In the blood business, Labor Day is the last hurdle of the donor-dry summer. Soon, college and corporate blood drives will get underway to replenish reserves. All that’s needed is to get through the holiday weekend with no chain-reaction freeway crashes or major train wrecks.

But a dwindling pool of donors nationwide could turn today’s seasonal shortages into a year-round drought, blood experts say. And Southern California would be hit especially hard. On average, just 5% of U.S. adults donate blood; here, it’s fewer than 3%.

The American Red Cross Blood Services of Southern California needs 1,500 units of blood every day to supply more than 150 hospitals in Los Angeles, Orange, San Diego and Ventura counties.

Already it must import 40% of that from the Midwest and rural areas in other parts of the country. An earthquake or bridge collapse could easily triple the organization’s needs.

“The general public presumes that nobody’s going to bleed to death because there’s not enough blood,” said Dr. Jeffrey McCullough, a professor of laboratory medicine at the University of Minnesota and an expert on the nation’s blood supply.

But getting donors, he said, “is more and more difficult, and the reforms make it more and more expensive.” An average adult has about 10 pints of blood, and a major trauma victim can need up to 100.

Generally, the public’s concern is blood safety, not supply. That’s been the case since the 1980s, when HIV-tainted blood infected more than 12,000 patients nationwide through transfusions.

Today a battery of tests screen blood for HIV, hepatitis, West Nile virus and other pathogens. A series of questions excludes donors who have visited countries with malaria or mad cow disease.

Temporary restrictions on everything from travel to tattoos often end up deterring donors permanently. A study by McCullough in the July issue of the journal Transfusion concluded that 37% of the U.S. population is now eligible to give blood, down from an estimated 60% in the 1990s.

“The blood supply is extraordinarily safe,” said Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania and a former member of a federal advisory committee on blood safety. “But you have to remember that having blood available is part of safety, too, particularly if you have some kind of disaster and you need a lot.”

The blood-bank system that people take for granted began during World War II as a way for citizens to help wounded soldiers on the front lines. Dr. Charles R. Drew – for whom the medical school south of Watts was named – discovered how to preserve and store blood and organized the first blood drive. Neither subsequent generations nor immigrants have embraced the donor habit as enthusiastically as the war generation.

“We don’t have a blood supply problem, we have a blood donor problem,” said Teresa Solorio, spokeswoman for American Red Cross Blood Services of Southern California. “It’s easier to get people to donate money than to donate blood.”

Meanwhile, even with the development of blood-conserving surgeries, the need for blood has risen because of medical advances and an aging population that needs hip replacements, heart surgery, cancer treatment and kidney transplants.

“As the baby boomers are getting older, they’re going to be needing more medical procedures,” said Dr. Ross M. Herron, the regional Red Cross center’s chief medical director. “And it’s going to fall to the Gen Xers and the millennial generation, just like Medicare and Social Security and everything else.”

Type O blood

Blood shortages occur in pockets across the nation, especially in Los Angeles, New York and other large metropolitan areas, which tend to be faster-paced and have less of a sense of community than parts of the Midwest and South, blood experts say. But natural disasters, for example the recent floods in Oklahoma, can mean less blood from states that usually have enough to export.

Recruiting new donors is even more urgent in Southern California because of its Latino population, whose blood type doesn’t always match that of Mid- western imports or even local donors.

Blood type, like eye color, is inherited. About 45% of whites have type O blood; an estimated 65% of Latinos have it. People with type O blood can receive only type O, and demand is growing as the Latino population grows.

Adding to the demand is the key role type O blood plays in emergencies: It alone can be transfused into patients with any of the four basic blood types – A, B, AB or O – without causing serious, even fatal, complications. This universality makes it crucial to have a supply for trauma patients who could bleed to death in the 20 minutes it takes to test and match blood.

A majority of blood donors in Southern California – 57% – are non-Latino whites, according to Red Cross figures; 23% are Latino.

The local Red Cross is targeting Latinos in an effort to “make our donor population match our patient population,” Herron said.

But because blood donors must present photo identification, potential donors who are in the United States illegally often fear detection, said Dr. Alexander J. Indrikovs, an associate professor of pathology at the University of Texas Medical Branch in Galveston.

Other barriers to increasing blood donations among Latinos are cultural.

“Many of us come to the U.S. with a culture that is not a culture of donating blood,” said Indrikovs, who is originally from the Dominican Republic. “We see it as necessary only when a family member needs blood.”

Until that changes, Indrikovs said, “we are going to be seeing increasing shortages.”

Family donations used to be more of a tradition in the United States when hospitals charged a “replacement fee” for transfused blood and families and friends of patients could pay it off by giving blood. Changing insurance and billing practices did away with that fee.

Today, the two nonprofit groups that supply most of the nation’s blood – the American Red Cross and America’s Blood Centers – rely heavily on college and corporate blood drives and on regular donors who give more than once a year. Families that host blood drives tend to do so because their personal experience has shown them how vital it is to have blood available when it’s needed.

But in Mexico and many other Latin American countries, Indrikovs said, it is far more common to sell blood than to donate it. In the United States, only plasma, the fluid part of blood, can be sold, and it is used in making some blood products. By law, only donated blood can be used in transfusions. Health officials believe that payment can motivate people to lie on questionnaires meant to screen out drug use and other health risks.

The donation rate in many Latin American countries, Indrikovs said, is less than 1%.

Changes urged

The Bioethics Center’s Caplan argues that blood banks nationwide need to streamline questionnaires, especially for repeat donors, keep longer hours and make the process more inviting for all donors.

“We haven’t made blood donation as painless, as simple and as rewarding as it should be,” he said.

For now, blood banks and hospitals juggle supplies and pray they get through holidays. So far, no hospital has run out of blood. But nationwide, 135 hospitals reported canceling elective surgeries on one or more days because of blood shortages in 2004, the most recent year for which statistics are available. That year, just 4.5% more blood was available for transfusions than was used, the smallest margin ever measured.

Blood suppliers aim to have a three- to five-day supply on hand to distribute to hospitals in case of emergencies. As of Friday, American Red Cross Blood Services of Southern California was down to about a 6-hour supply, or 217 units of O positive blood and 35 units of O negative, the most versatile of all.