OECD 413

Question 1

What is the main purpose of Test No. 413?

Answer 1

To fully characterize test chemical toxicity by the inhalation route for a subchronic duration (90 days) and to provide robust data for quantitative inhalation risk assessments.

Question 2

What types of substances can be tested under Test No. 413?

Answer 2

Nanomaterials, inhaled gases, vapors, and aerosols.

Question 3

What is the minimum group size for rodents in the main study?

Answer 3

10 male and 10 female rodents.

Question 4

What is the exposure duration and frequency for the rodents in the study?

Answer 4

6 hours per day for 5 days per week over a 90-day period.

Question 5

What is performed within 24 hours after the end of the exposure period?

Answer 5

Euthanasia and bronchoalveolar lavage (BALF) for all test chemicals.

Question 6

How are the lungs divided for analysis post-euthanasia?

Answer 6

Left Lung (LL) for histopathology and Right Lung (RL) for BALF analysis.

Question 7

What may the study director consider if the test chemical is likely to be retained in the lung?

Answer 7

Additional post-exposure observation (PEO) periods.

Question 8

What does lung burden (LB) inform on?

Answer 8

Lung clearance behavior.

Question 9

What optional investigations might be suggested for better characterizing overall toxicity?

Answer 9

Toxicokinetics and/or systemic toxicity evaluations.

Question 10

What is required for all test chemicals according to the latest revision?

Answer 10

Specific measurements of bronchoalveolar lavage fluid (BALF) to be performed.

Question 11

What should measurements of lung burden inform on?

Answer 11

Pulmonary deposition and retention of particles in the lung.

Question 12

What does the 2009 version require for particulate aerosols?

Answer 12

A mass median aerodynamic diameter (MMAD) of 1-3 µm with a geometric standard deviation (GSD) of 1.5-3.0.

Question 13

What is the new standard for testing nano-range aerosols?

Answer 13

MMAD of ≤2 µm with a GSD of 1-3.

Question 14

What should the study report include if the new aerosol standard cannot be met?

Answer 14

Justification and a description of efforts taken to meet it.

Question 15

What is the primary purpose of a range-finding study?

Answer 15

To inform the selection of concentration levels for a main study.

Question 16

What should be the maximum concentration tested based on?

Answer 16

Maximum achievable concentration, oxygen supply needs, and animal welfare considerations.

Question 17

What are the acute limits for aerosols according to the United Nations Globally Harmonized System?

Answer 17

Up to a maximum concentration of 5 mg/L for aerosols.

Question 18

What are the recommended housing conditions for animals during aerosol exposure?

Answer 18

Animals may be housed individually to prevent filtering of the test aerosol.

Question 19

What is the preferred mode of exposure for testing chemicals?

Answer 19

Nose-only exposure for studies of liquid or solid aerosols.

Question 20

What are the two study designs based on the nature of the test chemical?

Answer 20

Option A for gases, vapors, aerosols; Option B for chemicals likely retained in the lungs.

Question 21

What should the target concentrations selected allow for?

Answer 21

Identification of target organ(s) and demonstration of a clear concentration-response.

Question 22

What does NOAEC stand for?

Answer 22

No Observed Adverse Effect Concentration.

Question 23

What should be determined in preserved histopathological tissue specimens?

Answer 23

Particle burden of relevant organs.

Question 24

What should satellite groups be exposed to?

Answer 24

The same concentration levels as the main study groups.

Question 25

What should be evaluated in Option A of the satellite groups?

Answer 25

Recovery or delayed toxicity.

Question 26

What is the purpose of lung-associated lymph node (LALN) burden measurements?

Answer 26

To provide information on translocation.

Question 27

What is required to provide information on clearance kinetics?

Answer 27

Three time points ## Footnote This is essential for understanding the rate at which substances are cleared from the lungs.

Question 28

Why are LB measurements performed in males?

Answer 28

Males have a higher minute volume than females ## Footnote This may lead to greater lung burdens in males.

Question 29

What factors influence the scheduling of PEO-2 and PEO-3?

Answer 29

Expected rate of lung clearance and duration of post-exposure recovery period ## Footnote These factors help determine the timing of measurements.

Question 30

What is a concurrent negative control in animal studies?

Answer 30

Handled identically to the test group but exposed to filtered air ## Footnote This helps ensure that observed effects are due to the test chemical.

Question 31

What should be used as a vehicle whenever possible in studies?

Answer 31

Water ## Footnote Using water as a vehicle is preferred for consistency.

Question 32

What is recommended when using a vehicle other than water?

Answer 32

Use a vehicle control group instead of a negative control group ## Footnote This ensures accurate comparison of effects.

Question 33

What is the minimum number of concentration levels for range-finding?

Answer 33

≥ 1 concentration level + CTRL ## Footnote This includes 5 males and 5 females per group.

Question 34

What is the typical duration for range-finding studies?

Answer 34

5 - 28 days ## Footnote Duration may be longer for poorly soluble chemicals.

Question 35

What is the main study design for exposure?

Answer 35

≥ 3 concentration levels + (air or vehicle) CTRL ## Footnote Involves at least 10 males and 10 females per group.

Question 36

What are the exposure conditions for the main study?

Answer 36

6 hrs./day, 5 (or 7) days/week, for 13 weeks ## Footnote Total study duration should be at least 90 days.

Question 37

What are the two study design options based on chemical nature?

Answer 37

Option A: gases, vapors, aerosols; Option B: likely retained in lungs ## Footnote Different designs accommodate differing chemical properties.

Question 38

What should be demonstrated when a test chemical is prepared in a vehicle?

Answer 38

Its stability ## Footnote Stability is crucial for accurate testing.

Question 39

What is the significance of chamber airflow monitoring?

Answer 39

It provides an indirect means to control inhalation parameters ## Footnote Real-time monitoring is essential for study validity.

Question 40

What is the definition of nominal concentration in inhalation studies?

Answer 40

Mass of generated test chemical / total volume of air through the chamber ## Footnote This helps assess the efficiency of the test system.

Question 41

What is the Mass Median Aerodynamic Diameter (MMAD) standard for aerosols?

Answer 41

MMAD ≤ 2 µm with GSD of 1-3 ## Footnote This standard is important for ensuring appropriate aerosol size.

Question 42

What is the requirement for gross pathology and organ weights measurements?

Answer 42

Organs in bold type should be weighed wet soon after dissection ## Footnote This prevents loss of weight due to drying.

Question 43

What is the preferred lung for bronchoalveolar lavage (BAL)?

Answer 43

Right lung ## Footnote The right lung is generally preferred for consistency in measurements.

Question 44

What parameters are included in mandatory BALF analysis?

Answer 44

* Lactate dehydrogenase (LDH) * Total protein or albumin * Cell counts and differentials for macrophages, lymphocytes, neutrophils, eosinophils ## Footnote These parameters help assess lung health post-exposure.

Question 45

What is the significance of measuring lung burden (LB) in studies?

Answer 45

To assess retained poorly soluble solid aerosols in the lung ## Footnote This is crucial when appropriate analytical methods are available.

Question 46

When is PEO-1 scheduled after exposure termination?

Answer 46

Approximately 24 hours ## Footnote This timing allows for rapid clearance of deposited chemicals.

Question 47

What is the recommendation regarding lung burden measurement at post-exposure time points?

Answer 47

The same lung should be measured at all time points ## Footnote This ensures consistency in data collection.