Acetylene

Endpoint summary

Description of key information

There are no data for skin and eye irritation. Studies are not technically feasible as the substance is a gas at room temperature. There is no reported evidence of skin irritation in use.  There is no evidence for any irritant effects on the respiratory tract in humans at concentrations up to 20% (NOAEC 214,000 mg/m3)

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no study available

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Non-human data

No data available (studies are not technically feasible as the substance is a gas at room temperature).

Human data

Corrosive and irritant effects on the skin and eye are local concentration dependent phenomenon. There are no data indicating any evidence of local effects of acetylene gas on the skin or eye.A group of human volunteers were exposed to acetylene at a range of concentrations in order to assess its anaesthetic properties (Davidson, 1925).  The lowest concentration employed, 10%, caused feelings of mild intoxication and paraesthesia. There was no indication of local irritant effects at 20% for 1 hour (or higher exposures but >20% were less than 1 hour). Therefore the NOAEC for local irritation is considered to be 20% (200,000 ppm, equivalent to 214,000 mg/m3). ten Berge (2009) considered the potential effect of acetylene on mucous membranes of the respiratory tract. P450 -enzyme notably CYP, content in the nasal mucosa is among the highest of all extrahepatic tissues in many mammalian species, unlike humans. The acetylene concentration in the mucous membranes of the respiratory tract is in balance with the acetylene level in the inhaled air, controlled by the dimensionless Henry coefficient of 0.89. An acetylene concentration of 2663 mg/m3 is in equilibrium with 3 mg acetylene per litre mucous (= 0.115 mMol per litre mucous). At a biotransformation rate of 0.24 per hour an amount of 0.028 mMol acetic acid per litre mucous is produced (ten Berge, 2009). The average buffer capacity of human mucous is about 5 mMol per litre per pH unit (Holma & Hegg, 1989), so this level of acetylene exposure will hardly affect the pH of the mucous membranes of the respiratory tract. This supports the lack of local irritation reported above.

Citation

Holma B and HeggPO, 1989. pH and protein-dependent buffer capacity and viscosity of respiratory mucus, their interrelationships and influence on health. The Science of the Total Environment 84, 71-82.ten Berge, W (2009). Scientific reasoning for exempting in vivo mammalian inhalation toxicity studies on acetylene as part of the IUCLID5-file

Justification for classification or non-classification

Acetylene does not have irritant properties and does not warrant classification under CLP.