The Camp Fire was the most destructive wildfire in California history. The fire began in early November 2018 and lasted three weeks. It spread uncontrollably from the forest into the town of Paradise and burned down the whole town.

Soon after, researcher Keith Bein made attempts to study the fire's toxic effects. Little is known about toxic chemicals released when a whole town burns.

Last fall, Bein drove around 160 kilometers from his laboratory at the University of California, Davis, to the town of Paradise. It was his second attempt to enter the area in hopes of studying the fire's effects. But police refused to let him to enter. Only emergency responders and news reporters were permitted.

Public safety agencies have not yet established rules that say whether scientists are permitted into the restricted areas.

Fires like the Camp Fire burn thousands of kilograms of wires, plastic pipes and building materials. They leave behind dangerous chemicals in the air, soil and water. Things like lead paint and burned asbestos add to the danger, public health experts say.

Bein's experience of being turned away points to the problems of studying the health effects of massive disasters like wildfires and hurricanes. Scientists agree that both are becoming more common because of climate change.

Irva Hertz-Picciotto is director of the Environmental Health Sciences Center at the University of California, Davis, or UC Davis.

She told the Reuters news agency, "Everything that we're doing, it feels like this is a question nobody has asked before. And we have no answers."

The UC Davis researchers are examining soil from neighborhoods that burned during the Tubbs Fire of 2017.

The Tubbs Fire did its greatest damage to the city of Santa Rosa in northern California. Hertz-Picciotto said the researchers will compare soil from that area to soil from nearby land where only trees burned.

In the study, researchers have already found nearly 2,000 more chemical compounds in the soil from more affected areas than in soil from a nearby park. They are now working to identify the compounds.

For many years, scientists have studied the effects of wildfires on air, soil and nearby environments. But fires that go from the forest into large city areas used to be very rare.

Collective research

As natural disasters increase in size and frequency, American public health researchers are quickly developing new study areas.

For example, researchers are studying the health of pregnant women who were exposed to polluted air and water after Hurricane Harvey hit Houston in 2017. They are also studying the health of Puerto Ricans who stayed in their damaged homes after Hurricane Maria struck the island in 2017. Many of the homes developed fungi and mold.

Some of the studies are being financed by the National Institute of Environmental Health Sciences, or NIEHS.

Aubrey Miller is the top medical adviser at NIEHS. She said it is important to quickly learn about health risks to populations after disasters happen. So NIEHS has tried to reduce its approval time for financing research.

Searching Paradise

On a recent morning, teams from the U.S. Environmental Protection Agency, or EPA, searched through Paradise. They put burned paint cans, partly melted pesticide containers and other objects onto trucks for removal.

Rusty Harris Bishop is a toxics expert with the EPA. He worked on the Paradise cleanup. Bishop said removal teams take away whatever contaminants they find. But such cleanup measures are changing along with the public health science, he said.

Bein now plans to train as a firefighter in order to gain entrance into burned areas following the next big wildfire. He said that, as these types of fires become more common, "we really need to know how this is going to affect health."

I'm Jonathan Evans. And I'm Alice Bryant.

Sharon Bernstein wrote this story for Reuters news agency. Alice Bryant adapted it for Learning English. Ashley Thompson was the editor.

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toxic - adj. containing poisonous substances; poisonous

lead - n. a heavy and soft metal that has a gray color

asbestos - n. a soft gray mineral that does not burn, that was used especially as a building material in the past, and that can cause serious diseases of the lungs when people breathe its dust

compound - n. a substance created when the atoms of two or more chemical elements join together

backyard - n. the general area near and around someone's home

pesticide - n. a chemical that is used to kill animals or insects that damage plants or crops

contaminant - n. something that makes a place or a substance such as water, air, or food no longer suitable for use