Okay, so downwinders are people who live in an area that is downwind from something bad, like a nuclear explosion or a toxic chemical plant. When something like that happens, the wind can carry harmful particles and gases toward the downwinders, and they can breathe them in or get them on their skin. This can make them very sick, and sometimes it can even cause cancer or other long-term health problems.
One example of downwinders are the people who lived near the Nevada Test Site where the U.S. government tested nuclear bombs in the 1950s and 1960s. The wind carried radioactive particles toward nearby towns, and many people who lived there got sick. Even today, some people are still dealing with health problems from those tests.
Overall, being a downwinder is not a good thing, and it's important to make sure that people are aware of the risks and have ways to protect themselves if something bad happens downwind from them.