2C) PAH Risk Assessment Practice Flashcards

A set of vocabulary-style flashcards covering the sources, chemical characteristics, and risk assessment methodologies (specifically RPFs) for Polycyclic Aromatic Hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons (PAHs)

Ubiquitous contaminants that occur naturally in crude oil or are created through incomplete combustion from both natural and anthropogenic sources.

Natural Sources of PAHs

Forest fires, oil seeps, and volcanos.

Anthropogenic Sources of PAHs

Wood burning, internal combustion engines (vehicle exhaust), cigarette smoke, roofing or coal tar products, electric power generation, and petroleum.

PAH Chemical Characteristics

Compounds containing two or more aromatic rings with a pair of shared carbon atoms that are highly lipophilic.

EPA Priority PAHs

A list of 16 PAHs identified by the ATSDR in 2005 based on toxicity, potential for human exposure, frequency at hazardous waste sites, and available scientific information.

Substituted PAHs

A broader class of polycyclic aromatic compounds including more than 1500 chemicals with functional groups like $O ext{-}$, $N ext{-}$, $S ext{-}$, and $CH_3 ext{-}$.

Relative Potency Factors (RPFs)

A quantitative assessment tool introduced in 1993 to estimate the carcinogenic potency of various PAHs by comparing them to a standard, specifically Benzo[a]pyrene.

Benzo[a]pyrene (BaP)

The standardized PAH used as a reference point in RPF assessments, assigned a relative potency value of $1.0$.

Equipotency Assumption

The pre-1993 EPA quantitative risk estimate that assumed all carcinogenic PAHs were equally as potent as Benzo[a]pyrene, which often resulted in an overestimation of risk.

Group B2 Carcinogens

Probable PAH carcinogens to which the component-based RPF approach is typically applied.

Dibenz[a,h]anthracene

A PAH compound with an estimated relative potency of $1.0$, making it equipotent to Benzo[a]pyrene based on mouse skin carcinogenesis studies.

Chrysene

A PAH compound with a very low estimated relative potency of $0.0001$ (or $0.0044$ in some references) compared to Benzo[a]pyrene.

Dose Additivity

An assumption in the RPF approach for mixtures that the total toxicity is the sum of the individual toxicities of the component PAHs scaled for concentration.

Component-based Approach

A risk assessment method that requires toxicity data for individual chemicals within a mixture and assumes a common mechanism to calculate risk using RPFs.

Whole Mixture Approach

A risk assessment method that requires toxicity data on the mixture as a single entity; it can rely on mechanistic data but currently lacks adequate data and accepted methods.

Inhibitory Interactions

Evidence reported in literature that suggests PAH mixture components may interact in ways that reduce total toxicity, challenging the assumption of simple additivity.

Tox21 High-throughput Screening

A mechanistic-based approach suggested for future PAH risk assessment that includes a broader group of PAHs and evaluates noncancer endpoints.