Walking up Rainnie Drive in Halifax yesterday one could see the words: “One more block to save three lives” written in chalk on the ground.

A few steps later it read: “Except for gay, all blood types are needed.”

The duelling messages marked National Blood Donor Day and the beginning of National Blood Donor Week. But while Canadian Blood Services is trying to drum up interest in giving blood, a student group is railing against what it calls an outdated, discriminatory policy.

The Canadian Federation of Students is calling for an end to the blood services rule of refusing blood from homosexual men due to heightened risk of HIV/AIDS.

“The policy is based on stereotypes about the gay community that do not protect the Canadian blood supply,” said Nova Scotia CFS chair Elise Graham.

The CFS says it is unfair the policy does not take into consideration if the donors practise safe sex or are in a long-term monogamous relationship.

Blood services spokes­man Paul Doucet said he welcomes the discussion. However, he insists the policy is “based on science, not discrimination.

“There is a period between acquisition of the virus and the time it shows up in the test,” Doucet said.

“We test every unit, but there still is that measure of uncertainty between the time when the virus is acquired and the time when the test can pick it up. So that uncertainty leaves risk. Our position is that risk is not acceptable.”

Doucet said there are “hundreds of reasons” why people are blocked from donating blood, from intravenous drug use to visiting the United Kingdom during a certain time frame. He said only about 50 per cent of the population is even eligible to donate.

“It’s a policy that’s designed to protect the extraordinarily vulnerable hospital patients,” Doucet said.