The effect is most pronounced in counties with many drinking water wells, indicating that contamination by "produced water" from fracking is a likely cause.
On May 1, workers have a chance to confront Trump by turning the tricks of his trade back on him -- dealing in the language of power.
Dave Gilson is a senior editor at Mother Jones. Read more of his stories, follow him on Twitter, or contact him at dgilson (at) motherjones (dot) com. Get Dave Gilson's RSS feed.