But 35 years later, a big part of the problem appears to be technology itself.
Tons of computers, monitors, televisions and other electronic gizmos that contain hazardous chemicals, or "e-waste," may be poisoning people and ground water. Activists say the nation's biggest environmental problem may be the smallest devices, and this week they're launching campaigns to increase awareness about recycling cell phones, music players, handheld gaming consoles and other electronics.
In other Earth Day observances:
"They're small and lightweight, and the electronics industry markets (sees) them as disposable. Whenever you upgrade your (wireless) service, you can get a new flip phone for $50 and they never tell you to recycle the old one," said Kimberlee Dinn, campaign director for Washington, D.C.-based EARTHWORKS, a nonprofit that studies the environmental impact of mining, digging and drilling natural resources.
Environmentalists are particularly bothered by the recycling and reuse policies of cell phone manufacturers and distributors, and of Apple Computer Inc., maker of the iPod digital music player.
The biggest offenders are cell phones, said Dinn, because they pose a hazardous "double whammy" to the environment.
To build them, gold and other metals must be extracted from mines in western states, as well as Peru, Turkey, Tanzania and other countries. The Environmental Protection Agency ranks hard-rock mining as the nation's leading toxic polluter.
Then, at the end of their life cycles, many phones end up in landfills, where they may leak lead and other heavy metals that could pollute nearby ground water.
Americans have about 500 million obsolete, broken or otherwise unused cell phones, and about 130 million more are added each year — the equivalent of 65,000 tons of waste, according to the EPA.
Less than 2 percent are recycled — usually refurbished and resold to consumers in Latin America and Asia, or disassembled for gold and other parts, according to EARTHWORKS.
It's unclear what happens to the remainder, said Dinn, whose organization is launching a recycling campaign to coincide with Earth Day on Friday. Activists are asking consumers to download and print postage-paid labels and send unused phones to the Atlanta-based recycling organization CollectiveGood. The goal is to collect at least 1 million cell phones this year.
"We think a majority of those phones are waiting around in people's desk drawers," said Dinn, who came up with 30 unused cell phones in a recent sweep of the group's eight-person office.
But cell phone initiatives may not be enough to stem overall e-waste.
U.S. consumers retire or replace roughly 133,000 personal computers per day, according to research firm Gartner Inc. According to a study commissioned by San Jose-based Silicon Valley Toxics Coalition, roughly half of all U.S. households have working but unused consumer electronics products.
CEO Steve Jobs and Apple board members, including former Vice President Al Gore, have each received at least 400 faxes about the company's contribution to e-waste, said Robin Schneider, executive director of the Texas Campaign for the Environment. The group is asking Apple to reduce or eliminate recycling fees for consumers and build in-store recycling centers.
Apple charges most American consumers $30 to recycle unused or broken computers and laptops. And though Apple doesn't have a specific iPod recycling program, a service promoted by its corporate Web site sells consumers shipping labels and packaging materials for sending equipment to recycling vendors.