The Incredible Shrinking Man is a 1957 science fiction film directed by Jack Arnold and adapted for the screen by Richard Matheson from his novel The Shrinking Man.
Robert Scott Carey (Grant Williams), is a businessman who is on vacation on a boat, off the California coast, with his 5 ft 8 in (1.73 m) wife Louise (Randy Stuart) when he suddenly is contaminated by a radioactive cloud.
At the time, Louise was below deck getting refreshments, so she wasn't affected.
Subsequently, Scott, who is 6 ft 1 in (1.85 m) tall and weighs 190 pounds, thinks little of the cloud and doesn't appear to have been affected by it.
However, one morning, six months later, he notices that his shirt seems too big. He blames it on the cleaners. His wedding ring falls off his finger. As this trend continues, he believes he is shrinking.
At first Louise dismisses his fears as silly, but he continues to lose weight and height. Noticeably, this is shown when he looks her, previously six inches shorter than him, in the eye.
He visits a prominent research laboratory, and after numerous tests, learns that exposure to the radioactive mist and some normal pesticides caused his cells to shrink.
http://en.wikipedia.org/wiki/The_Incredible_Shrinking_Man
THE INCREDIBLE SHRINKING MAN