Acetylene

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

No additional data available

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

Human exposure

As early as the mid 1920’s it had been reported that acetylene had been successfully used, at very high concentrations, as an anaesthetic in over 2000 surgical procedures in humans without significant adverse effects (Horwitz, 1923, Davidson, 1925; Goldman and Goldman, 1925; Brandt, 1926, Franken and Schurmeyer, 1928 and Franken, 1930).

Today, the gas is still used in medicine and sport physiology and cardiology but in a rather different way. It is used as part of a clinical technique, often referred to as the inert gas re-breathing technique, to estimate cardiac output. The inert gases used are acetylene, or carbon dioxide or nitrous oxide and when acetylene is used as the blood-soluble inert gas, it is often called the acetylene re-breathing technique. There is a significant amount of literature reporting this procedure by investigators attempting to further understanding of cardiac output changes in humans during, for example, exercise, aging, existence at high altitude, zero gravity, cardiovascular illness and pregnancy and postpartum (Bell et al, 2003; Bell et al, 2001; Warburton et al, 1998; Pierson et al, 2003; Eakin et al, 1993; Johnson et al, 1999; Petrine et al, 1978; Triebwasser et al, 1977; Nystrom et al, 1986; Hoeper et al 1999; Sady et al, 1989; Carpenter et al, 1990; Bogaard and Wagner, 2006).

Typically (Hoeper et al, 1999), with nostrils occluded, a re-breathing bag is filled with a gas mixture, for example, of oxygen nitrogen, carbon monoxide helium and acetylene (3%; 3000 ppm). The total bag volume is about 60% of the patient’s vital capacity. The patient completely empties the bag in about 30 s. Cardiac output can be calculated from the rate of disappearance of acetylene from expired air (often measured by mass spectrometry). No reports of significant adverse effects in humans, associated with the acetylene re-breathing procedure have been found in any publications reviewed. In particular, with reference to pregnancy, Sady et al, 1989 reported use of the acetylene re-breathing procedure to measure changes in cardiovascular response to cycle exercise during and after pregnancy in 45 non-smoking women. In another example, Carpenter et al, 1990, examined the effect of maternal weight gain during pregnancy in 10 pregnant non-smoking women on exercise performance. One of the clinical techniques employed by Carpenter’s team was the acetylene re-breathing procedure.

Metabolic fate

Although, acetylene has been used at very high dose levels as an anaesthetic gas in human surgery and is generally considered as an asphyxiant (ACGIH 2001) without significant biotransformation, it has been shown that acetylene is actually metabolised to acetic acid, albeit to a very small extent (White, 1978). A highly reactive ketene intermediate may be formed but very rapidly transformed to acetic acid and it was estimated that no more than 1% of the inhaled amount of acetylene in humans is metabolised to acetic acid (see Appendix 1 to the CSR for detailed calculation; ten Berge, 2009). Therefore although acetylene, per se, may be considered devoid of developmental and reproductive potential, a more detailed consideration of the developmental and reproductive potential of its metabolite, acetic acid may be appropriate.

Acetic acid, a natural product, is a critical intermediate of primary metabolic processes such as the citric acid cycle and it has been calculated (see Appendix 1 to the CSR for detailed calculations; ten Berge, 2009) that the rate of formation of acetic acid in humans, due to exposure to 2500 ppm acetylene, is negligible compared the endogenous usage of acetic acid. It seems unlikely therefore that any systemic toxicity, including reproduction and developmental effects will be associated with the relatively small amounts of acetic acid derived from acetylene.

Consistent with these considerations, a recent review of acetic acid (EUDAR, 2008) concluded the following with respect to developmental and reproduction endpoints.

“Developmental studies in 3 species detected no evidence for a primary embryotoxic or teratogenic potential of acetic acid.”

“Considering that all humans are exposed from various foods throughout life and that acetic acid is a physiological metabolite in all living organisms, generational reproductive tests with animals are not deemed necessary.”

Therefore there is no evidence that acetic acid has developmental or reproductive potential.

Overall, there is a sufficient weight of evidence to conclude that there is no reproductive or developmental toxicity potential for humans exposed to concentrations of acetylene, up to concentrations of at least 2,500ppm (see Appendix 1 to the CSR for detailed calculations; ten Berge, 2009).

Short description of key information:
There is a sufficient weight of evidence to conclude that there is no reproductive toxicity potential for humans exposed to concentrations of acetylene, up to concentrations of at least 2,500ppm

Effects on developmental toxicity

Description of key information

There is a sufficient weight of evidence to conclude that there is no developmental toxicity potential for humans exposed to concentrations of acetylene, up to concentrations of at least 2,500ppm

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

See above (reproductive toxicity)

Justification for classification or non-classification

No classification is warranted under CLP as there is sufficient weight of evidence to conclude that there is no potential for reproductive or developmental toxicity.