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Overview

Polycyclic aromatic hydrocarbons (PAHs) are a large class of chemicals. There are several hundred聽PAHs, which usually occur as complex mixtures rather than as individual compounds. Different mixtures of聽PAHs聽may be formed depending on the process that forms them. The most well-known聽PAH聽is benzo[a]pyrene (BaP), the majority of the data on the health effects of聽PAHs聽comes from studies of this compound.听PAHs聽are formed during the incomplete burning of organic materials such as coal, oil, tobacco, and wood.

In this guidance, we will use the term 鈥�PAHs鈥� to refer to complex mixtures of聽PAHs聽that may include聽BaP.

How PAHs gets into the environment

PAHs聽may enter the environment from both human activities and natural processes that involve the burning of organic material. Burning of coal, wood and other solid fuels can release聽PAHs聽into the environment.听PAHs聽may also be present in vehicle emissions and cigarette smoke. Natural sources of聽PAHs聽include forest fires and volcanoes.

Exposure to PAHs

For the general public, food is the major source of exposure to聽PAHs.听PAHs聽largely found in food that has been smoked or cooked using methods such as in charbroiling, grilling and frying. On reviewing a food survey, the Food Standards Agency has determined that聽PAHs聽were typically found in low levels in food and that people do not need to change their eating habits.

Tobacco smoke is a major source of exposure to聽PAHs聽for smokers. In a smoker鈥檚 home, the majority of聽PAHs聽in the air may be from cigarette smoke.

Indoor air sources of聽PAHs聽include cooking and heating with open fires. Exposure to聽PAHs聽from incense and candle burning can also occur, however, as exposure would be expected to be low, it is unlikely to pose a significant risk to health.

Exposure to low levels of聽PAHs聽may also occur through contaminated soil or drinking water.

People working with聽PAHs聽may be exposed through breathing them in or by skin contact.

How exposure to PAH can affect your health

The presence of聽PAHs聽in the environment does not always lead to exposure, as you must come into contact with the chemical. You may be exposed by breathing, eating or drinking the substance or by skin contact. Following exposure to any hazardous chemical, the adverse health effects you may encounter depend on several factors, including the amount to which you are exposed (dose), the duration of exposure, the way you are exposed and if you were exposed to any other chemicals.

Any effects that may occur following exposure to聽PAHs聽largely depend on how exposure occurs. There are few reports on the health effects of single doses of聽PAHs, but health effects are more likely following exposure over long periods of time.

Studies on workers inhaling聽PAHs聽for a number of years showed increased cases of lung damage, breathing problems, skin irritation, weakened immune systems and heart disease.

PAHs and cancer

厂别惫别谤补濒听PAHs, including聽BaP, have been classified by the International Agency for Research on Cancer (IARC) as causing cancer in humans. The ability of some to cause cancer is stronger than others.

In experimental animal studies, some聽PAHs, including聽BaP, caused tumours in animals when they breathed, ate or had skin contact for long periods. Many studies on workers that have been exposed to聽PAHs聽for a long time suggest that breathing in聽PAHs聽may cause lung cancer, and skin contact with聽PAHs聽may cause skin cancer. Exposure over short periods is unlikely to have the same level of cancer risk as exposure over many years.

Pregnancy and the unborn child

Studies of women who were exposed to very high levels of聽PAHs聽and specifically聽BaP聽throughout pregnancy showed effects on the growth of the unborn child and post-natal development of the child鈥檚 nervous system. Chronic exposure to high levels such as those seen in these studies would not be expected in the UK.

Some studies have also shown that聽PAHs聽and specifically聽BaP聽can affect the fertility of men and women when they were exposed to high levels.

A small number of studies observing the development of children whose mothers were exposed to high levels of聽PAHs聽throughout pregnancy showed attention, intelligence and movement problems.

Chronic exposure to high levels such as those seen in these studies would not be expected in the UK.

What to do if you are exposed to PAH

It is very unlikely that the general population will be exposed to a level of聽PAHs聽high enough to cause adverse health effects. However, if you have any health concerns regarding exposure to聽PAHs, seek guidance from your聽GP聽or contact聽.

Additional sources of information

鲍碍罢滨厂:听

The information contained in this document from the UKHSA Radiation, Chemicals, Climate and Environmental Hazards Directorate is correct at the time of its publication.

贰尘补颈濒听[email protected] if you have any questions about this guidance聽or聽[email protected]聽if you have any other questions.