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Administrative data

Link to relevant study record(s)

Description of key information

PAH are absorbed rapidly through the pulmonary tract, the gastrointestinal tract and to a much lesser extent through skin. Metabolism is complex resulting mostly in hydroxylated species which in part may further be conjugated. Excretion is via urine, bile and faeces. Conjugates excreted in bile can be hydrolysed in the gut and reabsorbed.
Absorption through human skin will be not more than 2 % within and after 8 h of exposure. Permeation through rat skin is much more pronounced (ca. 8 fold).

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - dermal (%):
2

Additional information

ADME

Anthracene oil < 50 ppm BaP is composed of PAH. Toxicokinetics will strongly correlate to the respective properties fo these substances. Thus, anthracene oil toxicokinetics can be characterised based on information determined for PAH.

SUMMARY from WHO 1998/2003:

PAH are absorbed through the pulmonary tract, the gastrointestinal tract, and the skin. The rate of absorption from the lungs depends on the type of PAH, the size of the particles on which they are absorbed, and the composition of the adsorbent. PAH adsorbed onto particulate matter are cleared from the lungs more slowly than free hydrocarbons.

Absorption from the gastrointestinal tract occurs rapidly in rodents, but metabolites return to the intestine via biliary excretion.

Studies with 32P-postlabelling for the detection of DNA-adducts after percutaneous absorption of mixtures of PAH in rodents showed that components of the mixtures reach the lungs, where they become bound to DNA.

PAH are widely distributed throughout the organism after administration by any route and are found in almost all internal organs, but particularly those rich in lipids. Intravenously injected PAH are cleared rapidly from the bloodstream of rodents but can cross the placental barrier and have been detected in foetal tissues.

The metabolism of PAH to more water-soluble derivatives, which is a prerequisite for their excretion, is complex. In general, parent compounds are converted into intermediate epoxides (a reaction catalysed by cytochrome P450-dependent mono-oxygenases), which are further transformed by rearrangement or hydration to yield phenols or diols and – following secondary oxidation - to yield tetrols, which can themselves be conjugated with sulfuric or glucuronic acids or with glutathione. Most metabolism results in detoxification, but some PAH are activated to DNA-binding species, principally diol epoxides, which can initiate tumours.

PAH metabolites and their conjugates are excreted via the urine and faeces, but conjugates excreted in the bile can be hydrolysed by enzymes of the gut flora and reabsorbed. It can be inferred from the available information on the total human body burden that PAH do not persist in the body and that turnover is rapid. This inference excludes those PAH moieties that become covalently bound to tissue constituents, in particular nucleic acids, and are not removed by repair.

References:

WHO (1998). Selected non-heterocyclic polycyclic aromatic hydrocarbons. Environmental Health Criteria 202, Geneva, Switzerland, WHO (World Health Organisation) 1998

WHO (2003). HEALTH RISKS OF PERSISTENT ORGANIC POLLUTANTS FROM LONG-RANGE TRANSBOUNDARY AIR POLLUTION, JOINT WHO/CONVENTION TASK FORCE ON THE HEALTH ASPECTS OF AIR POLLUTION. WHO Regional Office for Europe, World Health Organization 2003

Dermal absorption

In synopsis of observations from comparative in-vivo and in-vitro studies (human vs. rodent) on spiked creosote, it is expected that not more than 2 % of a dermal dose will be absorbed through human skin within and after 8 h of exposure (Fasano 2007a,b). The conversion factor human vs. rat skin was found to be 0.12, which means that the dermal dose absorbable within 8 h is about 8-fold higher in rat than in human skin.