Whether for basketball, tennis, running, cross-training, skateboarding, or just for style, Americans purchased 361,929 pairs of sneakers in 2004. This was up 4.8 percent from the number of pairs bought in 2003.
Once the midsole fails to absorb shock, sneakers should be replaced. For the average person, that would mean replacing sneakers every six months. That translates to two pairs of sneakers trashed, recycled, or donated each year. Overall, in 2005, the US generated some 8 million tons of waste from footwear and clothing—approximately 54 pounds per person. But more than what happens to sneakers that die, there are other production-related environmental problems associated with these comfy shoes.
Hazardous sneaker materials
Sneakers made of PVC—a soft plastic used commonly in consumer products—pose severe environmental risks throughout their life cycle. The manufacture of PVC creates toxic pollution, threatening the health of both factory workers and the communities surrounding factory sites. When disposed of, lead, phthalates—which are industrial compounds used to make plastics soft—and other toxic additives can leach into the ground and drinking water supplies from landfills. Ninety percent of the phthalates used today are used to make PVC, and lead levels in the environment have increased by 1,000 times in the past few hundred years.
Incineration of PVC products produces dioxins and furans, which are among the most toxic environmental contaminants and are known carcinogens. Recycling is not an option with PVC plastic: one PVC item can contaminate a batch of 100,000 recyclable bottles.
The detrimental environmental impact of the T-shirt is rooted in the farming of conventional cotton, considered the world's most pesticide-intensive crop. In the United States, an estimated one-third pound of agricultural chemicals is used to produce a single cotton T-shirt. Thus, a 100 percent cotton T-shirt actually contains 73 percent cotton—the remaining 27 percent is made up of chemicals and chemical residues.
The various chemicals used to treat conventional cotton can harm beneficial insects and soil micro-organisms, pollute ground and surface water, and adversely affect the health of humans and wildlife—including fish, birds, and livestock. Additionally, up to 70 percent genetically modified organism (GMO) seeds are used in conventional cotton farming in the United States.
The farming of cotton is also water-intensive. Approximately 400 gallons of water are required to produce a single cotton T-shirt. Organic cotton farming is not exempt from this reality either. Organic cotton may be chemical-free, but its production still requires significant amounts of irrigated water (though on the plus side, water supplies aren't at risk of being contaminated).
Perhaps not-so-natural, leather used in any application—sneakers included—has many eco-drawbacks. Although desired by many, leather—the byproduct of animal skins—is ecologically harmful. For one, raising livestock for meat and leather production requires a great deal of feed, land, water, and fossil fuels. Factory farms generate 130 times the amount of excrement as the entire human population and the US Environmental Protection Agency (EPA) has noted that livestock pollution is the most damaging threat to American waterways.
But beyond livestock rearing, the process used to tan leather has long been noxious and polluting. Toxins from tanneries includes mineral salts, such as aluminum, iron, and zirconium, as well as formaldehyde and coal-tar derivatives. Certain oils and dyes used in the tanning process are cyanide-based. Similar to the rest of the world, more than 95 percent of American-made leather is chrome-tanned. The production of chrome-tanned leather contributes waste to the environment, including chromium, which is classified as a hazardous material by the EPA. Chromium released from tanneries can contaminate drinking water and is dangerous to ecosystems as well as humans. Tanneries also produce other pollutants, including protein, salt, hair, lime sludge, sulfides, and acids.
Not all sneakers are made of synthetic materials. Alternatives to sneakers made with PVC include those constructed from natural fibers such as hemp and jute. These natural fibers can be used for the uppers of sneakers. Jute is a renewable, biodegradable natural fiber that is retted (loosened from the stem by soaking in water) and woven together to create sneaker material.
Hemp is another natural fiber that can be grown organically and also biodegrades. The bark of hemp stalks contain bast fibers (long, soft fibers) that are woven together. These fibers can be returned to the earth after the sneaker has worn out. Additionally, hemp resists mold and bacteria.
There are also processes that can reduce the amount of toxins released from the production of rubber used for the outsoles of sneakers. By using natural materials such as vegetable oils and changing the processing methods, chemists have been able to develop a greener rubber outsole. With this process, 96 percent fewer toxic substances are released by weight. And yet sneakers with green rubber look, perform and cost the same as those with traditional rubber.
Related health issues
Sneakers produced using solvent-based adhesives contain volatile organic compounds (VOCs) such as urethane. These VOCs produce hazardous waste that could be carcinogenic to humans. Water-based adhesives are an alternative for gluing the midsole to the outsole of the sneaker without using chemicals.
In addition, the initial stages of rubber processing produce effluent at a volume of 25 to 40 times greater than the volume of rubber that is produced, and this effluent is deadly when discharged in water bodies because it contains either lead or zinc oxide. These heavy metals are harmful when released into water ecosystems, particularly those near plants where rubber is vulcanized.
- dioxins: Dioxins are chemicals that are produced in industrial processes, most often combustion. They contain chlorine that can harm humans, usually when ingested through food grown in soil where dioxins have accumulated.
- volatile organic compounds (VOCs): Organic solvents that easily evaporate into the air. VOCs are emitted by thousands of products, including paints, cleaning supplies, pesticides, building materials and furnishings, and may cause immediate and long-term health problems. VOCs are also considered a possible carcinogen, and can create ground-level ozone, the main component of smog.
- National Recycling Coalition NRC)
- Reuse-a-shoe Program (a partnership between Nike and the NRC)
- The Green Guide: On shoes
- American Apparel and Footwear Association
- The Greenpeace 2001 Athletic Shoe Shopping Guide
- American Apparel and Footwear Association - Shoe Stats 2005
- US Environmental Protection Agency - Municipal Solid Waste in the United States: 2005
- Illinois Attorney General - Madigan Announces Illinois Recall of Vinyl Baby Bibs Containing Lead
- Our Stolen Future - About phthalates
- Center for Environmental Health - Target Agrees To Reduce Use of PVC, a "Poison Plastic"
- The Center for Environmental Health - An Unnecessary Poison: Babies, Bibs, and Lead
- Organic Consumers Association - Clothes for a Change: Background Info
- Pesticide Action Network North America - The problems with conventional cotton
- Organic Exchange - About Organic Cotton brochure
- US Geological Survey - Water Facts
- Green Living Tips - Cotton and the Environment
- Cows are Cool - Leather: No Friend of the Earth
- US Environmental Protection Agency - Ground Water & Drinking Water: Factsheet on Chromium
- American Chemical Society - Green Shoes