Los Angeles once suffered some of the worst smog on Earth

From the 1940s through the 1960s, Los Angeles was blanketed by dense, eye-burning smog so severe that drivers sometimes couldn't see traffic lights. The issue led to the nation's first local air pollution controls and inspired the passage of the 1970 Clean Air Act.

Photochemical smog forms when sunlight reacts with car and industrial emissions

The hazy phenomenon's name is a combination of "smoke" and "fog" and is composed of chemical pollutants that can cause eye irritation, lung damage and harm to crops. Smog buildup is more common in cities with sunny climates, minimal wind and surrounding mountains that trap these chemicals.

How Los Angeles got its palm trees

Los Angeles is known for its warm weather and palm trees, but the latter haven't always been part of the landscape. As Hollywood's movie industry grew, so did the number of palm trees. As this article points out, most of the city's palm trees were planted in the 1930s through an unemployment relief program.

How scientists earned themselves a Nobel Prize by discovering what destroyed ozone

In 1974, chemists Mario Molina and F. Sherwood Rowland showed that chlorofluorocarbons—then used as aerosol propellants, refrigerants, and industrial solvents—rise into the stratosphere and, upon being struck by ultraviolet radiation, release chlorine atoms, which break apart ozone molecules. Their work earned them the Nobel Prize in chemistry in 1995.

In 1974, Los Angeles’s Community Analysis Bureau built a smart city

Los Angeles utilized aerial imaging and cluster analysis to gather and interpret civic data, leveraging surveillance technologies developed by the Department of Defense during the height of the Cold War. Instead of being used for military purposes, data insights helped direct social services to high-poverty neighborhoods.

The research pipelines being explored by the RIPE Project to improve photosynthesis

These include engineering plants with faster stomata, which would allow photosynthesis to resume more quickly amid fluctuations in available light due to clouds or shading from other plants, and resolving bottlenecks in the regeneration of RuBP, the molecule to which carbon dioxide is fixed during photosynthesis to initiate the Calvin cycle. (Some readers may experience a paywall.)

The Google Doodle honoring Jan Ingenhousz, who discovered oxygenic photosynthesis

Born in 1730, the Dutch scientist expanded on existing knowledge that plants produce and absorb gases in his 1779 paper, which detailed that light was necessary for the biochemical processes that produce oxygen in plant leaves. He also identified that all parts of plants produce carbon dioxide at night.

Hear firsthand how scientists and policymakers saved the ozone layer

In this episode, atmospheric chemist Susan Solomon and Protocol architect Stephen Andersen recount how scientific discovery, diplomacy, and public pressure drove the Montreal Protocol—and share lessons for tackling climate change.

Volatile chemical contamination can last in burn areas long after urban wildfires

Lead, arsenic, asbestos, and other chemicals have been found trapped in smoke-exposed rugs, couches, pillows, and other furniture that appeared otherwise undamaged from the 2025 LA wildfires. The gradual release of these substances has produced dangerous indoor air concentrations and contributed to increased emergency room visits and abnormal blood tests.

Why bacterial bioremediation may help counter the negative effects of past chemical solutions

Molecules such as DDT, a synthetic insecticide, and PFAS—"forever" chemicals used to make products resistant to heat, water, and grease—have historically been used across various industries but are now known to be harmful. Microbes that can convert some of these substances into nontoxic products, such as water and carbon dioxide, have already been identified, with ongoing research to find others.

A super-sniffer smelled her husband's Parkinson's disease years ahead of symptoms.

How MIT researchers have used genetic mutations to improve photosynthesis efficiency

Recognizing that RuBisCO—a protein that binds carbon dioxide to other compounds to produce the building blocks of organic molecules—often mistakenly binds oxygen, scientists performed directed evolution experiments to modify the geometry of a bacterial version of the protein to cause it to preferentially interact with carbon dioxide over oxygen.

The Clean Air Act became the cornerstone of modern air pollution control

Passed in 1970 and strengthened through multiple amendments, the Clean Air Act authorizes the EPA to set national air quality standards, regulate industrial and vehicle emissions, and reduce pollutants such as ozone, sulfur dioxide, and lead.

How LA brought water to its booming population

By the turn of the 20th century, Los Angeles had grown from a dusty, crime-ridden pueblo into a thriving metropolis. The only problem was that it was growing too fast. Here's the story of how the booming town created a massive water infrastructure to redirect area rivers to its residents.

Why the Antarctic climate enabled British scientists to discover the ozone hole

In the Antarctic stratosphere, polar conditions facilitate the formation of polar stratospheric clouds, which allow chlorine compounds from chlorofluorocarbons to accumulate. In 1985, British Antarctic Survey scientists detected massive springtime losses over Antarctica, as accumulated compounds destroyed significant amounts of ozone once sunlight returned.

Scientists determine the smells of objects in outer space

Using spectrographic techniques, scientists determine the chemical composition of planetary atmospheres, comets, and other objects in space. Combining these chemicals in labs on Earth has revealed locations in space that smell like nail polish remover, rotten fish, and urine.

Explore a real-time map of fine particle pollution from wildfires and other sources provided by the US Forest Service, which includes overlays for topography, street views, and satellite imagery.

Scientists can suck animal DNA from the air

A look at how researchers filtered the air around two zoos and identified genetic material from dozens of species, a technique that could help track and conserve wildlife.

Project STORMFURY explored modifying hurricanes with silver iodide

Between 1962 and 1983, researchers at the National Oceanic and Atmospheric Administration investigated whether weakening and controlling hurricanes was possible. The investigation showed very few hurricanes met the criteria for modification, despite successfully weakening two storms.

Exploring carbon compound pore structures contributed to improved gas mask filtration

During World War II, the British Coal Utilisation Research Association sought to improve the efficiency of coal as an energy source and studied the effectiveness of charcoal filters to keep soldiers safe. Rosalind Franklin's research there formed the basis of her PhD and led to five scientific papers.

A moldy cantaloupe supercharged penicillin production

In 1943, a moldy cantaloupe found at a market in Peoria, Illinois, yielded a strain that produced six times more penicillin. Though often credited to lab worker “Moldy Mary” Hunt, accounts differ on who actually brought in the fruit.

Read the academic article explaining how ancient smells can be dissected and recreated

This paper explores how biomolecular data on past scents can be teased out and then transformed into olfactory museum experiences, adding another component to our understanding of archaeology.

Discover the chemistry behind smoking foods, including the types of smoking and the source of smoking flavors and colors.

Revelations that apples were sprayed with the chemical Alar led to its ban in the 1980s

Almost three decades after Rachel Carson’s “Silent Spring,” a “60 Minutes” segment on the use of Alar, a chemical sprayed on apples, drew national attention and inspired supermarkets and schools to remove apples from their shelves and cafeterias. That same year, the Environmental Protection Agency took action against the use of the chemical in food.

How artificial photosynthesis can help make plastics and fuels using sunlight

These systems link a molecular light absorber to a catalyst that can synthesize fuels—such as ethanol—and ethylene, a precursor to plastics, in a carbon-neutral manner. Because these byproducts have greater energy concentrations than the carbohydrates produced by photosynthetic organisms, research is ongoing to engineer the necessary catalysts.

Explore this real-time global air quality map with data reported from more than 10,000 stations around the world.

Learn about historical uses of bioremediation, the oldest cleanup method on Earth

Biochemical reactions that decompose complex molecules into simpler ones have occurred on Earth for as long as life has existed and have gradually transformed the planet into a celestial body that is increasingly habitable to greater biodiversity. Along the way, modern, human-made bioremediation techniques began to take shape in Santa Maria, California, in the 1960s.

Scientists testing how climate change affected plants found in a yearslong simulation study that poison ivy grew 70% faster than it did without extra carbon dioxide.

Microforests in urban environments may help combat climate change

Areas of densely packed native trees and drought-tolerant plants within cities can pull carbon dioxide from the air, cool surrounding neighborhoods, and support local wildlife. The idea behind microforests traces back over 50 years to Japanese ecologist Dr. Akira Miyawaki, who promoted planting whole ecosystems to restore degraded land.

The history of Earth's breathable atmosphere, made possible by photosynthetic bacteria

Between 3.2 billion and 2.8 billion years ago, threadlike microorganisms called cyanobacteria began consuming available water vapor, carbon dioxide, and sunlight to produce oxygen. However, molecules released from Earth's interior by volcanoes consumed this oxygen via chemical reactions, preventing it from accumulating until volcanism had sufficiently decreased about 2.4 billion years ago.

The Montreal Protocol helped prevent significant quantities of greenhouse gas emissions

By phasing out ozone-depleting chemicals between 1990 and 2010, the Montreal Protocol prevented emissions equal to 135 gigatons of CO₂—avoiding an estimated 0.5 to 1 degrees Celsius of additional global warming by 2100.

Carboxylic acids are one reason teens are smelly

Scientists compared the smells of babies and teenagers and identified some of the compounds that make teens smelly. Carboxylic acids present in teens, they wrote, seemed to give off an "earthy, musty, or cheesy" scent. This 2024 research could help inform future odor-control products.

The food industry's hard-to-solve pollution

One-quarter of the world's greenhouse gas emissions result from food and agriculture. That whopping number includes production and post-farm processes like distribution. See a visualization of the data along with a breakdown explaining how each process contributes to emissions, and why it’s so difficult to improve the agriculture industry.

Listen to how the 1902 'poison squad' experiments changed food safety in America

As part of government research, a group of young men were paid to eat standard American food—replete with food additives like borax and formaldehyde—which revealed the dangers of unregulated food. The work was led by the first FDA commissioner, Harvey Wiley, who helped end the "century of the great stomachache."

How sunlight helps chlorofluorocarbons destroy the ozone molecules that block solar radiation

CFCs, which are used in old refrigerants, air conditioners, and aerosol sprays, do not react with atmospheric molecules. Once they reach the stratosphere, ultraviolet radiation breaks chlorine atoms off of them, which can each break apart more than 100,000 ozone molecules, thinning Earth's protective layer against ultraviolet radiation.

Go inside the global effort that led to the Montreal Protocol in this narrative podcast

Nobel laureate Mario Molina and other key voices recount how science and diplomacy converged to develop a plan to close the ozone hole, offering insight into history's most successful environmental treaty.

Browse a list of the most important scientific breakthroughs from each state

Although scientific discoveries involve experimentation, analysis, and collaborations among many individuals across a variety of locations, some observations, advancements, and breakthroughs have their origins in facilities within the US. These include the polio vaccine in Pennsylvania, the breathalyzer in Indiana, the observation of Pluto in Arizona, and the invention of nylon and Teflon in Delaware. (Some readers may experience a paywall.)

Watch a 1986 television special about the discovery of the ozone hole

The groundbreaking discovery of the Antarctic ozone hole in the mid-1980s marked a critical turning point, galvanizing international action to address the ozone-depleting properties of chlorofluorocarbons, which had been identified about a decade earlier. This environmental crisis was brought vividly to public attention through media pieces like this one.

Instead of consuming water and carbon dioxide to produce oxygen and sugar, anoxygenic photosynthesis involves alternative reactants and products.