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Toxicological information

Respiratory sensitisation

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Administrative data

Endpoint:
respiratory sensitisation: in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meets generally accepted scientific principles, acceptable for assessment.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1989

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Two groups of male Guinea Pigs were exposed 6h/d, 5d/w for 4 consecutive weeks to aerosolized ADCA at either 51 or 200 mg/m^3, or to filtered air as controls. One group was tested for specific sensitisation by challenge with ADCA before and after the exposure period.
The other group was tested for non-specific sensitization by challenge with histamine before and after the exposure period.
Specific airway conductance was measured during the challenge procedures.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Azodicarbonamide, ADA
- Analytical purity: 99.4%
- Source: Midewest Research Institute, Kansas city, MO, subcontractor of the National Toxicology Program, National Istitute of Envioronmental Health Sciences)
- Impurities: biurea<1%

Test animals

Species:
guinea pig
Strain:
Hartley
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Kingston, Stone Ridge, NY
- Age at study initiation: 8 Weeks ± 5 days (Animals received at 5 weeks, then a 3-week acclimation period was observed)
- Weight at study initiation: 513 ± 23 g
- Housing: Animals were housed in individual wire cages in three tiers in the exposure chambers throughout the study.
- Diet (e.g. ad libitum): Pelleted feed was available ad libitum outside of exposure hours.
- Water (e.g. ad libitum): Tap water was available at all times.
- Acclimation period: 3 weeks.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 75 ± 3°C
- Humidity (%): 40 - 70% Relative humidity
- Air changes (per hr): 12 ± 2
- Photoperiod (hrs dark / hrs light): 12 hours cycle.

IN-LIFE DATES: From: To: No data

Test system

Route of induction exposure:
inhalation
Route of challenge exposure:
inhalation
Remarks:
Inhalation before and after study. A skin test was performed on half of the animals one week after the inhaled challenge exposure.
Vehicle:
unchanged (no vehicle)
Concentration:
Concentrations were measured daily by gravimetric analysis of filter samples.
Levels 50.6 ± 3.5 mg/m^3 and 199.5 ± 23.2 mg/m^3 were observed.
No. of animals per dose:
10
Details on study design:
MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: Daily exposures (6h) five days per week for 4 weeks (20 exposures, total). Animals were dosed five consecutive days per week with 2 days exposure to (untreated) air between exposure periods (i.e. simulating exposure on five days of the working week for workers).
- Exposure period: 6 Hours
- Test groups: 51 mg/m^3 and 200 mg/m^3
- Control group: Sham dosed with filtered air, only.

B. CHALLENGE EXPOSURE
- No. of exposures: 2
- Day(s) of challenge: First challenge performed one week before the first day of exposure; second challenge performed two days after the last day of exposure.
- Exposure period: Histamine challenges - 45 minutes (5 minutes per concentration, 9 concentrations); ADA challenges - 10 minutes.
- Concentrations: Histamine challenges - 0.04, 0.08, 0.14, 0.37, 0.88, 1.77, 3.02, 6.35, and 12.8 mg/m^3.
ADA challenges - 200 mg/m^3 for control and 200 mg/m^3 exposure levels, 51 mg/m^3 for 51 mg/m^3 level.
- Evaluation (hr after challenge): Not applicable - evaluation was conducted by measurement of sGAW (Specific airway conductance); a positive challenge was defined as one in which a 50% reduction in sGAW versus baseline was observed.
Challenge controls:
Histamine dihydrochloride (Sigma chemical co., St Louis, MO), solution in distilled water.
Positive control substance(s):
none
Negative control substance(s):
other: Sham dosing with filtered air.

Results and discussion

Results:
Repeated ADA exposure did not increase the sensitivity of guinea pigs to either Histamine or ADA (non-specific or specific sensitisation, respectively).
There were no significant differences between pre- and post-exposure histamine response concentrations, either within or amongst the treatment groups.
Few guinea pigs responded to the ADA challenge with a 50% or greater reduction in sGAW either before or after the repeated ADA exposure.

Any other information on results incl. tables

Increases in the number of individual animals displaying a difference between pre- and post-exposure challenge-induced change in sGAW were similar for all dose groups (control, 51, and 200 mg/m^3).

The only response to intradermal injections (skin tests) was a concentration-related erythematous response. There were no statistically relevant differences between reaction sizes of ADA-exposed and control guinea pigs in the ADA challenge group at any observation time. Among the histamine-challenged groups, the mean reaction size of the 200 mg/m^3 group was significantly larger than that of the controls at 72 h.

Table 1: Results of histamine challenges before and after repeated exposure to azodicarbonamide (ADA)

 

Repeated exposure group

 

Control

51 mg/m3

200mg/m3

Pre-ADA exposure challenge

 

Baseline sGAW

0.971a

(0.384)

0.715

(0.366)

0.901

(0.026)

Response sGAWb

0.136

(0.063)

0.133

(0.087)

0.165

(0.077)

Histamine step

8.4

(0.7)c

8.4

(0.7)

8.1

(1.3)

 

Post-ADA exposure challenges

 

Baseline sGAW

0.357

(0.056)

0.306

(0.069)

0.338

(0.068)

Response sGAW

0.102

(0.039)

0.104

(0.040)

0.095

(0.041

Histamine step

8.7

(0.5)

8.3

(0.8)

8.5

(1.0)

 

Fraction responding at lower histamine step afterexposure

1/10

2/10

2/10

aMean (SD) units of sGAW – cmH2O-1.s-1

bsGAW meeting the criterion for positive response (reduced 50% from baseline)

cGroup mean (SD) value of the histamine concentration step (i.e. 1 – 9) inducing a positive response.

 

Table 2: Results of azodicarbonamide challenges before and after repeated exposure to azodicarbonamide (ADA)

 

Repeated exposure group

 

Control

51 mg/m3

200mg/m3

Pre-ADA exposure challenge

 

Baseline sGAW

0.632

(0.343)a

0.594

(0.262)

0.661

(0.452)

Challenge sGAWb

0.514

(0.238)

0.455

(0.205)

0.526

(0.286)

Differencec

-0.118

(0.322)

-0.140

(0.121)

-0.136

(0.310)

Fraction responding with 50% reduction in sGAW

1/10

1/10

1/10

 

Post-ADA exposure challenge

 

Baseline sGAW

0.370

(0.141)

0.464

(0.265)

0.368

(0.131)

Challenge sGAW

0.371

(0.174)

0.338

(0.090)

0.302

(0.053)

Difference

0.001

(0.171)

-0.126

(0.253)

-0.66

(0.100)

Fraction responding with 50% reduction in sGAW

0/10

2/10

0/10

 

Fraction of guinea pigs with greater challenge induced reduction (or less increase) in sGAW after repeated exposure than before

5/10

6/10

6/10

aMean (SD) units of sGAW – cmH2O-1.s-1

bsGAW after 20 min of inhalation of ADA at the repeated exposure concentration (200 mg/m3) for controls.

cDifference between baseline and post-challenge sGAW.

Applicant's summary and conclusion

Interpretation of results:
not sensitising
Conclusions:
The test substance ADCA did not induce sensitization to either the skin or respiratory tract in guinea pigs, following repeated inhalation exposure 5 days per week for four weeks.
Executive summary:

A study was conducted by Gerlach et. al., to investigate reports by industry workers exposed repeatedly by inhalation to azodicarbonamide (ADCA) or respiratory problems, possibly indicating pulmonary sensitisation. A non-invasive method was used for measuring specific airway conductance to evaluate the potential for repeated exposure to ADCA to cause respiratory sensitisation to the Guinea pig.

Two groups of 30 male guinea pigs were exposed to aerosolised ADCA for 6 hours per day, 5 days per week, for four weeks. Within each group, dose groups of ten animals were exposed to ADCA at 51 mg/m3, 200 mg/m3, or to filtered air (control group). One of the groups was assessed for specific airway sensitisation by a challenge procedure with inhaled ADCA exposure at the same concentration as the exposure concentration (or 200 mg/m3 in the case of the controls). The other group was assessed for non-specific sensitization by a challenge procedure with increasing concentrations of histamine. Challenge procedures were performed one week before the start and three days after the end of the exposure period. Skin tests for immunological responses to ADCA were also performed.

Repeated ADA exposure did not increase the senstivity of Guinea Pigs to either Histamine or ADA (non-specific or specific sensitisation, respectively). There were no significant differences between pre- and post- exposure histamine response concentrations, either within or amongst the treatment groups. Few Guinea pigs responded to the ADA challenge with a 50% or greater reduction in sGAW (Specific airway conductance) either before or after the repeated ADA exposure. Increases in the number of individual animals displaying a difference between pre- and post- exposure challenge-induced change in sGAW were similar for all dose groups (control, 51, and 200 mg/m3). The only response to intradermal injections (skin tests) was a concentration-related erythematous response. There were no statistically relevant differences between reaction sizes of ADA-exposed and control guinea pigs in the ADA challenge group at any observation time. Among the histamine-challenged groups, the mean reaction size of the 200 mg/m3 group was significantly larger than that of the controls at 72 h.

The test substance ADCA did not induce sensitization to either the skin or respiratory tract in guinea pigs, following repeated inhalation exposure 5 days per week for four weeks.