Spliced Magic. Elemental Magic, #6

Sylphie Seaton's life is about to get turned upside-down when elemental law enforcement agents show up on her doorstep looking for her brother Josh. He's wanted for the murder of a colleague, but she's convinced there must be more to the story. When she finally hears from Josh, Sylphie discovers the situation is much worse than she feared. His coworkers were rogue elementals attempting to genetically engineer supernatural abilities, and Josh was accidentally contaminated.
Now, Sylphie not only has to protect her brother from the law, but also find a way to reverse the unstable serum before it kills him. On the run with no one to turn to, Sylphie will risk everything to save her brother. But the conspiracy may go deeper than either of them ever imagined, and not even an acclaimed storm chaser can outrun this tempest.