Investigations on the subchronic toxicity of 2-methoxypropanol-1(acetate) in rats.

Wistar rats were exposed to 2-methoxypropylacetate-1 (2-MPAc-1) vapours in concentrations of 0, 110, 560 and 2800 ppm for (equiv. to 0; 0.6; 3.0 and 14.9 mg/L) for 4 weeks in chambers (6 hours/day; 5 days/week; five male and five female animals per group). The top concentration was equivalent to a 95% vapour saturation at 20 degrees C and the animals reacted to this with a moderate respiratory irritation during the 6 hours exposure times; at 560 ppm these effects were only slight. The top dose was also associated with a significantly reduced body weight development and some hematologic and biochemical alterations of little specificity. The most prominent effect was thymic atrophy. No effects were noted on the testes or on the cellularity in blood or bone marrow. 560 ppm were without systemic effects. Furthermore, 2-methoxypropanol-1 (2-MP-1), 2-MPAc-1 and 2-ethoxyethanol (EE) were administered in parallel by gavage to groups of five male Wistar rats daily for 10 days at near equimolar dose levels (1800, 2600 and 1800 mg/kg per day, respectively). At the end of the administration period the testes were investigated. There was a pronounced testicular atrophy in animals exposed to EE, whereas no adverse effects were observed with 2-MP-1 and 2-MPAc-1. The results of these studies indicate that 2-MP-1 and 2-MPAc-1 which previously had been shown to exert pronounced prenatal toxicity in rabbits and weak prenatal effects in rats are devoid of other forms of systemic toxicity in rats that are typically observed with ethoxyethanol and methoxyethanol.

Developmental toxicity of dimethylacetamide in rabbits following inhalation exposure.

(1) Dimethylacetamide was tested for developmental toxicity after inhalation exposure of pregnant Himalayan rabbits. Fifteen female rabbits per main group were exposed to dimethylacetamide vapours at concentrations of 0, 0.2, 0.7 or 2.0 mg/l (equivalent to 0, 57, 199.5 or 570 ppm) and five female rabbits per satellite group to 0 or 2.0 mg/l 6 h/day from day 7 post-insemination (p.i.) to day 19 p.i. All animals were observed until day 29 p.i. (2) No signs of maternal toxicity were seen in the does of the main groups (body weight and gross pathology) or in the does of the satellite groups (body weight, blood chemistry, histopathological findings of the liver). (3) Fetotoxic effects were caused at a concentration of 0.7 mg/l (e.g., increased skeletal variations) and 2.0 mg/l (e.g., significantly decreased fetal and placental weights, increase in soft tissue and skeletal variations). At 2.0 mg/l, there were also signs of a weak teratogenic effect expressed as a marginal, statistically not significant increase in soft tissue malformations (regarding the heart and great vessels). No compound-related effects were observed in the fetuses after exposure to 0.2 mg/l. (4) The highest concentration tested under these conditions (2.0 mg/l) was found to be a no-observable-adverse-effect-level (NOAEL) for the maternal Himalayan rabbit, whereas 0.2 mg/l was defined as the NOAEL for the developing organism.

Tri-isobutylphosphate: a prenatal toxicity study in rats.

To assess the prenatal toxicity to rats of the anti-foaming agent, tri-isobutylphosphate (CAS 126-71-6), a study was conducted in which daily dosages of 0, 100, 300 and 1000 mg/kg were administered to different treatment groups by gavage from day 6 to 15 of pregnancy. Dams were killed and foetuses examined on day 20 of pregnancy. Maternal effects during the dosing period included a dosage-related increase in the frequency, persistence and severity of post dosing salivation in all test groups and significantly increased water consumption at 1000 mg/kg. Bodyweight gain at 1000 and 300 mg/kg was lower than that of controls but the differences were not statistically significant. The lowest dosage of 100 mg/kg could be considered as the maternal 'lowest observed adverse effect level' (LOAEL) or 'no observed adverse effect level' (NOAEL) according to whether increased salivation is perceived to be a true toxic effect or simply a reaction to the taste of the test material. Neither litter values nor the prevalence of foetuses with abnormalities indicated any embryotoxic effects (including teratogenicity) at any dosage. The most notable feature of the results was the occurrence of a cluster of foetuses with the congenital abnormality referred to as 'hunched posture syndrome' or 'squat foetus syndrome'. However, the incidence of this finding was similar to that noted among background data for the same strain and, in the absence of any other embryotoxic findings, was considered likely to have arisen coincidentally.

Subchronic inhalation toxicity study of 2-ethylhexanol vapour in rats.

A 90-day subchronic inhalation toxicity study was performed on Wistar rats in accordance to OECD testing guidelines to evaluate the toxicological profile of 2-ethylhexanol, potential target organs, and a no-observable-adverse-effect-level (NOAEL). 10 males and 10 females per group were exposed to 2-ethylhexanol vapours at concentrations of 15, 40 and 120 ppm (the latter corresponding to the vapour saturation at 20 degrees C) 6 hours/day for 90 days. The respective controls inhaled clean air under the same conditions. No substance-related adverse effects were observed for body weight, body weight gain, mortality, organ weights, clinical biochemistry and haematological parameters including clotting time. Cyanide-insensitive palmitoyl-CoA oxidation, a marker for peroxisome proliferation, was found elevated in a subchronic study in Fischer 344 rats after gavage application of 500 mg/kg but not under the conditions of this 90-day subchronic inhalation study. There were no findings related to the treatment with 2-ethylhexanol either at necropsy or at histological examination. The highest concentration tested under these conditions (120 ppm) was found to be the NOAEL for male and female rats.

Toxicity of aliphatic amines: structure-activity relationship.

SARs may enable the evaluation of the toxic potential of chemicals by drawing conclusions from available data on structurally-related chemicals, thus reducing the need for further testing. The Advisory Committee on Existing Chemicals of Environmental Relevance (BUA) [1,2] of the German Chemical Society (Gesellschaft Deutscher Chemiker [GDCh]) has compiled data on the toxicity and ecological impact for several groups of chemicals [3, 4]. In the present review, some common toxicological properties for aliphatic amines were revealed after evaluation and comparison of the toxicity data.

Twenty-eight-day repeated-dose inhalation exposure of rats to diethylene glycol monoethyl ether.

This study was carried out to provide information on the effects of inhalation of diethylene glycol monoethyl ether, a substance used in industry which may be accidentally inhaled by man. Sprague-Dawley CD rats were exposed by inhalation to a test atmosphere containing diethylene glycol monoethyl ether in a nose-only exposure system for 6 hr a day, 5 days a week for 28 days. Mean exposure levels were 0. 09, 0.27, and 1.1 mg/liter. At the two lowest exposure levels the test substance was present entirely as vapor, but at the highest exposure level the test atmosphere was approximately equally divided by mass into respirable droplets (aerosol) and vapor. A comprehensive battery of toxicological evaluations including food consumption, body weight, clinical signs, hematology, and biochemistry revealed no evidence of a systemic effect of exposure. Histopathological examination showed changes indicative of mild nonspecific irritation in the upper respiratory tract of rats exposed at the two highest exposure levels. These changes consisted of foci of necrosis in the ventral cartilage of the larynx of rats exposed at 0.27 or 1.1 mg/liter and an increase in eosinophilic inclusions in the olfactory epithelium of the nasal mucosa of rats exposed at 1.1 mg/liter. The no observed adverse effect level for systemic effects was 1.1 mg/liter and the no observed adverse effect level for signs indicative of mild nonspecific irritation of the upper respiratory tract was 0.09 mg/liter.

Developmental toxicity of 2-butin-1,4-diol following oral administration to the rat.

Developmental toxicity of 2-butin-1,4-diol was determined in groups of 18-22 pregnant Wistar rats at dose levels of 10, 40 and 80 mg/kg bw/day administered by gavage from days 6 to 15 pc. At 80 mg/kg bw/day food consumption and maternal body weight were reduced and one dam died during the treatment period. At this dose level the incidence of affected fetuses per litter with accessory 14th ribs was increased. This variation is assessed as an embryotoxic effect resulting from non-specific stress on the dams. No teratogenic effects were caused by 2-butin-1,4-diol. The NOAEL on the maternal and the developing organism was 40 mg/kg bw/day.

Study on the developmental toxicity of orally administered isobutylidenediurea in rats.

Developmental toxicity of isobutylidenediurea (IBDU) was determined by oral administration to Wistar rats. The substance was administered as an aqueous suspension to 22-24 pregnant rats per group by gavage in daily doses of 100, 400 and 1000 mg/kg body weight from day 6 post-coitum (p.c.) to day 15 p.c. The control group received the vehicle only (0.5% aqueous carboxymethyl cellulose solution). There were no substance-related effects in the dams concerning food consumption, body weight, body weight gain, uterine weights and clinical or autopsy observations even at the highest dose of 1000 mg/kg body weight/day. The reproduction data revealed no biologically relevant differences between the control and treated groups. The incidence and type of the foetal external, soft tissue and skeletal findings, which were classified as malformations, variations and/or retardations observed in the treated foetuses were similar to the concurrent and/or historical control data. Thus, under the conditions of this study, no signs of maternal toxicity or embryo/foetotoxicity were induced by IBDU and the no-observable-adverse-effect level on the maternal and developing organism was 1000 mg/kg body weight/day.

A systematic approach for evaluating the quality of experimental toxicological and ecotoxicological data.

The evaluation of the quality of data and their use in hazard and risk assessment as a systematic approach is described. Definitions are proposed for reliability, relevance, and adequacy of data. Reliability is differentiated into four categories. Criteria relating to international testing standards for categorizing reliability are developed. A systematic documentation of evaluating reliability especially for use in the IUCLID database is proposed. This approach is intended to harmonize data evaluation processes worldwide. It may help the expert in subsequent assessments and should increase the clarity of evaluation.

Long-term inhalation toxicity of N-vinylpyrrolidone-2 vapours. Studies in rats.

In previous subchronic studies inhaled N-vinylpyrrolidone-2 (NVP) was haemotoxic, hepatotoxic and irritant to the nose. In the first of two long-term studies, study A, Sprague-Dawley rats were exposed by inhalation to 0, 5, 10 or 20 ppm NVP (6 hr/day, 5 days/wk) for 24 months. Satellite groups were killed after 3, 12 or 24 months. In study B, female Sprague-Dawley rats were exposed to 0 or 45 ppm NVP for 3 months and killed at 3 or 12 and 24 months post-exposure. In study A, survival was unaffected, but reduced body weight gain, haemotoxicity, effects on clinical chemistry parameters indicative of hepatotoxicity, increased liver weight, hepatocellular carcinomas, necrosis, reparative hyperplasia, adenomas and adenocarcinomas of the nasal cavity, and squamous cell carcinomas of the larynx were seen. Increased tumour incidence was seen only in the liver and upper respiratory tract. In study B, the effect of NVP on body weight evident at 3 months disappeared before 1 yr, but effects on liver pathology persisted throughout the subsequent 21-month exposure-free period, and a few liver tumours were seen at 2 yr. As NVP gave negative results in a battery of in vitro and in vivo genotoxicity tests, it appears that the tumours that arose were manifestations of a non-genotoxic mechanism.

Subchronic inhalation and oral toxicity of N-vinylpyrrolidone-2. Studies in rodents.

N-Vinylpyrrolidone-2 (NVP) is a monomeric compound used as an industrial intermediate. Nine of 11 studies previously reported involved exposure of rats (two different strains), mice or hamsters to NVP by the inhalation route at concentrations of up to 120 ppm (6 hr/day, 5 days/wk) over a period of 1 wk to 12 months. The remaining two studies involved exposure of rats to NVP through the drinking water or by gavage at dose levels of up to 100 mg/kg body weight/day. Reduced body weight gain was seen in rats exposed by inhalation to 5 ppm or more for 3 months and in mice and hamsters exposed to 45 ppm for only 1 day. Effects were seen on haematological (reduced haemoglobin, erythrocyte count, haematocrit) and clinical chemistry parameters (specially raised gamma-glutamyltransferase activity and decreases in plasma protein), liver weight increase and liver lesions (centrilobular single-cell necrosis and foci of hepatocellular alteration) in rats and mice but not hamsters. Rats exposed to 40 mg/kg body weight/day NVP or more for 3 months by gavage developed similar liver changes. Atrophy of olfactory epithelium and hyperplasia of nasal respiratory epithelium was seen in rats exposed by inhalation to 5 ppm NVP for 7 wk but not in response to 1 ppm for 13 wk (no observed-adverse-effect level, NOAEL). These studies indicated that the upper respiratory tract and the liver are the main targets for NVP toxicity.

Subchronic toxicity studies of 3-methyl-1-butanol and 2-methyl-1-propanol in rats.

1. 90-day subchronic toxicity studies with 3-methyl-1-butanol (MEB) and 2-methyl-1-propanol (MEP) were performed on rats to evaluate the toxicological profile of the compounds under conditions of drinking water studies, to identify the potential target organs, and to determine no-observable-adverse-effect-levels (NOAELs) respective of the substances. The test substances were administered to groups of 10 male and 10 female Wistar rats in drinking water at concentrations of 0, 1000 p.p.m. (about 80 mg/kg/d), 4000 p.p.m. (about 340 mg/kg/d) and 16,000 p.p.m. (about 1250 and 1450 mg/kg/d of MEB and MEP respectively). 2. 16,000 p.p.m. was found to be the maximal concentration for both alcohols applicable to rats in drinking water. Higher concentrations had an influence on palatability and could thus not be tested in drinking water studies. 3. At 16,000 p.p.m. MEB a marginal increase in the red blood cell count as well as a slight decrease in the mean corpuscular volume and the mean corpuscular hemoglobin content was observed in males only. These changes are considered to be treatment-related, although the toxicological significance of these findings is unclear. No other substance-related effects were found on body weight (b.w.), mortality, various parameters of clinical chemistry, organ weights, gross pathology and histopathology. 4000 p.p.m. MEB did not cause any substance-induced changes. Therefore, the NOAEL of MEB was defined as 4000 p.p.m. for male and 16,000 p.p.m. for female rats under conditions of oral application via drinking water. 4. MEP concentrations up to and including 16,000 p.p.m. did not induce any signs of toxicity and were therefore defined as the NOAEL respective of this substance for rats under conditions of drinking water application.

Investigation of the prenatal toxicity of orally administered diethylene glycol in rabbits.

Diethylene glycol was tested for prenatal toxicity after oral administration (gavage) to pregnant Himalayan rabbits. The substance was administered to 15 female rabbits per group by stomach tube in daily doses of 100, 400, or 1000 mg/kg body wt from Day 7 postinsemination (p.i.) through Day 19 p.i. The control group received the vehicle only (twice distilled water). There were no compound-related effects on the dams concerning food consumption, body weight, body weight gain, or clinical or necropsy observations even at the highest dose of 1000 mg/kg body wt/day. All data obtained on gestational parameters also revealed no biologically relevant differences between the control and treated groups. The fetal external, soft tissue, and skeletal findings, which were classified as malformations, variations, and/or retardations, were seen in the treated fetuses at a frequency similar to the corresponding and/or historical controls. Thus, under the conditions of this study, no signs of maternal toxicity or embryo-/fetotoxicity were induced by diethylene glycol. Therefore, a no-observable-adverse-effect level for diethylene glycol of > 1000 mg/kg body wt/day was established for both the maternal and the developing Himalayan rabbit.

Studies on the prenatal toxicity of 3-methyl-1-butanol and 2-methyl-1-propanol in rats and rabbits following inhalation exposure.

3-Methyl-1-butanol (MEB) and 2-methyl-1-propanol (MEP) were tested for their prenatal inhalation toxicity in pregnant Wistar rats or Himalayan rabbits. Twenty-five female rats and 15 female rabbits per group were exposed to MEB and MEP vapors at concentrations of 10, 2.5, or 0.5 mg/liter, 6 hr/day. The rats were exposed on Days 6-15 postcoitum (pc) and the rabbits were exposed on Days 7-19 postinsemination (pi). Control groups were exposed to clean air. The body weights of the animals of either species were determined several times throughout the studies. All rats and all rabbits were killed on Day 20 pc and Day 29 pi, respectively. The fetuses were removed from the uterus and examined for compound-related effects. The high concentration of 10 mg/liter caused a slight retardation of body weight gain in the dams of either species exposed to MEB and in the dams of rabbits exposed to MEP during the first days of the exposure period. Eye irritation was observed only in the MEB-treated rabbits during the period of exposure to 10 mg/liter. The fetuses of either species exhibited no signs of embryo-/fetotoxicity or teratogenic effects caused by MEP or MEB. Under the experimental conditions, 2.5 mg/liter was found to be a no-observable-adverse-effect level (NOAEL) for the dams of either species exposed to MEB and for the does exposed to MEP, whereas 10 mg/liter MEP was the NOAEL for the maternal rats. For both substances 10 mg/liter was defined as the NOAEL for the conceptuses of either species.

Assessment of structurally related chemicals: toxicity and ecotoxicity of acrylic acid and acrylic acid alkyl esters (acrylates), methacrylic acid and methacrylic acid alkyl esters (methacrylates).

BUA compiled the available data on toxicity and ecotoxicity for several acrylic and methacrylic acid esters and their corresponding acids. A comparison of these data revealed a qualitative similarity in the toxicological and ecotoxicological properties of the compounds considered. The data indicate that methacrylates are less reactive than the corresponding acrylates.

Prenatal toxicity of inhalation exposure to 2-methoxypropanol-1 in rabbits.

2-Methoxypropanol-1 was investigated for prenatal toxicity in Himalayan rabbits after inhalation exposure to 0, 145, 225, 350, and 545 ppm for 6 hr per day from Gestation Day 6 through 18. Maternally toxic effects were found with decreased body weights from Day 12 of gestation through the end of the study at 545 ppm. A dose-dependent increase of resorptions, fetal malformations, and variations was observed at 225, 350, and 545 ppm, whereas 145 ppm was devoid of exposure-related effects. The malformation rate at 545 ppm was 100%. The types of malformations mainly consisted of absent phalanges and absent or rudimentary metatarsal bones, malformed ribs, and a unique enlargement of sternebrae. The effects are very similar to those previously found with 2-methoxypropyl-acetate-1. The results of this study may have implications for the quantitative estimation of risks associated with 2-methoxy-propanol-1 impurities in the widely used isomer 1-methoxypropanol-2 which itself does not show developmental toxicity.

Lung deposition, lung clearance and renal accumulation of inhaled cadmium chloride and cadmium sulphide in rats.

Rats were exposed 6 h/day over 10 days to 0.3 mg/m3 of water soluble cadmium chloride and 0.2, 1.0 and 8.0 mg/m3 of insoluble cadmium sulphide, then killed at intervals over a 3-month period for serial measurements of lung, renal and faecal cadmium. CdCl2 and high-dose CdS animals showed a transient increase in lung weight. Clearance of both compounds was biphasic. Approximately 40% of deposited material was cleared during the 10-day exposure period. For CdCl2, only 9% of the lung burden was cleared rapidly after the last exposure (half-life 1.0 days) and 47% slowly (half-life 87 days), leaving a residual lung burden of 44%. For CdS, 41% of the lung burden was cleared rapidly (half-life 1.4 days) and 40% slowly (half-life 42 days), leaving a final residue 19%. In the CdS high-dose group, the retention of CdS in the lung was greater than that in the CdS low-dose groups, indicating that clearance mechanisms may possibly have been impaired in the high-dose group by too great a lung burden. For both compounds, faecal cadmium was initially high. Renal accumulation of cadmium was substantial for CdCl2 during the exposure period and continued over the following months until it represented approximately 35% of the total cadmium cleared from the lung. For CdS, renal accumulation was only 1% of the amount cleared from the lung. The bioavailability of Cd from CdS is thus poor, the majority being cleared from the lungs and excreted in the faeces. However, the bioavailability of inhaled CdS measured as cadmium in the kidney is greater than the bioavailability of orally ingested CdS.

Di-(2-ethylhexyl) phthalate: a short-term repeated inhalation toxicity study including fertility assessment.

In a study of the 28-day inhalation toxicity of di-(2-ethylhexyl) phthalate (DEHP) aerosols, 9-wk-old Wistar rats, 27 males (mean weight 226 g) and 17 females (mean weight 155 g) per group, were exposed in head-nose inhalation systems to DEHP aerosols of respirable particle size (mass median aerodynamic diameter < or = 1.2 microns) or air (controls). Exposure for 6 hr per day, 5 days per wk for 4 wk to target concentrations of 0, 0.01, 0.05 and 1.0 mg/litre gave estimated doses of 230, 11 and 2.3 mg/kg/day for the males, and 360, 18 and 3.6 mg/kg/day for females, on the assumption of 100% deposition and absorption. Clinical investigation and blood chemistry parameters did not reveal any treatment-related effects. At the end of exposure a statistically significant (16%) increase in relative lung weights, accompanied by increased foam-cell proliferation and thickening of the alveolar septi, was found in the males of the highest dose group. Absolute liver weights were significantly (8.75%) increased in females and relative liver weights were increased in both sexes in the highest dose group, but there were no corresponding histological effects. All these effects were reversed during the 8-wk post-exposure period. No testicular toxicity was observed histologically and no impact on mating performance and male fertility was detected after two matings of treated males with untreated females, 2 and 6 wk after the end of exposure. Electron microscopic examination of liver samples from two male and two female rats per group at the end of exposure and after the 8-wk post-exposure period did not reveal clear substructural changes that could be attributed to exposure or to peroxisome proliferation. The no-observed-effect level for all exposure-related findings was 0.05 mg/litre under the conditions used.

The effects of Thorotrast and quartz on the induction of lung tumors in rats.

In a long-term animal study, the combined and separate effects of Thorotrast (colloidal 232ThO2) and silica dust on the induction of lung tumors were investigated. Female Wistar rats were exposed for 29 d to aerosol concentrations of quartz of either 6 mg m-3, 30 mg m-3, or 0 mg m-3 (6 h d-1, 5 d wk-1). After inhalation, one-half of all exposed animals received a single intravenous injection of enriched Thorotrast (600 microL, 2960 Bq 228 Th mL-1). In all quartz-exposed groups the incidence of benign and malignant lung tumors turned out to be more than 40%. The additional Thorotrast treatment (lifelong exhalation of 220Rn) led to a marked shortening of latency times (first lung tumor was found 1 y after treatment) and to a higher total incidence in the animals exposed to 30 mg m-3 quartz (57 of 87 animals with lung tumors = 65.5%). In the group treated only with Thorotrast, three of 87 animals developed lung tumors. Statistical methods that correct for intercurrent mortality showed a significant increase of the lung tumor risk with respect to Thorotrast treatment, even for the low quartz groups with nearly similar incidences of lung tumors (in the group with ThO2, 39 out of 87 = 44.8%; in the group without ThO2, 37 out of 82 = 45.1%). The tumors were found predominantly in the peripheral regions of the lung and were preceded by proliferation and hyperplasia of the alveolar and bronchiolar epithelium. The results demonstrate a pronounced interactive effect of quartz and Thorotrast on carcinogenesis of the lung. The underlying possible mechanisms are discussed.

Studies on the prenatal toxicity of toluene in rabbits following inhalation exposure and proposal of a pregnancy guidance value.

Prenatal toxicity of toluene was determined in two separate studies by inhalation exposure of Himalayan rabbits. In the first study 15 artificially inseminated females per group were exposed to 30, 100, or 300 ppm and in the second study 20 artificially inseminated females per group inhaled 100 or 500 ppm. In each case the rabbits were exposed for 6 hours per day from day 6 post-insemination (p.i.) to day 18 p.i. The respective controls inhaled conditioned clean air under the same exposure conditions. No signs of maternal toxicity were observed. All data obtained on gestational parameters were found to be within the variation range reported for this rabbit strain. The fetal external, soft tissue and skeletal findings were seen in toluene exposed fetuses in a frequency similar to the corresponding and/or historical controls. Differences observed between the groups were not concentration dependent and were considered incidental rather than compound related. Therefore, toluene was not embryotoxic, fetotoxic, or teratogenic for rabbits exposed during the period of organogenesis. The highest concentration tested under these conditions (500 ppm) was found to be a no-observable-adverse-effect level (NOAEL) for both the adult and the fetal Himalayan rabbit. Based on these and previous results of animal studies of prenatal toxicity, a safety or uncertainty factor approach is considered for setting limits of exposure for women at workplaces. A pregnancy guidance value of 20 ppm is proposed.