Polycyclic aromatic hydrocarbons ( PAHs )

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PAHs (polycyclic aromatic hydrocarbons) is the collective term for aromatic compounds with condensed ring systems (well in excess of 100 substances).  PAHs lead to lung cancer following exposure by inhalation, to skin tumours following dermal exposure and are probably carcinogenic in humans following oral exposure.

Origin and incidence

PAHs are produced from incomplete combustion processes or pyrolysis of organic materials (wood, coal, petroleum, oil, tobacco, refuse) or foodstuffs (barbecuing, roasting, smoking, drying). PAHs always occur as mixtures. They are spread via smoke, particulate matter in the air and soot particles.

  • Given boiling points < 400 °C, PAHs usually occur in the air in gaseous form.

  • For combustion temperatures of < 1000 °C (e.g. house fire), 3-4-atom PAHs are generally formed. 

  • For temperatures of > 1000 °C (e.g. combustion engines), 5-7-atom PAHs are generally formed.

In the environment PAHs can be of natural or anthropogenic origin. Natural sources can be for example volcanic activity or forest fires. Anthropogenic sources particularly worth mentioning include motor vehicle traffic and industrial processes, but also cigarette smoke.

Chemical properties

PAHs are solid, usually colourless, chemically stable but photosensitive compounds. They are lipophilic (soluble in fat), are almost insoluble in water and have various boiling points depending on molecular mass (e.g. fluoranthene molecular mass = 202 g, boiling point = 383 °C; benzo(a)pyrene molecular mass = 252 g, boiling point = 496 °C).

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PAHs (polycyclic aromatic hydrocarbons) is the collective term for aromatic compounds with condensed ring systems (well in excess of 100 substances).  PAHs lead to lung cancer following exposure by inhalation, to skin tumours following dermal exposure and are probably carcinogenic in humans following oral exposure.

Origin and incidence

PAHs are produced from incomplete combustion processes or pyrolysis of organic materials (wood, coal, petroleum, oil, tobacco, refuse) or foodstuffs (barbecuing, roasting, smoking, drying). PAHs always occur as mixtures. They are spread via smoke, particulate matter in the air and soot particles.

  • Given boiling points < 400 °C, PAHs usually occur in the air in gaseous form.

  • For combustion temperatures of < 1000 °C (e.g. house fire), 3-4-atom PAHs are generally formed. 

  • For temperatures of > 1000 °C (e.g. combustion engines), 5-7-atom PAHs are generally formed.

In the environment PAHs can be of natural or anthropogenic origin. Natural sources can be for example volcanic activity or forest fires. Anthropogenic sources particularly worth mentioning include motor vehicle traffic and industrial processes, but also cigarette smoke.

Chemical properties

PAHs are solid, usually colourless, chemically stable but photosensitive compounds. They are lipophilic (soluble in fat), are almost insoluble in water and have various boiling points depending on molecular mass (e.g. fluoranthene molecular mass = 202 g, boiling point = 383 °C; benzo(a)pyrene molecular mass = 252 g, boiling point = 496 °C).

Important compounds

Important compounds

The US EPA list primarily takes environmental aspects into account (e.g. industrial emissions) and the selection featured covers PAHs from easily volatile to semi-volatile compounds. The recent EU recommendation targets carcinogenic and genotoxic PAHs in foodstuffs.

As one of the most carcinogenic compounds, benzo(a)pyrene was frequently designated as a guide substance. A conservative approach estimates the carcinogenic potential of the total PAH contamination in foodstuffs to be 10 times the detected concentration of benzo(a)pyrene.

However, the latest findings from foodstuff examinations of EU priority PAHs no longer support the status of benzo(a)pyrene as a guide substance. PAHs have therefore been regulated for certain foodstuffs since 1/9/2012 by using maximum levels of benzo(a)pyrene and the sum of benzo(a)pyrene (BaP), benzo(b)fluoranthene (BbF), benz(a)anthracene (BaA) and chrysene (CHR) as representative for the “EU priority PAHs”. The Scientific Committee on Food (2002) recommends keeping PAH contamination in foodstuffs as low as can reasonably be achieved.

Of the 16 EPA PAHs, routine practice often “only” specifies levels for 12 compounds.  Acenaphthene, acenaphthylene, naphthalene and fluorene have low recovery rates due to their volatility.  Similarly, some regulations only concentrate on the 6 semi-volatile PAHs benzo(a)pyrene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene and indeno(1,2,3-cd)pyrene.

U.S. EPA1
genotoxic (g) / carcinogenic (k)2
EU priority PAH3
genotoxic (g) / carcinogenic (k)2
Acenaphthene/ ?Benz(a)anthraceneg / k
AcenaphthyleneBenzo(c)fluorene/ k
Anthracene-/-Benzo(b)fluorantheneg / k
Benz(a)anthraceneg / kBenzo(b)fluorantheneg / k
Benzo(b)fluorantheneg / kBenzo(b)fluorantheneg / k
Benzo(k)fluorantheneg / kBenzo(ghi)peryleneg
Benzo(ghi)perylenegBenzo(a)pyreneg / k
Benzo(a)pyreneg / kChryseng / k
Chryseneg / kCyclopenta(cd)pyreneg / k
Dibenz(a,h)anthraceneg / kDibenz(a,h)anthraceneg / k
FluorantheneDibenzo(a,e)pyreng / k
Fluorene/ -Dibenzo(a,h)pyreneg / k
Indeno(1,2,3-cd)pyreneg / k
Dibenzo(a,i)pyrene
g / k
Naphthalene?
Dibenzo(a,l)pyrene
g / k
Phenanthrene?Indeno(1,2,3-cd)pyreneg / k
Pyrene- / ?5-Methylchryseneg / k

1  Environmental Protection Agency (EPA): priority list (1982)
2  cit. Scientific Committee on Food  (2002)
3 Commission Recommendation 2005/108/EC including benzo(c)fluorene, which was additionally recommended by the experts of the JECFA (Joint FAO/WHO Experts Committee on Food Additives).

PAH regulations (selection)

PAH regulations (selection)

PAHs in foodstuffs

 according to EUR LEX Regulation 1881/2006.

The sampling procedure and the criteria for sample processing and analytical methods for foodstuffs are regulated in Regulation (EC) 333/2007 as amended respectively.

 

MatrixMaximum level forReference level forSource

Water for human consumption
Benzo(a)pyrene and sum of benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene and indeno(1,2,3-cd)pyreneDirective 98/83/EC, Drinking Water Regulation, Federal Legal Gazette No. 304 (2001)
Fertilisers, soil additives, culture substrates and plant additivesSum of benzo(a)pyrene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene and indeno(1,2,3-cd)pyreneFertiliser Regulation, Federal Law Gazette No. 100 (2004)
Waste compost, certain aggregates16 EPA PAHsCompost Regulation, Federal law Gazette No. 292 (2001)
Emission controls: rye grass culture, meadow grass, tree leavesBenzo(a)pyrene, sum of 6 EPA PAHs (semi-volatile PAHs), sum of 12 EPA PAHsÖhlinger (2014)


Maximum Levels can be found in the EC Regulation 1881/2006 in its current version:

Food product

Maximum level in µg/kg for benzo(a)pyrene

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

Food product

Oils and fats (excluding cocoa butter and coconut oil) for direct consumption or as food ingredient

Maximum level in µg/kg for benzo(a)pyrene

2.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

10.0

Food product

Cocoa beans and derivative products

Maximum level in µg/kg for benzo(a)pyrene

5 µg/kg fat as of 1/4/2013

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

35 µg/kg fat from 1/4/2013 to 31/3/2015
30 µg/kg fat as of 1/4/2015

Food product

Coconut oil for direct consumption or as food ingredient

Maximum level in µg/kg for benzo(a)pyrene

2.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

20.0

Food product

Smoked meat and meat products

Maximum level in µg/kg for benzo(a)pyrene

5.0 until 31/8/2014
2.0 as of 1/9/2014

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

30 µg/kg from 1/9/2012 to 31/8/2014
12 µg/kg  as of 1/9/2014

Food product

Muscle meat from smoked fish and products; smoked crustaceans: max. level for muscle meat from extremities and rear abdomen; smoked prawns and prawn-like crustaceans (brachyra and anomura): max. level applies to muscle meat from extremities

Maximum level in µg/kg for benzo(a)pyrene

5.0 until 31/8/2014
2.0 as of 1/9/2014

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

30 µg/kg from 1/9/2012 to 31/8/2014
12 µg/kg  as of 1/9/2014

Food product

Smoked sprats and smoked sprats in tins (spratus spratus); mussels (fresh, refrigerated or frozen); heat-treated meat and meat products that are sold to consumer

Maximum level in µg/kg for benzo(a)pyrene

5.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

30.0

Food product

Smoked mussels

Maximum level in µg/kg for benzo(a)pyrene

6.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

35.0

Food product

Processed cereal-based foods and baby food for infants and young children

Maximum level in µg/kg for benzo(a)pyrene

1.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

1.0

Food product

Infant formula, follow-on formula, baby milk and follow-on milk

Maximum level in µg/kg for benzo(a)pyrene

1.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

1.0

Food product

Dietetic foods for medical purposes for infants

Maximum level in µg/kg for benzo(a)pyrene

1.0

Maximum level in µg/kg for sum of BaP, BbF, BaA and CHR (as LB*)

1.0

 

 *Lower concentration limits (LB=lower bound) are calculated assuming that all the values for the four substances lying below the detection level are Zero.

 

 

 

 

 

 

 


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