Sodium sulphate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Adequacy of study:

other information

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Results biologically implausible; insufficient documentation for assessment

Data source

Reference

Reference Type:

publication

Title:

Health aspects of sodium salts of sulfurous and sulfuric acids as environmental pollutants.

Author:

Denisov, Y.N. and Tkachev, P.G.

Year:

1990

Bibliographic source:

Gigiena i sanitariia. 9:11-13.

Materials and methods

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium sulphate

EC Number:

231-820-9

EC Name:

Sodium sulphate

Cas Number:

7757-82-6

Molecular formula:

Na2SO4

IUPAC Name:

disodium sulfate

Details on test material:

TS-Freetext:
Na2SO4 dust, not specified

Test animals

Species:

rat

Strain:

not specified

Sex:

male

Administration / exposure

Route of administration:

inhalation

Duration of treatment / exposure:

3 months

Frequency of treatment:

not given

Doses / concentrations

Remarks:

Doses / Concentrations:
dust concentration 1 mg/m3, with concurrent exposure to 500 mg/l in drinking water
Basis:

Control animals:

yes

Details on study design:

Post-exposure period: 1 month (size of recovery group not given)

Results and discussion

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

RS-Freetext:
small but significant changes in "summarized threshold
potential" (measure of brain irritability), liver
cholinesterase, blood cholinesterase, number of lymphocytes
and neutrophils, body weight, relative liver weigt;
depression of spermotagenesis, histopathological changes in
liver and testes, serious histopathological changes in the
lungs and several cases of pneumonomia, all fully reversible
after 1 month recovery. 
results similar to those found in concurrent studies with
sodium sulfite at 01. and 1 mg/m3 and a mixture of
sulfite/sulfate at 1 mg/m3.

Applicant's summary and conclusion

Conclusions:

In a 90 -day study in which rats were exposed to 1 mg/m3 sodium sulfate, or 0.1 and 1 mg/m3 of sodium sulfite or 1 mg/m3 of an unspecified mixture of both, together with 500 mg/l in drinking water , i.e an estimated dose of 60 mg/kg/d orally and 0.6 mg/kg/day by inhalation. Apart from the neuro-physiological and biochemical parameters described, body weight was also depressed, relative liver weight was decreased, histopathological evidence of serious lung damage and testicular damage was described.

A possible explanation of the finding from this study, is contamination of the dust used for the inhalation studies with heavy metals, e.g. cadmium. Spent sulfuric acid commonly contains heavy metals, so pre-refinery sodium sulfate made from such recycled material may well be contaminated.. In the absence of any analytical data, this cannot be verified.

Executive summary:

In a 90 -day study in which rats were exposed to 1 mg/m3 sodium sulfate, or 0.1 and 1 mg/m3 of sodium sulfite or 1 mg/m3 of an unspecified mixture of both, together with 500 mg/l in drinking water , i.e an estimated dose of 60 mg/kg/d orally and 0.6 mg/kg/day by inhalation. Apart from the neuro-physiological and biochemical parameters described, body weight was also depressed, relative liver weight was decreased, histopathological evidence of serious lung damage and testicular damage was described. Effects were similar for sulfites, sulfates and the mixture, but more severe and earlier for the sulfites. The description of the experiment is insufficient and no actual data are presented. The biological plausibility of such relatively severe effects at such low concentrations, from a compound normally abundantly present in drinking water and food is very much in doubt. There is no reason why a simple, non-reactive and freely circulating ion like sulfate would exert systemic effects when absorbed through the lungs at a fraction of the amount absorbed from the gastro-intestinal tract. These findings also strongly contrast with all other available data.