Ever since I first encountered the term "hazmat" I've been fascinated by it, so it's not surprising that I eventually wanted to use it as a story title. I was still writing a fair amount of horror at the time, and it generally came pretty easily, so I started writing the story without an outline, just with the notion of a little girl coming in contact with the most hazardous material imaginable. I got to what I estimated was the midpoint of the story, and then realized I didn't know how to end it.
Oh, I could think of endings -- I came up with three possibilities -- but I didn't like any of them very much.
So I put it aside and did other stuff. I always remembered it was there, though.
Meanwhile, I was planning out short story collections. I had been writing a lot of short fiction, but it was scattered across dozens of markets, and I wanted it all collected. I'd grown up reading collections and anthologies, and wanted my own. Specifically, I wanted them roughly sorted by genre. I wanted all my alternate reality stories in a collection called Crosstime Traffic, and all my hard(ish) science fiction in a collection called Celestial Debris, and so on.
And the title I settled on for my horror stories began as Toxic Stories, but then, after I started writing "Hazmat," became Hazmat & Other Toxic Stories.
I had enough stories to fill such a volume; I just needed to finish the title story.
But I didn't have an ending. For years, decades, I didn't have an ending.
And then finally, in March of 2016, I was looking at the story file and I realized that maybe I didn't need a big, splashy, terror-unleashed-on-an-unsuspecting-world ending. Maybe a quiet little personal ending would do.
So I wrote that.
Now, ordinarily I might have tried to sell the story to a paying market, but I'd had my planned collection hanging fire, waiting for this story, for so long...
So I put the collection together, published it myself through Misenchanted Press in May of 2016, and it was finally done.
And that's why it's the only place the story has been published.
That's it; here's your list of handy exits: