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Benzo(a) pyrene

BaP, benzo(d,e,f)chrysene, 3,4-benzopyrene

SPRI Emission Reporting Threshold
1.00 Kg/yr Pollutant Emissions to Air
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Pure Benzo(a)pyrene (BaP) is usually found as pale yellow crystals. It does not dissolve in water, but will dissolve in organic (carbon-containing) solvents. BaP is one of a group of compounds known as the Polycyclic Aromatic Compounds (PAHs).
What is it used for?
Only relatively small amounts of BaP are intentionally manufactured to be used in dyes.
Where does it come from?
The vast majority of BaP is released to the environment when combustion is incomplete (usually because there is insufficient oxygen). Thus, most BaP is released from vehicle exhausts and domestic wood and coal fires. Trace amounts are found in cigarette smoke. BaP is also released naturally from volcanoes and forest fires, but the amounts are very small compared to those released from man-made combustion sources.
How might it affect the environment?
The most serious environmental impact of BaP is its significant accumulation in organisms exposed to it. Aquatic organisms will also concentrate it. In water, BaP attaches strongly to sediments and any other solid matter. BaP released to soils tends to bind very strongly to the soils particles, but small amounts can leach to groundwaters. BaP is stable and can remain (and travel) in the environment for a long period of time - it is a Persistent Organic Pollutant (POP). Releases of BaP therefore cause concern at a global environmental level as well as on a local scale.
How might exposure to it affect human health?
Benzo(a)pyrene can enter the body either by inhalation of air containing benzo(a)pyrene, ingestion of water or food containing benzo(a)pyrene, or by dermal contact with benzo(a)pyrene, contaminated soil or products containing benzo(a)pyrene. Inhalation of benzo(a)pyrene may cause respiratory tract irritation. Exposure to benzo(a)pyrene may damage the reproductive system and cause cancer. Ingestion of benzo(a)pyrene may cause gastrointestinal irritation. Dermal contact with benzo(a)pyrene may lead to skin irritation. In the natural environment benzo(a)pyrene occurs as part of a mixture of Polycyclic Aromatic Hydrocarbons (PAHs). The full effects of benzo(a)pyrene on human health are unknown, however studies have shown that inhlalation of PAHs or dermal contact with PAHs for long periods of time can cause cancer. The International Agency for Research on Cancer has designated benzo(a)pyrene as a probable carcinogen. However, exposure to benzo(a)pyrene at normal background levels is unlikely to have any adverse effect on human health.
What steps are being taken to limit the potential impacts?
Releases of BaP are controlled through the UK Pollution, Prevention and Control (PPC) Regulations. European Directives concerned with regulating levels of BaP include that concerned with combating air pollution from industrial plants (84/360/EEC), that concerned with particulate matter, to which BaP becomes attached, (1999/30/EC) and it is listed as a "priority substance" for the Water Framework Directive. Its release is controlled at an international level through the UNECE POPs Protocol and it is listed as a candidate substance under the Helsinki and OSPAR Conventions which protect the marine environments of the Baltic Sea and north-east Atlantic Ocean respectively.