"EXPOSED," PLAN-B THEATRE COMPANY, Rose Wagner Center, through Nov. 4 (355-2787), running time: 90 minutes (no intermission)

Notes from an Atomic Energy Commission meeting on May 18, 1953, one day prior to a detonation at the Nevada Test Site: "Shouldn't we make a public announcement about the unusually high yield (fallout) of this device?" One official's reply: "That's not necessary. People in nearby communities probably won't notice."

That's just one of the many official government entries in local journalist-playwright Mary Dickson's spellbinding autobiographical docudrama, which had its world premiere last weekend.

In 31 scenes, the action shifts back and forth between 1950, when military leaders at the Pentagon were debating how to address Russia's newly acquired nuclear superiority, and as recently as 2007, when activists succeeded in halting plans for the Divine Strake underground atomic test.

"Exposed" looks at how innocent residents (whom the government considered nothing more than "a low-use segment of the population") became known as "downwinders," hundreds — more likely thousands — affected by fallout from above-ground and underground tests.

The downwinder segment of the population was considered to be mainly those living around St. George — in close proximity to the Nevada site. But Dickson's fact-based drama, which puts a compelling human face on the statistics, graphically indicates that the site's fallout over the past four decades stretches across the entire country and up into Canada.

"The clouds came and went, then the cancer came and the people went," says Preston Truman, a feisty old cowboy who used to watch the atomic blasts from his family's ranch near Enterprise.

Directed by Jerry Rapier, the six-member ensemble brings Dickson's story to life.

Joyce Cohen plays Dickson, beginning in 1985, when she was diagnosed with thyroid cancer at the age of 29, then follows her fact-finding journey as she probes the government cover-up. Teri Cowan plays Mary's younger sister, Ann Dickson DeBirk, who died in 2001 after a nine-year battle with lupus. Both women were among several in their close-knit Salt Lake City neighborhood who contracted various forms of cancer — all traced to the Nevada tests years earlier.

Cohen and Cowan are perfectly matched as sisters who share moments of trauma and humor.

Jason Tatom and Mark Fossen deliver commanding performances as two government officials, plus other roles. Fossen is especially good as an uptight, hand-wringing Howard Hughes.

Kirt Bateman and Teresa Sanderson carry a large portion of the drama in 15 roles — ranging from true-life characters (three of whom were in the audience on opening night) to some composites. (My one complaint is that a few additional, quick-change costume pieces might have made these roles easier to keep separate in the minds of audience members.)