Polycyclic Aromatic Hydrocarbons (PAHs)
Tailpipe exhaust is one source of PAHs to local Bay tributaries, where they build up in bottom sediments and can affect bottom-dwelling organisms.
PAHs are a chemical contaminant found in parts of the Bay watershed. As more areas of the watershed are developed, levels of PAHs in the Bay and its tributaries are increasing, potentially causing negative health effects in humans and wildlife.
Where do PAHs come from?
PAHs are formed by burning coal, gasoline and fuel oil. They are also a major part of asphalt and tar. Specific sources of PAHs include:
- Auto exhaust
- Leaking motor oil
- Coal-tar pavement sealants
- Tire particles
- Broken up asphalt from driveways and parking lots
- Historic and current manufacturing processes
PAHs are mostly transported by stormwater, which washes the contaminant from asphalt roads, driveways and parking lots into the nearest drain or stream. A study by the National Water Quality Assessment Program found that the most rapid increases of PAHs in sediments at the bottom of water bodies were found in watersheds with increasing development and motor vehicle traffic.
How do fish become contaminated with PAHs?
In water, PAHs attach to sediment, impacting bottom-dwelling organisms like oysters, plankton and some species of fish. As these organisms spend time in or near contaminated sediments, they accumulate PAHs in their tissues. PAHs are suspected to cause cancerous tumors in fish, particularly in bottom-dwelling species. Humans can be exposed to PAHs through ingestion, inhalation and skin contact, as well as eating contaminated fish.
What effects can PAHs have on human health?
PAHs have been shown to cause cancerous tumors in animals, even in single doses. Non-cancerous health effects are not well understood, but can include immune system suppression and red blood cell damage. In other organisms, such as fish and invertebrates, adverse health effects have included:
- Cataracts
- Fin erosion
- Liver abnormalities
- Inhibited reproduction
- Death