Atsdr Evaluation of Health Effects of Chemicals. Iv. Polycyclic Aromatic Hydrocarbons (PAHs): Understanding a Complex Problem

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances, such as tobacco and charbroiled meat. There are more than 100 PAHs. PAHs generally occur as complex mixtures (for example, as part of products such as soot), not as single compounds. PAHs are found throughout the environment in the air, water, and soil. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals, including PAHs (ATSDR, 1995), found at facilities on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) and which pose the most significant potential threat to human health, as determined by ATSDR and the Environmental Protection Agency (EPA). These profiles include information on health effects of chemicals from different routes and durations of exposure, their potential for exposure, regulations and advisories, and the adequacy of the existing database. Assessing the health effects of PAHs is a major challenge because environmental exposures to these chemicals are usually to complex mixtures of PAHs with other chemicals. The biological consequences of human exposure to mixtures of PAHs depend on the toxicity, carcinogenic and noncarcinogenic, of the individual components of the mixture, the types of interactions among them, and confounding factors that are not thoroughly understood. Also identified are components of exposure and health effects research needed on PAHs that will allow estimation of realistic human health risks posed by exposures to PAHs. The exposure assessment component of research should focus on (1) development of reliable analytical methods for the determination of bioavailable PAHs following ingestion, (2) estimation of bioavailable PAHs from environmental media, particularly the determination of particle-bound PAHs, (3) data on ambient levels of PAHs metabolites in tissues/fluids of control populations, and (4) the need for a critical evaluation of current levels of PAHs found in environmental media including data from hazardous waste sites. The health effects component should focus on obtaining information on (1) the health effects of mixtures of PAHs particularly their noncarcinogenic effects in humans, and (2) their toxicokinetics. This report provides excerpts from the toxicological profile of PAHs (ATSDR, 1995) that contains more detailed information.

Adverse effect of sub-chronic exposure to benzo(a)pyrene and protective effect of butylated hydroxyanisole on learning and memory ability in male Sprague-Dawley rat

“…In the soil of unpolluted areas, the content of PAHs is between 5-100 μg/kg, while in the soil of polluted areas, such as highway margins, the content of PAHs can reach a range of 2-5 mg/kg. In addition, the average content of PAHs in food is 0.002-0.9 mg/kg (Mumtaz et al, 1996). For its chemical characteristics, benzo(a)pyrene (B(a)P) is apt to produce a toxic effect in the central nervous system by passing through the blood-brain barrier (Saunders et al, 2006).…”

“…For its chemical characteristics, benzo(a)pyrene (B(a)P) is apt to produce a toxic effect in the central nervous system by passing through the blood-brain barrier (Saunders et al, 2006). In recent years, many studies have forcused on its neurotoxicity, but research on the mechanism is incomplete (Mumtaz et al, 1996). The Brain may be extremely susceptible to attack by reactive oxygen species derived from B(a)P and/or B(a)P metabolism due to its characteristics, such as high oxygen consumption, high iron and lipid content and low level of antioxidants (LeBel and Bondy, 1991).…”

Evaluation of interaction and combined toxicity of polyaromatic hydrocarbons (PAHs) and metals using human cell-based bioassays

“…These 17 PAHs is suspected to be more harmful than some of the others, there is a greater chance to get exposed to these PAHs and these PAHs were identified at the highest concentrations at National Priority List (NPL) hazardous waste sites (Mumtaz et al 1996). The National Priorities List (NPL) is the list of hazardous sites in the United States and its territories.…”

Formation of Polycyclic Aromatic Hydrocarbons and Nitrogen Containing Polcyclic Aromatic Compounds in Titan's Atmosphere, the Interstellar Medium and Combustion

“…PAHs produced in combustion processes are important contributors to pollution. They have been identified as both carcinogenic and mutagenic, and if left unchecked, can also lead to respiratory distress 5 . Although found in nature, PAHs in the environment are largely formed through anthropogenic processes such as occur in internal combustion engines.…”

“…Though a large number of PAHs exist, only about 17 PAHs are considered to have a profound effect on human health 5 . 5 .…”