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Saturday, October 22, 2011

A Treaty on Mercury?

Maria Cheng writes at Business Week:

Scientists are warning officials negotiating a global treaty on mercury that banning the deadly chemical completely would be dangerous for public health because of the chemical's use in vaccines.

The ban option is one of several proposals on the table for a meeting later this month in Nairobi, but a final treaty isn't expected until 2013.


The problem is that a proposed ban might include thiomersal [US spelling is thimerosal -- ed.], a mercury compound used to prevent contamination and extend the shelf life of vaccines, many scientists say. It is used in about 300 million shots worldwide, against diseases including flu, tetanus, hepatitis B, diptheria and meningitis.

"Not being able to use mercury is not a viable option," said David Wood, a WHO vaccines expert.

Wood said there isn't a viable alternative to thiomersal at the moment. If banned, pharmaceuticals would likely have to switch to preservative-free vaccines, which would complicate the supply chain and vaccination campaigns in poor countries, since the injections would have a much shorter shelf life. Costs would also spike since manufacturers would need to reconfigure their factories.

In 2009, the United Nations Environment Programme, or UNEP, began working on a legally binding global treaty on mercury. At the end of October, the third of five meetings to hammer out a treaty will take place in Nairobi.

"The document is a draft at the moment, so some of these proposals have to be taken with a grain of salt," said Tim Kasten, head of the chemicals branch at UNEP. Kasten said the amount of mercury in vaccines is so minute it doesn't threaten the environment. He said there could be provisions to allow mercury for certain uses, such as in dental fillings and vaccines.

But according to an annex in the draft document, there is currently no "allowable use exemption" for mercury products in pharmaceutical products, putting vaccines in the same category as banned mercury-containing paints and pesticides.

"That would be a terrible idea," said Paul Offit, an infectious diseases expert at the University of Pennsylvania. "It would be another tragic example of us not being able to explain to the public where the real risk lies."

Helen Branswell writes at The Canadian Press:
In some developed countries — Canada, the United States, the countries of Western Europe — thimerosal is no longer used in most pediatric vaccines. That shift was a response to concerns — since discounted — that with the high number of vaccines young children get, the cumulated exposure to thimerosal might pose a health risk.

Anti-vaccine activists also blamed thimerosal in childhood vaccines for rising levels of autism. But a Canadian study actually showed autism rates did not decline after thimerosal was removed from the vaccine formulations.

Canada has filed a position paper on the issue with the UNEP. While it says thimerosal will be phased out of vaccines used in Canada when safe alternatives are available, it believes there is no "legitimate safety reason to avoid the use of thimerosal-containing products for children or older individuals, including pregnant women."

The real impact of barring thimerosal use in vaccines would be felt in the developing world, the WHO and others said.

"The challenge in the rest of the world is that switching to single dose vaccines is going to make the logistics of vaccine delivery much more difficult," said Dr. Allison McGeer, an infectious diseases expert at Toronto's Mount Sinai Hospital.

"Most vaccines we have require a cold chain, so you have to keep them cold. That is already difficult to do in many countries. It's even more difficult to do if you increase the volume of the things you have to keep cold."