Zinc carbonate

Endpoint summary

Description of key information

Non-human information
The repeated dose toxicity of water soluble zinc sulphate and zinc monoglycerolate has been examined in a total of 3 subchronic oral feeding studies. Due to the different dosing regimens, the lowest NOAEL was determined to be 31.5 mg/kg bw/day of zinc monoglycerolate which equals a total zinc exposure of approximate 13 mg/kg bw/day. The zinc NOAEL derived from the feeding studies with zinc sulphate was determined to be 104 mg Zn/kg bw/day in mice and approximately 53.5 mg/kg bw/day in rats. At higher doses the most important effects in the rats were the development of hypocupremia, and significant changes in the pancreas (i.e., focal acinar degeneration and necrosis) and a decreased number of pigmented macrophages in spleen.
No longer term inhalation studies allowing to derive a robust NOEL for the inhalatory exposure of the respective zinc compounds has been identified. In a short term 3-day inhalation study with guinea pigs, a concentration of 2.3 mg ultrafine ZnO/m3 (3 hours/day) resulted in changes in neutrophils and activities of lactate dehydrogenase and alkaline phosphatase in the pulmonary fluid. At higher concentrations increased protein concentration, neutrophils, and enzyme activities in lung lavage fluids were seen, together with significant centriacinar inflammation of the pulmonary tissue. Inhalatory doses of 2.7 mg ultrafine ZnO/m3 for 5 days 3hours/day did not alter the lung function parameters in guinea pigs, but at 5 and 7 mg ultrafine ZnO/m3 exposure according to a similar pattern, a gradual decrease in total lung capacity, vital capacity and reduction of the carbon monoxide diffusing capacity was seen in combination with inflammatory changes and edema. The relevance of the findings in studies with ultra-fine zinc oxide fumes is unclear with respect to commercial grade zinc oxide, as the latter is of much larger particle size and can have different toxicological characteristics.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

See appendix on read across in iuclid section 13

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

no data

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

none

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

daily

Remarks:

Doses / Concentrations:
0%
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
0.05% (= male 31.52 mg/kg bw and female 35.78 mg/kg bw)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
0.2% (= male 127.52 mg/kg bw and female 145.91mg/kg bw)
Basis:
nominal in diet

No. of animals per sex per dose:

20 males
20 females

Details on study design:

Groups of 20 male and 20 female Sprague-Dawley rats were fed zinc monoglycerolate at dietary levels of 0, 0.05 or 0.2% (equal to 0, 31.52 or 127.52 mg/kg for males and 0, 35.78 or 145.91 mg/kg bw for females, respectively) for a period of 13 weeks in a study performed according to OECD 408. Asimilar group was fed 1% (equal to 719 and 805 mg/kg bw/day for males and females, respectively) of zinc monoglycerolate up to day 58 of the study when a deterioration in their clinical condition (poor physical health and reduced food intake) necessitated reducing the dietary level to 0.5% (equal to 632 and 759 mg/kg bw/day for males and females, respectively). However, as no improvement occurred these rats were killed on humane grounds on day 64 of the study.

Observations and examinations performed and frequency:

according to guideline

Sacrifice and pathology:

according to guideline

Statistics:

according to guideline

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Ophthalmological findings:

effects observed, treatment-related

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Details on results:

The rats fed 1% of test substance for 58 days and then 0.5% to day 64 had were killed before the end of the study due to ill-health developed hypocupremia manifested as a hypochromic microcytic regenerative type anaemia (low haemoglobin and haematocrit, decreased MCV and MCH, and increased MCHC, red blood cell and reticulocyte count). Enlargement of the mesenteric lymph nodes and slight pitting of the surface of the kidneys were noted. Severe pancreatic degeneration and pathological changes in the spleen, kidneys, incisors, eyes and bones were observed. The testes of all males showed hypoplasia of the seminiferous tubules to a varying degree and in addition the prostate and seminal vesicles showed hypoplasia. In all but one female the uterus was hypoplastic.

In the main study, a dietary level of 0.2% increases in plasma ALAT, alkaline phosphatase and creatine kinase were observed in males and in plasma creatine kinase in females. Total plasma cholesterol was reduced in both males and females. The changes were statistically significant but small in absolute terms. No changes in haematological parameters were seen at 0.05 and 0.2%. A dose related reduction in the quantity of abdominal fat was noted in male rats at 0.05 and 0.2%. Enlargement of the mesenteric lymph nodes was apparent in 6 out of 20 rats fed 0.2% and in one male fed 0.05%. Microscopic examination showed a reduction in the number of trabeculae in the metaphysis of the tibia of 5 male and 3 female rats fed 0.2%, 4 males and 1 female had a similar reduction in the metaphysis of the femur. Pancreatic cell necrosis was seen in both sexes at 0.2% and a slight, but statistically not significant increase could be noted at 0.05% (3 males and 1 female). This pancreatic cell necrosis was seen also in 1 control male. A reduction in the number of pigmentated macrophages in the red pulp of the spleen was observed in both sexes at 0.2% and a marginal reduction was also seen in males at 0.05%. In the animals given 0.05 and 0.2% no effects were found on the reproductive organs.

Dose descriptor:

NOAEL

Effect level:

31.52 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Dose descriptor:

LOAEL

Effect level:

53.8 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: changes in haemotological parameters, pancreatic cell necrosis; no effects were seen at LOAEL in reproductive organs

Critical effects observed:

not specified

Conclusions:

NOAEL in this study is 31.52 mg/kg bw (approximately 13.26 mg Zn2+/kg bw)

Executive summary:

Groups of 20 male and 20 female Sprague-Dawley rats were fed zinc monoglycerolate at dietary levels of 0, 0.05 or 0.2% (equal to 0, 31.52 or 127.52 mg/kg for males and 0, 35.78 or 145.91 mg/kg bw for females, respectively) for a period of 13 weeks in a study performed according to OECD 408. A similar group was fed 1% (equal to 719 and 805 mg/kg bw/day for males and females, respectively) of zinc monoglycerolate up to day 58 of the study when a deterioration in their clinical condition (poor physical health and reduced food intake) necessitated reducing the dietary level to 0.5% (equal to 632 and 759 mg/kg bw/day for males and females, respectively). However, as no improvement occurred these rats were killed on humane grounds on day 64 of the study. These rats developed hypocupremia manifested as a hypochromic microcytic regenerative type anaemia (low haemoglobin and haematocrit, decreased MCV and MCH, and increased MCHC, red blood cell and reticulocyte count). Enlargement of the mesenteric lymph nodes and slight pitting of the surface of the kidneys were noted. Severe pancreatic degeneration and pathological changes in the spleen, kidneys, incisors, eyes and bones were observed. The testes of all males showed hypoplasia of the seminiferous tubules to a varying degree and in addition the prostate and seminal vesicles showed hypoplasia. In all but one female the uterus was hypoplastic.

All other rats survived to the end of the 13 weeks treatment. At a dietary level of 0.2% increases in plasma ALAT, alkaline phosphatase and creatine kinase were observed in males and in plasma creatine kinase in females. Total plasma cholesterol was reduced in both males and females. The changes were statistically significant but small in absolute terms. No changes in haematological parameters were seen at 0.05 and 0.2%. A dose related reduction in the quantity of abdominal fat was noted in male rats at 0.05 and 0.2%. Enlargement of the mesenteric lymph nodes was apparent in 6 out of 20 rats fed 0.2% and in one male fed 0.05%. Microscopic examination showed a reduction in the number of trabeculae in the metaphysis of the tibia of 5 male and 3 female rats fed 0.2%, 4 males and 1 female had a similar reduction in the metaphysis of the femur. Pancreatic cell necrosis was seen in both sexes at 0.2% and a slight, but statistically not significant increase could be noted at 0.05% (3 males and 1 female). This pancreatic cell necrosis was seen also in 1 control male. A reduction in the number of pigmentated macrophages in the red pulp of the spleen was observed in both sexes at 0.2% and a marginal reduction was also seen in males at 0.05%. In the animals given 0.05 and 0.2% no effects were found on the reproductive organs.

Since the pancreatic cell necrosis, being without statistical significance at 0.05%, was also apparent in 1 control male and because the reduction in pigmented macrophages in the spleen was only marginal at 0.05% without any haematological changes the dose level of 0.05%, is considered as a NOAEL. This dose level is equal to 31.52 or 35.78 mg zinc monoglycerolate/kg bw for males and females, respectively, so the NOAEL in this study is 31.52 mg/kg bw (»13.26 mg Zn²⁺/kg bw)

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

13.3 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

repeated dose toxicity: inhalation

Remarks:

other: 5 d repeated exposure study

Type of information:

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

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

See appendix on read across in iuclid section 13

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Guinea pigs were exposed by nose only 3h/d for 5 d to ZnO ultrafine particles and examined after 1, 2, 3, 4 and 5 d post-exposure for functional changes and extent of damage in the lungs.

GLP compliance:

not specified

Limit test:

no

Species:

guinea pig

Strain:

Hartley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Wilmington, Mass
- Weight at study initiation: 240-300 g
- Housing: Animals were housed 4/cage
- Diet: Ad libitum, Charles River Guinea Pig Formula
- Water: Ad libitum
- Maintenance: According to guidelines of Division of Comparative Medicine at MIT, which is accredited by the American Association for Accreditation of Laboratory Animal Care (AALAC)
- Others: Observed in quarantine for 5 d for any externally detectable evidence of pulmonary disease before exposure to test material


ENVIRONMENTAL CONDITIONS
- Temperature: 23 °C
- Humidity: 30-50 %

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: no data

Remarks on MMAD:

MMAD / GSD: 0.05 µm/2.0

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Dynamic animal exposure chamber
- System of generating particulates/aerosols: Zinc turnings were heated at 480 °C in a crucible, and the zinc vapours were carried by a flow of argon gas to be contacted by purified air downstream in the furnace. The vapours react with oxygen to yield ultrafine zinc oxide particles upon condensation.
- Method of particle size determination: Test material aerosol was collected on pre-coated carbon grids using Thermosystem Model 3100 electrostatic precipitator and examined (400 to 600 particles) and photographed in a Philips 300 electron microscope
- Particle size distribution: Piezoelectric crystal TSI Model 3030


TEST ATMOSPHERE
- Analytical method used: Test material concentration was determined using Millipore GSWQ 47 mm filters for total aerosol collection and weighing of the filters on a Cahn electrobalance Model 21. Chemical analysis consisted of Atomic absorption spectrometry and electron spectroscopy used for chemical analysis (ESCA)
- Samples taken from breathing zone: Yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Measured by aerosol collection on Millipore GSWQ 47 mm filters, followed by weighing on a Cahn electrobalance Model 21

Duration of treatment / exposure:

3 h/d for 5 d

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
Experiment I: 7 mg/m3 (For details see Table 1 under 'Any other information on materials and methods incl. tables')
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
Experiment II: 2.7 mg/m3 (For details see Table 1 under 'Any other information on materials and methods incl. tables')
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
Experiment III: Single high-peak exposure at 34 mg/m3 , and terminated exposure (For details see Table 1 under 'Any other information on materials and methods incl. tables')
Basis:
analytical conc.

Remarks:

Doses / Concentrations:
Experiment IV: Single high-peak exposure: 25 mg/m3 and continuing exposure at: 4-8 mg/m3 (For details see Table 1 under 'Any other information on materials and methods incl. tables')
Basis:
analytical conc.

No. of animals per sex per dose:

5-8 animals in each experiment (For details on number of animals in each experiment - see Table 1 under 'Any other information on materials and methods incl. tables')

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: Based on the previous acute exposure study at 8 mg/m3 for 3 h and repeated dose study for 3h/d, 6 d exposure at 5 mg/m3: the following doses were selected: (a) 7 mg/m3 for 5 d : to address the time course of alterations of pulmonary function, (b) 2.7 mg/m3 for 5 d: to determine effects at lower concentration and (c) Two peak experiments (25-34 mg/m3): to address the effects of occasional peak exposure of test material during chronic low-level exposures

Positive control:

None

Observations and examinations performed and frequency:

OTHER: PULMONARY FUNCTION MEASUREMENT
- Number of animals: 5-8 animals
- Time schedule for examination: After 1, 2, 3, 4 and 5 exposure periods (3 h)
- Anesthetic used for examination: Yes (ketamine hydrochloride and xylazine - 100 mg/kg 1M and 15 mg/kg 1M, respectively)
- Pulmonary function parameters checked: ventilation, dynamic compliance, flow resistance, vital capacity (VC) and inspiratory capacity (IC), total lung capacity (TLC), Functional residual capacity (FRC) and residual volume (RV), single-breath diffusing capacity for carbon monoxide (CO) ( DLco) and apparent alveolar volume (VA)

Sacrifice and pathology:

None

Other examinations:

LUNG WEIGHT:
- Time schedule for examinations: After the last functional measurement
- Brief description of method: The chest was opened and the lungs were removed after exsanguination of animals. The heart and mediastinal tissues were dissected to measure the wet-lung weight. Dry-lung weight recording were obtained by drying the lungs at 45 °C for 48 h, followed by keeping in desiccator for 24 h.

Statistics:

Analysis of variance (ANOVA) was used to compare the means of variables across all exposure groups with the pooled control data. Significant differences (p ≤ 0.05) among group means were analysed for group differences by applying Dunnett's multiple range test. Correlations between variables were computed using StatView 512+©

Clinical signs:

not examined

Mortality:

not examined

Body weight and weight changes:

not examined

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Details on results:

ORGAN WEIGHTS: Extent of pulmonary damage was measured by:

- Wet-lung weight/Body weight ratio: (see Figure 6 )
(a) Experiment I (7 mg/m3): Ratio increased about 10 % on Day 2 and 29 % by Day 5
(b) Experiment II (2.7 mg/m3): No significant increase
(c) Experiment III (single high-peak exposure (34 mg/m3) with terminated exposure: Ratio increased 30 %, 49 %, 45 % and 19 % on Days 2-5 respectively
(d) Experiment IV (single high-peak exposure (25 mg/m3) with continued exposure at 4-8 mg/m3: No change on day of peak (Day 1), but increased about 45 %, 50 % -60 % on Days 2 and 3-5 respectively

- Wet-lung weight/Dry-lung weight ratio: (see Figure 6)
(a) Experiment I (7 mg/m3): Increased significantly only on Day 4
(b) Experiment II (2.7 mg/m3): No significant increase
(c) Experiment III (single high-peak exposure (34 mg/m3) with terminated exposure: Ratio increased 8 % on Day 2-4 and then decreased on Day 5
(d) Experiment IV (single high-peak exposure (25 mg/m3) with continued exposure at 4-8 mg/m3: Ratio increased by 10 % on Day 2 and remained constant till Day 5


OTHER FINDINGS: PULMONARY FUNCTION MEASUREMENT

- Tidal volume, respiratory frequency, airway resistance or compliance:
(a) Experiment I (7 mg/m3): No alterations
(c) Experiment III (single high-peak exposure (34 mg/m3) with terminated exposure and (d) Experimnet IV (single high-peak exposure (25 mg/m3)(with continued exposure at 4-8 mg/m3: Increased airway resistance and decreased compliance was observed at both peak exposures (see Figure 5)

- Lung volumes (TLC, VC, FRC and RV): Significant decrease below control was observed
(a) Experiment I (7 mg/m3): VC and TLC decreased -22 % and -18 %; No change in FRC and RV was observed (see Figure 1A)
(b) Experiment II (2.7 mg/m3): No change in lung volume (see Figure 2A)
(c) Experiment III (single high-peak exposure (34 mg/m3) with terminated exposure: TLC decreased -15 %, -22 %, -24 %, -17 %, on Days 2-5 respectively; VC decreased -17 %, -28 %, -25 % and 19 %, on Days 2-5 respectively; No change in FRC and RV was observed (see Figure 3A).
(d) Experiment IV (single high-peak exposure (25 mg/m3) with continued exposure at 4-8 mg/m3: TLC decreased -10 %, -32 %, -34 %, -28 % and -28 % on Days 1-5 respectively; VC also decreased in similar way; FRC decreased -17 %, -27% and -20 % on Days 2-4 respectively. No difference on Day 5; RV reduced -20 %, -30 %, -20 % and -10 % on Days 2-5 respectively (see Figure 4A)

- DLco and VA: Significant decrease below control was observed
(a) Experiment I (7 mg/m3): Only a slight increase was observed on the Day 1 of exposure (see Figure 1B)
(b) Experiment II (2.7 mg/m3): No change in DLco was observed (see Figure 2B)
(c) Experiment III (single high-peak exposure (34 mg/m3) with terminated exposure: VA decreased significantly by -10 % on Day 3; DLco decreased -40 %, -50 % and -25 % on Days 2, 3 and 5 respectively (see Figure 3B).
(d) Experiment IV (single high-peak exposure (25 mg/m3) with continued exposure at 4-8 mg/m3: VA only decreased on Day 3; DLco decreased -60 %, -40 %, -30 %, 25 % and -25 % on Days 1-5 respectively (see Figure 4B)

Dose descriptor:

NOAEL

Effect level:

2.7 mg/m³ air (analytical)

Sex:

male

Basis for effect level:

other: All measured parameters

Dose descriptor:

other: decreased lung volume

Effect level:

7 mg/m³ air (analytical)

Sex:

male

Basis for effect level:

other: Other: Pulmonary function measurement

Dose descriptor:

other: decrease of Lung volumes and diffusing capacity at peaks occurs rapidly and to a greater extent

Effect level:

25 - 34 mg/m³ air (analytical)

Sex:

male

Basis for effect level:

other: Pulmonary function measurement

Dose descriptor:

other: Pulmonary damage

Effect level:

7 mg/m³ air (analytical)

Sex:

male

Basis for effect level:

other: Wet-lung weight/Body weight ratio and Wet-lung weight/Dry-lung weight ratio

Dose descriptor:

other: Increased pulmonary damage at peak concentrations

Effect level:

25 - 34 mg/m³ air (analytical)

Sex:

male

Basis for effect level:

other: Wet-lung weight/Body weight ratio and Wet-lung weight/Dry-lung weight ratio

Critical effects observed:

not specified

Correlation analysis: Significant associations exists between TLC and DLco with the ratio of wet-lung weight to body weight (r = 0.93 and r = 0.70, respectively). A correlation also exists between the change in DLco and that of TLC ( r = 0.73). (see Figure 7). Association of decreased of lung volumes and DLco with the ratio of wet-lung weight to body weight indicates presence of pulmonary oedema.

Remarks on results on extent of pulmonary damage: The increased wet-lung weight to body weight ratios on peak exposures indicate high dose of ZnO given within a short period of time was more effective in inducing lung damage than an equivalent dose given over a longer period.

Remarks on results on Pulmonary function measurement: Nonpeak exposures induced gradual decreases in TLC and VC and diffusing capacity, whereas, in peak exposures, the changes occurred very rapidly.

Conclusions:

Under the test conditions, Exposures to 2.7 mg/ m3, using the same 3 hr/ day, 5 day time frame, did not alter any parameters measured.

Executive summary:

An inhalation study was conducted to evaluate the low-level exposures together with occasional intense exposures of ultrafine test material particles in guinea pigs.

 

5-8 Male Hartley Guinea pigs in each experimental group were given an exposure to different concentrations of test material, by nose-only for 3 h/d for 5 consecutive days. The animals were then evaluated for pulmonary function tests and extent of pulmonary damage after 1, 2, 3, 4 and 5 d post-exposure.

An exposure at concentration of 7 mg/m3 produced a gradual decrease in total lung capacity and vital capacity over the course of the exposure period. The carbon monoxide (CO) diffusing capacity (DLco) dropped abruptly to 30% below control levels on Day 4. Wet-lung weight/body weight ratios and wet-lung/ dry-lung weight ratios increased, indicating the presence of edema. Exposures to 2.7 mg/ m3, using the same 3 hr/ day, 5 day time frame, did not alter any parameters measured.

In two experiments a single high peak of test material (25-34 mg/m3) occurred with or without continued exposure. In both, lung volumes were decreased abruptly and to a greater extent than when peaks were absent. Continued exposure caused greater decrements in TLC and V C as well as decrements in FR C and RV than were observed when exposure was stopped. Peak exposures reduced DLco to 45%-60% below control. These values rose to 25%-30% below control with or without continued exposure. Increased airway resistance and decreased compliance were also observed at both peak exposures.

 

Under the test conditions, the short peaks occurring during normal low-level exposures can induce rapid pulmonary functional changes and greater extent of pulmonary damage and oedema.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

2.7 mg/m³

Study duration:

subacute

Species:

guinea pig

Quality of whole database:

No longer term inhalation studies allowing to derive a robust NOAEL for the inhalatory exposure of zinc compounds are available. The 5 days inhlation test in guinea pigs is a non-standard study, not suitable for classification

Additional information

The biological activities of zinc compounds are determined by their ability to release zinc under the respective exposure conditions. Hence, information on the effects of systemically available zinc allows the repeated dose toxicity assessment across all those zinc compounds covered in this safety report.

Non-human information

The repeated dose toxicity of water soluble zinc sulphate and zinc monoglycerolate has been examined in a total of 3 subchronic oral feeding studies. Due to the different dosing regimens, the lowest NOAEL was determined to be 31.5 mg/kg bw/day of zinc monoglycerolate which equals a total zinc exposure of approximate 13 mg/kg bw/day. The zinc NOAEL derived from the feeding studies with zinc sulphate was determined to be 104 mg Zn/kg bw/day in mice and approximately 53.5 mg/kg bw/day in rats. At higher doses the most important effects in the rats were the development of hypocupremia, and significant changes in the pancreas (i.e., focal acinar degeneration and necrosis) and a decreased number of pigmented macrophages in spleen.

No longer term inhalation studies allowing to derive a robust NOEL for the inhalatory exposure of the respective zinc compounds has been identified. In a short term 3-day inhalation study with guinea pigs, a concentration of 2.3 mg ultrafine ZnO/m³(3 hours/day) resulted in changes in neutrophils and activities of lactate dehydrogenase and alkaline phosphatase in the pulmonary fluid. At higher concentrations increased protein concentration, neutrophils, and enzyme activities in lung lavage fluids were seen, together with significant centriacinar inflammation of the pulmonary tissue. Inhalatory doses of 2.7 mg ultrafine ZnO/m³for 5 days 3hours/day did not alter the lung function parameters in guinea pigs, but at 5 and 7 mg ultrafine ZnO/m³exposure according to a similar pattern, a gradual decrease in total lung capacity, vital capacity and reduction of the carbon monoxide diffusing capacity was seen in combination with inflammatory changes and edema. The relevance of the findings in studies with ultra-fine zinc oxide fumes is unclear with respect to commercial grade zinc oxide, as the latter is of much larger particle size and can have different toxicological characteristics.

Human information

Upon supplementing men and women with 150 mg Zn/day (as zinc sulphate capsules), women appeared to be more sensitive than men to the effects of high zinc intake: clinical signs such as headache, nausea and gastric discomfort were more frequent among women and women but not men had decreased activities of serum ceruloplasmin and ESOD. In some earlier oral studies in which humans were supplemented with moderately high amounts of zinc (50 mg Zn/day), a reduction in ESOD activity was also observed and again women appeared to be more sensitive to this effect. Hence, a reduction in ESOD was thought to be a sensitive indicator of copper status. However, in more recent and more sophisticated studies using the same dose level, ESOD was only marginally reduced (without a correlation with changes in copper balance), while findings on more specific copper deprivation signs (decreased serum ceruloplasmin and platelet cytochrome c oxidase) indicated that a sub-optimal intake of zinc was more effective than a moderately high intake of zinc in inducing changes associated with a decreased copper status in postmenopausal women. Given this, and the degree of the observed ESOD reduction in comparison to the natural variability in its activity, the zinc-induced decrease in ESOD activity is considered to have marginal biological significance, if any and also because it may not have been caused by an interference with copper metabolism as deep tissue SOD increases as a function of zinc exposure was observed.

Overall, it can be concluded that from studies in which humans were supplemented with zinc (as zinc gluconate), that women are more sensitive to the effects of high zinc intake and that a dose of 50 mg Zn/day is the human NOAEL. This equals a daily exposure of 0.83 mg/kg bw. At the LOAEL of 150 mg Zn/day, clinical signs and indications for disturbance of copper homeostasis have been observed.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The lowest established NOAEL = 13.3 mg Zn/kg bw/day selected out of 3 subchronic oral feeding studies with soluble zinc sulphate and zinc monoglycerolate

Besides animal data, there are several human studies in which humans were supplemented with moderately high amounts of zinc (50 mg Zn/day) (as zinc gluconate) where a NOAEL of 50 mg Zn/ day is determined (equals 0.83 mg Zn/kg bw/day).

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: other; digestive: pancreas

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: lung

Justification for classification or non-classification

Zinc is essential for human growth and development, neurological functions and immunocompetence. The main clinical manifestations of zinc deficiency are growth retardation, delay in sexual maturation or increased susceptibility to infections (SCF, 2003). Health specialists recommend supplementing the diet with zinc in case human diet is zinc deficient. The maximum allowable daily intake has been established to be 50 mg zinc per day. Hence no classification is required.