Polycyclic Aromatic Hydrocarbons (PAHs) are aromatic compounds consisting of multiple fused benzene rings. They feature persistence, bioaccumulation and toxicity, widely existing in nature and human production activities, and pose potential threats to the environment and human health. At present, PAHs have been listed as key controlled environmental pollutants by many countries and regions, and relevant testing has become an important requirement for product export and market access.

I. Sources and Hazards of PAHs

1. Main Sources

• Natural Sources: Natural phenomena such as volcanic eruptions and forest fires generate a small amount of PAHs.

• Anthropogenic Sources:

• Incomplete combustion of fossil fuels (coal, petroleum, natural gas) (e.g., vehicle exhaust, industrial waste gas, domestic heating);

• Industrial production processes (such as coking, asphalt processing, thermal decomposition of plastics and rubber);

• Additives in products (PAHs may exist as impurities or auxiliaries in rubber, plastics, pigments, lubricants).

2. Health and Environmental Hazards

• Harm to Human Body: PAHs are highly carcinogenic (Benzo[a]pyrene is an internationally recognized Group 1 carcinogen), mutagenic and teratogenic. Long-term exposure may cause skin cancer, lung cancer, digestive tract cancers, and also damage the reproductive system and immune system.

• Environmental Hazards: PAHs are difficult to degrade in the environment. They can spread through air, water and soil, accumulate in animals and plants, enter the human body via the food chain, and impose long-term impacts on ecosystems.

II. Commonly Regulated PAH Substances

Regulations in different regions have slight differences in controlled PAH species. The internationally most frequently regulated 16 Priority PAHs (proposed by US EPA) include:

1. Naphthalene

2. Acenaphthylene

3. Acenaphthene

4. Fluorene

5. Phenanthrene

6. Anthracene

7. Fluoranthene

8. Pyrene

9. Benzo[a]anthracene

10. Chrysene

11. Benzo[b]fluoranthene

12. Benzo[k]fluoranthene

13. Benzo[a]pyrene

14. Indeno[1,2,3-cd]pyrene

15. Dibenzo[a,h]anthracene

16. Benzo[g,h,i]perylene

Among them, Benzo[a]pyrene (BaP) is the most toxic one, and it is often taken as a representative indicator of PAH contamination.