They’ve been at it again. In Montreal, a bunch of politicians and activists finished another round of negotiations among themselves about just how much of our freedom to take away in pursuit of a greener planet. That’s “green,” as in “envious” – of the people who were able to invent, build industries and develop economies in generations past, before the environmentalists convinced world “leaders” that products that improve human life, and the factories that make those products, must be limited in the name of the Earth.

Meanwhile, in Ntinda, Uganda, that country’s vice president was calling on world leaders to help save human lives – by supporting Uganda’s use of a chemical the fear of which galvanized the environmental movement decades ago.

On the surface, these are two different environmental stories: one about chemicals that supposedly might raise temperatures, and one about a chemical that can damage eggshells. But the underlying issue is the same: Should the law promote human life, or should it sacrifice human beings and their quality of life on the altar of Gaia?

Two to three million people die of malaria every year, Uganda’s health minister has said, because the U.S. government is afraid of a chemical called DDT. The United States does spend your tax dollars trying to fight malaria in Africa, but it won’t fund DDT. The money goes for things like mosquito netting over beds (even though not everyone in Africa even has a bed). The office that dispenses those funds, the Agency for International Development, acknowledges DDT is safe, but it will not spent a penny on it.

Why? Fifty years ago, Americans sprayed tons of DDT everywhere. Farmers used it to repel bugs, and health officials to fight mosquitoes that carry malaria. Nobody worried much about chemicals then. People really did just sit there and eat in clouds of DDT. When the trucks came to spray, people often acted as if the ice cream truck had come. They were so happy to have mosquitoes repelled. Huge amounts of DDT were sprayed on food and people, who just breathed it in. Did they all get cancer and die? Nope.

Amazingly, there’s no evidence that all this spraying hurt people. It killed mosquitoes. (DDT also kills bedbugs, which are now making a comeback.) It did cause some harm, however. It threatened bird populations by thinning eggshells. In 1962, the book “Silent Spring” by Rachel Carson made the damage famous and helped create our fear of chemicals. The book raised some serious questions about the use of DDT, but the legitimate nature of those questions was lost in the media feeding frenzy that followed. DDT was a “Killer Chemical,” and the press was off on another fear campaign. DDT was banned.

But fear campaigns kill people, too. DDT is a great pesticide. The amount was the reason for the DDT problems. We sprayed far more than is needed to prevent the spread of malaria. It’s sprayed on walls, and one spraying will keep mosquitoes at bay for half a year. It’s a very efficient malaria fighter. But today, DDT is rarely used. America’s demonization of it caused others to shun it. And while the U.S. government spends tax money fighting malaria in Africa, it refuses to put that money into DDT. It might save lives, but it might offend environmentalist zealots and create political fallout.

DDT was banned in America after we started celebrating Earth Day. Environmentalists made a lot of claims then – I have an amusing clip of an environmentalist exclaiming, “You are breathing probably the last of the oxygen!” Soon after that the environmentalists mounted their campaign against DDT. The result? A huge resurgence of malaria, more than 50 million dead, mostly children.

“If it’s a chemical, it must be bad,” said scientist Amir Attaran. “If it’s DDT, it must be awful. And that’s fine if you’re a rich, white environmentalist. It’s not so fine if you’re a poor black kid who is about to lose his life from malaria.”

Attaran is leading a campaign of hundreds of scientists urging the use of DDT to combat malaria. It’s needed especially in Africa, he says, because malaria kills thousands there every day. “If I were to characterize what USAID does on malaria,” he said, “I’d call it medical malpractice, I would call it murderous.”

Mr. Stossel is co-anchor of ABC News’ “20/20” and the author of “Give Me a Break.”