The first Earth Day, 39 years ago today, was a godsend for a country mired in war and riven by racial, political and cultural issues. Arriving suddenly—as a gift whose time had come—it offered folks something to unite around: the idea of an entire planet, our home, in peril.

It was a time when industrial pollutants made rivers burn and were killing the Great Lakes; smog and soot choked our cities; DDT—thanks to Rachel Carson—had become the national poster child for the abundant horrors of unregulated pesticide usage; old growth forests were devoured unchecked.

Images of environmental catastrophes—such as sea birds tarred by the 1969 Santa Barbara channel oil well blowout—helped drive home the point, and 20 million people rose as one on April 22, 1970 to seek change.

What we got, practically overnight, was the Environmental Protection Agency, the Clean Air Act, the Clean Water Act and the Endangered Species Act—our nation’s most powerful environmental protection tools.

Earthjustice was born during those times, created to establish citizens’ rights to wield the power of these laws and then to do so. Across the decades since, we and our allies have enforced and strengthened environmental laws to halt the degradation and build a different future.

We can claim impressive gains, but we can’t claim victory. We have learned that protecting the planet and building a sustainable future is not a one-time effort, but a constant responsibility we all share.

Nowhere is that more apparent than our efforts to defend people’s health from environmental damage.

Take mercury poisoning for example. In 1970, photos from Minamata, Japan depicted bodies twisted by the effects of mercury in wastewater from an industrial plant contaminating fish and shellfish. Public and private corruption kept the mercury flowing for years after it was discovered. World outrage finally shut down the poisoning, but its aftereffects continue to this day.

Since then, an enormous body of scientific evidence has accumulated, showing the many ways mercury gets into the environment and then into our bodies, and documenting how destructive it can be, especially for young children and pregnant women.

Despite all that, Earthjustice had no choice but to launch a major legal, legislative and public information campaign to force the federal government to set effective standards for controlling mercury emissions from cement kilns and power plants—the nation’s biggest emitters.

Finally, yesterday, as a result of our years of legal action, the Obama EPA announced that it will set standards that virtually eliminate mercury and other toxic pollutants from cement kilns. This stunning decision could save 1,000 lives a year and end the devastating harm brought upon hundreds of thousands more.

We are hopeful that our successful lawsuit to rein in mercury from coal-fired power plants will soon take effect. The Obama administration in February asked the Supreme Court to withdraw an appeal of that decision by the Bush administration.

Unfortunately, mercury is only one of many environmental toxins that are still allowed at harmful levels. Take pesticides. DDT-type pest killers are still used on our food and farms, along with nerve gas-based compounds and toxic fumigants. Earthjustice is pursuing cases to protect the health of farmworkers and children by reducing or eliminating the use of the most toxic pesticides.

Cleaning products are also on our radar screen. We have sued to force household cleaning product companies to obey a New York law that requires them to reveal the chemicals within their products. The case is shining a legal spotlight on the failure of the nation’s toxics program.

Earth Day—we’ve come a long way since 1970, and we’ll keep at it for for many decades to come.