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EC number: 700-990-0
CAS number: 68937-40-6
No studies on toxicokinetics are available for tBuTPP. The available
toxicity studies provide no or little information. Therefore the
assessment is primarily based on physicochemical properties, supported
by some toxicological indications.
The physical/chemical properties that are of importance to assess the
toxicokinetics behaviour of tBuTPP are:
Based on log Kow, t-BuTPP is relatively highly lipophilic and therefore
oral/GI-absorption by passive diffusion is expected to be limited.
Reasonably micellular solubilisation will be the major mechanism for
absorption, also because it has a low water solubility and a moderate
low molecular weight. Oral acute toxicity studies indicate some visible
adversal effects in GI-tract, adrenals, testes and lungs. This indicate
that absorption has occurred, although it gives no indication of the
amount of absorbed substance.
Due to the low vapour pressure of tBuTPP, respiratory exposure is
unlikely to occur on a large scale. However, when respiratory exposure
has occurred, absorption will be similar to oral absorption.
Because of its highly lipophilic character the dermal penetration of
t-BuTPP into the stratum corneum will be high. Because of its low water
solubility the rate of penetration from the stratum corneum into the
epidermis is likely to be low. This would be supported by the outcome of
the skin sensitization study (LLNA), in which the SI was >3 in all
concentrations tested, however, no dose-response was observed. One
theoretical explanation might be that the majority of the dermal applied
substance stays in the local stratum corneum and only a small fraction
has been absorbed into the epidermis.
Distribution, metabolism and excretion
Based on the physical chemical properties the substance will be
distributed into cells and to a lower extent into the extracellular
spaces. Since it’s highly lipophilic character it is anticipated that it
tends to be accumulated in adipose tissues and in lipophilic layers like
the stratum corneum. In one study (SE Hastings, Sauerhoff, 1981) a
significantly higher concentration of phosphates was found in the urine
of exposed animals. This was theoretically clarified by excretion of
metabolites. There is no indication of metabolism rate and excretion
T-BUTPP can be absorbed after oral and respiratory exposure, but the
amount of absorption cannot be predicted. Dermal absorption is
considered to be very low, but accumulation in the stratum corneum is
expected. No information is available about the distribution, metabolism
For risk assessment purposes, absorption via the oral and inhalation
route are assumed to be similar, based on the absence of effects in
90-day studies via both routes. For dermal absorption, it was assumed as
a worst-case that absorption was similar to oral absorption.
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