Doctor's index predicts heatstroke deaths among migrants walking through Arizona desert

An emergency room physician has devised a scientific index to predict the likelihood that illegal immigrants will die while walking through the Arizona desert during extreme heat conditions.

Dr. Samuel Keim concluded that the probability of death reaches 50 percent when temperatures climb to 104 degrees or higher.

"It's like a weather forecast," said the Rev. Robin Hoover, whose Humane Borders group maintains water stations at desert sites in southern Arizona and northern Mexico. "If he can forecast it to the U.S. Border Patrol, more of their agents can be scattered out looking for people in trouble."

Keim said he hopes to begin issuing daily forecasts by May, but he has not determined how to disseminate the information and with whom to share it.

"We're still negotiating that with various different entities," he said, declining to give specifics because of worries that the intense political debate surrounding illegal immigration could scare off potential participants.

Deaths of migrants on the Arizona-Mexico border have soared in recent years as tighter border security sends people to more remote desert areas. Some migrants cross 50 or more miles of desert before reaching a pickup point.

In July 2005, Border Patrol agents recovered 72 dead illegal immigrants in the agency's Tucson sector. Nearly all perished from heat exposure.

Ron Bellavia, commander of the Border Patrol's rescue operations in the Tucson area, said an index such as Keim's "would be an appropriate measure to probably reduce exposure or environmental injuries."

The forecasts could also be shared with groups near northern Mexican migrant-staging areas, where the warnings could be posted, Hoover said.

For years, the Border Patrol and the Mexican government have issued announcements about the desert's heat-related perils, but Keim said he does not know whether migrants read or heed them.

Keim matched heatstroke victims with dates of death and desert temperatures using data collected between 2002 and 2006 by the medical examiner's office in Pima County.

Keim, an associate professor at the University of Arizona and an emergency room physician in Tucson, said in recent years more than 100 adult male immigrants have died of heatstroke annually in Pima County.