Reaction products of sodium glucoheptonate with zinc sulfate and sodium hydroxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1992

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The present study examined the time course and dose-response of the pulmonary injury produced by inhaled ZnO in guinea pigs, rats, rabbits, and human volunteers. The test animals were exposed to 0. 2.5, or 5.0 mg/m3 ZnO for up to 3 h and their lungs lavaged. Both the lavage fluid and recovered cells were examined for evidence of inflammation or altered cell function.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Zinc oxide

EC Number:

215-222-5

EC Name:

Zinc oxide

Cas Number:

1314-13-2

Molecular formula:

OZn

IUPAC Name:

oxozinc

Details on test material:

particle size: < 0.1 µm diameter and 0.1 - 1 µm diameter

Specific details on test material used for the study:

The present study examined the time course and dose-response of the pulmonary injury produced by inhaled ZnO in guinea pigs, rats, rabbits, and human volunteers. The test animals were exposed to 0, 2.5, or 5.0 mg/m3 ZnO for up to 3 h and their lungs lavaged. Both the lavage fluid and recovered cells were examined for evidence of inflammation or altered cell function.

Test animals

Species:

other: guinea pigs, rats, rabbits

Strain:

other: Hartley guinea pigs, Fischer 344 rats, New Zealand rabbits

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
Male, viral antibody-free Hartley guinea pigs (300 to 400 g, Charles River Breeding Laboratories, Wilmington, Mass.), viral antibody-free Fischer 344 rats (200 to 250 g, Charles River Breeding Laboratories), and specific pathogen-free New Zealand rabbits (3 to 4 kg, Hare-Marland, Hewitt, N.J.) were used in these studies. Animals were housed in hanging, steel mesh cages and provided with water and standard laboratory animal chow (Purina, Indianapolis. Ind.) ad libitum.

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

clean air

Mass median aerodynamic diameter (MMAD):

0.17 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: nose-only exposure chamber
- System of generating particulates/aerosols: Briefly, zinc granules were heated to approximately 550°C in a crucible. Zinc vapors were carried downstream by inert argon gas in the furnace to react with oxygen, yielding a supersaturated atmosphere of ZnO vapor. This vapor condensed to yield ulirafine panicles of ZnO, which were mixed with filtered air in a series of cooling/dilution heads before entering the exposure chamber.
- Method of particle size determination: Particle size measurements were performed with a differential mobility analyzer (TSI Inc., St. Paul, Minn.). By using the Hatch-Choate conversion equations,the mass median diameter of these particles was determined.

TEST ATMOSPHERE
- Brief description of analytical method used: Airborne ZnO concentrations were monitored gravimetrically with Teflon® filters (Type FG, 0.2-µm, Millipore, Bedford, Mass.) and a Cahn balance (Model 21, Cahn Instruments, Cerritos, Calif.). Periodically, filters were analyzed by atomic absorption spectroscopy for zinc content.

TEST ATMOSPHERE (if not tabulated)
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): The count median diameter of the particles was 0.06 µn with a geometric standard deviation of 1.8. By using the Hatch-Choate conversion equations, the mass median diameter of these particles was 0.17 µm.

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: To check the 8-hr threshold limit value (TLV) of 5 mg/m3, which has been established for human exposure to ZnO fumes.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

2 - < 3 h

Remarks on duration:

2 hours (rabbit), 3 hours (guinea pigs and rats)

Concentrations:

0, 2.5 and 5 mg/m3 (lavage of lung fluid), 4.3 to 11.3 mg/m3 (determination of lung burden level) - higher concentrations of airborne ZnO were used in the lung burden studies to ensure detection of retained inhaled Zn above normal biological levels of Zn.

Control animals:

yes

Remarks:

Control animals were exposed to furnace gases consisting of air (29 L/min) and argon (1 L/min). The temperature delivered to the nose-only ports ranged from 25-30°C; relative humidity was approximately 30%.

Details on study design:

- Duration of observation period following administration: 0 - 24 h
- animals exposed to 2.5 and 5 mg/m3 ZnO: The tracheas were can-nulated sterilely with blunt needles (guinea pigs and rats) or infant endotracheal tubes (rabbits) and lavaged twice with sterile, pyrogen-free, phosphate-buffered saline (guinea pigs: 7 mL; rats: 3.5 mL; rabbits: 70% of total lung capacity). The lavage samples were saved and aliquoted for total cell counts, protein content (BioRad, Berkeley, Calif.), lactate dehydrogenase (LDH), and glucuronidase (Sigma Chemical Co., Si. Louis, Mo.). To examine functional effects of macrophages, cells in the lavage fluid from guinea pigs and rabbits were recovered by centrifugation (400 x g) for studying phagocytic function.The ability of macrophages to phagocytize particles was enumerated in two ways: (1) the phagocytic index was calculated as the percentage of macrophages engulfing particles and (2) phagocytic capacity was the percentage of viable macrophages engulfing four or more particles.
- animals exposed to 4.3 to 11.3 mg/m3 ZnO: The lungs were removed, weighed, ashed with acid, and analyzed for elemental Zn by atomic absorption spectroscopy.

Statistics:

In the animal studies, differences in lavage fluid parameters were analyzed by a one-way analysis of variance followed by a two-sided Dunnett's t-test where indicated. In the human studies, the absolute changes in lung function from pre- to postexposure values were compared by a paired t-test. A p value < 0.05 was considered statistically significant.

Results and discussion

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

other: Threshold limit value

Effect level:

5 mg/m³ air

Based on:

test mat.

Exp. duration:

2 h

Remarks on result:

other: see 'Remarks'

Remarks:

a single 2- to 3-h exposure to ZnO at the current threshold limit value (TLV) of 5 mg/m3 does elicit adverse health effects in several mammalian species.

Effect levels 2

Sex:

male

Dose descriptor:

other:

Remarks:

concentration inducing pulmonary effects in guinea pigs

Effect level:

2.5 mg/m³ air

Based on:

test mat.

Exp. duration:

2 h

Remarks on result:

other: see 'Remarks'

Remarks:

Pulmonary effects in rats and guinea pigs were also observed at a concentration of 2.5 mg/m3

Mortality:

no

Other findings:

Total cell counts, protein content, LDH, and p-glucuronidase were all significantly increased in guinea pigs 24 hr after a single 3-h exposure to 5 mg/m3. Significant increases in LDH (16-fold), P-glucuronidase (5-fold), and protein were also observed in the lavage fluid of guinea pigs exposed to 2.5 mg/m3 ZnO and studied 24 h later. Rats appeared nearly as sensitive in the magnitude of their cellular and biochemical response to ZnO inhalation. Protein content, LDH, p-glucuronidase, and cell counts were increased at 24 h after exposure to 5 mg/m3. Significant increases in LDH and p-glucuronidase were also observed as early as 4 h after exposure to 5 mg/m3 and at 24 h after exposure to 2.5 mg/m3 ZnO. Inflammatory changes in the lavage fluid were not observed in rats sacrificed immediately following exposure to ZnO. No lavage parameter examined was increased in rabbits after a 2-h exposure to 5 mg/m3 ZnO. P-glucuronidase was decreased in rabbits examined at 0 and 24 hr after exposure, although this decrease cannot be explained and may be biologically irrelevant. Phagocytosis of opsonized latex beads by alveolar macrophages from guinea pigs, but not rabbits, was altered by exposure to ZnO. The phagocytic capacity of guinea pig macrophages was markedly reduced; the phagocytic index was not significantly changed.

Any other information on results incl. tables

Although the lungs of guinea pigs and rats retained approximately 20% and 12% of the inhaled dose, respectively, rabbits retained only 5%.

Applicant's summary and conclusion

Conclusions:

Together, these studies demonstrate that a single 2- to 3-h exposure to ZnO at the current threshold limit value (TLV) of 5 mg/m3 does elicit adverse health effects in several mammalian species.

Executive summary:

The present study examined the time course and dose-response of the pulmonary injury produced by inhaled ZnO in guinea pigs, rats and rabbits. The test animals were exposed to 0, 2.5, or 5.0 mg/m3 ZnO for up to 3 h and their lungs lavaged. Both the lavage fluid and recovered cells were examined for evidence of inflammation or altered cell function. The lavage fluid from guinea pigs and rats exposed to 5 mg/m3 had significant increases in total cells, lactate dehydrogenase, b-glucuronidase, and protein content. These changes were greatest 24 h after exposure. Guinea pig alveolar macrophage function was depressed as evidenced by in vitro phagocytosis of opsonized latex beads. Significant changes in lavage fluid parameters were also observed in guinea pigs and rats exposed to 25 mg/m3 ZnO. In contrast, rabbits showed no increase in biochemical or cellular parameters fallowing a 2-h exposure to 5 mg/m3 ZnO. Differences in total lung burden of ZnO, as determined in additional animals by atomic absorption spectroscopy, appeared to account for the observed differences in species responses. Although the lungs of guinea pigs and rats retained approximately 20% and 12% of the inhaled dose, respectively, rabbits retained only 5%.