Ashes (residues), coal

Endpoint summary

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 Jan 2008 - 02 Apr 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

adopted on 27th July, 1995

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: SPF breeding, VELAZ s.r.o., Koleč u Kladna, Czech Republic, RČH CZ 21760152
- Age at study initiation: 6-7 weeks
- Weight at study initiation: males ca. 188 g, females ca. 138 g
- Housing: 2-3 rats of the same sex in one plastic cage (40x25x20 cm)
- Diet (e.g. ad libitum): complete pelleted diet for rats and mice in SPF breeding (ST 1 BERGMAN) ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30-70
- Air changes (per hr): ca. 15
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 19 Feb 2008 To: 20 Mar 2008

Route of administration:

oral: gavage

Vehicle:

other: 0.5% methylcellulose in water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing suspensions were prepared daily prior to administration. The test material was suspended in 0.5% methylcellulose in water.

VEHICLE
- Concentration in vehicle: The test material concentration in vehicle was adjusted accounting for body weight in order to achieve a constant administration volume of 1 mL/100 g bw.
- Amount of vehicle (if gavage): 1 mL/100 g bw

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

28 days

Frequency of treatment:

7 days/week

Dose / conc.:

0 mg/kg bw/day (actual dose received)

Dose / conc.:

250 mg/kg bw/day (actual dose received)

Dose / conc.:

500 mg/kg bw/day (actual dose received)

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: In a dose-range finding study, groups of 5 animals per sex per dose were given 250, 500, 750 and 1000 mg/kg bw of the test material daily for 14 days. No mortalities occurred. An increase in body weight gain was observed in males, especially at 500 mg/kg bw. No signs of toxicity and no impact on basic haematological parameters were noted. Macroscopic changes were seen in liver (marked structure, changed colour), kidneys (changed colour), stomach (haemorrhage on mucosa, change of mucosa), and uterus (dilatation) of some animals, the incidence of which showed, however, no dose-response.
On the basis of these results, three dose levels (250, 500, 1000 mg/kg bw were chosen for the main 28-day study.
- Rationale for selecting satellite groups: Two groups of 5 animals per sex per group were treated with vehicle or the highest dose.
- Post-exposure recovery period in satellite groups: 14 days

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

GENERAL CLINICAL OBSERVATION: Yes
- Time schedule: daily
This observation was made in order to record possible clinical effects after application and changes in animal behaviour.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: before the first administration and weekly thereafter.
Observation of animal behaviour in the cages: posture, position of eyelids, tonic or clonic movements, piloerection, stereotypes or bizarre behaviour.
Observation of animals during removal from the cages: reaction to handling, elasticity of skin, colour of mucous membranes, salivation, lacrimation, cleanliness of fur around foramina.

BODY WEIGHT: Yes
- Time schedule for examinations: before the first administration, weekly thereafter and at termination
The body weight was recorded on automatic balances with a group average computing module. The weight increment was computed as an average per group per day.

FOOD CONSUMPTION: Yes
- Time schedule: weekly
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes. The food consumption per animal per day was calculated from the weekly average values of each group.

FOOD EFFICIENCY: Yes
- Calculation of food conversion in %: weight increment/food consumption x 100.

WATER CONSUMPTION: Yes
- Time schedule for examinations: twice a week
Average values (water consumption per animal per day) were calculated for each week of the study.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: On days 29 (main groups) and 43 (satellite groups)
- Anaesthetic used for blood collection: Yes, light ether narcosis
- Animals fasted: No
- How many animals: all animals
- Parameters checked in table No.1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: On days 29 (main groups) and 43 (satellite groups)
- Animals fasted: No
- How many animals: all animals
- Parameters checked in table No. 2 were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: On days 28 (main groups) and 42 (satellite groups)
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No
- Parameters checked in table No.3 were examined.

MORTALITY CONTROL: Yes
- Time schedule: daily

FUNCTIONAL OBSERVATION: Yes
- Time schedule: in the last week of the administration period (main groups) and in last week of the recovery period (satellite groups)
During functional examination, the sensory reactivity on auditory, visual, proprioceptive stimuli and pupillary reflex were evaluated and motor activity assessment was conducted. Moreover the individual observations of grip strength were performed using dynamometer. Measurements were made on: 1) pectoral legs, 2) pelvis legs, 3) all four legs. Grip power was expressed in Newtons.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes. After gross necropsy of the cranial, thoracic and abdominal cavities, the organs for weighing and further histological examination were collected. The absolute weights of liver, kidneys, adrenals, testes, ovaries, epididymidis, uterus, thymus, spleen, brain, pituitary gland and heart were recorded. The relative organ weights were calculated thereafter. Organs for subsequent histopathological examination were removed and stored in fixative (neutral 4% formaldehyde).

HISTOPATHOLOGY: Yes (see table No.4). Tissue were processed by routine paraffin technique and stained by hematoxyline-eosine. Cryotome sections of liver and kidneys were stained by oil red for neutral lipids.

Statistics:

The Analysis of Variance (ANOVA) test (QC.Expert 2.5) was used for the statistical analysis (significance level 0.05). This statistical analysis was used for the results of haematology, blood chemistry, urinalysis, biometry of organs and body weight. Treated groups were compared to vehicle control group, the treated satellite group was compared to the satellite vehicle control group.

Details on results:

CLINICAL SIGNS AND MORTALITY
No mortalities occurred and no signs of toxicity were observed in any group.
One male treated with 500 mg/kg bw showed red staining around the snout on the day 16 of the study. In the absence of a dose-related response, this was considered to be incidental.
The activity (poise, gait, reaction to handling) of all animals was similar during the study and unchanged compared to the activity of animals in the control groups.
No changes were seen at any dose level during the examinations of skin, hair, eyes, lacrimation, visible mucous membrane, secretion, excretion and respiration.

BODY WEIGHT AND WEIGHT GAIN
No effects on the average body weight at any dose level in the main and satellite groups.
In males, a slightly lower body weight gains were recorded at 500 mg/kg bw in the first week and at 1000 mg/kg bw in the second week of administration. A mild increase in body weight gain measured at 250 mg/kg bw in the third week of study. In satellite males, a slightly higher body weight gain of the treated animals was seen in the fifth week of study. In females, only in the third week of study the body weight gain was slightly increased at 500 mg/kg bw. No effects on the body weight gain of satellite females was observed.

FOOD CONSUMPTION
Food consumption was slightly increased in males at 250 mg/kg bw in the third week. A slight decrease was observed in females of the 250 mg/kg bw group in the fourth week. No effects were observed in the satellite groups.

FOOD EFFICIENCY
Food conversion was slightly decreased in males at 1000 mg/kg bw in the second week and at 500 mg/kg bw in the first week. A slight increase was recorded at 250 mg/kg bw in the third week. In females, a slight increase was recorded at the all treated groups in the third week. A decrease was observed at 250 and 500 mg/kg bw in the fourth week. In satellite males, a slight increase in food conversion was recorded in the treated group only in the third and fifth week of study. In satellite treated females, a slight increase was observed in the fourth week and a slight decrease in the sixth week.

WATER CONSUMPTION
In males, a slight decrease in water consumption was observed at 1000 mg/kg bw in the first and second week, and a slight increase was noted at 250 mg/kg bw in the third and fourth week of study. In females, a slight decrease was observed at 250 and 1000 mg/kg bw in the second week and at 250 mg/kg bw also in the fourth week, while a slight increase was seen at 500 mg/kg bw in the fourth week. In satellite treated males, a slight decrease was recorded only the first week of study. In satellite treated females, a slight increase was recorded only in the fourth and fifth week of the administration period.

HAEMATOLOGY
Males
Prothrombin time and fibrinogen were increased in a dose-dependent manner (with statistical significance at 500 and 1000 mg/kg bw). A statistically significantly increased platelet count was recorded at 250 mg/kg bw. A decrease in erythrocyte count and haemoglobin value without statistical significance was noted at 500 mg/kg bw. Changes in differential leucocyte count were recorded at the middle and highest dose level (without statistical significance). Granulocytes value was increased and lymphocytes value was decreased. All other parameters were similar to the control group. All parameters were within physiologic limits.

Satellite males
A statistically significantly decreased erythrocyte count and an increase in the mean corpuscular volume were recorded in the treated group. Also prothrombin time was statistically significantly increased compared to the control group. A slightly decreased volume of haemoglobin and changes in differential leukocyte count were measured in the treated group. All other parameters were similar to the control group. All parameters were within physiologic limits.

Females
A slight decrease in total erythrocyte count and haemoglobin value was observed at 500 mg/kg bw. Platelet count was slightly increased and the total leukocyte count was slightly decreased in animals of the 1000 mg/kg bw group. An increased granulocyte value was recorded at 1000 mg/kg bw. Statistical analysis of the data revealed no significant intergroup differences. All other parameters were similar to the control group. All parameters were within physiologic limits.

Satellite females
Statistically significant changes in differential leukocyte count were recorded in the treated group. Prothrombin time was slightly increased.

CLINICAL CHEMISTRY
Males
All parameters were similar to the control group. Only a slightly increased value of creatinine was recorded at 250 mg/kg bw. Statistical analysis of the data revealed no significant intergroup differences. All observed parameters were within physiologic limits.

Satellite males
An increase in glucose without statistical significance was measured in the treated group. All other parameters were similar to the control group. Statistical analysis of the data revealed no significant intergroup differences. All observed parameters were within physiologic limits.

Females
All measured parameters were similar to the control group. Statistical analysis of the data revealed no significant intergroup differences. All observed parameters were within physiologic limits.

Satellite females
A satistically significant increase in ALP activity was recorded in the treated group. The glucose value was also significantly increased. A slightly decreased value of creatinine without statistical significance was recorded in the treated group. All other parameters were similar to the control group. All observed parameters were within physiologic limits.


URINALYSIS
Males
A statistically significant decrease in urine volume was recorded at 1000 mg/kg bw. At this dose level protein, urobilinogen and blood were observed in the urine of one animal and leucocytes were found in 2 animals. The urine of one control animal and one animal at the highest dose level showed a white cloud.

Satellite males
There were no treatment-related changes in urinary parameters. The urine of two treated animals and two control animals showed a yellow or white cloud. Statistical analysis of the data revealed no significant intergroup differences.

Females
There were no treatment-related changes in urinary parameters. Statistical analysis of the data revealed no significant intergroup differences.

Satellite females
There were no treatment-related changes in urinary parameters. Statistical analysis of the data revealed no significant intergroup differences.

NEUROBEHAVIOUR
Reaction to approximation, contact point, reaction to noise, reaction to pain and pupillary reflex of animals in all treated groups were the same as in the control groups. The numbers of up standings, emiction and defecation in the treated groups were similar to the control groups. No changes were observed in the values of grip strength of pectoral legs and pelvis legs. All inter and intra group differences in scores were considered to be a result of normal variation for rats of the strain and age used, and they were of no toxicological importance.

ABSOLUTE ORGAN WEIGHTS
Males
A statistically significant increase in thymus weight was recorded at 250 mg/kg bw. All treated groups showed a decrease in pituitary gland weight with statistical significance at 500 and 1000 mg/kg bw.

Satellite males
Thymus weight was significantly decreased in the treated group compared to the control group.

Females
Animals in all treated groups showed a decrease in pituitary gland weight with statistical significance at 250 and 1000 mg/kg bw. The weight of ovaries was decreased in all treated groups (without statistical significance). A Slightly decreased weight of adrenal glands was recorded at 1000 mg/kg bw.

Satellite females
The weight of adrenal glands was significantly decreased in the treated group.

RELATIVE ORGAN WEIGHTS
Males
Animals in all treated groups showed a decreased pituitary gland weight with statistical significance at 500 mg/kg bw. A slightly increased weight of thymus was recorded at 250 mg/kg bw.

Satellite males
No effects

Females
Animals in all treated groups showed a decreased pituitary gland weight with statistical significance at 250 and 1000 mg/kg bw. The weight of ovaries was decreased at all treated groups (without statistical significance).

Satellite females
The relative weight of adrenal glands in the treated group was significantly decreased compared to the control group. A slightly decreased weight of the pituitary gland was also recorded.

GROSS PATHOLOGY
Males
In 2/5 control animals, 3/5 animals in the 250 mg/kg bw group, 3/5 animals in the 500 mg/kg bw group and 1/5 animals in the 1000 mg/kg bw group, no macroscopic changes were observed.
In the thoracic cavity of one animal (1000 mg/kg bw) focal changes in the lungs (dark red foci) were diagnosed. In the abdominal cavity of 1 control animal and 3 animals in the 1000 mg/kg bw group, irregular colour or marked structure of the liver were seen. Irregular colour of kidneys was seen in 1 control animal, 2 and 3 animals in the 250 and 1000 mg/kg bw, respectively. Macroscopic changes were more often found in the stomach: mucous membrane congested (1 control animal, 2 and 1 animals in the 500 and 1000 mg/kg bw groups, respectively), focal changes of mucosa (punctiform stratum) in 1 animal at each of the 3 dose levels, and haemorrhage in 1 animal at 1000 mg/kg bw. Marked Peyer´s patches were recorded in 1 control animal. Reduced seminal vesicle in 1 control animal was diagnosed. In the cranial cavity no changes were diagnosed.

Satellite males
In 2/5 control and 2/5 treated animals no macroscopic changes were observed.
In the thoracic cavity of 2 control and 1 treated animal focal changes in the lungs (red stratum or grey colour of lobe) were diagnosed. In the abdominal cavity of 2 control and 1 treated animal irregular colour or marked structure of the liver were seen. Irregular colour of kidneys was noted in 2 treated animals and irregular colour of adrenal glands was observed 1 treated animal. Macroscopic changes were recorded in the stomach: focal changes of mucosa (red strata) in 2 control animals, and changed mucosa without plicas in 1 treated animal. In the cranial cavity no changes were diagnosed.

Females
In 3/5 control animals, 1/5 animals in the 250 mg/kg bw group, 2/5 animals in the 500 mg/kg bw group and 4/5 animals in the 1000 mg/kg bw no macroscopic changes were observed.
In the thoracic cavity 1 control animal and 1 animal in the 500 mg/kg bw group, focal changes in the lungs (red strata) and increase of salivary glands of were diagnosed. In the abdominal cavity 1 control animal and 3 animals in the 250 mg/kg bw group, irregular colour or marked structure of liver was observed. Irregular colour of kidneys was seen in 1 animal in the 250 mg/kg bw group, and focal changes in the kidneys (red strata) were noted in 1 animal in the 500 mg/kg bw group. Macroscopic changes were also recorded in the stomach: mucous membrane congested 1 animal at 500 mg/kg bw and focal changes of mucosa (such as red or russet strata or ulceration) in 2 animals in the 250 mg/kg bw group and 1 animal at each of the higher dose levels. Uterus dilatation with fluid was diagnosed in 3 control animals, 1 animal at 250 mg/kg bw, 4 animals at 500 mg/kg bw, and 2 animals at 1000 mg/kg bw. In the cranial cavity no changes were diagnosed.

Satellite females
In 2/5 control and 2/5 treated animals no macroscopic changes were observed.
In the thoracic cavity of 1 animal in each group, petechiae (punctiform haemorrhage) on thymus were diagnosed. In the abdominal cavity of 3 control and 1 treated animal, irregular colour or marked structure of liver was and adhesion of the adrenal glands were noted. Changed mucosa in the stomach was recorded in 1 treated animal. Uterus dilatation with fluid was diagnosed in 1 control and 2 treated animals. In the cranial cavity no changes were diagnosed.

HISTOPATHOLOGY: NON-NEOPLASTIC
Complete histological examination (i.e. examination of all collected organs) was performed only at the dose level of 1000 mg/kg bw and in the control group. At 250 and 500 mg/kg bw, examination of selected organs (organs showing changes in the control and the highest groups) was performed. Forestomach, stomach, liver, small intestine, kidneys, lungs, heart, trachea, thymus, spleen, adrenal glands, pituitary gland, brain, uterus, ovaries, testes, prostate glands and salivary glands were included in this examination.

Males
Stomach, small intestine and liver were affected. Erosion of stomach mucosa – focal damage of mucosa, which did not involve the full thickness of the mucous membrane, was described in 1 animal at 500 and 1000 mg/kg bw, respectively. Inflammation (mainly eosinophilous infiltration of stomach mucosa and/or submucosa) was diagnosed in 2 animals at 500 mg/kg bw and 1 animal at 1000 mg/kg bw. Desquamation of the epithelium was observed in 1 animal at 250 mg/kg bw and 2 animals at 1000 mg/kg bw. Focal inflammation in the liver (mononuclear infiltration) was detected in 1 control animal, 2 animals at each 250 and 500 mg/kg bw, and 3 animals at 1000 mg/kg bw. Foci of extramedullary haemopoiesis (presence of myeloid cells) were seen in 1 animal at 500 and 1000 mg/kg bw, respectively, and haemorrhage in 1 animal in the 1000 mg/kg bw group. Areactive necrosis of the mucosa was diagnosed in the small intestine of 2 animals at each 250 and 500 mg/kg bw and 1 animal at 1000 mg/kg bw. Changes in the salivary glands (basophil nodule) were observed in 1 animal at 1000 mg/kg bw.
In the haematopoietic and lymphatic systems, histological changes were diagnosed in thymus. Tubular structures in 3 control animals, 2 animals at 500 mg/kg bw and 1 animal at 1000 mg/kg bw; involution (proliferation of epithelial cells in medulla) 1 animal in the 500mg/kg bw group; and focal haemorrhages in the medulla of 1 animal at 250 mg/kg bw. Extramedullary haematopoiesis was found in the spleen of 3 control animals, 5 animals at 250 mg/kg bw and 3 animals at each 500 and 1000 mg/kg bw. The intensity of haematopoiesis was similar in all groups.
Only sporadic changes were seen in the urinary system: dystrophic changes of tubules (foci with basophil tubules and reinforcement of basal membrane) in 1 animal at 250 mg/kg bw and 2 animals at 1000 mg/kg bw; proliferation of fibrous tissue in 1 animal at 250 mg/kg bw; and pycnosis of nuclei of tubular epithelial cells in cortico-medullar zone or petty haemorrhage in 1 animal of the 1000 mg/kg bw group.
Interstitial inflammation in the prostate gland (with mononuclear infiltration) was diagnosed in 2 control animals, 1 animal at 500 mg/kg bw and 2 animals at 1000 mg/kg bw. Edema of interstitium was seen in 2 animals at 250 mg/kg bw, 3 animals at 500 mg/kg bw and 2 animals at 1000 mg/kg bw. The incidence of other pathological changes in the male genital tract was sporadic.
The presence of cysts or pseudocysts in the adenohypophysis was recorded in the pituitary gland of 2 control animals, 2 animals at 250 mg/kg bw, 3 animals at 500 mg/kg bw and 2 animals at 1000 mg/kg bw.
Inflammation of myocardium in was noted in 2 control animals and 1 animal at each 500 and 1000 mg/kg bw. Cartilaginous metaplasia was seen in the heart of 1 animal in the 500 mg/kg bw group.

Satellite males
Focal inflammation in the liver (mononuclear infiltration) was detected in 1 control and 3 treated animals. Extramedullary haemopoiesis (presence of myeloid cells) was noted in 1 treated animal, and haemorrhage in 1 control animal. Focal vacuolar dystrophy of the exocrine tissue was diagnosed in the pancreas of 2 control animals. Areactive necrosis of the mucosa in the small intestine was found out in 1 animal of each group. Desquamation of the epithelium or inflammation (eosinophilous infiltration) or erosion was described only in 1 treated animal.
In the haematopoietic and lymphatic systems, extramedullary haematopoiesus was diagnosed in the spleen of 3 control and all treated animals. The intensity of haematopoiesis was similar in both groups. Tubular structures in thymus were diagnosed only in 1 control animal.
Sporadic changes were noted in the urinary system: dystrophic changes of tubules (foci with basophil tubules and reinforcement of basal membrane) in 1 control and 2 treated animals and haematoma in cortex in 1 treated animal.
In the genital tract only chronic inflammation of the prostate gland in 2 animals of each group and oedema in the interstitium of the prostate gland in 1 animal of each group was described. Testes were not histologically affected.
The presence of cysts or pseudocyst in the adenohypophysis was recorded in the pituitary gland of 2 control and 3 treated animals.
Cartilaginous metaplasia in the heart of 2 treated animals and focal monocytolysis in 1 treated animal were noted.

Females
In the stomach, erosion of mucosa (focal damage of mucosa, which did not involve the full thickness of the mucous membrane) was seen in 1 control animal and 2 animals at 500 mg/kg bw. Desquamation of the epithelium was observed in 1 animal at 250 mg/kg bw and 2 animals at 1000 mg/kg bw. Inflammation was recorded in 1 animal at 500 mg/kg bw. Focal inflammation in the liver (mononuclear infiltration) was detected in 1 control animal, 2 animals at 250 mg/kg bw, and 3 animals at each 500 and 1000 mg/kg bw. Foci of extramedullary haematopiesis were recorded in 1 control animal and 1 animal in the 250 mg/kg bw group.
In the haematopoietic and lymphatic systems, histological changes were diagnosed in the spleen. Extramedullary haematopoiesis was seen in 5 control animals, 4 animals at 250 mg/kg bw, and 5 animals at each 500 and 1000 mg/kg bw. Pigmentation (increased amount of rust-brown pigmentation in red pulp) was detected in 2 control animals and 1 animal in the 250 mg/kg bw group. The intensity of haematopoiesis was similar in all groups. Tubular structures were observed in the thymus of 2 control animals, 3 animals at 250 mg/kg bw, and 2 animals at each 500 and 1000 mg/kg bw. No histological changes were observed in kidneys.
Hydrometra (dilatation of uterus with pellucid liquid, different degree) was detected in 1 control animal, 1 animal at 250 mg/kg bw, 3 animals at 500 mg/kg bw, and 2 animals at 1000 mg/kg bw.
The presence of pseudocysts in adenohypophysis was recorded in the pituitary gland of 2 animals at 250 mg/kg bw, 1 animal at 500 mg/kg bw and 4 animals at 1000 mg/kg bw.

Satellite females
In the liver of satellite animals inflammation was seen in 3 control and 2 treated animals. Only atrophy of phundal gland was recorded in the stomach of 1 animal in each group.
In the haematopoietic and lymphatic systems, extramedullary haematopoiesis was diagnosed in the spleen of all control and 4 treated animals. The intensity of haematopoiesis was similar in both groups. Pigmentation (increased amount of rust-brown pigmentation in red pulp) was found in 2 animals of each group. Tubular structures in the thymus were diagnosed in 3 control and 1 treated animals. Hydrometra was observed in the uterus of 1 control and 2 treated animals. Cysts in the pituitary gland were recorded in 3 control animals.

Dose descriptor:

NOAEL

Effect level:

>= 1 000 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: overall effects

Critical effects observed:

no

Conclusions:

The oral administration of the test substance Ashes (residues) to rats by gavage for a period of twenty-eight consecutive days at dose levels of 250, 500 and 1000 mg/kg/day produced no toxicologically significant changes in the parameters measured. No major functional changes in any organ systems or severe organ dysfunction were detected. Consistent changes in clinical biochemistry, haematology and urinalysis parameters indicating organ dysfunction were not recorded in any dose level. Histopathological examination showed slight pathological changes in both control and treated males (oedema in prostate glands).

Based on the results of laboratory investigations in clinical biochemistry, haematology and urinalysis and histopathological examination, the NOAEL (No-Observed-Adverse-Effect-Level) was considered to be 1000 mg/kg bw/day for both male and female rats.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well-documented publication meeting basic scientific principles.

Principles of method if other than guideline:

Inhalation toxicity study in male rats whole body exposed at two dose levels for 7, 50, 90 and 180 days.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Hilltop chronic respiratory disease (CRD)-free Sprague-Dawley rats
- Age at study initiation: 70 d
- Weight at study initiation: 334 - 372 g
- Housing: in pairs in stainless steel wire mesh cages, placed in a monolayer planar array perpendicular to the direction of aerosol flow


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/-2
- Humidity (%): 50 +/- 20
- Air changes (per hr): 30
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: MMAD about 2 µm
Volume median diameter (VMD) of 1.77 µm
Geometric standard deviation of 1.52

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Large (about 4 m³) exposure chambers

- Method of conditioning air: Air supplied to each chamber was filtered for removal of particulate, chemical and bacteriological contaminants.

- System of generating particulates/aerosols: The fly ash aerosols were generated using a Wright Dust Feed (WDF) mechanism by passing the dust flow from the WDF through a miniature cyclone designed to remove most particles and aggregates bigger than 2.5 µm in aerodynamic diameter. The cyclone and WDF cutter blade were constructed of mild steel (1.03% C, 0.5% Mn, 0.04% P and 0.05% S) to preclude nickel and chromium contamination of the aerosols. The standard WDF cutter blade is composed of 95% copper and contains less than 0.05% Al, Be, Cr, Fe, Mn, Ni and Zn. This standard blade was rapidly abraded during pilot studies of fly ash re-aerosolization while the use of the tempered, mild steel blade resulted in minimal abrasion during the chronic inhalation studies.

- Temperature, humidity, pressure in air chamber: about 21 +/- 2 °C and 50 +/- 20% relative humidity

- Air flow rate: The resulting aerosols were then passed through a 85Kr-discharger to reduce the particle electrostatic charge to Boltzmann equilibrium, and then mixed with the main air flow of about 2000 L/min entering the exposure chambers.

- Air change rate: 30 air-volume changes per h were passed through each chamber after passage through a Mine Safety Appliance Model 15-86475 CBR filter assembly.

- Method of particle size determination: During exposure of rats, the fly ash aerosols were continuously monitored using a Royco 225 light-scattering particle counter, providing a strip chart recording of particle number concentration. Comparison measurements were made using a Climet 208 light-scattering particle counter. Particle size distribution data were collected with these instruments operated in conjunction with a multichannel pulse height analyser.

TEST ATMOSPHERE
Samples were collected periodically with a small point-to-plane electrostatic precipitator designed to collect representative samples for evaluation by electron microscopy. These samples were studied using a Zeiss EM 10A transmission electron microscope and an ETEC Autoscan VI scanning electron microscope.
Size data from electron micrographs were collected using a Zeiss particle size analyser and log-normal functions were fit to the size distribution data using the grouped data of projected-area diameters and the maximum likelihood method described by RAABE (1971).
Ninety-min samples were collected at 21 L/ min using a Sierra 216 AL radial slot impactor in order to evaluate the aerodynamic size distributions of the aerosols. Size-separated fractions were collected on pre-weighed glass fibre filter substrates placed on the impactor stages. Collected masses were determined by weighing. The mass distribution data collected with the cascade impactor were analysed by fitting log-normal functions with respect to aerodynamic (resistance) diameter as defined by RAABE (1976). Mass concentrations were measured by collection of samples on pre-weighed glass fibre and membrane filters by weighing the samples collected for 90 min at 25 L/min. Chemical analyses were conducted using samples collected on Nuclepore filters by atomic absorption and instrumental neutron activation (COLES et al., 1979).

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

8 h/day for up to 180 consecutive days

Frequency of treatment:

daily

Dose / conc.:

0.67 mg/m³ air (analytical)

Remarks:

between 0.57 and 0.67 mg/m³

Dose / conc.:

4.3 mg/m³ air (analytical)

Remarks:

between 4.2 and 4.3 mg/m³

No. of animals per sex per dose:

(See Table 1 for details)
Series I: 9, 9 and 32 animals per dose exposed for 7, 50 and 90 days, respectively
Series II: 2 groups of 24 animals per dose exposed for 90 and 180 days, respectively

Control animals:

other: Controls were exposed to clean air under identical conditions

Details on study design:

In Series I (low dose), rats were removed and sacrificed for analysis after 7, 50 and 90 days of exposure.
Some of the 90-day animals were kept for a 23-day clearance period. Equal numbers of controls were also removed at the same time.

In Series II (high dose), exposed rats and controls were removed at 90 and 180 days for analysis.

Positive control:

no positive control used

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes, but no further details given

BODY WEIGHT: Yes
- Time schedule for examinations: at the beginning of the study and termination after 7, 50, 90 or 180 days.

LUNG BURDEN MEASUREMENTS:
Lungs were digested for analysis of aluminium content by atomic absorption spectroscopy

CALCULATION OF DEPOSITED FRACTION IN LUNG:
The total volumes of air inhaled during the exposure periods were multiplied by the appropriate average fly ash concentrations to yield the total mass of inhaled fly ash.

BIOCHEMICAL LUNG EVALUATIONS:
DNA, RNA and protein contents of homogenized lungs were determined.
Tracheal tissue culture techniques were used for determinations of mucus glycoprotein synthesis and secretion rates.

CELLULAR STUDIES:
Pulmonary alveolar macrophages and haematopoietic progenitor cell kinetics were analyzed.

Sacrifice and pathology:

PATHOLOGY:
Series I: 9, each of exposed and control rats were evaluated morphologically at 7, 50 and 90 days of exposure
Series II: 9, each of exposed and control rats were evaluated morphologically at 90 and 180 days of exposure

GROSS PATHOLOGY:
Lungs were collected, thoracic viscera were removed, the trachea was cannulated and the lungs were fixed by airway perfusion with Karnovsky's fixative, lung volumes were determined.

HISTOPATHOLOGY:
Lungs were analyzed by light microscopy (LM) and scanning electron microscopy (SEM).
Because intratracheal instillation of fixative might translocate either free inhaled particles or phagocytized particles, some of the animals were rapidly frozen for LM and SEM analyses.

Details on results:

CLINICAL SIGNS AND MORTALITY
No mortalities occured. No clinical signs of toxicity were observed in the animals of both dose groups.

BODY WEIGHT AND WEIGHT GAIN
No gross effects of exposure to fly ash on rat body weight were observed.

ORGAN WEIGHTS:
A small, but significant, increase in lung water content was observed after 7 days of exposure suggesting the presence of a mild oedema in these acutely exposed rats; longer periods of exposure did not seem to be associated with continued increased levels of lung water.

GROSS PATHOLOGY and HISTOPATHOLOGY: NON-NEOPLASTIC
No remarkable responses were observed in Series I. The longer and higher concentration Series II was conducted because of the negative results of Series I. The microbiological test before, during and after exposure for Series II showed no unusual or major bacterial invasion of the respiratory tract and it was completely free of any growth in culture for both controls and exposed animals at the end of the 180-day exposure.

Light microscope evaluation of large airway and pulmonary parenchyma showed exposed and control animals to be distinguished by only one histological feature; namely, exposed animals consistently had higher concentrations of pulmonary alveolar macrophages in the alveolar lumens and refractile brownish pigment was visible within these cells. The brown granular material within the macrophages was presumed to be fly ash. Also, the pulmonary alveolar macrophages in the lungs of exposed rats were significantly larger (p < 0.001) in observed diameter than those of control lungs (17.0µm for exposed versus 13.3 µm for controls). Alveolar septal walls occasionally were observed to contain small cellular aggregates consisting of some mononuclear leukocytes admixed with brownish particulate material (ash). The observed differences between exposed and control groups appeared to have minimal impact, if any, on the health status of the rats.

Scanning electron microscope evaluation of the lung airways focused on the centriacinar region, since this anatomical site is especially sensitive to damage by a variety of inhaled irritants. Morphological differences were not apparent between lungs of control and exposed rats. Back-scatter electron studies showed clumping and accumulation of particles in pulmonary alveolar macrophages.

LUNG BURDENS:
Rat lung homogenates were prepared from animals exposed to fly ash for 7, 50 or 90 days without clearance, or 90 days followed by 23 days clearance in Series I, and 90 or 180 days in Series II. The exposed rats had progressively increasing aluminium contents in their lungs at 7, 50 and 90 days of exposure. After the 23-day clearance period, the exposed rats contained essentially the same level of aluminium per lung as they did after 90 days of exposure.

CALCULATION OF DEPOSITION:
The body weights of the rats taken during exposure were used to estimate the total volume of fly ash aerosol breathed during the exposure periods.
Minute volumes were used in conjunction with the average measured aerosol mass concentrations to estimate the total mass of fly ash inhaled.
The lung burden of fly ash determined from the measured masses of Al in the lungs (assuming 12.6% Al in fly ash) were divided by the calculated total mass of inhaled fly ash to yield the apparent deposition fraction. For purposes of this calculation, clearance was assumed to be negligible. Hence, any clearance that did occur during exposure is reflected by a lower apparent deposition fraction. See Table 2 for details.

BIOCHEMICAL ANALYSES:
No significant changes were observed in the lung DNA contents.

MUCUS GLYCOPROTEIN SYNTHESIS AND SECRETION RATES:
Tracheal mucus glycoprotein secretion was decreased at 7, 50 and 90 days of exposure and increased at 180 days:
In Series I (low dose) a progressively decreasing rate of glycoprotein secretion by cultured rat trachea was observed after 50 and 90 days of exposure; the decrease after 90 days was significant. Since the tissue levels of glycoprotein in exposed rats (as % of control) remained approx. constant over this interval, the decreased rate of secretion suggests functional impairment of the secretory apparatus of the tracheal epithelial cells.
In Series II (high dose) glycoprotein secretion rates of exposed rats were increased above control values for rats exposed for 6 months.

CELLULAR STUDIES
Macrophages lavaged from lungs of exposed rats were more numerous and yielded more progenitor cell colonies in culture (at the 10% confidence level based on the Mann-Whitney rank-sum test) than from controls.

Dose descriptor:

NOAEC

Remarks:

systemic

Effect level:

4.2 mg/m³ air (analytical)

Based on:

other: test. mat. (respirable fraction of ashes)

Sex:

male

Basis for effect level:

other: No adverse or treatment-related systemic effects were observed up to and including the highest tested dose level

Dose descriptor:

LOEC

Remarks:

local

Effect level:

4.2 mg/m³ air (analytical)

Based on:

other: test. mat. (respirable fraction of ashes)

Sex:

male

Basis for effect level:

other: higher cellularity in alveolar septal walls, larger pulmonary alveolar macrophages and higher concentrations of pulmonary alveolar macrophages in the alveolar lumens

Critical effects observed:

no

Table 2

Deposition of inhaled fly ash in rats

Exposure time (days)	Number of animals	Lung aluminium^a (μg)	Minute volume^b(mL)	Inhaled fly ash^b (μg)	Lung burden^c (μg)	Apparent deposition fraction (%)
Series I
7	4	6.8	184	455	54	11.8
50	4	34.1	207	3260	271	8.3
90	4	54.2	207	6180	430	6.9
90 + 23 days of clearance	6	40.0	213	6360	317	5.0
Series II
90	6	218	217	40750	1730	4.2
180	6	545	230	83300	4330	5.2

^aNet after subtraction of control values; measured by atomic absorption spectroscopy

^bCalculated values

^cBased on 12.6 % Aluminium concentration

Conclusions:

Using light microscopy and scanning electron microscopy, histological and cellular observations showed large numbers of small fly ash particles in the lung. However, there was no evidence of spontaneous lung disease and the animals were in good health at the end of the 180 days of exposure to 4.2 mg/m³. No major adverse effects were observed.
The only effects observed included small changes in some biochemical parameters and increased numbers of macrophages in the lung lumens. Additionally, the observed increase in colony-forming units of alveolar macrophages in culture from exposed animals without increases in activity of haematopoietic progenitor cells was indicative of recruitment of macrophages within the lung and activation of lung reserve progenitors as a direct result of deposition of fly ash. This response was considered an important natural response to inhaled particles and not being unique to coal fly ash.
Based on these findings, 4.2 mg/m³ of coal fly ash was considered a NOAEC for systemic effects and a LOEC for local effects.

Endpoint conclusion

Dose descriptor:

NOAEC

4.2 mg/m³

Study duration:

subchronic

Species:

rat

Additional information

Oral

Ashes (residues) were tested for subacute oral toxicity in Wistar rats following OECD guideline 407 (adopted on 27th July, 1995) and in compliance with GLP ( ČEZ Energetické produkty, 2008, key). The test material was administered daily by gavage to groups of 5 male and 5 female rats as a suspension in 0.5% methyl cellulose at 0, 250, 500 and 1000 mg/kg bw/day for 28 days. Two additional (satellite) groups, each consisting of 5 male and 5 female rats, was concurrently treated with vehicle or the test material at 1000 mg/kg bw(day). These groups were observed for 14 days following the final exposure.

Clinical observations and health status control were performed daily. Body weight and food consumption were measured weekly and a detailed clinical observation was carried out once before the beginning of the treatment period and weekly thereafter. Water consumption was measured twice a week. Functional observations were performed in the last week of the study. Urinalysis, haematological and biochemical analysis as well as gross necropsy of animals of the main and satellite groups were conducted at the end of the treatment and observation periods, respectively. Selected organs were removed for weighing and histopathological examination.

There were no unscheduled deaths during the test. No clinical signs of toxicity were observed. The health condition of the animals was good during whole study and functional observation showed no effect of the test substance. No adverse effects on body weight gain were detected. No adverse effects on dietary intake or food conversion were noted.

Statistically significant changes in haematological values were observed in treated males compared to vehicle controls. Prothrombin time and fibrinogen values were increased at 500 and 1000 mg/kg bw/day. Platelet count was increased at 250 mg/kg bw/day. Males in the satellite group showed increased prothrombin time and mean corpuscular volume and decreased total erythrocyte count. However, most changes were marginal and all parameters measured were reported to be within physiological limits, thus not considered to be toxicologically relevant. No statistically significant changes were observed in females of the main and satellite groups.

Biochemical examinations showed statistically significant increases in alkaline phosphatase activity and glucose concentration in females of the satellite group at the dose level of 1000 mg/kg bw/day. All parameters measured were, however, reported to be within physiological limits. No effects were observed in males.

A statistically significant decrease in urine volume was seen in male rats of the main group treated with 1000 mg/kg bw/day. No further significant effects in urinary parameters were observed.

Slight but statistically significant changes in absolute and relative weights of some endocrine glands were seen in both males and females. Absolute thymus weight was increased in males at 250 mg/kg bw/day in the main group and at 1000 mg/kg bw/day in the satellite group. Absolute pituitary gland weight was decreased in males at 500 and 1000 mg/kg bw/day and in females at 250 and 1000 mg/kg bw/day. The relative weight of this gland was decreased in males at 500 mg/kg bw/day and in females at 250 and 1000 mg/kg bw/day. Correlations with microscopic changes were detected only in the pituitary gland. A slight increase in the incidence of cyst and pseudocysts was recorded at all treated groups and control groups. These morphological changes are commonly observed in the rat strain used. Differences in the incidence between control and treatment groups were considered to be of no toxicological significance.

Histopathological examination revealed inflammation of the liver both in treated and control animals of both sexes (with protracted effect in males). An increased incidence of oedema in the prostate gland was recorded in treated males of the main group and in both control and treated males of the satellite group. Due to absence of other changes in biochemical parameters showing functional disturbance, this was considered to be of no toxicological importance.

Based on the overall results of the study, the NOAEL (No-Observed-Adverse-Effect-Level) was considered to be 1000 mg/kg bw/day for both male and female rats.

 

Dermal

No data available

 

Inhalation

Young adult male Sprague-Dawley rats were exposed in a whole body exposure chamber to fly ash in two series of experiments. In the first series, animals were exposed to 0.6 mg/m³, 8 h/day for 7, 50 and 90 consecutive days. No relevant morphological effects were observed, and therefore a longer and higher concentration series was conducted. In the second series, animals were exposed to 4.2 mg/m³ of fly ash, 8 h/day for 90 and 180 consecutive days. In both series, negative control animals were exposed to clean air under identical conditions. The fly ash was obtained from the electrostatic precipitator hoppers of a power plant burning western, low-sulphur, high-ash coal, and size-classified to remove most particles larger than 3 µm in aerodynamic diameter. The analyzed MMAD was about 2 µm and the GSD 1.52.

Animals were observed for mortalities and clinical signs, and body weights were recorded prior to and at the end of the corresponding exposure periods. Gross pathology and histopathological examinations were conducted only on lung tissue. Other examinations included measurements of fly ash lung burden as well as lung DNA, RNA and protein contents. Furthermore, tracheal tissue culture techniques were used for determinations of mucus glycoprotein synthesis and secretion rates; pulmonary alveolar macrophages and haematopoietic progenitor cell kinetics were analyzed.

No unscheduled mortalities occurred, no effects on body weight and no clinical signs of toxicity were noted. No pathological effects were found in the lower exposure group. In the high exposure group, light microscope evaluation of large airway and pulmonary parenchyma showed higher concentrations of pulmonary alveolar macrophages in the alveolar lumens and refractile brownish pigment was visible within these cells, which was considered to be fly ash. The pulmonary alveolar macrophages in the lungs of exposed rats were significantly larger compared to the control animals. Alveolar septal walls occasionally were observed to contain small cellular aggregates consisting of some mononuclear leukocytes admixed with brownish particulate material. The observed differences between exposed and control groups appeared to have minimal impact, if any, on the health status of the rats.

Scanning electron microscope evaluation of the lung airways focused on the centriacinar region, since this anatomical site is especially sensitive to damage by a variety of inhaled irritants. Morphological differences were not apparent between lungs of control and exposed rats. Back-scatter electron studies showed clumping and accumulation of particles in pulmonary alveolar macrophages.

Deposition of fly ash increased time-dependently and the maximal lung burden was ca. 4 mg at the end of the 180-days exposure period. No significant changes were observed in the lung DNA contents (RNA and protein contents not reported). In the first series of experiments (low dose), a progressively decreasing rate of glycoprotein secretion by cultured rat trachea was observed. In the second series (high dose), glycoprotein secretion rates of exposed rats were increased above control values for rats exposed for 6 months. Macrophages lavaged from lungs of exposed rats were more numerous and yielded more progenitor cell colonies in culture than from controls.

In summary, using light microscopy and scanning electron microscopy, histological and cellular observations showed large numbers of small fly ash particles in the lung. However, there was no evidence of spontaneous lung disease and the animals were in good health at the end of the 180 days of exposure to 4.2 mg/m³. No major adverse effects were observed. The only effects observed included small changes in some biochemical parameters and increased numbers of macrophages in the lung lumens. Additionally, the observed increase in colony-forming units of alveolar macrophages in culture from exposed animals without increases in activity of haematopoietic progenitor cells was indicative of recruitment of macrophages within the lung and activation of lung reserve progenitors as a direct result of deposition of fly ash. This response was considered an important natural response to inhaled particles and not being unique to coal fly ash. Based on these findings, 4.2 mg/m³ of respirable coal fly ash was considered a NOAEC for systemic effects and a LOEC for local effects (Raabe et al., 1982).

In another study, the effects of coal fly ash on lung pathology and the immune system in rats were examined. Groups of 20 male Wistar rats were exposed in whole body exposure chambers to 0, 10, 30, or 100 mg coal fly ash/m³ for 6 h/day, 5 days/week for 4 weeks. Additionally, 4 groups of 3 animals were exposed to 0 and 100 mg coal fly ash/m³ for 1 week, or for 1 week followed by a 3-week recovery period in clean air. The MMAD (mass median aerodynamic diameter) of the particles ranged between 1.9 and 2.8 µm. Clinical signs and body weight were recorded daily and at weekly intervals, respectively. Histopathology of the lung, urinalysis, haematology, and clinical chemistry were also performed.

No changes in condition, health, or behaviour were observed. Animals exposed to 100 mg/m³ gained slightly, but significantly, less weight than the controls. A concentration-related increase in absolute and relative lung weight was observed in animals exposed for 4 weeks. Both absolute and relative liver weights were lower in the animals of the 10 and 100 mg/m³ exposure group compared to controls, without showing a concentration-response relationship. Animals exposed to 100 mg/m³ for 1 week, and for 1 week with a 3-week recovery period, showed a significantly increased lung weight.

No treatment-related changes were observed in urine volume or density or in haematological parameters. Mean alkaline phosphatase activity was statistically significantly higher and mean total protein value was statistically significantly lower in the 100 mg/m³ group than in controls. No differences in the other groups and no treatment-related changes were observed in the other parameters.

At macroscopical examination of the 4-week-exposed rats, lungs of coal fly ash-exposed animals were diffusely dark red/black. The mediastinal lymph nodes were enlarged in half of the rats of all exposure groups, and were dark red in most of the animals exposed to 30 mg/m³ and in all animals exposed to 100 mg/m³. Lungs of rats exposed for 1 week had a normal pink appearance. No histological changes were detected in control lungs. After 1 week of exposure to 100 mg/m³, free coal fly ash particles in bronchi and bronchioles, alveoli, and alveolar septa were occasionally observed. However, alveolar macrophages diffusely throughout the whole lung were moderately laden with black material. Alveolar septa showed slightly increased cellularity.

After 4 weeks of exposure, the number of free particles as well as alveolar macrophages appeared to be slightly increased. However, all macrophages were laden with black material in a concentration-related way varying from very slight/slight in the 10 mg/m³ group, to slight/moderate in the 30 mg/m³ group, to moderate/severe in the 100 mg/m³ group. The alveolar septa showed slightly to moderately increased cellularity (presumably caused by proliferation of type II cells), a mononuclear cell infiltrate (mainly macrophages and monocytes), and a minimal fibrotic reaction (fibroblasts and collagen) in animals exposed to 100 mg/m³. An increased number of perivascular lymphocytes was also noticed in this group. The severity and incidence of the lung changes showed clearly concentration-related increases, since animals exposed to the lower concentrations showed less and less severe changes. In the mediastinal lymph nodes black deposits were seen similar to the lungs. Lymphocytic hyperplasia was mainly observed in the paracortical area. In addition, prominent germinal centres were regularly observed in exposed rats. These changes were increased in a concentration-related manner.

After a 1-week exposure followed by a 3-week recovery period, the histological picture was identical to that after exposure for 1 wk. Free particles were detected at the surface of trachea, bronchi, bronchioles, and alveoli in all coal fly ash-exposed rats. Coal fly ash mostly appeared as aggregates of particles smaller than 1μm. Alveolar macrophages in coal fly ash-exposed rats appeared to be larger than those from control rats. In the other organs examined, no histological changes were observed.

Taken together, subacute inhalation of respirable coal fly ash in rats resulted in an accumulation of fly ash particles in lungs, slight fibrotic pulmonary reaction, slight to severe lymphocytic hyperplasia in mediastinal lymph node and slightly to moderately increased septal cellularity at 100 mg/m³. The fibrotic reaction and the overall severity grade of the other effects observed were considered adverse effects due to the high particle load, and therefore 100 mg/m³ was the LOAEC (local) in this study. At 10 and 30 mg/m³, no fibrotic reactions were observed. Both incidence and severity of other lung changes was lower and considered a natural adaptive reaction as a result of the (physical) particle insult, and not adverse effects in terms of test substance specific toxicity. Therefore, 30 mg/m³ was considered a NOAEC for local effects in the lung. No toxicologically significant systemic effect was observed at any concentration. The NOAEC for systemic effects was therefore 100 mg/m³ (Dormans et al., 1999).

The respirable fraction of Ashes (residues) typically accounts for approximately 10% of the total mass (s. Particle size distribution). Accordingly, the local and systemic NOAEC values mentioned above correspond to a local NOAEC of 300 mg/m³ and a systemic NOAEC of 1000 mg/m³ based on total Ashes (residues), respectively.

In a further study, the effects of coal fly ash inhalation on deposition of metal ions and histopathological changes in the liver and serum enzymes were studied. The test material consisted of the fine fraction of coal fly ash obtained from the electrostatic precipitators of a thermal power station in Uttar Pradesh, India. More than 90% of the particles in the exposure chambers were less than 5 µm in diameter. Two groups of 6 male rats were exposed to 14.4 mg/m³ coal fly ash (analytical concentration), 4 h/day, 5 days/week for 4 weeks in a whole body or a nose only exposure chamber, respectively. Groups of rats exposed to compressed air under the respective same conditions served as controls.

No mortalities occurred and a marginal but not significant decrease in body weight gain in the fly ash groups was reported. A significant increase in absolute and relative liver weight was observed in fly ash-exposed animals (exposure type not specified). At the end of the exposure period, a significant increase in alkaline phosphatase and serum glutamate pyruvate transaminase activity was noted in whole body fly ash-exposed rats (values for nose only-exposed rats not reported). Histopathological findings were reported only for the liver (exposure type not specified, incidence not reported). These included a mild infiltration of mononuclear cells in and around the portal veins, hypertrophy of lining cells of bile ducts and portal veins being protruded toward their lumens, and thickening of the walls of the portal veins. Infiltration of mononuclear cells in and around the portal triads appeared to be laden with foreign particles. Hepatocytes showed necrotic changes with marked karyorrhexis and lytic changes. Kupffer cells were hypertrophied. Infiltration of foreign particles in coarse form was observed within the hepatocytes.

The distribution of Cd, Cr, Cu, Mn and Pb in lung, liver and kidneys was estimated. Cd, Cu and Pb concentrations in kidney, Cr in lungs and Mn in liver of whole body-exposed rats were significantly increased compared to control values. In nose only-exposed rats, a statistically significant increase in the concentrations of Cd (lung, liver and kidney), Cr (lung), Cu, (lung and kidney) and Pb (lung and kidney) was seen. In all cases, concentrations were increased by less than a half order of magnitude (Mani et al., 2007).

On the basis of these findings, the authors concluded that coal fly ash is a source of heavy metals potentially toxic to humans as these metals would translocated from the lung and deposit in other organs, in which toxicity would manifest. However, due to several deficiencies in study design (only one concentration level tested, reduced number of animals used, limited observations and examinations) and documentation of results (particularly in regard to histopathological findings), this study is of limited value for hazard assessment. Furthermore, the proposed mechanism of toxicity involving bioaccumulation of heavy metals, present in fly ash as impurities, is questionable as increases in metal concentration were marginal. Therefore, no clear conclusion can be drawn as to a causal relationship between subacute inhalation exposure to coal fly ashes and the hepatotoxic effects described.

Human data on the pneumoconiotic effects of coal fly ash (pulverised fuel ash, PFA) derived from a number of studies in UK workers of the electricity supply industry throughout 1950 to 1977 has been reviewed by Bonnell et al. (1980). The results of the studies indicate that PFA is unlikely to give rise to pneumoconiosis caused by working in coal-combusted power plants, other than in subjects with previous exposure in underground coal mining. The main components of ashes (residues) are silicon dioxide (SiO₂), aluminium oxide (Al₂O₃) and iron oxide (Fe₂O₃). In particular, SiO₂ in form of crystalline silica (quartz) is a major toxicological concern when it is present as respirable particles with a MMAD < 5 µm. In this context, several epidemiologic studies demonstrate that workers have a significant risk of developing chronic silicosis when they are exposed to respirable crystalline silica over a working lifetime at a mean concentration of 0.05 mg/m³ (NIOSH, 2002). Therefore, for the respirable fraction of crystalline silica this concentration is regarded as a LOAEC for chronic silicosis in humans.

Justification for classification or non-classification

The available data on the repeated dose toxicity of Ashes (residues) as well as of the respirable fraction of fly ashes is conclusive but not sufficient for classification.