Formaldehyde

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

No studies were available which are directly related to this endpoint (e.g. OECD Guideline 415, 416, or 422). However, no studies are needed because it is not to be expected, that formaldehyde reaches the reproductive organs and there is no evidence for effects on fertility and gonads in experimental animals after long-term oral or inhalation exposure. Toxicokinetic data (see summary end discussion Toxicokinetics) suggested only local effects at the site of entry.

Link to relevant study records

Reference

Endpoint:

extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reproductive effects observed:

not specified

Additional information

Effects on fertility

In a two-years drinking-water study in rats comparable with OECD Guideline 453 (Til et al., 1989, Section Repeated dose toxicity: oral) no adverse effects on the reproductive organs were recorded even at the high dose level of 109 mg/kg bw/day in females and 82 mg/kg bw/day in males that induced local effects in the stomach. These negative results for reproductive organs are confirmed by the long-term drinking water study of Tobe et al. (1989; Section Repeated dose toxicity: oral) in rats or a chronic inhalation study in rats and mice (CIIT, 1981; Section Repeated dose toxicity: inhalation) comparable to OECD Guideline 453 and further oral and inhalation studies in rats, mice and dogs (see waiving Section Effects on fertility). This lack of systemic effects to reproductive organs (independent on the route of exposure) are in accord with toxicokinetic data (see endpoint summary of section repeated dose toxicity) suggesting only local effects at the site of entry.

No conclusions can be drawn from the limited data in humans (see waiving Section Effects on fertility).

A short summary and evaluation on reproductive effects is also presented in a recent review by IARC (2006); details are given in the following Section of the endpoint summary.

Ozen et al (2002 and 2005) performed subacute and subchronic inhalation studies with FA particularly addressing testes.
Ozen et al. 2002 exposed rats to formaldehyde at different periods (subacute and subchronic) and concentrations (0; 12.2; 24.4 mg/L). Body and testis weights were recorded and compared with control groups. The metals described below were determined in rat testicular tissue by atomic absorption spectrometry by using wet ashing. It is concluded that that subacute or subchronic exposure to formaldehyde have caused growth retardation and altered levels of trace elements, including copper, zinc and iron, in testicular tissue, and may induce further oxidative damage on testicular tissue leading to spermatozoa abnormalities.

Ozen et al. 2005 used 18 albino Wistar rats divided into three groups, exposed to 0 (control), 5 and 10 ppm FA gas for a total of 91 days, 8 h/day, five days a week. Serum testosterone levels were determined using a chemiluminescent enzyme immunoassay. Testicular tissues were stained with Hematoxylin-Eosine and Hsp70 immunohistochemically. Diameters of seminiferous tubules and serum testosterone levels in animals inhaling FA were significantly decreased. In seminiferous epithelium stained for Hsp70, compared to those in the control group, the spermatogenetic cells in the experimental groups demonstrated an obvious increase in immunoreaction spermatides in the adluminal region and especially in the cytoplasm of spermatocytes. Immunoreaction of Hsp70 was detected in the spermatogonias of animals exposed to FA inhalation as opposed to those of the control group. Compared to the control, there was a significant increase in the immunoreactions observed not only in the cytoplasm of primary spermatocytes, but also spermatides in the adluminal region of the seminiferous tubules.
Both studies lack reporting of key clinical data necessary for interpretation such as body and test weights, clinical data and symptoms etc. and no dose response relationship in testes was observed. It’s not clear whether Bouin’s solution was used for fixation of testes in order to avoid artefacts. However, it is clear that excessive systemic toxicity can be expected at the concentrations used which was reflected in all study groups in the few clinical parameters given in the publications (e.g. by body weight gains).  As there is no experimental indication of systemic availability of FA, it can only be speculated that the effects observed are secondary to excessive general toxicity and irritation/corrosion.

There are many publications reporting adverse effects on male fertility with intraperitoneal (i.p.) application of aqueous FA solutions. Apart from the fact that these irritating or corrosive solutions might distribute directly into the scrotal sac causing local toxicity to the testes, i.p. administration is often accompanied with severe general toxicity leading to secondary effects such as testes effects. In addition, It should be noted that i.p. administration is a completely non-physiological and irrelevant route of exposure per se.

Taskinen et al. (1999) investigated whether exposure to formaldehyde, organic solvents or other chemicals in the wood-processing industry affects the fertility of women. For this purpose, a retrospective study on time to pregnancy was conducted among female wood workers who had given birth during 1985–1995. Data on pregnancy history, time to pregnancy, occupational exposures, and potential confounders were collected by a questionnaire; 64% (699/1,094) participated. The exposure assessment was conducted by an occupational hygienist. The data on time to pregnancy were analyzed with the discrete proportional hazards regression. Exposure to formaldehyde was significantly associated with delayed conception:

adjusted fecundability density ratio, FDR, was 0.64 (95% CI 0.43–0.92). At high exposure if no gloves were used, the FDR was 0.51 (% CI 0.28–0.92). Exposure to phenols, dusts, wood dusts, or organic solvents was not related to the time to pregnancy. Additionally, an association was observed between exposure to formaldehyde and an increased risk of spontaneous abortion (concerning previous spontaneous abortions, reported by the women). Associations between exposure to formaldehyde or to organic solvents and endometriosis, and between exposure to organic solvents or to dusts and salpingo-oophoritis were also suggested.

However, this publication shows a number of deficiencies:

- No analytical measurements. Exposures were estimated based on mailed questionnaires. Exposures were estimated from an undefined sampling time; when sampling was not available estimates relied upon sampling from an unrelated industry (i.e., cosmetology).

- Methanol is a co-exposure that was not accounted for.

- Pregnancy outcomes were evaluated based on recall, in a mailed questionnaire. The period of recall extended over a decade, likely introducing substantial recall bias.

- The number of women evaluated was not reported for the fecundability ratio; rather this report presented only FDR and 95% confidence limits.

- The highest risk in the study was calculated for those not wearing gloves (FDR = 0.51) when compared to formaldehyde exposure (FDR = 0.57) or other exposure categories (FDR = 1.09, 0.96 and 0.64 for low, medium and high exposure groups, respectively). This fact that not wearing gloves presents the greatest risks calls into question all conclusions related to any cause and effect for formaldehyde in the study.

- The exposure categories overlapped, raising serious concerns about assignment of individuals to the exposure bands.

Given these deficiencies, the conclusion of the study is questionable.

Duong et al. (2011, supporting) reviewed the literature on reproductive effects in humans and animals starting from 450 references including studies published in Chinese language mostly in peer reviewed journals. Animal studies by all routes of exposure were included. After removal of abstacts, animal studies dating from before 1980, and non-English publications (except Chinese and human studies), 18 human and 46 animal studies were reviewed in detail. By a metaanalysis of the mainly retrospective human studies the authors observed an increased risk for spontaneous abortions (1.76, 95% CI 1.20-2.59; p=0.002) and all adverse pregnancy outcomes (1.54, 95% CI 1.27-1.88; p<0.001) for formaldehyde exposed women. But differential recall, selection bias, or confounding cannot be ruled out. Animal studies suggest positive associations between formaldehyde exposure and reproductive toxicity, mostly in males. Potential mecchanisms are offered, like genotoxicity, oxidative stress apoptosis, and alterations of enzymes, hormones, or proteins. This review is a valuable collection of literature, including studies from China, but as a critique, generally no effort is made to analyse strengths and weaknesses of the single publications in order to arrive at some weight of evidence assessment.

Khalil et al. (2017) investigated effects on the reproductive system after dosing male Swiss mice with 25 mg FA/kg bw/d over 65 consecutive days. A 40% solution of FA (possibly formalin) was diluted in water to “working stock solutions” without giving further details. The dosing volume per mouse was not specified. FA exposure affected steroidogenesis and several testicular enzymes. Under consideration of the bolus application severe effects on the stomach are to be expected with unknown systemic sequelae and missing data in this respect is a severe deficiency. This relatively new oral gavage study  is hampered by several important drawbacks: detailed information is missing on the dosing solution, histopathology of the stomach, the primary portal of entry, was not carried out, and only one dose level of FA was used such that a dose response relationship cannot be assessed. Furthermore, the relatively steep rise in blood levels obtained by gavage leads to some uncertainty in risk assessment for humans exposed via food or liquid intake.

Effects on developmental toxicity

Description of key information

There is no evidence for adverse effects of formaldehyde on embryo and fetal development at dose levels inducing local maternal effects and secondary decrease in body weights and growth.

Link to relevant study records

Reference

Reference 1

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

Acceptable with some restrictions: No data about purity of the test substance or stability in food; only low dose tested without maternal toxicity; some evaporation of formaldehyde prior to consumption presumed (resulting in lower dose levels). Study limited to a restricted number of parameters (e.g. data on visceral or skeletal alterations only in stillborn pups or pups which died later in post natal observation period, no data on maternal weight gain). No statistical analysis.

Principles of method if other than guideline:

Teratogenic effects in dogs after oral exposure via the food.

GLP compliance:

not specified

Limit test:

no

Specific details on test material used for the study:

- Specification
40% formalin (presumably stabilized with 10% methanol)

Species:

other: dog

Strain:

other: Beagle

Details on test animals or test system and environmental conditions:

- Source: Closed breeding colony of the same laboratory
- Sex: Female
- Age/weight at study initiation: no data / ca. 12 kg
- Dogs received certified diet (dog pellets, Nafag AG, Gossau, Switzerland).
- 4-5 pregnant dogs in one indoor cubicle plus outdoor run; animals single in whelping rooms 1 week before term.

Route of administration:

oral: feed

Vehicle:

other: Solution of the required daily dose in 2 ml were prepared weekly and sprayed on the pellets prior to feeding. Pellets were consumed within 5-10 min (authors statement: no volatilization; comment: some evaporation expected).

Details on exposure:

Concentration in food: 0, 125 and 375 ppm (0, 0.012, 0.037%)
food consumption per day: 300 g per animal per day corresponding to 0, 3.1, or 9.4 mg/kg bw/day (authors calculation).
Controls received the plain diet.

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

No details

Duration of treatment / exposure:

Day 4 after mating up to day 56

Frequency of treatment:

once daily

Duration of test:

Normal birth. Pups observed up to 9 months after birth

Dose / conc.:

125 ppm

Remarks:

- 0.012%
- 3.1 mg/kg bw/day

Dose / conc.:

375 ppm

Remarks:

- 0.037%
- 9.4 mg/kg bw/day

No. of animals per sex per dose:

9-10 pregnant bitches (10-11 mated bitches)

Control animals:

yes, concurrent vehicle

Maternal examinations:

- Body weight Yes, maternal weight determined at weekly intervals.
- Food consumption See above
- Clinical signs No data

Ovaries and uterine content:

No data

Fetal examinations:

External malformations examined immediately after birth and after 8 weeks. Autopsy of stillborn pups and those lost before weaning. Further parameters: total pups at birth, total live pups at birth, total pups at weaning, mean live (or total) pups per litter at birth and at weaning, mean litter size, sex ratio, mean pup weight (measured daily after birth for 8 days).
Skeletal and visceral malformations examined only in stillborn or pups who died postnatal.

Statistics:

no

Indices:

no data

Historical control data:

no data

Details on maternal toxic effects:

No effects.

No data about clinical symptoms and maternal weight gain. No effects on number of pregnant bitches, number of litters and mean length of gestation (range or SD not given). No local maternal effects in the gastro-intestinal tract expected (max. concentration 0.037% in the diet)

Dose descriptor:

LOAEL

Effect level:

> 9.4 mg/kg bw/day (nominal)

Basis for effect level:

other: study not sufficient for identifying a NOAEL, no local effects expected (max. concentration in the diet: 0.037%)

Abnormalities:

no effects observed

Details on embryotoxic / teratogenic effects:

No effects.

No effects on parameters listed above. Mean values given but no data on SD, SE or range. No skeletal or visceral malformation in stillborn pups or pups which died later (no further details).

Dose descriptor:

LOAEL

Effect level:

> 9.4 mg/kg bw/day (nominal)

Basis for effect level:

other: study not sufficient for identifying a NOAEL

Abnormalities:

not specified

Developmental effects observed:

not specified

No effects on behaviour, appearance, motility and muscular co-ordination in dogs observed for a more prolonged period.

Conclusions:

No developmental effects in dogs exposed via the diet to doses up to 9.4 mg/kg bw/day but limited number of parameters examined.

Executive summary:

Study meets generally accepted scientific standards but limited number of parameters examined. Further deficiencies: No data about purity of the test substance; only low dose tested without maternal toxicity; some evaporation of formaldehyde prior to consumption presumed (resulting in lower dose levels). Study limited to a restricted number of parameters (e.g. data on visceral or skeletal alterations only in stillborn pups or pups which died later in post natal observation period, no data on maternal weight gain). No statistical analysis.

Pregnant Beagle dogs (9-10 pregnant bitches per dose) were exposed from day 4 after mating up to day 56 to a diet containing formaldehyde at dose levels of 0, 3.1, or 9.4 mg/kg bw/day. The dose levels (max. 9.4 mg/kg bw) and concentrations (max. 0.037% in the diet) were relative low (no local effects expected). No toxic effects were reported in the bitches (but no data on body weight gain). External malformations were examined immediately after birth and after 8 weeks. Autopsy was performed on stillborn pups and those lost before weaning. Further parameters: total pups at birth, total live pups at birth, total pups at weaning, mean live (or total) pups per litter at birth and at weaning, mean litter size, sex ratio, mean pup weight (measured daily after birth for 8 days). Concerning the investigated parameters no developmental toxicity was detected.

Conclusion: no developmental effects in dogs exposed via the diet to doses up to 9.4 mg/kg bw/day but limited number of parameters examined.

Reference 2

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Comparable to OECD guideline 414 with acceptable restrictions [partly without details on results (irritation, symptoms, necropsy); co-application of methanol (used for stabilisation of formalin solution)].

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

not specified

Limit test:

no

Specific details on test material used for the study:

Aqueous formaldehyde solution containing 12-15% methanol (presumably formalin); source: Fisher Scientific Co.
No further data

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

- Source: Charles-River Breeding Labs, Wilmington, Mass., USA
- Sex: emale (virgin) & male
- Age/weight at study initiation: 60-90 days-old mice, no further data
- Housing conditions:
housed individually, certified diet and tape water ad libitum; 22-24°C; rel. air humidity 45-50%; 12 h light/12 h dark.

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Stock solution diluted with destilled water. Intubation of the dose on a 1% body weight basis (v/w). Thus, 1 mL formaldehyde per 100 g bw was applied. Concentrations: 0, 0.7, 1.5, 1.8%.

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

Mating period 1 day; no further details

Duration of treatment / exposure:

Gestation day 6-15

Frequency of treatment:

once daily

Duration of test:

Termination at day 19 of gestation.

Dose / conc.:

74 mg/kg bw/day

Remarks:

[0.7%] of applied solution

Dose / conc.:

148 mg/kg bw/day

Remarks:

[1.5%] of applied solution

Dose / conc.:

185 mg/kg bw/day

Remarks:

[1.8%] of applied solution

No. of animals per sex per dose:

29-76 dams

Control animals:

yes, sham-exposed

Maternal examinations:

- Body weight: Yes
- Food consumption: No data
- Clinical signs: Only data on mortality
- Necropsy: no data (comment: local effects in the gastro-intestinal tract expected)

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of resorptions: Yes

Fetal examinations:

- General: Live fetuses, litter size, Nr. of live and dead foetuses, foetal weight, Sex ratio, pre and post-implantation loss;
- Skelet: Yes
- Soft tissue: Yes
- External: yes

Statistics:

Suitable methods used for statistical analysis ((Mann-Whitney U Test, Fisher exact test), level of significance p<0.05.

Indices:

No data

Historical control data:

No data

Details on maternal toxic effects:

Decreased body weight gain, but significant only in the low dose group. High dose was lethal to 22 out of 34 dams. One out of 35 dams died at the mid dose level. No mortality at 74 mg/kg bw. Data on repeated oral dose toxicity in Section 7.5.1 suggested local effects in the gastro-intestinal tract even at the low dose level (concentration 0.7%).

Dose descriptor:

LOAEL

Effect level:

74 mg/kg bw/day (nominal)

Basis for effect level:

body weight and weight gain

Abnormalities:

effects observed, treatment-related

Localisation:

other: decreased body weight

Details on embryotoxic / teratogenic effects:

No statistically significant effects on examined developmental parameters. However, at 185 mg/kg bw/day the average of resorptions/litter was doubled compared to concurrent control (but not significant). External, visceral and skeletal examinations of foetuses revealed no teratogenic effects (details presented in a Table) although the high dose resulted in high mortality rate of dams.

Dose descriptor:

NOAEL

Effect level:

185 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: highest dose level tested, also no malformations

Abnormalities:

no effects observed

Developmental effects observed:

no

Developmental effects of formaldehyde in mice after oral exposure via gavage
Tested parameter	Control	Dose in mg/kg bw/day
	Vehicle	74	148	185
No. of dams receiving the test substance	76	29	35	34
No. of dams alive on day 18	76	29	34	12
Number of pregnant dams	69	26	28	8
Average weight gain day 6-17	17.9+-0.42	16.5+-0.46*	17.2+-0.74	16.6+-1.04
Mean number of implants/dam	13.2	13.0	13.5	12.5
Number of resorptions	69	25	37	15
Average % of resorptions/litter	7.5	7.4	9.8	15.0
Average % of foetal deaths/litter	1.4	0.59	1.6	2.0
Sex ratio	403/428	137/174	169/166	40/43
Number of stunted fetuses	2	2	2	1
Average no. of live fetuses/dam	12.1	12.0	12.0	10.4
Average foetal weight in g	0.969+-0.012	0.954+-0.018	0.992+-0.021	0.953+-0.036
*: significant

Conclusions:

No developmental toxicity in mice at dose levels inducing maternal toxicity after oral exposure via gavage.

Executive summary:

Study is comparable to OECD guideline 414 with acceptable restrictions [partly without details on results (irritation, symptoms, necropsy); co-application of methanol (used for stabilisation of formalin solution)].

In this gavage study 29 -76 pregnant mice per dose group were exposed to 0, 74, 148, 185 mg/kg bw/day formaldehyde (concentration of applied solution: 0, 0.7, 1.5, 1.8%) once daily at gestation day 6-15 (termination at gestation day 19). Maternal toxicity was obvious at 74 mg/kg bw/day (decreased body weight gain); data on local effects in the gastro-intestinal tract are not available, however, these effects are expected even at the low dose level (compare with data in Section 7.5.1). No embryo- or fetotoxic effects and no teratogenic effects were reported at any dose level, although 185 mg/kg bw/day resulted in a high mortality rate in pregnant mice.

Conclusion: No developmental toxicity in mice at dose levels inducing maternal toxicity after oral exposure via gavage.

Reference 3

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Comparable to OECD guideline 414 with acceptable restriction (exposure restricted to gestation day 6-15; virus infection in dams of all groups)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes

Remarks:

(BIO-RESEARCH LABORATORIES LTD)

Limit test:

no

Specific details on test material used for the study:

paraformaldehyde (T-353)
Batch No. 732540 from Fischer Scientific Co.
Purity: 95%, with the majority of the remaining 5% being water with a trace of formic acid

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

- Age/weight at study initiation: 13 weeks / 221-277 g
- Housing conditions: housed individually, certified diet and tape water ad libitum; 18-24°C; rel. air humidity 30-70%; 12 h light/12 h dark.
- diet and water not during exposure

Route of administration:

inhalation: gas

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

Exposure chamber 600 l volume; equilibration period 0.5 h each day followed by further 5.5 h exposure; formaldehyde gas was generated by depolymerizing paraformaldehyde at a temperature of 80°C and pressure 2 psi; formaldehyde gas was carried from the generator at a rate of 0.5 L/min into a heated manifold and diluted with 4.5 L/min of dehumidified campressed air.
Gas metered into the inhalation chambers of the 3 treated groups to achieve the desired chamber concentrations. Mean chamber temperature ranged from 17 to 23°C, and mean relative humidity ranged from 48 to 77%.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

3 samples per day (3 x 1.75 h); samples analyzed by the chromotropic acid method.

Details on mating procedure:

Mating:placing 1 female with 1 male overnight; mating determined by the presence af spermatozoa in the vaginal lavage; the day of positive identification af spermatozaa termed day 0 of gestation.

Duration of treatment / exposure:

day 6 to day 15 of gestation

Frequency of treatment:

6 h/day

Duration of test:

Sacrifice and caesarian section at gestation day 20 (GD20).

Dose / conc.:

2 ppm

Dose / conc.:

5 ppm

Dose / conc.:

10 ppm

No. of animals per sex per dose:

25

Control animals:

yes, concurrent no treatment

yes, sham-exposed

Maternal examinations:

- Body weight: weighed on days 0, 6, 9, 13, 16 and 20 of gestation
- Food consumption: measured between days 0 to 6, 6 to 9, 9 to 13, 13 to 16 and 16 to 20 of gestation
- Clinical signs: at least once each day
- Necropsy: at termination full gross pathological examination

Ovaries and uterine content:

The reproductive tract dissected out, the ovaries removed and the corpora lutea counted; uterus weighed and uterine contents examined and the number and position of live fetuses, dead fetuses, early (endometrial gland with or without some placental tissue), middle (discernible placental and fetal tissue present) and late (fetal structure apparent) resorptions were recorded.
The fetuses were removed from the uterus and given s.c. T61 euthanasia solution; uterus of each animal judged to be nonpregnant stained with 10% aq (vlv) ammonium suiphide solution and examined for implantation sites.

Fetal examinations:

Each fetus examined for external malformations; fetal weight and sex determined.
Visceral malformations examined in approximately 50% of the fetuses in each litter, heads of these fetuses removed and fixed in Bouin's fluid for examination by the technique of Wilson; the other 50% of each liter examined for skeletal malformations after staining with Alizarin Red S.
Abnormalities classified as major malformations, minor anomalies or common variants.

Statistics:

Suitable methods used for statistical analysis (one-way analysis of variance, Mann-Whitney U- test, Fisher exact test, Student's t- test), level of significance p<0.05.

Indices:

No details

Historical control data:

No data

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight: Significantly decreased body weight gain (GD 9-12) and body weights (GD 13 & 16) at 10 ppm
Corrected body weight (minus gravid uterine weight): weight gain GD 6-20 and weight at GD20 were sigificantly lower at 10 ppm

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

at 10 ppm sigificant decrease at GD 6-16

Description (incidence and severity):

yellow fur (no adverse effect), no further effects reported. No evidence of maternal toxicity at 2 and 5 ppm (no data about local irritation)

Details on maternal toxic effects:

No data on local effects in the upper respiratory tract available, however, effects expected at >= 5 ppm

Dose descriptor:

NOAEC

Effect level:

5 ppm (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Details on embryotoxic / teratogenic effects:

No effects on parameters listed in material and methods except significantly increased incidence in reduced ossification of the pubic and ischial bones (variation) at the mid and high dose level compared to shame exposed control but not untreated control (within historical range or ischial bone slightly above historical range). This effect was considered to be related to the larger litter size and slightly lower fetal weights at these dose levels.

Dose descriptor:

NOAEC

Effect level:

10 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: highest dose level tested

Abnormalities:

no effects observed

Developmental effects observed:

no

At a dose level of >=5 ppm local effects in the nasal cavity of dams are expected (compare with data in Section 7.5.3 and endpoint summary in Section 7.5). It can be speculated that 2 ppm is the NOAEC for maternal toxicity (related to these local effects).

Conclusions:

No embryo- or fetotoxic effects in rats at concentrations inducing maternal toxicity.

Executive summary:

The study is comparable to OECD guideline 414 with acceptable restriction (exposure restricted to gestation day 6-15; virus infection in dams of all groups).

Pregnant Sprague-Dawley rats (25 per dose level) were exposed at gestation day (GD) 6 -15 for 6 h/day to 0, 2, 5, 10 ppm. The study was terminated at GD20. Maternal toxicity was detected only at 10 ppm (decreased body weight gain and food consumption; no data about irritation but local effects in the nasal cavity expected at >= 5 ppm). No effects of toxicological relevance were found on parameters of developmental toxicity, the NOAEC was 10 ppm.

Conclusion: No embryo- or fetotoxic effects in rats at concentrations inducing maternal toxicity.

Reference 4

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Requirements of OECD guideline 414 fulfilled except data on maternal toxicity (no data on food consumption, body weight during exposure period and clinical symptoms or local effects in the nasal cavity).

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

not specified

Limit test:

no

Specific details on test material used for the study:

37% formalin (stabilized with 10% methanol)
No further data

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

- Source: IFFA-Credo breeding laboratories, France
- Age/weight at study initiation: No data / 180-220 g (acclimatization period at least 5 days)
- Housing conditions:
certified diet and tape water ad libitum; 22-24°C; rel. air humidity 45-55%; 12 h light/12 h dark.

Route of administration:

inhalation: gas

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

Whole body exposure in a 200 l inhalation chamber with air flow 10-20 m³/h
Generation of test atmosphere: air 21-25°C and rel. humidity 45-55%; air flow through a flask containing the test substance; concentration varied by passing air amount.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis by spectrophotometry; periodically samples collected (no further details).

Details on mating procedure:

3 females caged with one male overnight.

Duration of treatment / exposure:

day 6 to day 20 of gestation

Frequency of treatment:

6 h/day

Duration of test:

Termination at gestation day 21

No. of animals per sex per dose:

25 females treated (21-24 pregnant rats for evaluation)

Control animals:

yes, sham-exposed

Maternal examinations:

- Body weight: Yes, at day 0, 6 and 21 (not during exposure period)
- Food consumption: No data
- Clinical signs: No data

Ovaries and uterine content:

- Examination of uterine content
Gravid uterine weight determined
Number of corpora lutea
Number of implantations/resorptions

Fetal examinations:

Examination of foetuses
- General: Live fetuses, litter size, Nr. of live and dead foetuses, foetal weight, Sex Ratio, pre and post-implantation loss
- Skelet: Yes (one half of viable foetuses)
- Soft tissue: Yes (one half of viable foetuses)
- External malformations examined.

Statistics:

Suitable methods used for statistical analysis (Yates' corrected chi squared test, Students's t-test, Mann-Whitney U test); level of significance p<0.05.

Indices:

no

Historical control data:

not documented

Clinical signs:

not specified

Description (incidence and severity):

No data

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Significant effects on maternal body weight only at the high dose level (determined gestation day 6 and 21). But no measurement during exposure period (at least every 3rd day of exposure period recommended).

Food consumption and compound intake (if feeding study):

not specified

Description (incidence and severity):

No data

Dose descriptor:

NOAEC

Effect level:

5 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

LOAEC

Effect level:

10 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: maternal toxicity

Dose descriptor:

NOAEC

Effect level:

10 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Dose descriptor:

LOAEC

Effect level:

20 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

No effects on parameters listed in section 3 except decreased fetal weight of males and females in the high dose group. A slight but significant decrease in foetal weight of males at 20 ppm was also reported. Also no effects on skeletal or visceral variations.

Dose descriptor:

NOAEC

Effect level:

40 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

Dose descriptor:

NOAEC

Effect level:

10 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: overall effects

Dose descriptor:

LOAEC

Effect level:

20 ppm (nominal)

Based on:

test mat.

Basis for effect level:

other: decrease in weight

Abnormalities:

not specified

Developmental effects observed:

not specified

Developmental effects in rats exposed via inhalation for 6 h/day on gestation day 6-20 Mean +- SD
Parameter	0 ppm	5 ppm	10 ppm	20 ppm	40 ppm
Number of pregnant females	24	21	23	21	24
Incidence of pregnancy (%)	96	84	92	84	96
Body weight gain of dams (g)	104+-21	111+-24	106+-18	104+-15	51+-25**
Implantation sites per litter	14.1+-3.3	13.4+-3.6	14.1+-2.2	15.0+-2.0	15.0+-2.0
Total foetal loss per litter	0.6+-0.7	0.4+-0.6	0.6+-0.7	0.6+-0.9	0.6+-1.1
Resorption sites per litter	0.6+-0.7	0.4+-0.6	0.6+-0.7	0.6+-0.7	0.6+-1.1
Live foetuses per litter	13.5+-3.2	13.0+-3.3	13.7+-2.2	14.4+-1.9	14.3+-2.7
Foetal sex ratio	0.89	1.16	1.06	1.01	0.91
Mean weight of male pups	5.61+-0.06	5.54+-0.06	5.52+-0.08	5.35+-0.06*	4.42+-0.09**
Mean weight of female pups	5.24+-0.06	5.31+-0.06	5.22+-0.07	5.09+-0.06	4.27+-0.09**
* : p<0.05; ** : p<0.01;

Conclusions:

No teratogenic effects in rats after inhalation exposure; effects on fetal weight at >= 20 ppm are considered to be due to maternal toxicity.

Executive summary:

In this study the requirements of the OECD guideline 414 were fulfilled except data on maternal toxicity (no data on food consumption, body weight during exposure period and clinical symptoms[local effects expected]).

21 -24 pregnant Sprague-Dawley rats per dose level were exposed via inhalation for 6 h/day on day 6 to day 20 of gestation to 0, 5, 10, 20, or 40 ppm and sacrificed at gestation day 21. Significant effects on maternal body weight were detected only at the high dose level (determined only gestation day 6 and 21). However, maternal toxicity due to local effects in the nasal cavity are expected at >= 10 ppm (compare with data in Section 7.5.3). No developmental effects were found except decreased fetal weight of males and females in the high dose group and a slight but significant decrease in foetal weight of males at 20 ppm.

Conclusion: No teratogenic effects; effects on fetal weight at >= 20 ppm might be due to maternal toxicity.

Additional information

Developmental toxicity

In a study comparable to OECD Guideline 414 (with acceptable restrictions) pregnant Sprague-Dawley rats (25 per dose level) were exposed at gestation day (GD) 6 -15 for 6 h/day to 0, 2, 5, 10 ppm (Martin, 1990; FCC, 1985). The study was terminated at GD20. Maternal toxicity was detected onlyat 10 ppm (decreased body weight gain and food consumption; no data about irritation). At the 5 and 10 ppm levels, an apparently significant concentration-related decrease in ossification was detected in the bones of the pelvic girdle, but this was associated with larger litter sizes with decreased fetal weights in both these groups. The slightly lower fetal weights were considered to be due to the larger litter sizes. Since noeffects of toxicological relevance were found on parameters of developmental toxicity, the developmental toxicity NOAEC was 10 ppm (Martin, 1990; FCC, 1985). In conclusion, no embryo- or fetotoxic effects were detected in rats at concentrations inducing maternal toxicity.

 

In a further teratogenicity study in rats (Saillenfait et al., 1989) no teratogenic effects were detected even at inhaled concentrations up to 40 ppm (0, 5, 10, 20, 40 ppm; 6 h/days at gestation day 6-20). Only effects on fetal weight were reported at ≥ 20 ppm. Significant reduction in body weight and absolute weight gain of dams was found at 40 ppm. No data were reported on clinical signs or local effects; however, local irritant effects are clearly to be expected at ≥ 10 ppm (compare with data in Section Repeated dose toxicity)

 

In an oral developmental toxicity study (Marks, 1980) pregnant mice were exposed via gavage to 0, 74, 148, or 185 mg/kg bw/day formaldehyde (concentration of applied solution: 0, 0.7, 1.5, 1.8%) at gestation day 6-15. Maternal toxicity was reported at 74 mg/kg bw/day or greater (lethality and decreased body weight gain); data on local effects in the gastro-intestinal tract are not available; however, these local effects are expected even at the low dose level/concentration in dams (compare with data in Section Repeated dose toxicity: oral). No embryo- or fetotoxic effects and no teratogenic effects were reported at any dose level, although 185 mg/kg bw/day resulted in a high mortality rate in dams. In conclusion, no developmental toxicity was found in mice at dose levels inducing maternal toxicity after oral exposure via gavage.

 

There were inconsistent findings in epidemiological studies on spontaneous abortions; however, no conclusion can be drawn due to limitations of these studies (see IUCLID Section 7.10.2; WHO, 1989; developmental toxicity).

 

A summary and evaluation on reproductive and developmental effects is also presented in a recent review by IARC (2006): “Eleven epidemiological studies have evaluated directly or indirectly the reproductive effects of occupational exposures to formaldehyde. The outcomes examined in these studies included spontaneous abortions, congenital malformations, birth weights, infertility and endometriosis. Inconsistent reports of higher rates of spontaneous abortion and lowered birth weights were reported among women occupationally exposed to formaldehyde. Studies of inhalation exposure to formaldehyde in animal models have evaluated the effects of formaldehyde on pregnancy and fetal development, which have not been clearly shown to occur at exposures below maternally toxic doses. ”

 

Merzoug and Toumi (2017) observed alterations of behavior and hemato-immune parameters in pregnant Wistar rats with significantly increased cortisol and decreased 17beta-estradiol. Offspring showed a significant decrease of several growth-related parameters and especially a nearly 90 % reduction of live fetuses. Rats were treated over 10 days before mating and then until GD 19. They were dosed with 2 mg FA/kg bw/d (from 37 % formalin) administered in a volume of 1 mL/kg bw corresponding to 2000 mg/L similar to the highest concentration used by Til et al. (1989). Under consideration of the bolus application severe effects in the stomach are to be expected but no information is available. However, detailed information is missing on the dosing solution, histopathology of the stomach, the primary portal of entry, was not carried out, and only one dose level of FA was used such that a dose response relationship cannot be assessed. Furthermore, the relatively steep rise in blood levels obtained by gavage leads to some uncertainty in risk assessment for humans exposed via food or liquid intake. So it remains unclear whether the effects observed are secondary to severe general toxicity and irritation.

Justification for classification or non-classification

The available data on toxicity for reproductiondo not trigger classification and labeling according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008).