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Toxicological evaluation and limit values for Methyl-tertiary-butyl ether (MTBE), Formaldehyde, Glutaraldehyde, Furfural

1. General description

1.1 Identity

Molecular formula: C5H8O2
Structural formula: OHC-CH2-CH2-CH2-CHO
Molecular weight: 100.12
CAS-no.: 111-30-8
Synonyms: Glutardialdehyde
Glutaral
Pentanedial
1,3-Diformylpropane

1.2 Physical / chemical properties

Description: The pure chemical is a colourless oily liquid, but commercial solutions often have an amber tint and an odour similar to spoiled fruit.
Purity: 99.7%.
Glutaraldehyde is commonly available as 2, 25, or 50% aqueous solutions with acidic pH.
Melting point: -14 ° C
Boiling point: 187-189 ° C (with decomposition)
Density: 1.061 g/ml
Vapour pressure: 16.5 mmHg (2.2 kPa) at 20°C. There is some confusion about the purity of the test substance used: IUCLID (1996) gives the same value for pure glutaraldehyde and for a 50% aqueous solution, ACGIH (1991) gives a vapour pressure of 0.0152 mmHg (2.0 Pa at 20°C) for a 50% solution. In SUBFAC, vapour pressures (20°C) has been calculated to 24.9 mmHg for a 100% solution, 19.4 mmHg for a 50% solution, and 2.7 mmHg for a 2% solution.
Vapour density: 3.4 (air = 1)
Conversion factor: 1 ppm = 4.2 mg/m3 20° C
1 mg/m3 = 0.240 ppm 1 atm
Flash point: 71 ° C
Autoignition temp.: 225 ° C
Solubility: Water: miscible (aqueous solution: pH 3.7).
Soluble in alcohol, benzene, and ether.
logPoctanol/water: - 0.22
Stability: At acid pH, glutaraldehyde forms an intramolecular ring structure, which further polymerises. At alkaline pH, glutaraldehyde polymerises into long chain molecules without ring structures.
Glutaraldehyde polymerises when heated.
Odour threshold, air: 0.04 ppm (0.17 mg/m3).
Odour threshold, water: 100 mg/l
Taste threshold, water: 100 mg/l
The reliability of the odour and taste thresholds in water could not be evaluated.
References: Merck Index (1996), IUCLID (1996), Beauchamp (1992).

1.3 Production and use

Glutaraldehyde is synthesised in a two-step process: ethyl or methyl vinyl ether is reacted with acrolein to produce ethoxy or methoxy dihydropyran, respectively, which is then hydrolysed to produce glutaraldehyde and ethanol or methanol, respectively (CIR 1996).

Next to formaldehyde, glutaraldehyde is the most used aldehyde. It has widespread uses as a bactericide, a tanning agent, a fixative for electron microscopy, as a preservative in cosmetics (maximum 0.1% in EU) and in sterilising surgical, endoscopic, anaesthetic, and dental instruments. In the US, it has many additional uses, e.g. as a direct and indirect food additive, and in packaging materials for food (CIR 1996).

Glutaraldehyde has also been used to treat a number of skin disorders, including epidermolysis bullosa, hyperhydrosis, herpes zoster, herpes simplex, dyshidrosis, onychomycosis, and warts (Beauchamp et al. 1992).

1.4 Environmental occurrence

Glutaraldehyde does not appear to occur naturally.

It may be formed in air by the reaction between cyclic alkenes and ozone and hydroxyl radicals (Beauchamp et al. 1992), however, no concentrations are given.

1.5 Environmental fate

Air

No information has been found.

Water/ waste water

In the DOC die-away-test carried out according to EU guideline, there was a 90-100% biodegradation of glutaraldehyde after 28 days (IUCLID 1996).

The elimination rate of glutaraldehyde in industrial sewage was concentration dependent with 30-60 mg/l being eliminated 100% after 5 hours and 300 mg/l being eliminated < 20% after 7 days (IUCLID 1996).

Bioaccumulation

In a test for bioaccumulation using Escherichia coli and incubation for 30 minutes at pH = 4 and concentrations of 0.1-0.4 mg/l of glutaraldehyde, the bioaccumulation was linear with 0.03 mg/mg (dry weight) at the lower concentration of 0.1 mg/l and 0.13 mg/mg (dry weight) at the concentration of 0.4 mg/l. (IUCLID 1996).

1.6 Human exposure

Humans can be exposed to glutaraldehyde in numerous clinical and occupational settings, as indicated by its many different uses. In Germany, exposure to glutaraldehyde was determined in hospital operating and patients rooms, where cleaning solutions containing glutaraldehyde were used. When a cleaning solution containing 0.025% glutaraldehyde was used, the TLV (0.2 ppm, 0.8 mg/m3) was not exceeded. However, when a cleaning solution containing 0.15% glutaraldehyde was used, 0.57 ppm (2.4 mg/m3) glutaraldehyde was detected in the air. (Binding & Witting 1990 - quoted from Beauchamp et al. 1992).

In two Swedish hospitals, where a 2% alkaline glutaraldehyde solution was used to disinfect equipment, the exposure levels ranged from <0.01 to 0.57 mg/m3, with most of the measurements being in the range of 0.02 to 0.14 mg/m3 (Norbäck 1988).

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