2-dimethylaminoethanol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported, published 1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles.

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

not reported, published 1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles.

Reason / purpose for cross-reference:

reference to other study

Guideline:

other: no data

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY)
- Age at study initiation: approx. 8 weeks old.
- Weight at study initiation: 167 g for males and 121 g females
- Fasting period before study: not reported
- Housing:
- Diet (e.g. ad libitum): Purina Certified Rodent Chow 5002, Ralston Purina Co., St. Louis, MO ad libitum, except during exposures
- Water (e.g. ad libitum): yes, except during exposures
- Acclimation period: yes

ENVIRONMENTAL CONDITIONS
- Temperature (°C): not reported
- Humidity (%): not reported
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation

Type of inhalation exposure:

not specified

Vehicle:

other: no data

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 1300-liter stainless-steel and glass chambers
- Method of holding animals in test chamber: not reported
- Source and rate of air: not reported
- Method of conditioning air: not reported
- System of generating particulates/aerosols: DMEA vapor was generated by metering the liquid into a heated, spiral-grooved evaporator with a countercurrent airstream, similar in design to the one used by Carpenter et al. (1975).
- Temperature, humidity, pressure in air chamber: 25°C and 46%,
- Air flow rate: 300 liters/min
- Air change rate: not reported
- Method of particle size determination: not reported
- Treatment of exhaust air: not reported

TEST ATMOSPHERE
- Brief description of analytical method used: The CC column was a 5 ft X 1/4 in stainless-steel column packed with 20% SP-2100 on 80/ 100 mesh Supelcoport (Supelco, BeIlefonte, PA), maintained at 200°C.
- Samples taken from breathing zone: yes

VEHICLE (if applicable) no

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Chamber concentrations of DMEA were analyzed at approximately 40-min intervals with a Perkin-Elmer 3920B gas chromatograph (CC) equipped with a flame ionization detector. Chamber atmosphere samples were automatically injected into the GC with the use of a Perkin-Elmer environmental sampler.

Duration of treatment / exposure:

9 exposures during 11-day period (2 days without exposure between Exposure Days 5 and 6)

Frequency of treatment:

6h/d, 5d/w

Dose / conc.:

98 ppm (analytical)

Dose / conc.:

288 ppm (analytical)

Dose / conc.:

586 ppm (analytical)

No. of animals per sex per dose:

10

Control animals:

yes

Details on study design:

5 male rats were assigned to the control, middle and high concentration groups for possible ultrastructural evaluation of nerve tissue (not performed since no behavioral abnormalities or light microscopic lesions of nerve tissue were observed).

- Dose selection rationale: not reported
- Rationale for animal assignment (if not random): randomized
- Rationale for selecting satellite groups: no satttelite groups
- Post-exposure recovery period in satellite groups:

All animals were sacrificed on the morning after the ninth exposure.

Observations and examinations performed and frequency:

- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: were measured during the 16-hr urine collection period.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: were measured during the 16-hr urine collection period.

OPHTHALMOSCOPIC EXAMINATION: Yes, (evaluation of the eye with a light source and magnifying lens)
- Time schedule for examinations: not reported
- Dose groups that were examined: not reported

HAEMATOLOGY: Yes
- Time schedule for collection of blood: made the morning following the last DMEA exposure day (except for recovery animals).
- Anaesthetic used for blood collection: Yes (methoxyflurane)
- Animals fasted: No
- How many animals: not reported
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: made the morning following the last DMEA exposure day (except for recovery animals).
- Animals fasted: No
- How many animals: not reported
- Parameters checked in table [No.2] were examined.

URINALYSIS: Yes
- Time schedule for collection of urine:during a 16-hr period prior to sacrifice from rats held in polycarbonate metabolism cages
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined: Semiquantitative measurements on urine: included pH, protein, bilirubin, urobilinogen, glucose, ketones, and blood. In addition, osmolality determinations (Cryomatic osmometer, Advanced Instruments, Inc., Needham Heights, MA) and microscopic evaluations of the urine sediment were performed.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: not reported
- Dose groups that were examined: not reported
- Battery of functions tested: sensory activity / grip strength / motor activity / other: see Table 3

OTHER: Organ weight determinations, gross pathologic examination, and blood and urine sample collections were made the morning following the last DMEA exposure day (except for recovery animals).

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see Table 4). Histopathologic examinations were performed on tissues from rats of the control and middle exposure groups (due to complete mortality in the high exposure group), with nasal turbinates also being evaluated for the low exposure group rats.

Other examinations:

Organ weights: brain, kidney, liver, lungs, testes, and adrenals.

Statistics:

Results of quantitative continuous variables were intercompared among the DMEA concentration levels and the control group by Bartlett’s homogeneity of variance (Sokal and Rohlf, 1969), analysis of variance (ANOVA), and Duncan’s multiple range test (Snedecor and Cochran, 1967). Duncan’s test was used when a significant F value from an ANOVA was observed. For heterogeneous group variances, the groups were compared by ANOVA for unequal variances (Brown and Forsythe, 1974) and either Student’s t test or Cochran’s t test (Snedecor and Cochran, 1967) was used. Corrected Bonferroni probabilities were used for t test comparisons (Miller, 1966). The fiducial limit of 0.05 (two-tailed) was used as the critical level of significance for all comparisons. For the calculation of the LC50, the method of Finney (1964) was used.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

all animals in the high exposure group

Mortality:

mortality observed, treatment-related

Description (incidence):

all animals in the high exposure group

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

less than controls

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

concentration-related decrease

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

effects observed, treatment-related

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

significant different from controls

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

significant different from controls

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

significant different from controls

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

significant different from controls

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

eyes and nasal mucosa

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Table 2

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
All animals of the 586 ppm group died or were sacrificed in a moribund state 4-8 days after the initiation of exposures. Four of fifteen males of the 288 ppm group died 8-12 days after the initiation of exposures.

BODY WEIGHT AND WEIGHT GAIN
There was a concentration-related effect on body weight in this study. Weight loss occurred after one exposure in both sexes of the 288 and 586 ppm groups, with the final mean body weight of the 288 ppm group being about 75% of preexposure values. Although the 98 ppm group gained weight, they gained 35% less than controls (Table 1).

FOOD CONSUMPTION
There was also a statistically significant concentration-related decrease in food consumption for both the 98 and 288 ppm groups.

WATER CONSUMPTION
Mean water consumption was equivalent for all groups.

OPHTHALMOSCOPIC EXAMINATION
The ophthalmic examination indicated that animals of the 288 ppm group had conjunctivitis, including chemosis, and corneal opacity.

HAEMATOLOGY, CLINICAL CHEMISTRY, URINALYSIS
Most of the serum chemistry, hematology, and urinalysis values for the 288 ppm group were statistically significantly different from control values, a further indication of the stressed and debilitated condition of the animals. No similar exposure-related effects were observed for the 98 ppm exposure group, except for a statistically significant decrease in urine volume for both sexes.

NEUROBEHAVIOUR
No effects

ORGAN WEIGHTS
The absolute and relative (as a percentage of body weight) organ weight values for the 288 ppm group were significantly different from those of control values (Table 1). Because of the substantial reduction in body weight gain, as well as the lack of histological evidence for organ toxicity at the higher concentration (288 ppm), the few statistically significant differences in organ weight values for the 98 ppm group (Table 1) were not considered to result from specific organ toxicity.

GROSS PATHOLOGY
At necropsy, gross changes included ocular opacity, thymic atrophy, and reduced body fat in most rats of the 288 ppm group.

HISTOPATHOLOGY: NON-NEOPLASTIC
The principal histologic lesions were in the upper respiratory tract of the 98 and 288 ppm groups (Table 2) and in the eyes of the 288 ppm group. In the nasal tissues of the 98 ppm group, rhinitis, squamous metaplasia, and ulceration of the nasal mucosa were observed. Similar lesions occurred at a higher incidence in the 288 ppm group (Table 2). Additional nasal lesions in the 288 ppm group included respiratory epithelial degeneration (presence of necrotic cells scattered throughout the epithelium) and erosion (much of the pseudostratified ciliated columnar epithelium was absent-primarily stem cells remained) and degeneration of the olfactory mucosal epithelium. The nasal lesions were primarily limited to the anterior portions of the nose. The incidence and severity of the nasal lesions indicated increased toxicity with increasing exposure concentration.
Mild squamous metaplasia of the laryngeal epithelium was observed histologically in the 288 ppm group. However, metaplasia did not extend into the upper trachea or into the lung. The macroscopic observation of thymic atrophy in the 288 ppm exposure group was verified by the microscopic observation of decreased numbers of cortical lymphocytes. The microscopic lesions in the eyes of the 288 ppm group primarily occurred in the cornea (with some involvement of the anterior chamber) and ranged from corneal edema to ulcerative keratitis. Although the nervous system was a suspected target organ, microscopic lesions of the central (brain) or peripheral (sciatic nerve) nervous systems were not observed.

Dose descriptor:

NOAEC

Remarks on result:

not determinable

Remarks:

no NOAEC identified

Critical effects observed:

not specified

TABLE 1
Terminal Body Weight and Selected Organ Weights for F-344 Rats of the DMEA 2-Week Inhalation Study^a
Parameter	Males			Females
	Control	98 ppm	288 ppm	Control	98 ppm	288 ppm
Body wt (g)	198	184**	126**	137	131**	94**
	(10.4)	(12.2)	(10.9)	(3.8)	(3.1)	(3.6)
Brain wt (g)	1.70	1.65*	1.63**	1.64	1.62	1.54**
	(0.04)	(0.05)	(0.03)	(0.05)	(0.05)	(0.04)
Brain/body wt (%)	0.86	0.90	1.30**	1.19	1.23	1.65**
	(0.04)	(0.04)	(0.12)	(0.04)	(0.04)	(0.08)
Liver wt(g)	7.91	7.32	5.07**	5.04	4.69**	3.97**
	(1.00)	(0.69)	(0.50)	(0.23)	(0.34)	(0.34)
Liver/body wt (%)	3.99	3.98	4.03	3.67	3.57	4.23**
	(0.35)	(0.19)	(0.30)	(0.18)	(0.21)	(0.29)
Kidney wt (g)	1.53	1.49	1.24**	1.09	1.09	1.05
	(0.14)	(0.08)	(0.06)	(0.05)	(0.05)	(0.09)
Kidney/body wt (%)	0.77	0.81*	0.99**	0.79	0.83	1.12**
	(0.04)	(0.02)	(0.08)	(0.05)	(0.04)	(0.09)
Lung wt (g)	1.08	0.98	1.02	0.80	0.88	0.83
	(0.19)	(0.12)	(0.19)	(0.10)	(0.14)	(0.18)
Lung/body wt (%)	0.54	0.53	0.81**	0.58	0.67	0.88**
	(0.09)	(0.05)	(0.11)	(0.07)	(0.11)	(0.18)
Adrenal wt (g X 10^2)	4.88	4.35	5.73	5.00	4.95	5.89
	(1.97)	(1.07)	(0.89)	(1.21)	(1.34)	(0.53)
Adrenal/body wt (% X 10^2)	0.25	0.24	0.45**	0.36	0.38	0.63**
	(0.09)	(0.06)	(0.05)	(0.09)	(0.11)	(0.04)
Testes wt (g)	2.34	2.41	1.94**
	(0.26)	(0.18)	(0.17)
Testes/body wt (%)	1.18	1.32**	1.54**
	(0.11)	(0.10)	(0.06)
^aValues represent mean (±SD) for 7 to 10 rats. * p <0.05 from control. ** p <0.01 from control.

TABLE 2
Incidence of Selected Nasal Tissue Histopathologic Lesions in F-344 Rats Exposed to DMEA Vapor for 2 or 13 Weeks and Sacrificed the Day after the Final Exposure
	2-week study^a						13-week study^b
	Males			Females			Males			Females
DMEA concentration (ppm):	0	98	288	0	98	288	0	24	76	0	24	76
Total No. examined	10	10	7	10	10	10	10	10	10	10	10	10
Unremarkable	10	1	0	9^c	5	0	9^d	8	0	9^d	8	1
Rhinitis	0	5	6	0	5	7	0	2	0	0	2	7
Squamous metaplasia	0	8	7	0	2	10	0	0	9	0	0	4
Epithelial erosion	0	1	4	0	0	0	0	0	0	0	0	0
Mucosal ulceration	0	4	6	0	2	8	0	0	0	0	0	0
Degeneration of olfactory mucosa/epithelium	0	0	1	0	0	9	0	0	0	0	0	0
Degeneration of respiratory epithelium	0	0	0	0	0	4	0	0	8	0	0	7
Atrophy of olfactory epithelium	0	0	0	0	0	0	0	0	10	0	0	3
Microcysts in respiratory epithelium	0	0	0	0	0	0	0	0	10	0	0	3
^aAll animals of the 586 ppm group died on study and were not histologically evaluated. Incidence values in the table also do not include those four male rats of the 288 ppm group which died on study. ^bRats of the 8 ppm group were not histologically evaluated as only minimal rhinitis was observed in 2 rats/sex of the 24 ppm group. ^cOne control had a hemorrhage in the nasolacrimal duct. ^dOne control had minimal mineralization of the olfactory epithelium.

Conclusions:

DMAE acts primarily as an ocular and upper respiratory tract irritant. No NOAEL was identified

Executive summary:

In the 2-week study, F-344 rats exposed to 98,288, or 586 ppm DMEA for 9 days (6 hr/day) during an 11 -day period exhibited signs of respiratory and ocular irritation (except the 98 ppm group). All animals of the 586 ppm group and 4 of 15 male rats of the 288 ppm group died. Body weight values for the 288 ppm group were reduced to about 75% of preexposure values, while the 98 ppm group gained 35% less weight than controls. Statistically significant differences in clinical pathology parameters (288 ppm group) and in organ weight values (288 and 98 ppm groups) probably resulted from the decreased food consumption and not from specific target organ toxicity. In the groups evaluated histologically (the 98 and 288 ppm groups) the eye and nasal mucosa were the primary target organs.

Data source

Reference

Reference 1

Reference Type:

other: primary source

Title:

Dimethylethanolamine: Acute, 2-week and 13-week Inhalation Toxicity Studies in Rats

Author:

Klonne, D.R., Dodd, D.E., Pritts, I.M., Nachreiner, D.J., Fowler, E.H., Troup, C.M., Hman, E.R. and Ballantyne, B.

Year:

1987

Bibliographic source:

Fund. and Appl. Tox. 9 (1987) 512-521

Reference 2

Reference Type:

secondary source

Title:

Toxicology Data Summary Sheet

Author:

Atochem North America

Year:

1989

Bibliographic source:

Toxicology Data Summary Sheet

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Deviations:

not applicable

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-dimethylaminoethanol

EC Number:

203-542-8

EC Name:

2-dimethylaminoethanol

Cas Number:

108-01-0

Molecular formula:

C4H11NO

IUPAC Name:

2-(dimethylamino)ethanol

Details on test material:

DMEA (CAS 108-01-O) was obtained from Union Carbide Corp. (South Charleston, WV). Compositional analyses before and after each study indicated
that the material was at least 99% pure.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY)
- Age at study initiation: approx. 9 weeks old.
- Weight at study initiation: 180 g for males and 130 g females
- Fasting period before study:
- Housing:
- Diet (e.g. ad libitum): Purina Certified Rodent Chow 5002, Ralston Purina Co., St. Louis, MO ad libitum except during exposures
- Water (e.g. ad libitum): yes, except during exposures
- Acclimation period: yes

ENVIRONMENTAL CONDITIONS
- Temperature (°C): not reported
- Humidity (%): not reported
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

not specified

Vehicle:

other: no data

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 4320-liter stainless-steel and glass chambers
- Method of holding animals in test chamber: not reported
- Source and rate of air: not reported
- Method of conditioning air: not reported
- System of generating particulates/aerosols: DMEA vapor was generated by metering the liquid into a heated, spiral-grooved evaporator with a countercurrent airstream, similar in design to the one used by Carpenter et al. (1975).
- Temperature, humidity, pressure in air chamber: 25°C and 46%,
- Air flow rate: 800-1000 liters/min
- Air change rate: not reported
- Method of particle size determination: not reported
- Treatment of exhaust air: not reported

TEST ATMOSPHERE
- Brief description of analytical method used: The CC column was a 5 ft X 1/4 in stainless-steel column packed with 20% SP-2100 on 80/ 100 mesh Supelcoport (Supelco, BeIlefonte, PA), maintained at 200°C.
- Samples taken from breathing zone: yes

VEHICLE (if applicable) no

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Chamber concentrations of DMEA were analyzed at approximately 40-min intervals with a Perkin-Elmer 3920B gas chromatograph (CC) equipped with a flame ionization detector. Chamber atmosphere samples were automatically injected into the GC with the use of a Perkin-Elmer environmental sampler.

Duration of treatment / exposure:

13 wk

Frequency of treatment:

6h/d, 5d/wk

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

8 ppm (analytical)

Remarks:

corresponding to 29.2 mg/m³

Doses / concentrations 2

Dose / conc.:

24 ppm (analytical)

Remarks:

corresponding to 87.5 mg/m³

Doses / concentrations 3

Dose / conc.:

76 ppm (analytical)

Remarks:

corresponding to 277.1 mg/m³

No. of animals per sex per dose:

20

Control animals:

yes

Details on study design:

10 male rats were assigned to the control, middle and high concentration groups for possible ultrastructural evaluation of nerve tissue (not performed since no behavioral abnormalities or light microscopic lesions of nerve tissue were observed).

- Dose selection rationale: not reported
- Rationale for animal assignment (if not random): randomized
- Rationale for selecting satellite groups: to investigate recovery of effects of treatment
- Post-exposure recovery period in satellite groups: 5 week

One-half of all rats per sex per group were sacrificed after at least 2 days of exposure during the 14th week of the study; the remaining rats were sacrificed after 5 complete weeks of recovery.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations checked in table [No.3] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: daily

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: were measured during the 16-hr urine collection period.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: were measured during the 16-hr urine collection period.

OPHTHALMOSCOPIC EXAMINATION: Yes, (evaluation of the eye with a light source and magnifying lens)
- Time schedule for examinations: not reported
- Dose groups that were examined: not reported

HAEMATOLOGY: Yes
- Time schedule for collection of blood: made the morning following the last DMEA exposure day (except for recovery animals).
- Anaesthetic used for blood collection: Yes (methoxyflurane)
- Animals fasted: No
- How many animals: not reported
- Parameters checked in table [No.1] were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: made the morning following the last DMEA exposure day (except for recovery animals).
- Animals fasted: No
- How many animals: not reported
- Parameters checked in table [No.2] were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: during a 16-hr period prior to sacrifice from rats held in polycarbonate metabolism cages
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined: Semiquantitative measurements on urine: included pH, protein, bilirubin, urobilinogen, glucose, ketones, and blood. In addition, osmolality determinations (Cryomatic osmometer, Advanced Instruments, Inc., Needham Heights, MA) and microscopic evaluations of the urine sediment were performed.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: not reported
- Dose groups that were examined: not reported
- Battery of functions tested: sensory activity / grip strength / motor activity / other: see Table 3

OTHER: Organ weight determinations, gross pathologic examination, and blood and urine sample collections were made the morning following the last DMEA exposure day (except for recovery animals).

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see Table 4). Additional histopathologic examinations were performed on rats from the control and high exposure groups, with nasal turbinates also being evaluated for the middle exposure group rats.

Other examinations:

Organ weights: brain, kidney, liver, lungs, testes, and adrenals.

Statistics:

Results of quantitative continuous variables were intercompared among the DMEA concentration levels and the control group by Bartlett’s homogeneity of variance (Sokal and Rohlf, 1969), analysis of variance (ANOVA), and Duncan’s multiple range test (Snedecor and Cochran, 1967). Duncan’s test was used when a significant F value from an ANOVA was observed. For heterogeneous group variances, the groups were compared by ANOVA for unequal variances (Brown and Forsythe, 1974) and either Student’s t test or Cochran’s t test (Snedecor and Cochran, 1967) was used. Corrected Bonferroni probabilities were used for t test comparisons (Miller, 1966). The fiducial limit of 0.05 (two-tailed) was used as the critical level of significance for all comparisons. For the calculation of the LC50, the method of Finney (1964) was used.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

lower in 76 ppm-group, returned to control during the recovery period

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

effects observed, treatment-related

Description (incidence and severity):

corneal opacity which regressed during the night

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

nasal lesions

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY
No animals died during the study.

BODY WEIGHT AND WEIGHT GAIN
The body weight gains for both sexes of the 76 ppm group were statistically significantlly lower than control values for most of the latter half of the 13 week exposure regimen (Table 1). The body weight gain valuesfor the 76 ppm group returned to control values during the recovery period. There were no exposure-related alterations of body weight gain for rats exposed to 8 or 24 ppm of DMEA.

OPHTHALMOSCOPIC EXAMINATION
Corneal opacity occurred in the 24 and 76ppm groups at the end of the daily exposure, beginning approximately 2-3 weeks after initiation of exposures. The opacity regressed during the night-time nonexposure hours. There was also a moderate incidence (approximately 25%) of audible respiration in rats of the 76 ppm group.

HISTOPATHOLOGY: NON-NEOPLASTIC
Exposure related nasal lesions were observed histologically at the termination of exposures in both sexes of the 76 ppm group, but were generally not observed in rats of the 24 ppm group (Table 2). The lesions were limited to the anterior nasal cavity and included squamous metaplasia, microcysts (cystic intraepithelial glands) mucous cell hyperplasia of the respiratory epithelium, mild rhinitis, and atrosoluphy of the dorsal olfactory epithelium. The incidence and severity of these lesions were decreased at the end of the recovery period, indicating some degree of repair. Additionally, 4/ 10 males had laryngitis and two of these rats also had tracheitis. No similar lesions were found in female rats. Vacuolization of the corneal epithelium was observed in 3/10 female rats of the 76 ppm group at the termination of exposures but not at the end of the recovery period.

Effect levels

1

Dose descriptor:

NOEC

Effect level:

24 ppm

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

mortality

2

Dose descriptor:

NOEC

Effect level:

87.5 mg/m³ air

Based on:

act. ingr.

Sex:

male/female

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

mortality

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

TABLE 1
Body Weight Gain for F-344 Rats Exposed to DMEA Vapor for 13 Weeks and Maintained for a 5-Week Recovery Period^a
Interval (weeks)	Mean exposure concentration (ppm)
	0	8	24	76
	Males
8^b	108 ± 12.2	112 ± 8.6	113 ± 11.1	102 ± 8.0*
14^c	154 ± 11.5	157 ± 9.9	157 ± 10.2	147 ± 10.6*
19^d	167 ± 16.7	166 ± 7.1	172 ± 13.2	169 ± 9.2
	Females
8	54 ± 4.7	53 ± 5.9	51 ± 5.0	49 ± 6.8**
14	73 ± 5.4	70 ± 5.8	70 ± 6.3	64 ± 6.6**
19	76 ± 6.8	73 ± 7.7	71 ± 5.1	71 ± 4.0
^aValues represent mean ± SD. ^bWeek 8 was the first week that a consistent statistically significant depression in body weight gain was observed for both sexes of the 76 ppm group. ^cFinal weight gain value obtained after two or three exposures during Week 14. ^dEnd of 5-week postexposure recovery period. * p<0.05 from controls. ** p <0.01 from controls.

TABLE 2
Incidence of Selected Nasal Tissue Histopathologic Lesions in F-344 Rats Exposed to DMEA Vapor for 2 or 13 Weeks and Sacrificed the Day after the Final Exposure
	2-week study^a						13-week study^b
	Males			Females			Males			Females
DMEA concentration (ppm):	0	98	288	0	98	288	0	24	76	0	24	76
Total No. examined	10	10	7	10	10	10	10	10	10	10	10	10
Unremarkable	10	1	0	9^c	5	0	9^d	8	0	9^d	8	1
Rhinitis	0	5	6	0	5	7	0	2	0	0	2	7
Squamous metaplasia	0	8	7	0	2	10	0	0	9	0	0	4
Epithelial erosion	0	1	4	0	0	0	0	0	0	0	0	0
Mucosal ulceration	0	4	6	0	2	8	0	0	0	0	0	0
Degeneration of olfactory mucosa/epithelium	0	0	1	0	0	9	0	0	0	0	0	0
Degeneration of respiratory epithelium	0	0	0	0	0	4	0	0	8	0	0	7
Atrophy of olfactory epithelium	0	0	0	0	0	0	0	0	10	0	0	3
Microcysts in respiratory epithelium	0	0	0	0	0	0	0	0	10	0	0	3
^aAll animals of the 586 ppm group died on study and were not histologically evaluated. Incidence values in the table also do not include those four male rats of the 288 ppm group which died on study. ^bRats of the 8 ppm group were not histologically evaluated as only minimal rhinitis was observed in 2 rats/sex of the 24 ppm group. ^cOne control had a hemorrhage in the nasolacrimal duct. ^dOne control had minimal mineralization of the olfactory epithelium.

Applicant's summary and conclusion

Conclusions:

DMAE acts primarily as an ocular and upper respiratory tract irritant. 24 ppm is the NOEC.

Executive summary:

In the 13-week sub-chronic study, F-344 rats were exposed to 0, 8, 24, or 76 ppm DMEA for 6 hr/day, 5 days/week for 13 weeks. These doses correspond to 29.2, 87.5 and 277.1 mg/m³. The principal exposure-related changes were transient comeal opacity in the 24 and 76 ppm groups; decreased body weight gain for the 76 ppm group; and histopathologic lesions of the respiratory and olfactory epithelium of the anterior nasal cavity of the 76 ppm group and of the eye of several 76 ppm group females. Rats maintained for a 5-week recovery period only exhibited histological lesions of the nasal tissue, with the lesions being decreased in incidence and severity. DMEA acts primarily as an ocular and upper respiratory tract irritant and toxicant at vapor concentrations of 76 ppm, while 24 ppm or less produced no biologically significant toxicity in rats. Thus, 24 ppm (= 87.5 mg/m³) was considered to be the no-observable-effect level.