Toxicokinetics - trdoer40218

Carcinogenic PAHs

Noncarcinogenic PAHs

Benzo(a)anthracene

Acenaphthene

Benzo(a)pyrene

Acenaphthylene

Benzo(b)fluoranthene

Anthracene

Benzo(k)fluoranthene

Fluorene

Dibenz(a,h)anthracene

Fluoranthene

Chrysene

Naphthalene

Indeno(1,2,3-c,d)pyrene

Pyrene

Phenanthrene

There are minimal data, animal or human, on the systemic toxicities of the

PAHs and virtually no data on the acute effects of the compounds. Toxic effects

that have been observed include a variety of skin lesions and noncancer lung

diseases.

Toxicokinetics

Animal data indicate that the PAHs are readily absorbed after exposure by

inhalation or oral intake and distributes to many tissues in the body. However,

intestinal absorption of the PAHs is dependent upon the presence of bile in the

stomach. The PAHs are absorbed via dermal exposure as shown by both human

and animal studies, although very little is distributed to tissues (USEPA 1982).

Following absorption, metabolism via the cytochrome P-450 monooxygenase

system is required for detoxification to more water-soluble forms of the

compounds for efficient elimination from the body. The unmetabolized PAHs

are not believed to be carcinogenic. During the detoxification process, some

PAHs are metabolically activated to their carcinogenic intermediates. These

intermediates can then bind to cellular macromolecules such as DNA, RNA, and

proteins, resulting ultimately in the induction of cancer. For any of the PAHs,

however, the majority of the metabolism results in detoxified metabolites that

are rapidly excreted.

Ecological effects

The PAHs as a group of contaminants constitutes the largest number of

chemicals of interest identified at manufactured gas plant sites.

No standard freshwater toxicity tests have been reported for polycyclic

aromatic hydrocarbons (except naphthalene) as a class or specific compounds.

There are some data for bioconcentration during tests with model ecosystems, or

for short exposure periods.

Lu et al. (1987) conducted studies with benzo(a)pyrene in a terrestrial-aquatic

model ecosystem and observed bioconcentration factors after 3 days ranging

from 930 for the mosquitofish to 134,248 for Daphnia pulex. Bioconcentration

factors for Daphnia magna and Hexagenia sp. for a shorter time were 200 to

3,500. English sole and white suckers from populations with high frequencies of

neoplasia had elevated levels of PAHs in their stomach contents.

D66

Appendix D Toxicological Profiles