Health Stream Article - Issue 32 December 2003

PET Urban Myth Hits Australia

Australian consumers were recently alarmed by a widely circulated email claiming that reuse of PET (polyethylene terephthalate) bottles for storing water and other beverages constituted a cancer risk. The email was a revival of a scare that hit the US about two years ago, which alleged that a potentially carcinogenic plasticiser used in the manufacture of PET could leach from the plastic at dangerous levels if the bottles were reused for a prolonged period. The email urged users to discard PET bottles after no more than one week of use.

The local origin of the email appears to have been an employee of the Queensland Department of Natural Resources and Mines, who sent the message to friends and colleagues, who in turn passed it on to numerous other individuals and email lists. Although the email was not an officially sanctioned communication, the fact that the sender was a government employee (in fact a Workplace Health and Safety Officer), conferred a degree of plausibility that may not otherwise have occurred.

The email caused alarm among members of the public, with several hundred people contacting state and federal health departments and other regulatory authorities. The topic was raised on talkback radio shows, and the CRC also received a number of enquiries on the issue. According to media reports, military authorities in one state were on the verge of removing all PET bottled beverages from their facilities, similar action was being taken by many school tuck shops, and warnings were being included in school newsletters. The level of public concern prompted Food Standards Australia New Zealand (FSANZ) to issue a Fact Sheet refuting the claims made in the email (1). This was further supported by statements from the Plastics and Chemicals Industries Association and the Soft Drink Association.

The errors and inaccuracies in the email and the background and apparent origins of this particular urban myth are outlined below:

• the email stated that the plasticiser, abbreviated as DEHA, was diethylhydroxylamine.
  This compound is not a plasticiser and has a strong fishy smell which would make it very apparent in water. The plasticiser abbreviated as DEHA is in fact diethylhexyl adipate.

• the email stated that DEHA is used in making PET bottles.
  This compound is not used in the manufacture of PET, and is not present either as a raw material, byproduct or breakdown product of PET.

• the email contained an abstract of a paper from the 2001 Annual meeting of the Society for Risk Analysis, reporting the migration of four compounds including DEHA from PET bottles into stored water.
  This report by a Masters student was not subject to peer review or verification prior to publication on the internet. Subsequent investigation indicated the reported "detection" of chemicals was in fact due to background contamination from laboratory plasticware, not leaching of compounds from the PET bottles under test.

Paradoxically, the email also contained a summary from a report by the Swiss Federal Laboratories for Materials Testing and Research on migration of organic compounds from PET bottles (2). This was presumably included as supporting evidence for the initial abstract but actually contained several findings which refuted the alleged risk:

• the concentrations of plasticisers detected in test bottles in the Swiss study were the same as those in blank water samples which had not been in contact with PET (in other words the "detections" again represented background contamination, not leaching from PET bottles)
• the calculated lifetime cancer risks from permanent (ie daily) exposure to such concentrations of DEHA were below the 1 in a million level (a level of 1 in a million cancer risk from daily exposure to a chemical over a lifetime of 70 years is commonly taken as a reference for a negligible health risk level (3))
• the concentrations were "distinctly below" the WHO Guideline Values for Drinking-water Quality (WHO Guideline Values are designed to be protective for health while assuming daily consumption of 2 litres of water at the specified concentration over a 70 year lifetime)

FSANZ noted that although PET bottles are not intended for reuse, they do not present a chemical hazard if reused for a prolonged period. However they advise that bottles should be thoroughly rinsed and allowed to dry between uses to avoid potential microbiological risks from bacterial contamination.

The DEHA plasticiser is used in the manufacture of some plastics including PVC flexible films used for food packaging. Health authorities have assessed evidence on the toxicity of DEHA, and determined that the tiny amounts that leach into food from packaging during storage and microwave cooking are well below the levels where toxic effects might occur in people consuming the food or beverages.

The allegations contained in the email were not supported by rigorous scientific evidence, but achieved wide circulation due to the speed and pervasiveness of electronic communications, and unwarranted credibility due to the identity of the initial Australian source. This incident illustrates the problems of disseminating unverified rumours of health risks rather than referring them to appropriate and knowledgable authorities, particularly when the message may be perceived to have official status.

(1) www.foodstandards.gov.au
Fact Sheets 2003, FSANZ finds plastic drink bottles not a safety risk, 3 October.
(2) Report available from:
www.sodis.ch/files/Report_EMPA.pdf
(3) For comparison, cancer deaths account for about 25% to 30% of all deaths in developed countries. Thus a person's lifetime cancer risk is about 250,000 to 300,000 in 1 million. An additional risk of 1 in 1 million from daily exposure to a specific chemical therefore represents a tiny increase in overall risk.
As a non-cancer comparison, the risk of the Earth being struck by a large object from space capable of causing a one-million-megaton explosion (the so-called dinosaur killer asteroid) has been estimated at about 1 in 1 million per year or about 70 in 1 million over a human lifetime. (Rain of Iron and Ice: The very real threat of comet and asteroid bombardment. John S Lewis (Helix Books) ISBN: 0201154943).