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Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information

Read across approach

In the absence of substance-specific data, the reproductive toxicity of diarsenic trioxide is assessed based on reviews and/or data for inorganic arsenic compounds.

Diarsenic trioxide is readily soluble in water (17.8 g/L at 20°C). Upon dissolution in water, it reacts acidically to trivalent arsenite ions which are not subject to any relevant degree of oxidation for up to 72 hours (Klawonn, 2010). Read-across from toxicological data on inorganic arsenites to diarsenic trioxide is justified without restrictions. However, it is also known that in the human body, inorganic arsenic compounds are converted apart from As(III) also to As(V). Upon becoming systemically available, As(V) is rapidly partly converted to As(III). As(III) species are considered to be more toxic and bioactive than As(V) species. The difference in toxicological potency between As(III) and As(V) cannot be quantified exactly and may vary between routes of exposure and/or type of toxicological effects. Generally, risk assessments are conducted for "inorganic arsenic compounds" as a group, and do not differentiate between various species. Following a conservative approach, the toxicity of diarsenic trioxide is therefore considered to be determined by the release of soluble inorganic species (trivalent arsenites and pentavalent arsenates) which do not differ substantially in potency and may be interconverted both in the environment and in the body. Consequently, it is justified to apply read across to soluble inorganic arsenic compounds to evaluate the systemic effects, including reproductive toxicity, of diarsenic trioxide.

General remarks

A large number of investigations in animals and humans on the toxic effects of inorganic arsenic compounds following repeated exposure are available, and these have been reviewed on several occasions by renowned scientific organizations. Given the overwhelming volume of data, a complete set of individual Robust Study Summaries (RSS) was not developed. Instead, an overview of available investigations is presented below.

When evaluating the results of the animal and human studies, it is important to remember that there are considerable differences in arsenic biotransformation between species and between individuals of a same species (see section on Toxicokinetics). Also, a number of aspects raise issues regarding the usefulness of some studies for quantifying, comparing and interpreting results, especially regarding relevance to humans and risk assessment. These include definition of the arsenic species analysed, concentrations/doses, types of cells, simulation of natural exposure for example (Cohen et al., 2013). Therefore, for the hazard assessment, preference is given to human data.

Reproductive / fertility effects of inorganic arsenic compounds

Inhalation exposure

Effects in humans:

No studies were located regarding reproductive effects in humans after inhalation exposure to inorganic arsenicals (ATSDR, 2007).

Effects in animals:

The effect of diarsenic trioxide on reproductive performance was investigated in female (CD) rats exposed to 0.08–20 mg As/m3 (preliminary study) or 0.2–8 mg As/m3 (definitive study) for 6 h daily from 14 days prior to mating through Gestation Day 19. No changes occurred in the precoital interval (time to mating), mating index (percentage of rats mated) or fertility index (percentage of matings resulting in pregnancy), thus yielding a NOAEL of 8 mg As2O3/m3 (Holson et al., 1999; cited in ATSDR, 2007).

Oral route

Effects in humans:

Ingestion of arsenic in drinking water has been associated with adverse reproductive outcomes in humans. For example, a study of 96 women in Bangladesh who had been drinking water containing ≥0.10 mg As/L (approximately 0.008 mg As/kg/day) for 5–10 years reported a significant increase in spontaneous abortions, stillbirth and preterm birth compared to a non-exposed group (Ahmad et al., 2001; cited in ATSDR, 2007). A significant association between concentrations of arsenic in the water >0.05 mg/L (approximately 0.006 mg As/kg/day) and spontaneous abortions were found in another study of 533 women from Bangladesh (Milton et al., 2005; cited in ATSDR, 2007). A study of 202 women from West Bengal (India) reported that exposure to arsenic concentrations of arsenic ≥0.2 mg/L in drinking water (approximately 0.02 mg As/kg/day) during pregnancy were associated with a 6-fold increased risk of stillbirth (von Ehrenstein et al., 2006; cited in ATSDR, 2007). An earlier study of 286 women in USA found no significant association between arsenic in the drinking water (0.0016 mg/L; approximately 0.00005 mg As/kg/day) and spontaneous abortions (Aschengrau et al., 1989; cited in ATSDR, 2007).

A study was conducted to establish the Biomarkers of Exposure to Arsenic (BEAR) prospective pregnancy cohort in Gómez Palacio, Mexico, to better understand the effects of iAs exposure on pregnant women and their children. Two hundred pregnant women were recruited for this study. Concentrations of iAs in drinking water (DW-iAs) and maternal urinary concentrations of iAs and its monomethylated and dimethylated metabolites (MMAs and DMAs, respectively) were determined. Birth outcomes were analyzed for their relationship to DW-iAs and to the concentrations and proportions of maternal urinary arsenicals. DW-iAs for the study subjects ranged from < 0.5 to 236μg As/L. More than half of the women (53%) had DW-iAs that exceeded the World Health Organization’s recommended guideline of 10μg As/L. DW-iAs was significantly associated with the sum of the urinary arsenicals (U-tAs). Maternal urinary concentrations of MMAs were negatively associated with newborn birth weight and gestational age. Maternal urinary concentrations of iAs were associated with lower mean gestational age and newborn length. Biomonitoring results demonstrated that pregnant women in Gómez Palacio are exposed to potentially harmful levels of DW-iAs. The data support a relationship between iAs metabolism in pregnant women and adverse birth outcomes and the results underscore the risks associated with iAs exposure in vulnerable populations (Laine et al., 2015).

A study was conducted to evaluate the associations between individual-level prenatal arsenic exposure with adverse pregnancy outcomes and child mortality in a pregnancy study among 498 women nested in a larger population-based cohort in rural Bangladesh. Creatinine-adjusted urinary total arsenic concentration, a comprehensive measure of exposure from water, food, and air sources, reflective of the prenatal period was available for participants. Self-reported pregnancy outcomes (livebirth, stillbirth, spontaneous/elective abortion) were ascertained. Generalized estimating equations, accounting for multiple pregnancies of participants, were used to estimate odds ratios and 95% confidence intervals in relation to adverse pregnancy outcomes. Vital status of livebirths was subsequently ascertained through November 2015. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals in relation to child mortality. The study author observed a significant association between prenatal arsenic exposure and the risk of stillbirth (greater than median; adjusted OR = 2.50; 95% CI = 1.04, 6.01). The study author also observed elevated risk of child mortality (greater than median; adjusted HR = 1.92; 95% CI = 0.78, 4.68) in relation to prenatal arsenic exposure (Shih et al., 2017).

To study whether the associations between maternal arsenic exposure and birth outcomes were trimester-specific, the study author conducted a birth cohort study of 1390 women from 2014 to 2016 in Wuhan, China. They examined associations between total urinary arsenic concentrations in three trimesters and birth weight, birth length and the risk of small for gestational age (SGA), and the differences of these associations across trimesters using generalized estimating equations. Maternal urinary arsenic concentrations varied across trimesters and were weakly correlated. Arsenic concentrations in the 3rd trimester, but not in the 1st and 2nd trimesters, were associated with birth outcomes. For each doubling of arsenic levels in the 3rd trimester, birth weight was decreased 24.27 g (95% confidence interval (CI): -46.99, -1.55), birth length was decreased 0.13 cm (95% CI: -0.22, -0.04), and the risk for SGA birth was increased 25% (95% CI: 1.03, 1.49). Further, stratified analyses indicated that these associations were only observed in female infants. The study author findings indicate maternal arsenic levels in the 3rd trimester seemed to have significant impacts on birth outcomes, and also emphasize the public health interventions relevance to arsenic exposure in late pregnancy (Liu et al., 2018).

Effects in animals:

Reproductive performance was not affected in female rats that received gavage doses of 8 mg As/kg/day (as As2O3) from 14 days prior to mating through gestation day 19 (Holson et al., 2000; cited in ATSDR, 2007). Reproductive indices that were evaluated included the precoital interval (time to mating), mating index (percentage of rats mated), and fertility index (percentage of matings resulting in pregnancy). In a 3-generation study in mice given sodium arsenite in drinking water at an average dose of 1 mg As/kg/day, there was a significant increase in the incidence of small litters and a trend toward a decreased number of pups per litter in all three generations of the treated group (Schroeder and Mitchener 1971; cited in ATSDR, 2007).

A study was conducted to examine the effects of in utero exposure to inorganic arsenic at the U.S. Environmental Protection Agency (EPA) drinking water standard (10 ppb) and at tumor-inducing levels (42.5 ppm) on reproductive end points and metabolic parameters when the exposed females reached adulthood. Pregnant CD-1 mice were exposed to sodium arsenite [none (control), 10 ppb, or 42.5 ppm] in drinking water from gestational day 10 to birth, the window of organ formation. At birth, exposed offspring were fostered to unexposed dams. The study author examined reproductive end points (age at vaginal opening, reproductive hormone levels, estrous cyclicity, and fertility) and metabolic parameters (body weight changes, hormone levels, body fat content, and glucose tolerance) in the exposed females when they reached adulthood. Arsenic-exposed females (10 ppb and 42.5 ppm) exhibited early onset of vaginal opening. Fertility was not affected when females were exposed to the 10-ppb dose. However, the number of litters per female was decreased in females exposed to 42.5 ppm of arsenic in utero. In both 10-ppb and 42.5-ppm groups, arsenic-exposed females had significantly greater body weight gain, body fat content, and glucose intolerance. The study author concluded that exposure to both a human-relevant low dose and a tumor-inducing level led to early onset of vaginal opening and to obesity in female CD-1 mice (Rodriguez et al., 2016).

In one male reproductive toxicity intervention study, the group of rats was treated with sodium arsenite at the dose of 50 ppm in drinking water for 49 days. Arsenic treatment resulted in adverse morphological and histopathological changes in testis of rats including reduced epithelial height and tubular diameter and increased luminal diameter. Arsenic treatment significantly increased testicular thiobarbituric acid reactive substance (TBARS) levels while catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GSR) activities, and plasma and intra-testicular testosterone concentrations, were decreased significantly. Lipid peroxidation (LPO) was significantly suppressed (Jahan et al., 2015).

In a male reproductive toxicity study in rats, adult Wistar male rats were exposed to sodium arsenite or arsenate at concentrations of 0.01 mg/L or 10 mg/L for 56 d in drinking water. Sodium arsenite at both concentrations and sodium arsenate at 10 mg/L produced reduction in daily sperm production, in number of spermatids in the testis, and in sperm in the epididymal caput/corpus regions. Changes in epididymal morphometry were variable and region specific. Total and progressive sperm motility and sperm morphology did not differ markedly between controls and animals exposed to As. The body and reproductive organs weights, as well as testosterone concentration, remained unchanged among all groups. Based on the study results the study author concluded that As exposure in drinking water over 56 d produced damage in male reproductive functions in adult rats, suggesting that fertility problems might occur (Souza et al., 2016).

In a male reproductive toxicity study, the impact of sodium arsenite and arsenate on sperm quality and fertility was studied. After 56 d exposure, male Wistar rats were mated and pregnant females were evaluated by fertility indexes. Clearly, exposure to 10 mg/L arsenite reduced daily sperm production via H2O2 overproduction and germ cells loss. Animals from this group also showed a decrease in epididymal sperm counts and percentage of sperm with intact membranes. Moreover, they presented low fertility potential and high preimplantation loss. In contrast, 10 mg/L arsenate caused oxidative stress in testis, mineral imbalance in epididymis, and sperm membranes damage, with no effects on fertility. Both arsenic compounds at 0.01 mg/L altered reproductive parameters. The study author concluded that arsenite is more harmful than arsenate to sperm quality and male fertility, with negative influences in early pregnancy (Lima et al., 2018).

Developmental effects of inorganic arsenic compounds

Inhalation route

Effects in humans:

Developmental effects associated with occupational and environmental exposure to airborne arsenic have been investigated in a series of studies at the Ronnskar copper smelter in northern Sweden. In comparison to a northern Swedish reference population, female employees of the smelter had a significantly increased incidence of spontaneous abortion, and their children had a significantly increased incidence of congenital malformations and significantly decreased average birth weight. Increased incidence of spontaneous abortion and decreased average birth weight of children were also found in populations living in close proximity to the smelter. However, while these data are suggestive of developmental effects associated with occupational and environmental exposure from the smelter, the reported effects are not large, the analyses include only limited consideration of potential confounders (e.g., smoking), and there are no data relating the apparent effects specifically to arsenic exposure (Nordström et al., 1978a, 1978b, 1979b; cited in ATSDR, 2007). A case-control study of stillbirths in the vicinity of a Texas arsenic pesticide factory that included an estimation of environmental arsenic exposures using atmospheric dispersion modelling and multiple regression analysis considering arsenic exposure, race/ethnicity, maternal age, median income, and parity as explanatory variables reported a statistically significant increase in the risk of stillbirth in the highest exposure category (>100 ng As/m3, midpoint=682 ng/m3). However, further analysis showed that this increase in risk was limited to people of Hispanic descent, who the researchers speculated may be an especially sensitive population due to a genetic impairment in folate metabolism. Also, the interpretation of this study is limited by small numbers of cases and controls in the high exposure group, lack of data on smoking, potential confounding exposures to other chemicals from the factory, and failure to take into account previous years of deposition in the exposure estimates (Ihrig et al., 1998; cited in ATSDR, 2007).

Effects in animals:

Arsenic has been shown to produce developmental effects by inhalation exposure in laboratory animals, although it is unclear whether or not the effects occur only at maternally toxic doses. Mice exposed to 22 mg As/m3 (as As2O3) for 4 hours on days 9–12 of gestation had serious developmental effects (significant increases in the percentage of dead fetuses, skeletal malformations, and the number of fetuses with retarded growth), while those exposed to 2.2 mg As/m3 had only a 10% decrease in average fetal body weight, and those exposed to 0.20 mg As/m3 had no effects. However, this study is limited by failure to quantify malformations on a litter basis, discuss the nature and severity of the observed malformations, or report on the occurrence of maternal effects (Nagymajtényi et al., 1985; cited in ATSDR, 2007). No increases in fetal resorptions, fetal mortality, or malformations, and no decreases in fetal body weight occurred when rats were exposed to 0.2–8 mg As/m3 (as As2O3), 6 hours daily from 14 days prior to mating through gestation day 19 (Holson et al., 1999; cited in ATSDR, 2007).

In a prenatal developmental toxicity study in rats, inorganic arsenic, as arsenic trioxide (As (+3), As2O3), was administered via whole-body inhalational exposure to groups of 25 Crl:CD(SD)BR female rats for 6 h per day every day, beginning 14 days prior to mating and continuing throughout mating and gestation. Exposures were begun prior to mating in order to achieve a biological steady state of As (+3) in the dams prior to embryonal-fetal development. In a preliminary exposure range-finding study, half of the females that had been exposed to arsenic trioxide at 25 mg/m3 died or were euthanized in extremis. In the definitive study, target exposure levels were 0.3, 3, and 10 mg/m3. Maternal toxicity, which was determined by the occurrence of rales, a decrease in net body weight gain, and a decrease in food intake during pre-mating and gestational exposure, was observed only at the 10 mg/m3 exposure level. Intrauterine parameters (mean numbers of corpora lutea, implantation sites, resorptions and viable fetuses, and mean fetal weights) were unaffected by treatment. No treatment-related malformations or developmental variations were noted at any exposure level. The NOAEL for maternal toxicity was 3.0 mg/m3; the NOAEL for developmental toxicity was greater than or equal to 10 mg/m3, 760 times both the time-weighted average threshold limit value (TLV) and the permissible exposure limit (PEL) for humans. Based on the results of the study, the study author concluded that arsenic trioxide, when administered via whole-body inhalation to pregnant rats, is not a developmental toxicant (Holson et al., 1999).

Oral route

Effects in humans:

Chronic exposure of women to arsenic in the drinking water has been associated with infants with low birth weights in Taiwan and Chile (Yang et al., 2003; Hopenhayn et al., 2003a; cited in ATSDR, 2007). Similar associations have been made between late fetal mortality, neonatal mortality and post-neonatal mortality and exposure to high levels of arsenic in the drinking water (up to 0.86 mg/L during over a decade), based on comparisons between subjects in low- and high-arsenic areas of Chile (Hopenhayn-Rich et al., 2000; cited in ATSDR, 2007). More recently, von Ehrenstein et al. (2006 cited in ATSDR, 2007) reported no significant association between exposure to concentrations of ≥0.1 mg/L arsenic in drinking water (approximately 0.008 mg As/kg/day) (n=117; 29 women were exposed to ≥0.5 mg/L) and increased risk for neonatal death or infant mortality during the first year of life in a study of a population in West Bengal, India. No overall association between arsenic in drinking water and congenital heart defects was detected in a case-control study in Boston, although an association with one specific lesion (coarctation of the aorta) was noted (Zierler et al., 1988 cited in ATSDR, 2007). A study of 184 women with neural tube defects in the offspring living in a Texas county bordering Mexico found that exposure to levels of arsenic in the drinking water >0.010 mg/L (range or upper limit not specified) did not significantly increase the risk for neural tube defects (Brender et al., 2006 cited in ATSDR, 2007).

A study was conducted to examine the association between low-level arsenic in drinking water and small for gestational age (SGA), term low birth weight (term LBW), very low birth weight (VLBW), preterm birth (PTB), and very preterm birth (VPTB) in the state of Ohio. Exposure was defined as the mean annual arsenic concentration in drinking water in each county in Ohio from 2006 to 2008 using Safe Drinking Water Information System data. Birth outcomes were ascertained from the birth certificate records of 428,804 births in Ohio from the same time period. Multivariable generalized estimating equation logistic regression models were used to assess the relationship between arsenic and each birth outcome separately. Sensitivity analyses were performed to examine the roles of private well use and prenatal care utilization in these associations. Arsenic in drinking water was associated with increased odds of VLBW (AOR 1.14 per µg/L increase; 95% CI 1.04, 1.24) and PTB (AOR 1.10; 95% CI 1.06, 1.15) among singleton births in counties where <10% of the population used private wells. No significant association was observed between arsenic and SGA, or VPTB, but a suggestive association was observed between arsenic and term LBW. The study author concluded that arsenic in drinking water was positively associated with VLBW and PTB in a population where nearly all (>99%) of the population was exposed under the current maximum contaminant level of 10 µg/L (Almberg et al., 2017).

A study was conducted to determine whether maternal arsenic exposure is associated with neural tube defects (NTD) risk in Northern China. The study authors case-control study was conducted in 11 countries or cities in Shanxi and Hebei provinces during 2003-2007. A total of 774 mothers were included as participants: 511 controls and 263 cases (including 123 with anencephaly, 115 with spina bifida, 18 with encephalocele, and 7 with other NTD subtypes). The arsenic concentration was measured in a specific section of hair that grew from 3 months before to 3 months after conception. The study authors found a higher hair arsenic concentration in the NTD cases with median (inter-quartile range) of 0.093 (0.025-0.387)μg/g hair than that in the controls with a value of 0.082 (0.030-0.414)μg/g hair. Maternal hair arsenic concentration above its median of the controls was associated with an increased risk of the total NTDs with an adjusted odds ratio (OR) of 1.32 [95% confidence interval (CI): (0.91-1.92)], which was not statistically significant (p = 0.14), although the crude OR without adjusting for the confounders of 1.68 (95% CI: 1.24-2.27; p < 0.001) suggested that hair arsenic is a risk factor of NTDs. There was no dose-response relationship between maternal hair arsenic concentration and the risk of total NTDs. Similar phenomena were found for anencephaly and spina bifida, respectively. Based on the study results, the study authors concluded that maternal periconceptional arsenic exposure may not significantly contribute to the risk of NTD development in Northern China; other risk factors need to be further examined in future studies (Wang et al., 2019).

Effects in animals:

There is a considerable number of other studies in animals suggesting that ingested inorganic arsenic may produce developmental effects, which however involved such high doses that also produced overt maternal toxicity (ATSDR, 2007). For example, rats treated with a single gavage dose of 23 mg As/kg as arsenic trioxide on GD 9 had a significant increase in postimplantation loss and a decrease in viable fetuses per litter, while those treated with 15 mg As/kg showed no effects (Stump et al., 1999; cited in ATSDR, 2007). Rats treated by daily gavage with 8 mg As/kg/day starting 14 days before mating and continuing through gestation had significantly reduced fetal body weights and significantly increased incidences of several skeletal variations (unossified sternebrae, slight/moderate sternebrae malalignment) that the researchers considered to be consequences of developmental growth retardation (Holson et al., 2000; cited in ATSDR, 2007). Exposure of rats to 2.93–4.20 mg As/kg/day throughout gestation and for 4 months postnatally resulted in alterations in neurobehavioral parameters in the offspring, including increased spontaneous locomotor activity and number of errors in a delayed alternation task; maternal behaviour was not affected (Rodriguez et al., 2002; cited in ATSDR, 2007). Studies in mice found increased fetal mortality, decreased fetal body weight, a low incidence of gross malformations (primarily exencephaly), and an increase in skeletal malformations in mice given single gavage doses of 23–48 mg As/kg during gestation, but with no effects at 11 mg As/kg (Baxley et al., 1981; Hood et al., 1978; cited in ATSDR, 2007). Similarly, in mice treated with 24 mg As/kg/day as arsenic acid on days 6–15 of gestation, there was a significant increase in the number of resorptions per litter (42% vs. 4% in controls) and significant decreases in the number of live pups per litter (6.6 vs. 12.3 in controls) and mean fetal weight (1.0 g vs. 1.3 g in controls), while no developmental effects were found at 12 mg As/kg/day (Nemec et al., 1998; cited in ATSDR, 2007). Hamsters treated with a single gavage dose of 14 mg As/kg during gestation also had increased fetal mortality and decreased fetal body weight, with no effect at 11 mg As/kg (Hood and Harrison 1982; cited in ATSDR, 2007). However, the most sensitive species was the rabbit, which had increased resorptions and decreased viable fetuses per litter at 1.5 mg As/kg/day and a developmental NOAEL of 0.4 mg As/kg/day, following repeated gavage dosing with arsenic acid during gestation (Nemec et al., 1998; cited in ATSDR, 2007).

In a developmental toxicity study, CD-1 mice and New Zealand White rabbits were orally gavaged with arsenic acid dosages of 0, 7.5, 24, or 48 mg/kg/d on gestation days (GD) 6 through 15 (mice) or 0, 0.19, 0.75, or 3.0 mg/kg/d on GD 6 through 18 (rabbits) and examined at sacrifice (GD 18, mice; GD 29, rabbits) for evidence of toxicity. Two high-dose mice died, and survivors at the high and intermediate doses had decreased weight gains. High-dose-group fetal weights were decreased; no significant decreases in fetal weight or increases in prenatal mortality were seen at other dosages. Similar incidences of malformations occurred in all groups of mice, including controls. At the high dose in rabbits, seven does died or became moribund, and prenatal mortality was increased; surviving does had signs of toxicity, including decreased body weight. Does given lower doses appeared unaffected. Fetal weights were unaffected by treatment, and there were no effects at other doses. These data revealed an absence of dose-related effects in both species at arsenic exposures that were not maternally toxic. In mice, 7.5 mg/kg/d was the maternal NOAEL; the developmental toxicity NOAEL, while less well defined, was judged to be 7.5 mg/kg/d. In rabbits, 0.75 mg/kg/d was the NOAEL for both maternal and developmental toxicity (Nemec et al., 1998).

In a prenatal developmental study in rats, arsenic trioxide was administered orally beginning 14 days prior to mating and continuing through mating and gestation until GD 19. Exposures began prior to mating in an attempt to achieve a steady state of arsenic in the bloodstream of dams prior to embryo-foetal development. Groups of 25 Crl:CD(SD) BR female rats received doses of 0, 1, 2.5, 5 or 10 mg/kg/day by gavage. The selection of these dose levels was based on a preliminary range-finding study, in which excessive post-implantation loss and markedly decreased foetal weight occurred at doses of 15 mg/kg/day and maternal deaths occurred at higher doses. Maternal toxicity in the 10 mg/kg/day group was evidenced by decreased food consumption and decreased net body weight gain during gestation, increased liver and kidney weights, and stomach abnormalities (adhesions and eroded areas). Transient decreases in food consumption in the 5 mg/kg/day group caused the maternal NOAEL to be determined as 2. 5 mg/kg/day. Intrauterine parameters were unaffected by arsenic trioxide. No treatment-related foetal malformations were noted in any dose group. Increased skeletal variations at 10 mg/kg/day were attributed to reduced foetal weight at that dose level. The developmental NOAEL was thus 5 mg/kg/day. Based on the study, the study author concluded that orally administered arsenic trioxide cannot be considered to be a selective developmental toxicant (i.e. it is not more toxic to the conceptus than to the maternal organism), nor does it exhibit any propensity to cause neural tube defects, even at maternally toxic dose levels (Holson et al., 2000).

In a developmental neurotoxicity study, 28 pregnant Sprague-Dawley rats were exposed to arsenate (AsV) via drinking water (0, 23.6, 47.7, 71.0 ppm) (n = 5–7/group) from GD 6 through 22 with targeted doses of 0, 2.33, 4.67, 7.00 mg/kg/day, respectively. Offspring were dosed by gavage daily with the same mg/kg AsV dose as intended for their dam from postnatal day (PND) 1 to 21. Gestational water intake was reduced at all AsV doses but returned to control levels on lactational day (LD) 1 when control water was returned. Gestational body weight was reduced only at the highest dose on GD 22 and lactational body weight was unaffected. Food intake was unaffected. iAs exposure did not alter offspring body weight (PNDs 1–21) or age at fur development and bilateral ear opening. Incisor eruption, however, was significantly delayed in offspring of the 4.67 and 7.00 mg/kg groups. Further, all iAs groups were significantly delayed in bilateral eye opening. Righting reflex (PNDs 3–6) was unaffected, while slant board performance (PNDs 8–11) was significantly poorer at the highest dose. Brains of culled pups (PND 1) showed dose-dependent increases of iAs. There were no significant AsV-related effects on PND 21 brain regional concentrations of dopamine, DOPAC, HVA, 5-HT or 5-HIAA (Moore et al., 2019).

In a study conducted to examine developmental and behavioral alterations induced by iAs exposure, pregnant Wistar rats were exposed to 0.05 and 0.10 mg/L iAs through drinking water during gestation and lactation. Sensory-motor reflexes in each pup were analyzed and the postnatal day when righting reflex, cliff aversion and negative geotaxis were recorded. Functional Observational Battery (FOB) and locomotor activity in an open field were assessed in 90-day-old offspring. Results show that rats exposed to low iAs concentrations through drinking water during early development evidence a delay in the development of sensory-motor reflexes. Both FOB procedure and open-field tests showed a decrease in locomotor activity in adult rats. Based on the study results, the study author concluded that exposure to the above-mentioned iAs concentrations produces dysfunction in the CNS mechanisms whose role is to regulate motor and sensory development and locomotor activity (Gumilar et al., 2015).

Overall conclusion

Chronic exposure of women via drinking water and inhalation has been suggested as being associated with developmental toxicity and an impairment of birth outcome. Inorganic arsenic has also been shown to be embryotoxic and teratogenic in experimental animals; however, most studies have used high parenteral arsenic dosing, which might have involved maternal toxicity. Only recently have experimental studies without maternal toxicity shown foetal growth retardation, neurotoxicity and alteration in pulmonary structure following oral dosing at relevant exposure levels, often in the form of arsenate. Due to the major differences between species, direct extrapolation from animals to humans cannot be made. However, the comparison of the susceptibility to arsenic of various species during embryonic and foetal development appears to indicate the importance of metabolism for developmental toxicity.

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Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available

Effects on developmental toxicity

Description of key information

The information on developmental toxicity is discussed together with the information on reproduction / fertility effects (see above).

Effect on developmental toxicity: via oral route
Endpoint conclusion:
adverse effect observed
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
adverse effect observed
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on sufficient human evidence that meets the classification criteria given in Table 3.7.1 (a) of Regulation (EC) No. 1272/2008, a self-classification for diarsenic trioxide as known human Reproductive toxicant Category 1A- H360 (May damage fertility or the unborn child) is proposed (see endpoint summary).

Additional information