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Description of key information

Short description of information on toxicokinetics:
Elimination: 93-97% eliminated in 24hrs, mainly in urine as 2-(2-butoxyethoxy)acetic acid.
Dermal absorption rate: Rat: 0.73-1.46mg/cm2/hr


Short description of key information on absorption rate:
Humans: 0.035mg/cm2/hr (damage ratio 2.0+/-1.0)
Humans: 0.29mg/cm2/hr (damage ratio <1.0)
Rat: 0.51mg/cm2/hr (damage ratio 1.9)

Rat: 4.4mg/cm2 absorbed over 48 hour period.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

A study examined the absorption and elimination of radio-labelled 2 -(2 -butoxyethoxy)ethanol in rats following 24hr dermal occluded exposure and established that the main route of elimination is overwhelmingly via the urine and the metabolite 2 -(2 -butoxyethoxy)acetic acid. The glucoronidate conjugate was also found at significant levels (5 -8%). Females appeared to absorb and therefore excrete larger quantities than males and the dermal absorption rate was estimated to be 0.73 and 1.46mg/cm2/hr for males and females respectively. Washing studies showed that 90%+ of externally applied substance could be removed after 5 minutes exposure by skin washing.

In a study using rats, 2 -(2 -butoxyethanol) was found to be rapidly eliminated following oral, ip or sc dosing with ~7-11% of the dose excreted in air and 78 -86% excreted in urine over the course of the four day study, although most was eliminated within 24 hours. There was no significant transfer of the substance to the carcasses of the test animals.

An in vitro dermal absorption study using rat skin showed that 2 -(2 -butoxyethoxy)ethanol is able to pass through full thickness rat skin at a rate of 0.51mg/cm2/hr and can cause slight but significant permanent damage (increased permeability - damage ratio 1.9). This figure is very similar to that derived from the in vivo study above.

Two in vitro dermal absorption studies using human skin showed that 2 -(2 -butoxyethoxy)ethanol is able to pass through the stratum corneum but gave somewhat conflicting permeation results of 0.29 and 0.035mg/cm2/hr at a slow rate (35ug/cm2/hr). Both did however show that permanent damage is low to insignificant and that there is a lag time of approximately 2 hours for substance to cross the skin and appear in the receptor fluid. Since the higher result is also more recent and obtained using radiolabelled material, it should be used in preference. These results do confirm that the permeation rate in humans is less than rats; a conservative factor of 2 can be used.

A study examined the absorption and elimination of radio-labelled 2 -(2 -butoxyethoxy)ethanol in rats following 24hr dermal occluded exposure and established that the main route of elimination is overwhelmingly via the urine and the metabolite 2 -(2 -butoxyethoxy)acetic acid. The glucoronidate conjugate was also found at significant levels (5 -8%). Females appeared to absorb and therefore excrete larger quantities than males and the dermal absorption rate was estimated to be 0.73 and 1.46mg/cm2/hr for males and females respectively. Washing studies showed that 90%+ of externally applied substance could be removed after 5 minutes exposure by skin washing.

In a study using rats, dermal penetration of a 2 -(2 -butoxyethanol) applied to semi-occluded skin was around 4.4mg/cm2 over a 48 hour period. About 70% of the applied dose was absorbed, with the rest likely lost from evaporation, demonstrating likely complete absorption potential. Urinary excretion was the main route of elimination. The state of skin (either hairy or clipped) made minimal difference to absorption. Further experiments showed that if the substance was washed off after 5 minutes, absorption was minimal - less than 2.5% of that seen with the first set of experiments.

In a study designed to generate data to confirm or disprove a hypothesis that rates of dermal penetration can be predicted from the octanol water partion coefficient, the rate of 2 -butoxyethoxyethanol penetration in vitro through human skin was determined. The rate of flux of neat substance was ~600 ±80ug/cm2/hr and increased slightly to ~800±70ug/cm2/hr in the presence of water (50% aqueous solution).