10/09/2004

Need for identifying occupational exposure levels for y-Butyrolactone (GBL)

The Nordic Expert Group for Criteria Documentation of Health Risks from
Chemicals and the Dutch Expert Committee on Occupational Standards comment on
y-Butyrolactone (GBL).

y-Butyrolactone (GBL) is used as an intermediate for the production of other
chemicals, as a solvent, and as a binder in foundry. Non-occupational use
results from its natural occurrence in fruits and berries, its use as an
experimental drug in treatment of alcohol withdrawal symptoms and narcolepsy.
Due to its euphoric/hallucinogenic properties the abuse of GBL and
g-hydroxybutyrate (GHB) has increased dramatically in several countries.

GBL is a colourless oily liquid with a mild caramel odour. It has a relatively
low vapour pressure, a boiling point of 206ºC, and is miscible with
water.

Little information is available regarding occupational exposure. In the USA in
1981-1983 it has been estimated that over 40 000 workers were potentially
exposed and of these about 2/3 are exposed in printing and publishing and in
textile mill industries.

GBL is easily absorbed after ingestion and to some extent also absorbed through
the skin. The enzymatic hydrolysis to GHB in the body is rapid and extensive.
GBL is distributed to all organs mainly as GHB. The latter is further
metabolised by catabolic enzymes, and finally eliminated as CO2 and urinary
metabolites.

GBL has a low to moderate acute toxicity in experimental animals and causes CNS
depression both in humans and animals. GBL causes eye irritation in rabbits,
whereas no conclusions can be drawn regarding sensitisation. Repeated oral
doses of approximately 1 000 mg/kg body weight/day caused death in mice and
rats. No toxic effects, apart from reduced weight gain, were elicited at lower
doses. An overall evaluation of an extensive database for genotoxicity
indicates that GBL is not genotoxic. There is no support for a carcinogenic
effect in experimental animals. An evaluation for carcinogenicity by IARC in
1999 concluded that GBL is not classifiable as to its carcinogenicity in
humans. GBL might affect testicular development in young rats and may reduce or
block ovulation in adult rats.

There is a need for identifying occupational exposure levels and additional
toxicological information regarding acute local and reproductive
effects.

Based on available data CNS depression is considered the critical effect from
GBL exposure. Reproductive toxicity (reduced ovulation) found in animals cannot
be fully assessed with respect to human health at present.

Further Information


AplusA-online.de - Source: European Agency for Safety and Health at Work