What is air pollution?
The World Health Organisation (WHO) describes air pollution as ‘…contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere’ (1). A wide range of different substances can contaminate our air: anything from car fumes to desert dust. Exactly what is in the air you are breathing will depend on where you are, the time of year and the weather.
Air pollution is not a new problem in the UK. Factory emissions and domestic coal burning produced sulphur dioxide and soot, which led to the Great Smog in London in 1952 that killed thousands of people (2). The 1956 and 1968 Clean Air Acts helped tackle these pollutants, but people now in their 60s and 70s, grew up breathing in emissions from leaded petrol and summertime smog.
The sources of air pollution may have changed over recent decades, for example fewer domestic coal fires and home incinerators, increased traffic and pesticide use, but we are all still breathing polluted air.
Why is it a problem?
In 2010, air pollution contributed to 3.2 million premature deaths worldwide (3) and to over 400,000 premature deaths in the European Union (4). A 2010 House of Commons report on air quality stated that: 'poor air quality reduces the life-expectancy of everyone in the UK by an average of 7 to 8 months and up to 50,000 people a year may die prematurely because of it’ (5). Health problems resulting from exposure to air pollution have been estimated to cost individuals, businesses, and our health services over £20 billion every year (6).
In 2016 the Environment, Food and Rural Affairs Select Committee described air pollution in the UK as a ‘public health emergency’ (7).
Air pollution and disease
Air pollution is known to be associated with a range of illnesses. In 2013 the International Agency for Research on Cancer (IARC) classified outdoor air pollution as carcinogenic to humans (i.e. capable of causing cancer) (8). It also classifies various indoor air pollutants, such as tobacco smoke and coal fire emissions as carcinogenic (9). Exposure to asbestos can cause lung disease and lung cancer (10). (See more on the Health and Safety Executive website).
Mould and fungal spores can trigger allergies or make existing health conditions worse (11, 12) and exposure to radon can also cause lung cancer (13, 14). In addition, those whose bodies are less able to compensate for the harmful effects of air pollution, due to ill health or old age, are also vulnerable. For example, particulate matter can exacerbate cardiovascular diseases, and asthma sufferers are more susceptible to several air pollutants (15).
Air pollution and breast cancer
Research suggests that high levels of air pollution may also be associated with higher incidence of breast cancer. It is important to note that whilst not all studies demonstrate a clear correlation between high levels of air pollution and increased breast cancer risk, there is evidence to suggest that many of the chemicals present in air pollution are linked to an increased risk of the disease.
Outdoor air pollution
Exposure to traffic-related air pollution has been linked with an increased breast cancer risk in several studies (e.g.16, 17, 18). One Canadian study found that women living in the areas with the highest levels of pollution were almost twice as likely to develop post-menopausal breast cancer compared to those living in the least polluted areas (19).
The main compounds in traffic-related pollution responsible for this increased risk are unknown, however studies suggest that benzene and certain polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, as well as nitrogen oxides (e.g. NO and NO2) may be responsible (20, 21, 22).
It is unclear whether long term exposure to particulate matter is associated with increased breast cancer risk, as results of studies vary. Research from China (23) and the U.S. (24) found long-term exposure to particulate matter (specifically PM2.5) was associated with elevated risk of breast cancer. Exposure may contribute to the development of breast cancer by particulate matter acting as an oestrogen mimic (25). (For more on the adverse effects of oestrogen mimics, see our background briefing on EDCs and breast cancer).
Exposure to particulate matter may affect mammographic breast density. A large, population-based US study found that women with a higher breast density - known to be a breast cancer risk factor - had higher exposure to PM2.5 compared to those with a lower breast density (26). Other studies which examined long term exposure to particulate matter in nurses found no association between exposure to particulate matter and breast cancer risk (27, 28).
Indoor air pollution
Several chemicals polluting our air indoors have been linked to breast cancer.
Air fresheners, and other artificially scented products, frequently contain limonene. Limonene reacts with ozone (present in air) to form formaldehyde (29). Research has linked formaldehyde to an increased risk of breast cancer, even at low concentrations (30).
Many household products including kitchen cleaners, detergents and cosmetics contain hormone disrupting chemicals such as phthalates, musks and alkylphenols. These chemicals have been detected in human breast tissue (31, 32) at concentrations which are functionally capable of mimicking oestrogen activity and so lead to an increased risk of breast cancer (33). These products are commonly used in the home and are found in indoor air.
The incomplete burning of coal, oil, gas, and organic substances like tobacco or meat produces polycyclic aromatic hydrocarbons (PAHs). They are a serious problem in developing countries where open fires are used for cooking, but can still pollute the air of home and workplaces in the UK. PAHs have been shown to increase risk for breast cancer (34, 35, 36).
Benzene from gas fumes and tobacco smoke has been designated by IARC as a known human carcinogen. Occupational exposure to benzene increases the risk of developing breast cancer (37, 38, 39).
Some flame retardants, commonly used to reduce the flammability of household furnishings, also pollute our indoor air. They can act as oestrogen mimics (40) and in laboratory studies have been linked to an increased proliferation of breast cancer cells, as well as a potential to reduce the anti-cancer effects of the breast cancer drug tamoxifen (41).
Organic solvents such as toluene, methylene chloride, trichloroethylene and formaldehyde, are found in outdoor and indoor air pollution. They are present in cleaning products and some cosmetics. Several studies have linked occupational exposures to organic solvents with increases in breast cancer incidence (42, 43). Some solvents, used in the manufacture of computer components, cleaning products and cosmetics, have been shown to cause mammary tumours in laboratory animals (44).
The mostly commonly known source of indoor air pollution is second hand tobacco smoke, which contains hundreds of harmful chemicals, including arsenic, benzene and vinyl chloride. Numerous studies have investigated whether there is a link between active or passive smoking and breast cancer, however results are conflicting (45). Nonetheless, there is strong support for the plausibility for an association between smoking and breast cancer (46), and several recent studies and meta-analyses suggest there is a moderate increase in breast cancer risk for those who smoke or are passive smokers (e.g. 47, 48, 49).
People are vulnerable to the effects of exposure to air pollution during gestation in the womb and early childhood. Some pollutants, when breathed in by the mother, can cross the placenta to the developing baby (50). Environmental effects may last a lifetime, but may take decades to become apparent (51). For example one recent study (52) found that girls that had experienced higher exposure to traffic pollution during gestation reached one pubertal milestone several months earlier than girls that had been exposed to lower levels of traffic pollution.
What is Breast Cancer UK's position
Breast Cancer UK supports:
- We support calls for the introduction of a new Clean Air Act, which would:
- Tackle the sources of modern air pollution such as diesel
- Safeguard the legal protections in this area provided by EU legislation
- Improve on existing legislation, both EU and domestic, to ensure that we enshrine the right to breathe clean air in law
- Stricter regulation of the chemicals found in household goods. The phasing out of the use of toxic flame retardants in the manufacture of furniture.
- Stricter regulation of pesticides and their use
- More funding for research into the health implications of air pollution, and specifically on the links between air pollution and breast cancer
For more information, download our background briefing on air pollution
Please see here for references.
Last updated June 20, 2017