A WILLING buyer in a market with plenty of willing sellers, Barzin Bahardoust is finding life surprisingly hard. For years he has been trying to pay Canadians for their blood plasma—the viscous straw-coloured liquid in blood that has remarkable therapeutic powers. When his firm, Canadian Plasma Resources (CPR), tried to open clinics in Ontario in 2014, a campaign by local activists led to a ban by the provincial government on paid plasma collection. Undeterred, he tried another province, Alberta—which also banned the practice last year. Then, on April 26th, when CPR announced a planned centre in British Columbia, its government said it too was considering similar legislation. CPR has managed to open two centres, in far-flung Saskatchewan and New Brunswick. Even these have faced opposition.

The global demand for plasma is growing, and cannot be met through altruistic donations alone. Global plasma exports were worth $126bn in 2016—more than exports of aeroplanes. But paid plasma raises ethical, social and medical concerns: that it will lead to health catastrophes, as in the 1980s when tainted blood spread HIV and hepatitis; that it exploits the poor; and that it reduces the supply of “whole” blood, which is almost all donated voluntarily.

None of these worries is well-founded. But Canadian reservations about paid plasma are shared across most of the world. America, China, parts of Canada and some European countries are among the few places that permit it. Those countries are extremely effective in securing supplies: three-quarters are collected in America alone, and another 10% in China, Germany, Hungary and Austria, where payment is also allowed. Of over 1,000 plasma-collection centres worldwide, 700 are in America (see article). Jan Bult, head of a trade association representing companies that manufacture more than half of the world’s plasma products, says none collects plasma in countries that have banned compensation.

Only countries that pay for plasma are self-sufficient in it. (Italy, where donors are given time off work, is close to self-sufficiency.) Half of America’s plasma is shipped to Europe—20m contributions-worth. Canada imports 80% of its plasma products from America. Australia imports 40% of its plasma products, too.

Drug firms from countries that have banned pay-for-plasma do much of their collection in America. Three of the largest collection companies are European: Grifols of Spain, Shire of Ireland and Octapharma of Switzerland. The parent company of another big collector, CSL Behring, is Australian. Together these four firms run nearly eight out of ten plasma-collection centres. Some of their manufacturing capacity is in America, but much is located elsewhere. Switzerland, which collects very little plasma, exported $26bn-worth of plasma products in 2016.

Exported plasma is used to manufacture pharmaceuticals and is distinct from the plasma that, with red and white blood-cells and platelets, is used for transfusion. That saves lives when blood is lost, say, in traumatic accidents or surgery. But whole blood is rarely traded across borders, and very rarely involves payment. The World Health Organisation’s safety guidelines recommend voluntary donations.

Happily, demand for transfusions is declining. Blood-bank management and modern medicine have both grown more efficient. Kevin Wallis, who has managed blood stocks at a holding-centre in south London for nearly 20 years, says that hospitals once used three units of blood for a hip operation, but these days often use none. Despite population growth, the number of red blood-cell units used by hospitals in England has dropped from 2m a year 15 years ago to 1.4m now.

Pharmaceutical plasma is different. It is heat-treated or bathed in chemicals to sterilise it, reducing associated risks. It has all manner of uses. If blood fails to clot properly, as in haemophiliacs, a plasma product helps. A plasma product can restore an immune system weakened, for example, by chemotherapy. A complication known as Rhesus disease, in which the blood type of a fetus is incompatible with the mother’s was responsible for 10% of stillbirths in America as recently as the 1960s. These days plasma products can save the child.

Historically, these products were derived from plasma collected when volunteers donated whole blood. But demand has outpaced donation. So the proportion of plasma products derived from whole blood has declined from 40% in 1990 to 13% in 2015. Plasma today is mostly collected via apheresis, a process where whole blood is extracted, spun in a centrifuge, and the plasma is skimmed off. Red blood-cells are then mixed with an anticoagulant and transfused back into the donor. Blood-donation can take just 10-15 minutes. Apheresis usually takes at least an hour.

Plasma replenishes more quickly than red blood-cells. So donors can give more at one session, and far more frequently. In most countries whole-blood donors can give around 500ml of blood, which yields just 250ml of plasma, at most once every two months. Plasma donors can give up to 800ml of plasma—and in America are allowed to do so twice a week. This quickly adds up. In a year a plasma donor could give over 80 litres of the stuff, compared with just 1.6 litres from a whole-blood donor. Mr Bult says paid repeat donors, who have been intensively screened, help keep plasma products safe.

But a stigma about paying for blood lingers. Sue Lederer, of the University of Wisconsin, dates it to 1970, when Richard Titmuss published “The Gift Relationship”, a book suggesting paid blood was both ethically wrong and less effective than a voluntary system. Often American donors would be compensated not in cash but in chits redeemable at nearby liquor stores, an insalubrious practice nicknamed “ooze for booze”. Prisoners could also trade plasma for days off their sentences.

Then, in the 1980s, half of the world’s tens of thousands of haemophiliacs were infected with HIV or hepatitis by contaminated plasma products. Thousands died from AIDS-related illnesses. Many argued that paying for blood had encouraged donors to lie about dangerous behaviour, such as risky sex or drug use. Official inquiries took place in Canada and Ireland. In France and Japan, health officials and businessmen were jailed. In America, pharmaceutical companies settled class-action lawsuits. The scandal has cast a long shadow. The British government announced an independent inquiry last November.

It remains legal to pay for whole-blood donation in America today. But hospitals refuse to accept it. Today’s plasma, however, is safe from the contamination risks of the past. Modern screening and sanitisation are extremely effective. Graham Sher, chief executive of Canadian Blood Services, a non-profit, says plasma products from paid donors are “as safe as those from our unpaid donors”.

Other prejudices against pay-for-plasma are equally deep-seated. Some data, for example, lend weight to the suspicion that it preys on the poor. American plasma centres are concentrated in less well-off bits of the country. Typically they are in postal districts where 27.4% of the population are poor, according to The Economist’s analysis of census data. This is much higher than the average American poverty rate of 16.5%.

The other worry, shared by Dr Sher, is that paying for plasma may lead to a reduction in whole-blood donation. But, if that were true, the problem would be intensifying, as pay-for-plasma centres have nearly doubled worldwide in the past five years. But Peter Jaworski, of Georgetown University, is sceptical, suggesting that, anecdotes aside, the evidence shows paid plasma donation “does not crowd out voluntary blood-donation”. Americans, for example, continue to donate as much voluntary blood per head as do Canadians.

The aversion to paid-for plasma carries its own risks. According to Grifols, the geographic imbalance puts supplies of plasma products at risk. At the plasma industry’s main annual conference, held this year in Budapest in March, over-reliance on imports from America was a hot topic. Representatives from several countries (including Canada) recognised they must do more to diversify their supplies. Making it legal to pay for plasma is an obvious first step.