Although many plastics are safe to reuse, some contain components that may be harmful to humans and the environment. Certain plastics can leach harmful chemicals over time, especially if the user exposes the materials to heat (see References 1). These plastics are easy to pick out by their resin identification codes, the numbers that appear in the middle of the recycling symbol -- three arrows that form a triangle -- imprinted on most plastic containers.
Number 3 Plastics
Plastics labeled with resin code 3 are polyvinyl chlorides, many of which contain phthalates, a group of chemicals that can interfere with the endocrine system (see References 2 and 3). There is also some evidence of a link between exposure to phthalates and allergy and respiratory problems (see References 4). Heating food or water in PVC containers increases the risk of releasing phthalates from the material (see References 1).
Number 6 Plastics
Plastics labeled 6 are polystyrenes, frequently used for takeout containers, food packaging and disposable food items, such as plastic plates, bowls and cutlery (see References 2). Polystyrene contains styrene, which the U.S. Environmental Protection Agency considers a suspected carcinogen, as well as a toxin that may damage gastrointestinal, kidney and respiratory function (see References 5). The World Health Organization's International Agency for Research on Cancer classifies styrene in Group 2B -- possibly carcinogenic to humans (see References 6).
Number 7 Plastics
Many, but not all, plastics marked 7 are polycarbonates, which contain Bisphenol A. While there are not enough data on the effects of BPA to reach strong conclusions, the U.S. Food and Drug Administration is currently studying the chemical in-depth, due to concerns about possible risks it poses to the development and health of the brain and prostate gland, particularly in infants and children (see Resources 1). The European Union has already banned the use of plastics containing BPA for baby bottles (see Resources 2).
The risk of chemicals leaching into water from plastics may be less of a concern than microbial contaminants (see References 1). While intact plastic containers may be no more likely to harbor bacteria than those made of other materials, improper cleaning may lead to such contamination (see Resources 3). Some drinking containers not designed for reuse, for example, have narrow openings, making them particularly difficult to thoroughly clean and dry.
- Johns Hopkins Bloomberg School of Public Health: Researcher Dispels Myth of Dioxins and Plastic Water Bottles
- American Chemistry Council: Plastic Packaging Resins
- U.S. Environmental Protection Agency: Phthalates Chemical Summary
- "Occupational & Environmental Medicine"; Phthalates and Human Health"; R. Hauser and A. M. Calafat; November 2005
- U.S. Environmental Protection Agency; EPA Settles Case Against Phoenix Company for Toxic Chemical Reporting Violations; February 2004
- World Health Organization: Styrene in Drinking Water
Grace Grimm has been a professional writer since 2008. Her work on birding and the environment has appeared in "The Jack Pine Warbler: The Magazine of Michigan Audubon," "The Pine Press" and on numerous websites. She is an ecologist with a bachelor's degree in zoology and a master's degree in conservation biology.
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