Images of black rain pelting one of the world’s oldest civilizations, after the United States and Israel bombed Iran’s oil depots this week, are tough to unsee. Many news outlets are calling it “acid rain”—a term that may understate the problem, since the smog caused by this bombing is likely even more toxic than typical air pollution. While there’s stiff competition for the most horrifying headline out of this war so far (given the disregard for civilian lives and the complete lack of an endgame), this one feels particularly surreal—a nightmarish blast from the past.
Acid rain is not a phrase we have heard much in recent years. That’s because it is a problem that was largely solved during the first Bush administration. The phrase was probably first coined in the nineteenth century by a chemist named Robert Angus Smith, to describe the polluted rain in Manchester, England—a place whose industrial pollution was hauntingly described by Elizabeth Gaskell in her novel North and South, as well as by Friedrich Engels in The Condition of the Working Class in England—but it was not taken seriously by North American scientists, or popularized in the United States, until the 1960s, when ecologist Gene Likens discovered that air pollution caused by fossil fuels, when transmitted by rain into ecosystems, was devastating animal and plant life. At that point, acid rain became a target of serious campaigning, argument, and, of course, denial—much like climate change is today. When I was a child in the 1970s and ’80s, acid rain was one of the leading environmental problems in public discourse.
The Reagan administration, whose environmental policy was helmed by James Watt, a millenarian Christian who opposed most environmental regulation because Jesus was just about to come back anyway, did not care about acid rain. But when Reagan’s vice president, George H.W. Bush, ran for president in 1988, he needed a swing issue to appeal to voters who were tired of right-wing Reaganism, one that would be authentic to him as an older-style Republican who enjoyed the outdoors. So he promised to address acid rain.
Amazingly enough, he kept that promise, fighting congresspeople in his own party to do so, ultimately enacting the Clean Air Act Amendments of 1990. Those reforms set up a “cap and trade” system for acid rain. The system worked far better than expected, achieving far more reduction in acid rain at lower cost than anticipated, by dramatically reducing power plant pollution.
Acid rain is an underrated triumph of regulation. It’s part of how we know we can solve the climate crisis and many other problems associated with fossil fuel pollution. Now, however, it’s also a lesson in how important it is to defend such gains: The images from Iran show that one bad policy decision can literally bring back life-threatening pollution overnight. Iranians have been advised to stay indoors, as the black rain can have serious health effects, including chemical burns and lung damage.
Toxic, black rain adds another layer—literally—of horror to what Iranians are enduring. But although it won’t be as immediate or as extreme, acid rain could be coming for us too. Trump’s domestic policies may bring this old problem back to the U.S.
Last year, Likens—the scientist whose discoveries made so much difference in the fight against acid rain in the last century—told The Guardian that Trump’s current assault on clear air and clean water regulations could pitch the U.S. back into a new era of acid rain. Now 91, Likens was in meetings all day as I wrote this column and therefore could not comment (understandably, the man is in demand). In the 2025 Guardian interview, he called acid rain a “major environmental success story” and warned that if Trump relaxed controls on emissions, “we are going to destroy that success story.”
This won’t happen here overnight, and one mitigating factor is that there are so many fewer coal plants than there were in the acid rain days (something that Trump would also love to change, of course). But there are other sources—and therefore, other urgent causes for worry. In February, Trump’s Environmental Protection Agency specifically weakened restrictions on sulphur dioxide emissions from gas-burning power plants. Sulphur dioxide (as acknowledged by the EPA’s own website) was one of the leading causes of acid rain.
We tend to dissociate from images like those of the black rain in Iran, feeling awful about them but also confident they won’t affect us. But Trump is a worldwide problem, and at the same time as his regime is committing potential war crimes in Iran, it is also destroying our own society and ecosystems in ways that will take years to repair. Acid rain is a problem no one ever wanted. Leave it to Trump—a creature fundamentally of the reactionary 1980s—to bring back one of the most unpleasant and deadly features of that decade, undoing progress led by a member of his own political party.