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Polycyclic Aromatic Hydrocarbons. What they are and why we should care. PAH – Just what are they?. Polycyclic – composed of multiple rings Aromatic – deals with the number of electrons in the pi bonding system Hydrocarbon – composed of hydrogen and carbon atoms. Okay, so what?.

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polycyclic aromatic hydrocarbons

Polycyclic Aromatic Hydrocarbons

What they are

and why we should care

pah just what are they
PAH – Just what are they?
  • Polycyclic – composed of multiple rings
  • Aromatic – deals with the number of electrons in the pi bonding system
  • Hydrocarbon – composed of hydrogen and carbon atoms
okay so what
Okay, so what?

In short, they damage DNA. DNA damage can lead to cancer… And everybody just loves cancer, right?

But how is the damage done?

DNA’s structure basically has a bunch of flat molecules stacked on top of each other – and PAH are also flat.

PAH can intercalate between the base pairs in DNA

Once between the base pairs, the PAH can react with the bases or with the phosphate backbone of DNA.

In a nutshell, the PAH bound to DNA can lead to either the breaking of the DNA backbone or to mutations during transcription.

- Oxidation of PAH by enzymes in the liver

However, the resulting product binds DNA.

and where are these things found
And where are these things found…?

In short, lots of places –

  • Cigarette smoke
  • Vehicle exhaust
  • Wood smoke
  • Burnt food

Generally, they result from the incomplete combustion of fuels and other organic substances (i.e. tobacco or that overcooked steak).

how do we get exposed
How do we get exposed?
  • Breathing air containing PAHs in the workplace of coking, coal-tar, and asphalt production plants; smokehouses; and municipal trash incineration facilities.
  • Breathing air containing PAHs from cigarette smoke, wood smoke, vehicle exhausts, asphalt roads, or agricultural burn smoke.
  • Coming in contact with air, water, or soil near hazardous waste sites.
  • Eating grilled or charred meats; contaminated cereals, flour, bread, vegetables, fruits, meats; and processed or pickled foods.
  • Drinking contaminated water or cow's milk.
  • Nursing infants of mothers living near hazardous waste sites may be exposed to PAHs through their mother's milk.


what s being done
What’s being done?
  • The Occupational Safety and Health Administration (OSHA) has set a limit of 0.2 milligrams of PAHs per cubic meter of air (0.2 mg/m³).
  • The National Institute for Occupational Safety and Health (NIOSH) recommends that the average workplace air levels for coal tar products not exceed 0.1 mg/m³ for a 10-hour workday, within a 40-hour workweek. There are other limits for workplace exposure for things that contain PAHs, such as coal, coal tar, and mineral oil.