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Acute Toxicity: inhalation

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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:
From May 29, 2009 to July 13, 2009
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Guideline Study
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
no
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Nickel sulfate hexahydrate
- Substance type: Soluble in water
- Physical state: blue, crystalline solid
- Expiration date of the lot/batch: not applicable
- Stability under test conditions: Stable for duration of testing
- Storage condition of test material: Stored at room temperature with a nitrogen pad inserted into container after initial testing
- Other: The sample was aerosolized after being ground in a coffee mill (Cuisinart, Model DCG-20N) until it passed through a 425 micron USA
standard testing sieve and then further ground in a ball mill for 48 hours. Nitrogen was added to the ball mill prior to grinding for 48 hours.
Documentation of the methods of synthesis, fabrication, or derivation of the test substance is retained by Sigma-Aldrich, 3050 Spruce St., St. Louis, Mo 63103.

Test animals

Species:
rat
Strain:
other: Sprague-Dawley derived, albino
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Ace Animals, Inc., Boyertown, PA
- Age at study initiation: Young adult (8-10 weeks)
- Weight at study initiation: Males 242-372 grams; Females 185-241 grams
- Housing: The animals were singly housed in suspended stainless steel caging with mesh floors which conform to the size recommendations in the most recent Guide for the Care and Use of Laboratory Animals DHEW (NIH). Litter paper was placed beneath the cage and was changed at least three times per week.
- Diet (e.g. ad libitum): Purina Rodent Chow #5012
- Water (e.g. ad libitum): Tap water was supplied ad libitum by an automatic water dispensing system
except during exposure.
- Acclimation period: 8, 14 or 17 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 57-68%
- Air changes (per hr): 284
- Photoperiod (hrs dark / hrs light): 12-hour light/dark cycle

Administration / exposure

Route of administration:
other: aerosolized dust
Type of inhalation exposure:
nose only
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Mini Nose Only Inhalation Chamber, ADG Developments LTD
- Exposure chamber volume: 6.7 liters
- Method of holding animals in test chamber: Animals individually housed in polycarbonate holding tubes
- Source and rate of air: Air compressor (JUN-AIR, Model #6-15); Compressed air tank (Airgas); Average Total Air=31.7 Lpm
- Method of conditioning air:
- System of generating particulates/aerosols: The test substance was aerosolized using a modified Wright Dust Generator driven by a variable speedmotor (Dayton, Model #4Z538A) D.C. speed control with 0-100 potentiometer. The test substance was packed into the dust container (Wright, Model OF 183 or 183A) and compressed to 250 Ibs/in2 using a lab press (Carver, Model C). The container was then fitted with a stainless steel cutting head(Model OF 1945S or 1935S) and cutting blade (Model OF 191 SS or 1905S). Compressed air was supplied to the dust generator at 30 psi. The aerosol ized dust was then fed directly into the chamber through the dust outlet assembly.
- Method of particle size determination: An eight-stage Andersen cascade impactor was used to assess the particle size distribution of the test atmosphere. Samples were withdrawn from the breathing zone of the animals at two intervals during each exposure. The filter paper collection stages were weighed before and after sampling to determine the mass collected upon each stage. The aerodynamic mass median diameter and geometric standard deviation were determined graphically using two-cycle logarithmic probit axes.
- Temperature, humidity, pressure in air chamber: Temperature Range 20-23oC; Relative Humidity Range 62-72; Average Total Air 31.7 Lpm


TEST ATMOSPHERE
- Brief description of analytical method used: Compressed airflow was measured with a Mass Flowmeter (Omega, Model #FMA-5613). Chamber airflow was monitored throughout the exposure period and recorded periodically.

The temperature and relative humidity within the exposure tube as well as the room were monitored continuously during each exposure. The measurements inside the exposure tube were made with a Humidity-Temperature Indicator (Taylor, Model #5502) and room conditions were measured with a Temperature-Humidity Monitor (Dickson, Model #TH550). Temperature and relative humidity values were recorded every 15 minutes for the first hour of exposure and every 30 minutes thereafter.

Gravimetric samples were withdrawn at six intervals from the breathing zone of the animals during each exposure. Samples were collected using 25 mm glass fiber filters (GFIB Whatman) in a filter holder attached by 1/4 inch tygon tubing to a vacuum pump (Reliance Electric, Model #G557X). Filter papers were weighed before and after collection to determine the mass collected. This value was dividedby the total volume of air sampled to determine the chamber concentration. Sample airflows were measured using a Mass Flowmeter (Omega, Model #FMA-561 0).

- Samples taken from breathing zone: yes


VEHICLE -no vehicle was used


TEST ATMOSPHERE (if not tabulated)
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): The MMAD was estimated based on the particle size distribution as measured with an Andersen Cascade Impactor.

0.063 mg/L; MMAD=2.4 um, GSD=2.02 (sample #1)/2.13 (sample #2)
0.53 mg/L; MMAD=3.0 um, GSD=2.00 (sample #1)/2.03 (sample #2)
2.12 mg/L; MMAD=2.8 um(sample #1)/2.9 um(sample #2), GSD=1.93 (sample #1)/1.97 (sample #2)
5.08 mg/L; MMAD=2.7 um, GSD=1.83 (sample #1)/1.83 (sample #2)


CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: Prior to initiation of the full inhalation study, pre-test trials were conducted to establish generation procedures to achieve, to the extent possible, the targeted chamber concentration and desired particle size distribution (mass median aerodynamic diameter between 1 and 4 um).
Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
>= 4 h
Concentrations:
Target Exposure levels: 0.06, 0.5, 2.0, and 5.0 mg/L
Actual (Gravimetric) Exposure levels: 0.063, 0.53, 2.12, and 5.08 mg/L
No. of animals per sex per dose:
5 males and 5 females per exposure level. The females assigned to test were nulliparous and non-pregnant.
Control animals:
no
Details on study design:
- Duration of observation period following administration: up to 14 days or until death occurred
- Frequency of observations and weighing: Observations occurred once daily; Body weights were recorded prior to exposure and again on Days 7 and 14 or after death.
- Necropsy of survivors performed: Yes - Surviving rats were euthanized via CO2 inhalation on Day 14. Gross necropsies were performed on all
decedents and euthanized animals. Tissues and organs of the thoracic and abdominal cavities were examined.
- Other examinations performed: body weight, gross toxicity, behavioral changes, gross evaluations
Statistics:
Biostat 2007 Professional Build 3.6.0.0, AnalystSoft, BioStat - statistical analysis program, Version
2007 was used for data analysis of LC50 and confidence limit calculations.

Results and discussion

Preliminary study:
Not applicable
Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
2.48 mg/L air
95% CL:
> 1.3 - < 4.5
Exp. duration:
4 h
Mortality:
Cumulative mortality observed (number of mortalities observed/total number of animals tested) at each exposure level:
0.063 mg/L: 0/5 males; 0/5 females
0.53 mg/L: 0/5 males; 0/5 females 
2.12 mg/L: 1/5 males; 0/5 females (death occurred one day after exposure)
5.08 mg/L: 5/5 males; 5/5 females (1 male and 1 female death occurred in exposure chamber; remaining deaths occurred within 3
days of exposure)
Clinical signs:
0.063 mg/L: Immediately following exposure and throughout the 14-day observation period all animals appeared active and healthy.
0.53 mg/L: Immediately following exposure and throughout the 14-day observation period all animals appeared active and healthy.
2.12 mg/L: Immediately following exposure to the test atmosphere, one male appeared hypoactive and exhibited abnormal respiration. This male wasfound dead one day after exposure. All surviving animals appeared active and healthy immediately following exposure and throughout the 14-day observation
period.
5.08 mg/L: Following exposure to the test atmosphere, the surviving rats exhibited clinical signs including abnormal respiration, hypoactivity, abnormal posture and/or ano-genital staining.
Body weight:
Individual body weights of the animals were recorded prior to test substance exposure (initial) and
again on Days 7 and 14 (termination) or after death.

0.063 mg/L: Although five rats failed to gain or lose body weight through Day 7, all animals gained weight over the entire observation period.
0.53 mg/L: Although one rat failed to gain body weight through Day 7, all animals gained weight over the entire observation period.
2.12 mg/L: Although two male survivors lost body weight through Day 7, all survivors gained weight over the entire observation period.
5.08 mg/L: Although there were no survivors to weigh on Day 7, all decedents except for one had a lower weight at death than their initial starting weight.
Gross pathology:
0.063 mg/L: No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.
0.53 mg/L: No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.
2.12 mg/L: Gross necropsy of the decedent revealed discoloration of the lungs and liver, and rigor mortis. No gross abnormalities were noted for any of the euthanized animals necropsied at the conclusion of the 14-day observation period.
5.08 mg/L: Gross necropsy of most decedents revealed discoloration of the lungs, liver and/or intestines, distention of the stomach and/or intestines, and/or rigor mortis. For one male and one female decedent the thymus appeared gray with dark spots.
Other findings:
0.063 mg/L:  There were no signs of gross toxicity, adverse pharmacologic effects, or abnormal behavior.
0.53 mg/L: There were no signs of gross toxicity, adverse pharmacologic effects, or abnormal behavior.
2.12 mg/L: There were no additional findings.
5.08 mg/L: There were no additional findings.

Any other information on results incl. tables

Not reported

Applicant's summary and conclusion