Cancer myth: Plastics used for food storage and cancer

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Origin of the myth

Recently, several emails were forwarded warning that Sheryl Crowe had developed breast cancer by leaving her bottle of water in the car. The email claims that plastic bottles and food containers contain chemicals called dioxins which cause reproductive and developmental problems, liver damage and cancer.

Current evidence

Dioxins are organic environmental pollutants released by burning of waste, especially
PVC and aromatic compounds commonly used in hospitals. These dioxins, after being
released into the atmosphere, are taken up by fish and animals and stored in fat.
People are exposed to dioxins most by eating meat and fish that is high in fat. Dioxin
exposure in Australian is low.[1]

The plastics used to store water and food do not contain dioxins, however many contain two other chemicals that may be of concern: phthalates and bisphenol A.[2]

Phthalates

Some studies have linked high blood concentrations of phthalates with changes in levels of some hormones and genital abnormalities in infants who are exposed to phthalates.[3, 4]

Six phthalates, including DEHP, have been banned from the toy market in the European
Union (EU). The EU’s chemical policy works on the precautionary principle, which means that chemicals can be banned even if there is no scientific consensus that a chemical is harmful.[5]

The Report on Carcinogens is a list of known or reasonably anticipated human carcinogens (cancer causing substances). Phthalates are not included in this list.[6]

Leaching is the process of removing a substance from a solid by dissolving it in a liquid.
The phthalates used in packaging could not affect us unless they leached from the
plastic and into our food or drink. Studies indicate that phthalates can leach from
plastics. The Australian National Industrial Chemicals Notification and Assessment
Scheme (NICNAS) and the US Food and Drug Administration (FDA) confirm that
substances used to make plastics can leach into food.[7-9]

Phthalates do not bioaccumulate – that is the body does not retain them and they are
lost faster than they are absorbed.[10]  Several studies have been done to assess the
amount of exposure to phthalates in people. The highest estimate of exposure is still
well within the margins of what is considered safe.[7]

Bisphenol A

Bisphenol A, or BPA is used in production of food containers and food can linings. It is also a synthetic form of the female hormone oestrogen. Bisphenol A was first thought to be harmful in the 1930s when animal experiments indicated that the chemical may disrupt normal hormone function. A lot of research has been done since then, and the Centre for the Evaluation of Risks to Human Reproduction (CERHR) has done a review of studies done on BPA on rats and concluded that in high doses, BPA can alter the age of puberty. The same review found that, even in high doses, BPA does not cause birth defects, alter fertility or cause prostate cancer.[11]

BPA is not found on the Report on Carcinogens, and a report from the International Agency for Cancer Research declares that there is limited evidence that Bisphenol A causes cancer in animals and is not classifiable as to its carcinogenicity to humans.[6, 12]

Studies indicate that Bisphenol A can leach into water and food.[11]  Studies that conclude that Bisphenol A disrupts hormone function use doses one thousand times higher that what the general population is exposed to. Some studies suggest that BPA can be harmful even in doses of fractions of micrograms. The European Union, which is aggressive in its regulation of chemicals, has affirmed the safety of BPA and criticizes the studies done on small doses as being badly conducted and methodologically flawed.[11, 13]

Summary

Currently there is limited scientific evidence suggesting a link between the use of plastics
and cancer. The general safety of many of these, and other, chemicals is constantly under
review throughout the world. Agencies in Australia, America and Europe have all conducted
reviews in the past three years and maintain a watching brief. At this time, the possibility of adverse effects arising from plastics cannot be ruled out definitively. It is important to follow directions when using plastics to store or cook food.

References

1. Food Standards Australia New Zealand (FSANZ). Dioxins in Food: Questions and Answers. 2007 [cited 2008 02/01/2007]; Available from: http://www.foodstandards.gov.au/newsroom/factsheets/factsheets2004/dioxinsinfoodquestio2458.cfm
2. Halden, R. Researcher Dispels Myth of Dioxins and Plastic Water Bottles. 2004 [cited; Available from: http://www.jhsph.edu/publichealthnews/articles/halden_dioxins.html.
3. Duty, S.M., et al., Phthalate exposure and reproductive hormones in adult men. Hum Reprod, 2005. 20(3): p. 604-10.
4. Main, K.M., et al., Human breast milk contamination with phthalates and alterations of endogenous reproductive hormones in infants three months of age. Environ Health Perspect, 2006. 114(2): p. 270-6.
5. European Union. Phthalate-containing soft PVC toys and childcare articles. Activities of the European Union: Summaries of legislation 2006 [cited 2008 03/01/2008]; Available from: http://europa.eu/legislation_summaries/consumers/consumer_safety/l32033_en.htm
6. U.S. Department of Health and Human Services, 11th Report on Carcinogens. 2005,  Public Health Service - National Toxicology Program,.
7. Center for the Evaluation of Risks to Human Reproduction (CERHR), NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Di(2-Ethylhexyl) Phthalate (DEHP), Center for the Evaluation of Risks to Human Reproduction (CERHR), Editor. 2006, National Toxicology Program - US Department of Health and Human Services,.
8. Meadows, M. Plastics and the Microwave. FDA Consumer 2002 [cited 2008 03/01/2008]; Available from: http://permanent.access.gpo.gov/lps1609/www.fda.gov/fdac/features/2002/602_plastic.html
9. National Industrial Chemicals Notification and Assessment Scheme (NICNAS), Draft Phthalate Hazard Assessments and Hazard Compendium, NICNAS, Editor. 2007, NICNAS.
10. Heudorf, U., V. Mersch-Sundermann, and J. Angerer, Phthalates: toxicology and exposure. Int J Hyg Environ Health, 2007. 210(5): p. 623-34.
11. Center for the Evaluation of Risks to Human Reproduction (CERHR), NTP-CERHR Expert Panel Report on the Reproductive and Developmental Toxicity of Bisphenol A, Center for the Evaluation of Risks to Human Reproduction (CERHR), Editor. 2006, National Toxicology Program - US Department of Health and Human Services,.
12. International Agency for Research on Cancer (IARC), Volume 71: Re-Evaluation of Some Organic Chemicals, Hydrazine and Hydrogen Peroxide, in IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, IARC, Editor. 1999, IARC: Lyon, France.
13. European Food Safety Authority (EFSA), Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food on a request from the Commission related to 2,2-BIS(4-HYDROXYPHENYL)PROPANE (Bisphenol A), Scientific Panel on Food Additives Flavourings Processing Aids and Materials in Contact with Food, Editor. 2006, EFSA.

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