Zinc nitrate

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

Not applicable

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Relative toxicity of inhaled metal sulfate salts for pulmonary macrophages

Author:

Skornik WA & Brain JD

Year:

1983

Bibliographic source:

Am. Rev. Respir. Dis. 128: 297-303

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Since the pulmonary macrophages are responsible for particle clearance, toxicity of test materials can be assessed by their ability to affect the phagocytic clearance capacity of pulmonary macrophages . This was measured in terms of macrophage endocytosis of colloidal gold particles instilled intra-tracheally in Syrian hamsters after 4 h exposure to a range of concentrations of the test material.

GLP compliance:

no

Test type:

other: Pulmonary study

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Zinc sulphate

EC Number:

231-793-3

EC Name:

Zinc sulphate

Cas Number:

7733-02-0

Molecular formula:

H2O4S.Zn

IUPAC Name:

zinc sulfate

Details on test material:

- Name of test material (as cited in study report): Zinc sulfate and ZnSO4

Test animals

Species:

hamster, Syrian

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Wilmington, MA
- Age at study initiation: 3-5 months
- Weight at study initiation: 90-110 g
- Housing: Individually in wire cages
- Diet (e.g. ad libitum): Purina Rat Chow, ad libitum
- Water: Ad libitum

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

other: water

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Open wire mesh, stainless steel and Lucite exposure chamber
- Exposure chamber volume: 170 L
- Source and rate of air: Air, which passed through a charcoal and particulate filter was used at 0-70 L/min
- Method of conditioning air: Aerosol was passed through a 4 L drying and mixing chamber, to evaporate the water from primary droplets, resulting in dry particles in aerosol cloud
- System of generating particulates/aerosols: 6 jet Teflon Collison nebulizer (from BOl, Inc., Waltham, MA)
- Nebuliser incoming pressure: 22 psig
- Output rate: 15 L/min
- Capacity of nebuliser: 12.8 µL of solution was aerosolized by every jet air
- Method of particle size determination: Done using tagged particles (Technetium-99m) in a concentric channel centrifugal aerosol spectrometer
- Temperature, humidity, pressure in air chamber: 20 to 24 °C, 48 to 64 %


TEST ATMOSPHERE
- Brief description of analytical method used:
(a) Gravimetric analyses of pre-weighed filters were done using Mettler balance (Model HL52; Mettler Instrument Co., Princeton, NJ).
(b) Chemical analyses of sulfate ions were performed by extracting the sulfate ions from the filter by dissolving in water and shaking on a platform shaker. Then the extracted sample is treated with barium chloride to obtain a colloidal suspension of barium sulfate . The turbidity of the suspension is measured spectrophotometrically at 420 nm and the sulfate concentration was determined by comparing to standard Na2SO4 solutions. The concentration of sulfate in the chamber atmosphere was expressed as milligrams per cubic meter of sulfate ions.
- Samples taken from breathing zone: Yes (~240 L of air sampled over a 60 min period)
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): 0.59 µm/1.46

Analytical verification of test atmosphere concentrations:

yes

Remarks:

Sulfate analysis

Duration of exposure:

4 h

Concentrations:

0.8, 3.1, 6.5 and 20.3 mg/m3

No. of animals per sex per dose:

6-12 animals

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 48 h
- Frequency of observations and weighing: 1, 28 and 48 h
- Necropsy of survivors performed: yes, anesthetised with sodium methohexital (0.52 g/kg bw), i.p.
- Other examinations performed:
(a) Morphologic studies: The pooled cells recovered in a total of 12 lung washings were centrifuged to form a pellet. The pellet was embedded in paraffin or Epon and sectioned for examination by light microscopy
(b) Effects of different concentrations of test material on pulmonary macrophage endocytosis and determination of EC50
(c) The numbers of pulmonary macrophages recovered by lung lavage
(d) Mean pulmonary macrophage volumes as a function of time after exposure: Estimated from cell volume distributions plotted from the Coulter Channelyser-1000

Statistics:

Statistical analysis of data was carried out using Linear regression and an iterative maximal likelihood method and differences between mean values were considered significant when P < 0.05.

Results and discussion

Preliminary study:

Not applicable

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

other: Reduced macrophage phagocytosis

Effect level:

>= 3.1 mg/m³ air (analytical)

Exp. duration:

4 h

Effect levels 2

Sex:

male

Dose descriptor:

other: EC50

Effect level:

4.5 mg/m³ air (analytical)

Exp. duration:

4 h

Mortality:

Not reported

Clinical signs:

other: Not applicable

Body weight:

Not applicable

Gross pathology:

Not applicable

Other findings:

- Other observations:
(a) Morphologic studies: 80 % of cells recovered from pulmonary lavage of exposed animals were always mononuclear. Red blood cells, polymorphonuclear leukocytes, lymphocytes, or ciliated cells were occasionally present in the lung washings.
(b) Effects of different concentrations of test material on pulmonary macrophage endocytosis and determination of EC50: See Table 1 & Figure 1.
(c) Numbers of pulmonary macrophages recovered by lung lavage: See Table 2.
(d) Mean pulmonary macrophage volumes as a function of time after exposure: See Table 3
(e) EC50 determination for decrease in phagocytosis: The potency of the metal ions was similar to that of sulfate ions.

Any other information on results incl. tables

Table 1: Effects of zinc sulfate on percent of radiolabelled¹⁹⁸AU colloid ingested in one hour^#

SO4^2 -(mg/m^3)	Hours after exposure
	1	24	48
0.0 (control)	80.2 ± 1.8 %	80.2 ± 1.8 %	80.2 ± 1.8 %
0.8	79.2 ± 2.1	82.3 ± 4.0	-
3.1	55.2 ± 4.8*	77.7 ± 3.7	75.6 ± 2.4
6.5	24.7 ± 7.5*	65.7 ± 3.0*	83.4 ± 4.1
20.3	5.8 ± 0.9*	17.8 ± 3.7*	-

# = All values are expressed as mean ± standard error

* = Significant change from control hamsters exposed to filtered air (p ≤ 0.05)

The pulmonary effects of test material were measured in terms of gold (administered by intra-tracheal instillation) ingestion by macrophages and the results indicate its extent of alterations of pulmonary phagocytic defense mechanism.

For determination of EC₅₀(concentration of test material to produce a 50 % decrease of phagocytosis) a dose-response curve was plotted by taking particle concentrations and the percent inhibition of macrophage endocytosis on the x and y axis respectively (See Figure 1)

Table 2: Effect of zinc sulfate on recoverable pulmonary macrophages (x 10⁶)^#

SO4^2-(mg/m^3)	Hours after exposure
	1	24	48
0.0 (control)	6.10 ± 0.19	6.10 ± 0.19	6.10 ± 0.19
0.8	7.53 ± 0.47	6.36 ± 0.30	-
3.1	7.15 ± 0.39	5.87 ± 0.44	6.54 ± 0.99
6.5	5.19 ± 0.80	4.38 ± 0.71*	8.65 ± 0.55*
20.3	4.28 ± 0.30*	6.25 ± 0.92	-

# = All values are expressed as mean± standard error

* = Significant change from control hamsters exposed to filtered air (p ≤ 0.05)

Table 3: Effect of zinc sulfate at EC₅₀(4.5 mg/m³) on pulmonary macrophage volume (µm³)

SO4^2-(mg/m^3)	Hours after exposure
	1	24	48
0.0 (control)	771 ± 18	-	-
4.5 (ZnSo4)	630 ± 18*	680 ± 22*	730 ± 20

Applicant's summary and conclusion

Interpretation of results:

other:

Remarks:

Criteria used for interpretation of results: expert judgment

Conclusions:

Under the test conditions, macrophage endocytosis of particulates caused by the test material was significantly reduced at ≥ 3.1 mg/m3 with an EC50 value of 4.5 mg/m3 for sulfate ions (equivalent to zinc ions).

Executive summary:

A study was performed to assess the acute inhalation toxicity of zinc sulfate aerosols on the phagocytosis of insoluble particles by pulmonary macrophages in hamsters.

Male Syrian golden hamsters were exposed for 4 h to 0.8-20.3 mg/m³of ZnSO4 aerosols, followed by intratracheal instillation of insoluble gold colloid particles. Following gold instillation, the lungs were lavaged with physiological saline (0.85 NaCI) and aliquots of 12 lung washes were observed for cell and radioactive analyses. The parameters observed included macrophage endocytosis, numbers of pulmonary macrophages recovered by lung lavage and mean pulmonary macrophage volumes as a function of time. The concentration of aerosol causing a 50% inhibition in pulmonary macrophage endocytosis (EC50) was also determined.

Reduced macrophage endocytosis of test particles at ≥ 3.1 mg/m³and pulmonary macrophage volume was observed after one hour of exposure. The macrophage numbers were increased at low concentration, followed by depression at higher concentration. The concentration of test material that would produce a 50 % decrease in phagocytosis (EC₅₀) was determined to be 4.5 mg/m³.

Under the test conditions, macrophage endocytosis of particulates caused by the test material was significantly reduced at ≥ 3.1 mg/m3 with an EC₅₀value of 4.5 mg/m³ for sulfate ions (equivalent to zinc ions) mg/m³of sulfate ions (equivalent to zinc ions).