The approach to finding alternatives to animals in scientific procedures is widely referred to as the three Rs: replacement, refinement and reduction.
Practically speaking, this means trying to avoid the use of living animals, minimising the number used, and reducing their suffering and distress during any experiments.
Before scientists in the UK can use animals for research, they are expected by grant bodies and licensing authorities to have considered the three Rs.
One tried-and-tested replacement is the LAL (limulus amoebocyte lysate) assay made from the blood of horseshoe crabs (pictured). This test can detect toxic compounds in drugs, products and devices, and it has replaced the need to use live rabbits since the 1970s.
Another route is cell culture. Animal and human cells grown in a lab can allow scientists to test for toxicity. Stem cells, which can turn into any cell in the body, are also promising.
Computer models are used to predict the effects of particular chemicals on the body. But, according to observers, while the models of the human body are getting ever more sophisticated, to be useful these programmes still need to be fed with data from "real experiments".
In December, last year, the European commission launched an initiative named AXLR8, to identify promising areas of research that could lead to a refinement, reduction or replacement of animals in research.
One of the goals of AXLR8 is to use "fewer, and one day potentially no, animals" in experiments.
"Current reliance on high-dose animal toxicity studies … is a source of uncertainty in human health risk assessment," says a notice on the AXLR8 website. "Conventional animal tests are, in general, quite time consuming, costly in both economic and animal welfare terms, and offer little mechanistic understanding of how chemicals act in the body."
The European commission hopes that recent advances in molecular and cellular biology, such as knowledge about the way genes work and how proteins are built, will prove a rich area for progress in the search for alternatives to animal experiments.
The AXLR8 mission statement adds that, "instead of focusing on signs of gross toxicity at high doses in living animals, an alternative, '21st century' approach advocated by leading scientific and regulatory authorities … is to work towards a mechanistic understanding of how chemicals interact with cellular response pathways in the human body at environmentally relevant exposure levels".
• This article was amended on 1 January 2011: The original main heading was replaced because its wording - 'Animals don't show how chemicals act in humans' – was not sufficiently accurate as a paraphrasing of the AXLR8 statement that "Conventional animal tests ... offer little mechanistic understanding of how chemicals act in the body."