Snowflake, AZ / Marcus Sedgwick.

Enhanced descriptions from Syndetics:

Ash boards a Greyhound bus heading to the place where Bly was last seen: Snowflake, Arizona. Six thousand feet up in the wide red desert, Ash meets Mona, her dog, her goat, and her neighbors, and finds stepbrother Bly, too.

In their ramshackle homes, the walls lined with tinfoil, almost all the residents of Snowflake are sick. But this isn't any ordinary sickness: the chemicals and technologies of modern life are poisoning them. They call themselves canaries, living warning signs that humans have pushed the environment too far, except no one seems to be taking their warnings seriously. The healthy "normies" of Snowflake have written them off as a bunch of eccentrics, and when Ash too falls ill, the doctor's response is "It's all in your mind."

Snowflake, AZ contemplates illness and health--both our own and our planet's. As Ash lives through a cycle of illness and recovery and loss, the world beyond is succumbing to its own affliction: a breakdown of civilization only distantly perceived by Ash and the isolated residents of Snowflake, from which there may or may not be a chance for recovery. This provocative novel by one of our most admired storytellers explores the resilience of love and community in the face of crisis.