 24.6

0.99 ± 0.17

18.1 ± 1.6

30

75 (9/12)

100 (9/9)

10.2

5 (3)

14.7 ± 1.6

3.33 ± 8.11

75.9 ± 13.5

1.05 ± 0.23

17.3 ± 1.9

80

83 (10/12)

80 (8/10)

7.0

1 (1)

13.9 ± 4.6

7.59 ± 21.71d

76.1 ± 11.1d

0.82 ± 0.40

17.3 ± 5.6

aNumber of live births means and standard deviations.

bCauda sperm count means and standard deviations are expressed as×109.

cDaily sperm production means and standard deviations are expressed as×106.

dThere were no sperm in the sperm motility and morphology sample from one animal (n =11).

Table 2

Structural malformations observed at birth

 

 

Observationa

 

 

 

 

 

 

 

H2S exposure concentration (ppm)

Frontal bone defect

Kinked tail

Agenesis of the tail

Anophthalmia

Small rearlegs and body

Skin and dermis

detachment

Hypognathia

 

10

1 (1)

1 (1)

1 (1)

 

1 (1)

 

 

30

 

1 (1)

 

1 (1)

 

7 (1)

2 (1)

80

 

 

1 (1)

 

 

 

 

 

aData presented are for individual animals. The number of litters affected is in parentheses

Table 3

Acquisition of developmental landmarks in pups exposed to H2S

 

 

Developmental landmarka

 

H2S exposure

Conc. (ppm)

 

Pinnae

detachment

 

Negative

geotaxis

 

Incisor

eruption

 

Eyelid

separation

 

Vaginal

patency

 

Balano-preputial

separation

0

3.4 ± 1.1 (9)

8.0 ± 1.0 (7)

10.9 ± 1.3 (9)

14.6 ± 0.9 (8)

35.2 ± 1.9 (9)

42.3 ± 2.1 (9)

10

3.6 ± 1.2 (11)

8.6 ± 0.5 (5)

11.5 ± 0.5 (11)

15.1 ± 0.5 (11)

33.3 ± 1.2 (11)

43.9 ± 2.3 (11)

30

3.1 ± 0.6 (9)

8.3 ± 0.8 (6)

12.0 ± 1.7 (9)

14.8 ± 0.8 (9)

32.7 ± 2.6 (9)

42.9 ± 2.3 (9)

80

3.3 ± 1.0 (8)

7.8 ± 0.8 (6)

11.3 ± 1.4 (8)

15.0 ± 0.8 (8)

33.5 ± 1.5 (8)

43.1 ± 1.6 (7)

 

a Data presented represent postnatal age at which the entire litter has met criterion (± SD). Data in parentheses represent group size.

 

 

Applicant's summary and conclusion

Conclusions:
Neither maternal or male rats exposed to H2S demonstrated evidence of chemical-induced toxicity to reproduction. The low incidence of
developmental effects in pups and the lack of any dose-respose relationship suggest that H2S is not a developmental toxicant either.
Executive summary:

In this study, it was examined whether perinatal exposure by inhalation to hydrogen sulfide (H2S) had an adverse impact on pregnancy outcomes, offspring prenatal and postnatal development, or offspring behavior. Virgin male and female Sprague–Dawley rats (12 rats/sex/concentration) were exposed (0, 10, 30, or 80 ppm H2S; 6 h/day, 7 days/week) for 2 weeks prior to breeding. Exposures continued during a 2-week mating period and then from GD 0 through GD 19. Exposure of dams and their pups (eight rats/litter after culling) resumed between postnatal day (PND) 5 and 18. Adult male rats were exposed for 70 consecutive days. Offspring were evaluated using motor activity (PND 13, 17, 21, and 60±2), passive avoidance (PND 221 and 62±3), functional observation battery (PND 60±2), acoustic startle response (PND 21 and 62±3), and neuropathology (PND 23±2 and 61±2). There were no deaths and no adverse physical signs observed in F0 male or female rats during the study. A statistically significant decrease in feed consumption was observed in F0 male rats from the 80-ppm H2S exposure group during the first week of exposure. There were no statistically significant effects on the reproductive performance of the F0 rats as assessed by the number of females with live pups, litter size, average length of gestation, and the average number of implants per pregnant female. Exposure to H2S did not affect pup growth, development, or performance on any of the behavioral tests. The results of our study suggest that H2S is neither a reproductive toxicant nor a behavioral developmental neurotoxicant in the rat at 80 ppm or lower concentrations.