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Environmental factors

Environmental factors on this page are factors that can occur in our surroundings that have been the subject of research to investigate whether they are associated with risk of breast cancer.

Study results have show these environmental factors, including working as a hairdresser and use of hair dyes, electro-magnetic radiation, antiperspirants and plastic bottles (BPA) to be unproven or unlikely to influence risk of breast cancer. 

Working as a hairdresser

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no conclusive evidence that working as a hairdresser or barber is associated with increased risk of breast cancer.

A large number of studies have been undertaken, and while these studies had some limitations, none showed any link between working as a hairdresser or barber and increased risk of breast cancer.

Evidence classification: Inconclusive

The evidence for any association between occupation as a hair dresser and risk of breast cancer is inconclusive.

There have been methodological limitations in the studies, however a substantial number of cohort studies show no association and therefore an increase in risk seems unlikely.

Methodological limitations of the studies include lack of information on confounders and the level of occupational exposure.

Evidence 

The International Agency for Research on Cancer (IARC) has concluded that occupational exposure to chemicals in hair products is probably carcinogenic to humans, based on a small increased risk of bladder cancer, and animal studies.1 However, many epidemiological studies, including the largest case-control studies and cohort studies, have not shown any association with risk of breast cancer.1

A meta-analysis of 7 cohort studies and 5 case-control studies showed no association between working as a hairdresser and risk of breast cancer, although some of these studies did not include complete information on confounders and the level of occupational exposure.2

Female hairdressers in Nordic countries, as a group, have been found to have a higher risk of breast cancer than women in other occupations.3 A study of the cancer-free sisters of the women with breast cancer from the Nordic study found no association between workplace exposure to dyes or inks and the risk of premenopausal or postmenopausal breast cancer.4 There was also no evidence of a linear dose-response relationship.

Read the full Review of the Evidence

References
  1. International Agency for Research on Cancer (2010). Some aromatic amines, organic dyes, and related exposures, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, volume 99, IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, Lyon.
  2. Takkouche B, Regueira-Méndez C & Montes-Martínez A (2009). Risk of cancer among hairdressers and related workers: a meta-analysis. International Journal of Epidemiology 38(6):1512–1531.
  3. Pukkala E, Martinsen JI, Lynge E, et al. (2009). Occupation and cancer: follow-up of 15 million people in five Nordic countries. Acta Oncologica 48(5):646–790.
  4. Ekenga CC, Parks CG & Sandler DP (2015). Chemical exposures in the workplace and breast cancer risk: a prospective cohort studyInternational Journal of Cancer 137(7):1765–17.
Use of hair dyes

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no conclusive evidence that personal use of hair dyes is associated with an increased risk of breast cancer. Study findings have been inconsistent, with the best quality studies showing no association.

Hair dyes can be permanent, semi-permanent or temporary. Each type contains chemical compounds that could be absorbed through the skin, especially on the scalp.

Some hair dyes have been found to damage cells in the laboratory and to cause cancer in rats when ingested. Some hair straighteners contain formaldehyde, which is known to cause cancer.

Evidence classification: Inconclusive

The evidence for any association between use of chemical hair dyes or hair relaxers (straighteners) and risk of breast cancer is inconclusive.

There are inconsistent findings across studies. However, findings from the higher-quality (cohort) studies do not support an association.

Proposed mechanisms

Hair dyes can be classified as permanent, semi-permanent or temporary. Each type contains chemical compounds that could be absorbed through the skin, especially on the scalp. Concerns about potential carcinogenic effects of hair dyes arose after they were found to have genotoxic effects in vitro and to cause cancer in rats after oral administration (but not topical application).1 Some hair relaxers contain formaldehyde, which is a known carcinogen.1

Evidence 

The International Agency for Research on Cancer (IARC) reported on a meta-analysis of 14 studies (two cohort and 12 case-control studies)2, which did not find any association between use of hair dyes, including permanent hair dyes and intense exposures, and risk of breast cancer.1

A recent meta-analysis of 8 case-control studies reported an increased risk of breast cancer for 'ever use' of hair dyes compared with 'never use'.3 Weaknesses of this analysis included the recall bias associated with case-control studies, the significant heterogeneity between studies, and a lack of uniform adjustment for confounding factors.

A cohort study found no association between 'ever use' of hair dyes (compared with 'never use') and breast cancer risk, and no evidence of a dose-response relationship with increasing duration or intensity of use.4

No association between use of chemical hair relaxers and breast cancer risk was found in a cohort study of African-American women.5 Two more recent case-control studies have reported inconsistent findings of an association between use of chemical hair relaxers and risk of breast cancer.6,7

Read the full Review of the Evidence

References
  1. International Agency for Research on Cancer (2010). Some aromatic amines, organic dyes, and related exposures, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, volume 99, IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, Lyon.
  2. Takkouche B, Etminan M, Montes-Martinez A (2005). Personal use of hair dyes and risk of cancer: a meta-analysis. JAMA: The Journal of the American Medical Association 293(20): 2516‒2525.
  3. Gera R, Mokbel R, Igor I & Mokbel K (2018) Does the use of hair dyes increase the risk of developing breast cancer? A meta-analysis and review of the literature. Anticancer Research 38:707–716.
  4. Mendelsohn JB, Li QZ, Ji BT, et al.(2009). Personal use of hair dye and cancer risk in a prospective cohort of Chinese women. Cancer Science 100(6):1088–1091.
  5. Rosenberg L, Boggs DA, Adams-Campbell LL et al. (2007). Hair relaxers not associated with breast cancer risk: evidence from the Black Women’s Health Study. Cancer Epidemiology, Biomarkers & Prevention 16(5):1035–1037.
  6. Llanos AAM, Rabkin A, Bandera EV, et al. (2017) Hair product use and breast cancer risk among African American and White women. Carcinogenesis 38(9):883‒892.
  7. Brinton LA, Figueroa JD, Ansong D, et al. (2018) Skin lighteners and hair relaxers as risk factors for breast cancer: results from the Ghana breast health study. Carcinogenesis 39(4):571‒579.
Electromagnetic radiation - low-frequency

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no conclusive evidence that low-frequency electromagnetic radiation is associated with an increased risk of breast cancer. Available studies are mainly of low quality. 

Everyone is exposed to some low-frequency electromagnetic radiation, however it is difficult to measure the amount that people are exposed to. Low-frequency electromagnetic radiation is produced by both natural sources and artificial sources.

Natural sources for this type of radiation include the earth, sun and thunderstorms. Artificial sources include overhead powerlines, electric wiring and common appliances such as televisions, computers and hair-dryers.

Evidence classification: Inconclusive

The evidence for any association between exposure to low frequency electromagnetic fields and risk of breast cancer is inconclusive.

The evidence is comprised mainly of case-control studies and is limited by differences in measuring exposures and high heterogeneity between studies. The evidence shows no association with postmenopausal breast cancer and is inconsistent for premenopausal breast cancer.

Proposed mechanisms

Extremely low frequency (ELF) electromagnetic fields are generated naturally in the environment but the main sources are artificial, related to the generation, transmission and use of electricity at a frequency of 50 Hz. Artificial sources include overhead powerlines, electrical wiring and common household electrical appliances.

Low frequency EMFs do not cause direct damage to cells or DNA and there is no established carcinogenic mechanism.1

Evidence 

The International Agency for Research on Cancer (IARC) concluded that there was inadequate evidence in humans for the carcinogenicity of ELF magnetic fields in relation to all cancers, including breast cancer.1 IARC concluded that ELF electrical fields are ‘not classifiable as to their carcinogenicity in humans’ (Group 3).

Four recent meta-analyses 2-5, which included only case-control studies and with considerable overlap between included studies, found no association between ELF electromagnetic fields and risk of postmenopausal breast cancer, although findings for premenopausal breast cancer were mixed. There were substantial differences in the methods used to quantify exposure, and generally high heterogeneity between studies.

A recent large Dutch cohort study found no association between occupational exposure to ELF electromagnetic fields and risk of breast cancer in postmenopasual women.6

Read the full Review of the Evidence

References
  1. International Agency for Research on Cancer (2002). Non-ionising radiation. Part 1: static and extremely low-frequency (ELF) electric and magnetic fields, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 80, IARC Working Group on the Evaluation of Carcinogenic Risk to Humans, Lyon, http://monographs.iarc.fr/ENG/Monographs/vol80/index.php.
  2. Zhang Y, Lai J, Ruan G, et al. (2016) Meta-analysis of extremely low frequency electromagnetic fields and cancer risk: a pooled analysis of epidemiologic studies. Environment International 88:36–43.
  3. Zhao G, Lin X, Zhou M, et al. (2014) Relationship between exposure to extremely low-frequency electromagnetic fields and breast cancer risk: a meta-analysis. European Journal of Gynaecological Oncology 35(3):264–269.
  4. Chen Q, Lang L, Wu W, et al. (2013) A meta-analysis on the relationship between exposure to ELF-EMFs and the risk of female breast cancer. PloS One 8(7):e69272.
  5. Chen C, Ma X, Zhong M, et al. (2010) Extremely low-frequency electromagnetic fields exposure and female breast cancer risk: a meta-analysis based on 24,338 cases and 60,628 controls. Breast Cancer Research & Treatment 123(2):569–576.
  6. Koeman T, van den Brandt PA, Slottie P, et al. (2014). Occupational extremely low-frequency magnetic field exposure and selected cancer outcomes in a prospective Dutch cohort. Cancer Causes & Control 25:203–214.
Electromagnetic radiation - radiofrequency

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no conclusive evidence that radiofrequency electromagnetic radiation is associated with risk of breast cancer. A small number of studies have been undertaken, and the best quality studies did not show any association between radiofrequency electromagnetic radiation and increased risk for breast cancer.

Radiofrequency electromagnetic radiation (EMR) is produced by both natural sources and artificial sources. Common sources of radiofrequency EMR radiation include mobile phones, magnetic resonance imaging (MRI) used in medical diagnosis, high-power TV and radio transmitters, and microwave ovens.

Evidence classification: Inconclusive

The evidence for any association between exposure to radiofrequency electromagnetic fields (RF-EMF) and risk of breast cancer is inconclusive

Few epidemiological studies have examined any association between RF-EMF and risk of breast cancer, except for mobile phone use. Several large cohort studies have not found an association between use of mobile phones and risk of breast cancer.

Background

Electromagnetic radiation (EMR) is a form of non-ionising radiation consisting of waves of electric and magnetic fields. Radiofrequency (RF) EMR occurs at frequencies between 30 kHz and 300 GHz. This type of non-ionising radiation is produced by both natural sources and artificial sources. The most common source is use of mobile phones. Other sources include high-power TV and radio transmitters, induction heating, and microwave ovens.

Evidence 

The International Agency for Research on Cancer (IARC) concluded that there was inadequate evidence to draw conclusions about the carcinogenicity of exposure to RF electromagnetic fields (personal, occupational and environmental exposures) with regard to breast cancer.1,2

A large national Danish cohort study did not find an association between mobile phone use and risk of breast cancer.3 Similarly, a large prospective cohort study in the United Kingdom did not find an association between ‘ever use’ versus ‘never use’ of mobile phones and risk of any cancer type, including breast cancer, after 7 years of follow-up.4 It also did not find an association between daily use of a mobile phone, or use of a mobile phone for 10 or more years, and risk of breast cancer.

A non-epidemiological, ecological study found a correlation between average density of FM broadcasting transmitters per 10 000 km2 in 23 European countries and incidence of breast cancer.5 A population-based case-control study in the United States did not find an association between residential exposure to 60 Hz magnetic fields and breast cancer risk.6

Read the full Review of the Evidence

References
  1. International Agency for Research on Cancer (2013). Non-ionising radiation. Part 2: radiofrequency electromagnetic fields, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, volume 102, IARC Working Group on the Evaluation of Carcinogenic Risk to Humans, Lyon, http://monographs.iarc.fr/ENG/Monographs/vol102/index.php.
  2. Baan R, Grosse Y, Lauby-Secretan B, et al. (2011). Carcinogenicity of radiofrequency electromagnetic fields. Lancet Oncology 12(7):624–626.
  3. Schüz J, Jacobsen R, Olsen JH, et al. (2006). Cellular telephone use and cancer risk: update of a nationwide Danish cohort. Journal of the National Cancer Institute 98(23):1707–1713.
  4. Benson VS, Pirie K, Schuz J, et al. (2013). Mobile phone use and risk of brain neoplasms and other cancers: prospective study. International Journal of Epidemiology 42(3): 792–802
  5. Hallberg Ö (2016). Cancer incidence vs FM radio transmitter density. Electromagnetic Biology and Medicine 35(4):343–347.
  6. Davis S, Mirick DK & Stevens RG (2002). Residential magnetic fields and the risk of breast cancer. American Journal of Epidemiology 155(5):446–454.
Deodorants and antiperspirants

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no conclusive evidence that use of deodorants or antiperspirants is associated with an increased risk of breast cancer. Only a very small number of poor quality studies have been done.

Deodorants and antiperspirants may contain chemicals such as parabens and aluminium compounds and are applied close to where breast cancer develops. This has led to a concern that using them might increase the risk of breast cancer. However, studies have not found an association between these chemicals and breast cancer risk.

Evidence classification: Inconclusive

The evidence for any association between deodorants or antiperspirants and risk of breast cancer is inconclusive. 

The evidence is limited in amount and quality. A small number of poor-quality human epidemiological studies have found no association between deodorants or antiperspirants and risk of breast cancer.

Proposed Mechanisms

Deodorants are applied topically to prevent body odour. Some deodorants contain chemical preservatives called parabens. There is no evidence of an association between exposure to parabens and risk of breast cancer.

Antiperspirants are a type of deodorant that prevent sweating by blocking the sweat glands; they often do this by including aluminium-based compounds.  Although aluminium has been found in breast cancer cells, similar levels of aluminium are also found in non-cancerous breast tissue and there is some evidence that aluminium, much like other minerals, is stored by, rather than triggers the development of, cancerous tissue.1 Aluminium salts have not been shown to be either genotoxic or carcinogenic.1

Evidence 

Two meta-analyses2,3 of the same two case-control studies, only one of which was population-based, did not find an association between use of deodorants or antiperspirants and risk of breast cancer.

A systematic review of 19 studies concluded that there was no biological or human epidemiological evidence to support the hypothesis that use of antiperspirants containing aluminium increases the risk of breast cancer.4

A more recent case-control study is of too low quality to provide reliable findings.5

Read the full Review of the Evidence

References
  1. Willhite CC, Karyakina NA, Yokel RA, et al. (2014). Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminium, aluminium oxides, aluminium hydroxide and its soluble salts. Critical Reviews in Toxicology, 44(Suppl 4): 1-80
  2. Hardefeldt PJ, Edirimanne S, Eslick GD (2013). Deodorant use and breast cancer risk. Epidemiology 24(1):172.
  3. Allam MF (2016). Breast cancer and deodorants/antiperspirants: a systematic review. Central European Journal of Public Health 24(3):245.
  4. Namer M, Luporsi E, Gligorov J, et al. (2008). L’utilisation de déodorants/antitranspirants ne constitue pas un risqué de cancer du sein. Bulletin du Cancer 95:871–880.
  5. Linhart C, Talasz H, Morandi EM, et al. (2017). Use of underarm cosmetic products in relation to risk of breast cancer: a case-control study. EBioMedicine 21:79–85
Plastic bottles and BPA

Inconclusive

The evidence is too limited to determine the likelihood of an association with increased or decreased risk of breast cancer.

There is no evidence that plastic bottles and bisphenol A (BPA) are associated with increased risk of breast cancer.

Only a very small number of poor quality studies have been done, and they have not found an association between BPA and risk of breast cancer.

BPA is a chemical that is found in plastics used in some water bottles and as coatings inside food cans. It is a synthetic form of the hormone oestrogen. This has led to concerns that it might increase the risk of breast cancer.

Evidence classification: Inconclusive.

The evidence for any association between exposure to bisphenol A (BPA) and risk of breast cancer is inconclusive. 

Only an extremely limited amount of low-quality evidence is available.

Proposed mechanisms

BPA is a synthetic oestrogen that occurs in polycarbonate plastics that are used to store food and beverages, such as some water bottles, bottle tops and the coating inside food cans.

BPA is considered to be an ‘endocrine-disrupting chemical’.1

Evidence 

The International Agency for Research on Cancer (IARC) concluded that BPA was not classifiable as to its carcinogenicity to humans (Group 3).2 No epidemiological evidence was available, and the evaluation was based on limited evidence from experimental animal studies.

The human epidemiological evidence regarding any association between exposure to BPA and the risk of breast cancer comes from only 2 case-control studies.3,4 Neither of these studies found an association.

Read the full Review of the Evidence

References
  1. Del Pup L, Mantovani A, Cavaliere C, et al. (2016). Carcinogenetic mechanisms of endocrine disruptors in female cancers. Oncology Reports 36(2):603-12
  2. IARC (1999). IARC Monographs on the evaluation of carcinogenic risks to humans. Volume 71. Re-evaluation of some organic chemicals, hydrazine and hydrogen peroxide. (1999: Lyon, France)
  3. Trabert B, Falk RT, Figueroa JD, et al. (2014). Urinary bisphenol A-glucuronide and postmenopausal breast cancer in Poland. Cancer Causes & Control 25(12):1587–1593.
  4. Yang M, Ryu JH, Jeon R, et al. (2009). Effects of bisphenol A on breast cancer and its risk factors. Archives of Toxicology 53:281–285.



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