A public health expert says his research shows out-of-towners travel to New York City with the specific aim of killing themselves — what researchers call "suicide tourism."

Public health expert David Vlahov reported Monday at the annual meeting of the American Public Health Association in Washington, D.C. that his research shows that one in 10 suicides committed in Manhattan since 1990 involved nonresidents.

Vlahov is the director of the Center for Urban Epidemiological Studies at the New York Academy of Medicine. He and his colleagues studied suicides in the city between 1990 and 2004 and found that 407 of 7,634 were committed by nonresidents.