Polycyclic Aromatic Hydrocarbons (PAHs) Testing Service for Electronics and Electrical Appliances

Polycyclic Aromatic Hydrocarbons (PAHs) Testing

1、PAHs Introduction

Polycyclic aromatic hydrocarbons refer to aromatic hydrocarbons containing two or more benzene rings, abbreviated as PAHs. They are primarily formed in two structural configurations: non-fused rings, which include biphenyls, polyphenyls, and polyaryl aliphatic hydrocarbons; and fused rings, where two carbon atoms are shared between two benzene rings.

2、PAHs Sources

The sources of polycyclic aromatic hydrocarbons are divided into natural and anthropogenic sources.

Natural sources mainly arise from the biosynthesis processes of terrestrial and aquatic plants and microorganisms. Additionally, PAHs are found in natural fires in forests and grasslands, volcanic emissions, as well as in fossil fuels, lignin, and sediments. Typically, the background level of PAHs in soil is 100–1000 μg/kg. In freshwater lakes, the background level is 0.01–0.025 μg/L; in groundwater, it is 0.001–0.01 μg/L; and in the atmosphere, it is 0.1–0.5 ng/m³.

Anthropogenic sources primarily result from the incomplete combustion or pyrolysis under reducing conditions of various fossil fuels (such as coal, petroleum, and natural gas), wood, paper, and other carbon-containing hydrocarbons. Simple hydrocarbons and aromatic hydrocarbons can form large quantities of PAHs during high-temperature pyrolysis. It is particularly noteworthy that over 150 types of polycyclic aromatic hydrocarbons have been detected in the smoke exhaled by smokers.

3、PAHs Classification

Based on the connectivity of benzene rings, polycyclic aromatic hydrocarbons are categorized into biphenyls and polyphenyls, polyaryl aliphatic hydrocarbons, and fused aromatic hydrocarbons.

(1) Biphenyls and Polyphenyls

Compounds formed by benzene rings connected via σ bonds are called biphenyls. Derivatives of biphenyls and polyphenyl compounds are named with biphenyl as the parent structure. Their structure and properties are similar to those of monocyclic aromatic hydrocarbons.

(2) Polyaryl Aliphatic Hydrocarbons

Polyaryl aliphatic hydrocarbons are compounds formed by replacing hydrogen atoms in aliphatic hydrocarbons with several benzene rings. These compounds are named with the phenyl group as a substituent and the aliphatic hydrocarbon as the parent structure. Their structure and properties are similar to those of monocyclic aromatic hydrocarbons.

(3) Fused Aromatic Hydrocarbons

Fused aromatic hydrocarbons refer to compounds where two or more benzene rings share two adjacent carbon atoms.

Naphthalene is the most abundant compound in coal tar, constituting about 10% of high-temperature coal tar. Its molecular formula is C₁₀H₈, formed by two benzene rings sharing two adjacent carbon atoms. Naphthalene appears as white flaky crystals, with a melting point of 80°C and a boiling point of 218°C. It is insoluble in water but soluble in hot alcohol and other organic solvents. It is volatile, sublimes easily, and has a distinct odor.

Anthracene is found in coal tar, with a content of approximately 0.25%. Its molecular formula is C₁₄H₁₀, consisting of three fused benzene rings. Phenanthrene is also present in coal tar and is an isomer of anthracene.

(4) Other Fused Aromatic Hydrocarbons

Aromatic hydrocarbons mainly originate from coal tar, from which fused aromatic hydrocarbons such as indene, fluorene, and acenaphthene can be isolated. These are aromatic hydrocarbons fused with alicyclic rings. Tetraphene and pyrene are examples of higher fused aromatic hydrocarbons. Additionally, derivatives of anthracene and phenanthrene are fused aromatic hydrocarbons with significant carcinogenic effects, commonly referred to as carcinogenic hydrocarbons.

4、Migration and Transformation

PAHs released into the atmosphere due to incomplete combustion of fuels are typically bound to various types of solid particles and aerosols. Therefore, the distribution, retention time, migration, transformation, and deposition of PAHs in the atmosphere are influenced by multiple factors (such as particle size, atmospheric physics, and meteorological conditions). In the lower atmosphere, particles with a diameter of less than 1 μm can remain for several days to weeks, while particles with a diameter of 1–10 μm can only persist for a few days at most. PAHs in the atmosphere enter soil, water bodies, and sediments through dry and wet deposition, eventually entering the biosphere.

5、Toxicity and Hazards

Due to their toxicity, genotoxicity, mutagenicity, and carcinogenicity, PAHs can cause multiple harms to the human body, such as damage to the respiratory, circulatory, and nervous systems, as well as harm to the liver and kidneys. They are recognized as major organic pollutants affecting human health.

6、PAHs Presence

PAHs are commonly found in petroleum products, rubber, plastics, lubricants, rust inhibitors, and incompletely burned organic compounds. Besides power tools, PAHs are present in many electrical products. A common example is the use of release agents during the extrusion of plastic particles to prevent adhesion to molds; these release agents may contain PAHs.
Materials that may contain polycyclic aromatic hydrocarbons: charcoal, crude oil, wood tar, tar (natural), pharmaceuticals, dyes, plastics, rubber, pesticides (anthropogenic), lubricants, release agents, capacitor electrolytes, mineral oils, asphalt (anthropogenic), insecticides, fungicides, mosquito coils, tobacco smoke, gasoline anti-icing agents (anthropogenic).

Materials that may contain polycyclic aromatic hydrocarbons: plastic handles/plastic packaging boxes/rubber handles/plastic and rubber products with odors.

7、Current Testing Scope for PAHs:

Consumer products such as electronics and electrical machinery;

Rubber products, plastic products, automotive plastics, and rubber parts;

Food packaging materials, toys, container materials, etc.;

Other materials, etc.;

8、Regulatory Requirements

European Union: 76/769/EEC / Germany: GS certification, LFGB / United States: EPA / China: GB, GB/T, GHZ.