That research showed the severity of health effects linked to exposure to dust from the towers, which included heavy metals, silica, wood dust, asbestos fibers and other contaminants. Ten percent of enrollees developed asthma within six years , and firefighters saw drops in lung function. A 2013 paper reported greater-than-expected rates of thyroid and prostate cancer among rescue and recovery workers; a paper published this March showed higher rates of pulmonary fibrosis.

What the World Trade Center data couldn’t reveal was whether that event was unique, or if other disasters might similarly spread toxins in a way that could lead to long-term effects. So in 2010 , the N.I.H.’s environmental health sciences institute began awarding research grants quickly after an event and made other changes to make it easier to gather human health data after a disaster.

The series of hurricanes and wildfires that began in 2017 led to a burst of those quick-response grants. Several of those researchers, including Dr. Kumar, agreed to discuss their initial findings with The New York Times in advance of the publication of their reports. The researchers said their work has shown health effects that they say have surprised them.

One of the grant recipients was Irva Hertz-Picciotto , an epidemiologist and director of the Environmental Health Sciences Center at the University of California, Davis . After the wildfires that struck Northern California in the fall of 2017, she used an online survey to get health information from thousands of people exposed to the smoke. She wanted to know whether they were still experiencing health effects, and how those effects changed over time.

“There’s been a conventional wisdom that when people have symptoms from fires, they are transient and there’s not persistence,” Dr. Hertz-Picciotto said. But her research showed that wasn’t the case for the California fires: Months after the initial exposure, about 15 percent of respondents who had never had asthma reported asthmalike symptoms.

“That’s not something that happens every day,” she said. “It does go against the grain of the current view of what those impacts are, and how long-term they can be.”

Dr. Hertz-Picciotto’s team also gathered ash from near homes that had burned, and found it contained almost 2,000 chemicals that weren’t present in ash gathered from undeveloped areas. She said she suspected exposure to those contaminants explained the high rate of respiratory symptoms months afterward.