HIDROCARBUROS POLIAROMATICOS PDF

Human exposure[ edit ] Human exposure varies across the globe and depends on factors such as smoking rates, fuel types in cooking, and pollution controls on power plants, industrial processes, and vehicles. A wood-burning open-air cooking stove. Smoke from solid fuels like wood is a large source of PAHs globally. Burning solid fuels such as coal and biofuels in the home for cooking and heating is a dominant global source of PAH emissions that in developing countries leads to high levels of exposure to indoor particulate air pollution containing PAHs, particularly for women and children who spend more time in the home or cooking.

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Human exposure[ edit ] Human exposure varies across the globe and depends on factors such as smoking rates, fuel types in cooking, and pollution controls on power plants, industrial processes, and vehicles.

A wood-burning open-air cooking stove. Smoke from solid fuels like wood is a large source of PAHs globally. Burning solid fuels such as coal and biofuels in the home for cooking and heating is a dominant global source of PAH emissions that in developing countries leads to high levels of exposure to indoor particulate air pollution containing PAHs, particularly for women and children who spend more time in the home or cooking.

Particulate air pollution, including smog, is a substantial cause of human exposure to PAHs. Emissions from vehicles such as cars and trucks can be a substantial outdoor source of PAHs in particulate air pollution. PAHs typically disperse from urban and suburban non-point sources through road run-off , sewage , and atmospheric circulation and subsequent deposition of particulate air pollution.

Biological degradation by microbes is a dominant form of PAH transformation in the environment. However, the overall distribution also suggested that the PAHs in London soils had undergone weathering and been modified by a variety of pre-and post-depositional processes such as volatilization and microbial biodegradation. PAHs in peatlands[ edit ] Managed burning of moorland vegetation in the UK has been shown to generate PAHs which become incorporated into the peat surface.

Cancer[ edit ] PAHs have been linked to skin , lung , bladder , liver , and stomach cancers in well-established animal model studies. An 18th-century drawing of chimney sweeps. Historically, PAHs contributed substantially to our understanding of adverse health effects from exposures to environmental contaminants , including chemical carcinogenesis. In , Yamigawa and Ichicawa were the first to experimentally produce cancers, specifically of the skin, by topically applying coal tar to rabbit ears.

This component was later linked to a characteristic fluorescent pattern that was similar but not identical to benz[a]anthracene , a PAH that was subsequently demonstrated to cause tumors. In the s and later, epidemiologists from Japan, the UK, and the US, including Richard Doll and various others, reported greater rates of death from lung cancer following occupational exposure to PAH-rich environments among workers in coke ovens and coal carbonization and gasification processes.

The structure of a PAH influences whether and how the individual compound is carcinogenic. When the DNA sequence is altered in genes that regulate cell replication , cancer can result.

Mutagenic PAHs, such as benzo[a]pyrene, usually have four or more aromatic rings as well as a "bay region", a structural pocket that increases reactivity of the molecule to the metabolizing enzymes.

The activity of these enzymes may at times conversely protect against PAH toxicity, which is not yet well understood. In this stage, an initiated cell a cell that has retained a carcinogenic mutation in a key gene related to cell replication is removed from growth-suppressing signals from its neighboring cells and begins to clonally replicate.

Excessive closure of these channels after exposure to PAHs results in removing a cell from the normal growth-regulating signals imposed by its local community of cells, thus allowing initiated cancerous cells to replicate.

These PAHs do not need to be enzymatically metabolized first. Low molecular weight PAHs are prevalent in the environment, thus posing a significant risk to human health at the promotional phases of cancer. Cardiovascular disease[ edit ] Adult exposure to PAHs has been linked to cardiovascular disease.

This enzyme then metabolically processes the PAHs to quinone metabolites that bind to DNA in reactive adducts that remove purine bases. The resulting mutations may contribute to unregulated growth of vascular smooth muscle cells or to their migration to the inside of the artery, which are steps in plaque formation.

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