A growing number of scientifically validated alternatives are being used in place of animals in biomedical research and product safety testing, and have significantly reduced animal use in many areas. In the 2025 Massachusetts legislative session, lawmakers will consider bills that would further this expansion of using alternatives when available, as well as legislation to prohibit the sale of cosmetics newly tested on animals.
Before new methods are cleared for use, they first undergo rigorous evaluation by government agencies. Scientists in industry, academia, and federal laboratories develop and refine alternatives, which are then assessed by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM). ICCVAM’s recommendations guide U.S. agencies in updating their regulations, while in Europe, the European Centre for the Validation of Alternative Methods (ECVAM) plays a similar role.
The guiding principles behind these efforts are known as the “Three Rs”: Replacement, Reduction, and Refinement. Introduced in the 1950s by British biologists William Russell and Rex Burch, these concepts are central to ethical progress in laboratory animal use. “Replacement” refers to the use of non-animal systems, such as cell cultures, computer simulations, and synthetic models, in place of live animals. “Reduction” involves minimizing the number of animals used in experiments by improving study design. “Refinement” focuses on alleviating pain and distress and enhancing the quality of animals’ lives through better handling, housing, and medical care.
Animals are used in laboratories for many purposes, from testing the safety of consumer products to serving as models in biomedical research and education. Each year, tens of millions of animals are used worldwide to assess the risks of cosmetics, drugs, cleaning products, pesticides, industrial chemicals, and more. They are also used to train students in biology, anatomy, and surgery. While opinions vary on whether continued use of animals is necessary, most agree that when scientifically valid alternatives exist, they should be used.
Some believe that animals suffer needlessly, especially when animal tests fail to accurately predict human responses. Others argue that no alternative can fully replicate a living organism and that public health could be at risk without animal testing. The MSPCA believes that the truth lies between these extremes and that investing in alternatives offers common ground for scientists and animal advocates to work together toward more humane, effective methods.
A variety of replacement strategies are now in use. In vitro (test-tube) procedures are widely used in cancer research, reducing the need for animals while saving time and money. Veterinary schools are replacing live animals in surgical training with synthetic models like SynDaver’s lifelike canine simulator, which has features designed to replicate anatomy and physiological responses. In 2017, the U.S. Coast Guard adopted human simulators for combat trauma training, replacing thousands of animals previously subjected to procedures such as gunshot wounds and amputations.
Efforts to reduce the number of animals used in experiments have also gained ground. For example, the classic LD50 test, which measured the dose of a substance needed to kill half a group of test animals, once required as many as 200 animals. It has now largely been replaced by the “limit test,” which uses only 6 to 10 animals and limits the number of test doses. Similarly, non-invasive imaging technologies such as MRI and CAT scans now allow researchers to monitor disease progression without euthanizing animals, reducing the total number needed.
Refinement techniques have also improved animal welfare. The traditional Draize eye irritancy test used rabbits and often caused significant discomfort. A newer method, the low-volume eye test (LVET), uses a much smaller dose and more closely simulates human experience, resulting in less pain. Other in vitro models, such as reconstructed human corneal epithelium, are now able to identify potential eye irritants without any animal use. Improved anesthetics and post-surgical care have become more widely available, further reducing distress.
Handling methods are also evolving. Tail restraint, a common way to hold mice for procedures, has been shown to cause significant stress. Recent studies show that alternatives like hand cupping or the use of tunnels result in calmer animals and more reliable results. Environmental enrichment has also become more common. For example, group housing allows monkeys to engage in social behaviors, while structural additions in frog tanks reduce boredom and isolation.
Some of the most exciting developments involve emerging technologies. Organ-on-a-chip devices simulate the structure and function of human organs using living cells and advanced microfluidics. These systems are already in use to model the liver, lung, kidney, heart, and intestine, with the long-term goal of developing a multi-organ system that mimics full-body physiology. Advances in genetic engineering may play a role as well.
Federal agencies are also advancing change. In February 2020, the Environmental Protection Agency (EPA) issued guidance that reduces or eliminates testing on birds and fish during pesticide registration, saving nearly a thousand animals each year. The National Institutes of Health (NIH) announced in 2025 that all grant applicants must consider non-animal methods, noting that “this new emphasis on human-based research will accelerate medical advances, save animals, and help NIH achieve its crucial mission of improving human health.” As more and more institutions expand their development and use of non-animal alternatives, we will continue to make progress in protecting animals used in research and testing.
