10 Problems the World Quietly Solved, Like the Ozone Hole Scientists Expect to Heal by 2066

Lead was first added to gasoline in the early 1920s to make engines run better, and for decades it went into almost every tank in the world. Most high-income countries had banned it by the 1980s, but in the early 2000s, 86 countries still used it.

In July 2021, Algeria, the last country still selling leaded gas for cars and trucks, ran out of its last supplies. The UN Environment Programme announced that leaded gas was gone from every country in the world, and the UN Secretary-General called it “an international success story.”

In the 1980s, scientists found a hole in the ozone layer over Antarctica, opened by chemicals such as CFCs from spray cans, refrigerators and air conditioners. In 1987, countries agreed in the Montreal Protocol to phase them out.

A UN-backed assessment presented in January 2023 found that nearly 99% of the banned substances had been phased out. If current policies stay in place, the ozone layer should return to its 1980 levels by about 2040 over most of the world, 2045 over the Arctic and 2066 over Antarctica. The next full assessment is due at the end of 2026.

Acid rain forms when sulfur dioxide and nitrogen oxides from smokestacks mix with water in the air, and in the 1980s it was blamed for damaged forests and lakes. In 1990, the U.S. set up the Acid Rain Program to cut those emissions from power plants.

The EPA says annual sulfur dioxide emissions from power plants have fallen by more than 95% and nitrogen oxides by more than 89%. Wet sulfate deposition, the standard measure of acid rain, dropped by more than 70% between 1989–1991 and 2020–2022, and the number of monitored lakes and streams getting more acid than they can handle improved by 81%.

London had a cold winter in 1952, and homes burned huge amounts of coal to keep warm. From Friday, Dec. 5, to Tuesday, Dec. 9, still air trapped the smoke over the city. Visibility dropped to a few meters, and in the Isle of Dogs, people could not see their own feet.

Laws followed, including the Clean Air Acts of 1956 and 1968, which banned black smoke and moved homes and factories to smokeless fuels. The Met Office says nothing on the scale of the 1952 Great Smog has ever happened again.

The EPA tracks six common air pollutants, from carbon monoxide to fine particles and lead. Between 1970 and 2025, total emissions of the six dropped by 78%.

Over the same years, the U.S. economy grew 349%, Americans drove 197% more miles, energy use rose 46% and the population grew 67%. In other words, the air got cleaner while the country got bigger, busier and richer.

Big ships burn heavy fuel oil, and for years it could contain up to 3.5% sulfur. When it burns, the sulfur turns into sulfur oxides, which can lead to acid rain.

On Jan. 1, 2020, a new global limit came into force: ships outside special emission control areas may use fuel with no more than 0.50% sulfur, and inside those areas, only 0.10%. The International Maritime Organization forecast that the rule would cut sulfur oxide emissions from ships by 77%, about 8.5 million metric tons.

In 2025, about 5 billion passengers flew, and 24 million bags were mishandled. That sounds like a lot, but the rate keeps falling.

The 2026 Baggage IT Insights report from the aviation IT company SITA says the mishandled-bag rate dropped 23% in 2025 alone, the biggest improvement outside the pandemic years, and has fallen by close to three-quarters since 2007. The report credits real-time data sharing, AI routing, biometric bag drop and connected passenger devices.

For centuries, rinderpest swept through cattle herds in Europe, Asia and Africa, and the World Organisation for Animal Health calls it the deadliest cattle disease in history. The last case was found in 2001.

In May 2011, the organization declared rinderpest eradicated in all 198 countries with animals that could catch it, and the UN’s food agency followed in June. It was only the second disease ever wiped out, after smallpox, and the first one that affected animals.

On Jan. 30, 2025, the World Health Organization confirmed that Niger had stopped the spread of onchocerciasis, better known as river blindness. It is the first country in Africa and the fifth in the world to do it, after Colombia, Ecuador, Mexico and Guatemala.

It wasn’t Niger’s first win: the country had already eliminated Guinea worm disease in 2013. Worldwide, WHO says 54 countries have now eliminated at least one neglected tropical disease.

When the eradication campaign began in 1986, Guinea worm disease affected an estimated 3.5 million people a year in 21 countries in Africa and Asia. In 2025, only 10 human cases were reported, a drop of more than 99.99%.

There is no medicine or vaccine for it. The campaign has relied on people filtering their drinking water through cloth, on health workers teaching villages how the parasite spreads, and on treating ponds with a safe larvicide. The work goes on in six African countries: Angola, Cameroon, Chad, Ethiopia, Mali and South Sudan.