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About Animal Testing

Humane Society International / Global

What is animal testing?

The term “animal testing” refers to procedures performed on living animals for purposes of research into basic biology and diseases, assessing the effectiveness of new medicinal products, and testing the human health and/or environmental safety of consumer and industry products such as cosmetics, household cleaners, food additives, pharmaceuticals and industrial/agro-chemicals. All procedures, even those classified as “mild,” have the potential to cause the animals physical as well as psychological distress and suffering. Often the procedures can cause a great deal of suffering. Most animals are killed at the end of an experiment, but some may be re-used in subsequent experiments. Here is a selection of common animal procedures:

• Forced chemical exposure in toxicity testing, which can include oral force-feeding, forced inhalation, skin or injection into the abdomen, muscle, etc.
• Exposure to drugs, chemicals or infectious disease at levels that cause illness, pain and distress, or death
• Genetic manipulation, e.g., addition or “knocking out” of one or more genes
• Ear-notching and tail-clipping for identification
• Short periods of physical restraint for observation or examination
• Prolonged periods of physical restraint
• Food and water deprivation
• Surgical procedures followed by recovery
• Infliction of wounds, burns and other injuries to study healing
• Infliction of pain to study its physiology and treatment
• Behavioural experiments designed to cause distress, e.g., electric shock or forced swimming
• Other manipulations to create “animal models” of human diseases ranging from cancer to stroke to depression
• Killing by carbon dioxide asphyxiation, neck-breaking, decapitation, or other means

What types of animals are used?

Many different species are used around the world, but the most common include mice, fish, rats, rabbits, guinea pigs, hamsters, farm animals, birds, cats, dogs, mini-pigs, and non-human primates (monkeys, and in some countries, chimpanzees). Video: Watch what scientists have to say about alternatives to animal testing .

It is estimated that more than 115 million animals worldwide are used in laboratory experiments every year. But because only a small proportion of countries collect and publish data concerning animal use for testing and research, the precise number is unknown. For example, in the United States, up to 90 percent of the animals used in laboratories (purpose-bred rats, mice and birds, fish, amphibians, reptiles and invertebrates) are excluded from the official statistics, meaning that figures published by the U.S. Department of Agriculture are no doubt a substantial underestimate.

Within the European Union, more than 12 million animals are used each year, with France, Germany and the United Kingdom being the top three animal using countries. British statistics reflect the use of more than 3 million animals each year, but this number does not include animals bred for research but killed as “surplus” without being used for specific experimental procedures. Although these animals still endure the stresses and deprivation of life in the sterile laboratory environment, their lives are not recorded in official statistics. HSI believes that complete transparency about animal use is vital and that all animals bred, used or killed for the research industry should be included in official figures. See some animal use statistics .

What’s wrong with animal testing?

For nearly a century, drug and chemical safety assessments have been based on laboratory testing involving rodents, rabbits, dogs, and other animals. Aside from the ethical issues they pose—inflicting both physical pain as well as psychological distress and suffering on large numbers of sentient creatures—animal tests are time- and resource-intensive, restrictive in the number of substances that can be tested, provide little understanding of how chemicals behave in the body, and in many cases do not correctly predict real-world human reactions. Similarly, health scientists are increasingly questioning the relevance of research aimed at “modelling” human diseases in the laboratory by artificially creating symptoms in other animal species.

Trying to mirror human diseases or toxicity by artificially creating symptoms in mice, dogs or monkeys has major scientific limitations that cannot be overcome. Very often the symptoms and responses to potential treatments seen in other species are dissimilar to those of human patients. As a consequence, nine out of every 10 candidate medicines that appear safe and effective in animal studies fail when given to humans. Drug failures and research that never delivers because of irrelevant animal models not only delay medical progress, but also waste resources and risk the health and safety of volunteers in clinical trials.

What’s the alternative?

If lack of human relevance is the fatal flaw of “animal models,” then a switch to human-relevant research tools is the logical solution. The National Research Council in the United States has expressed its vision of “a not-so-distant future in which virtually all routine toxicity testing would be conducted in human cells or cell lines”, and science leaders around the world have echoed this view.

The sequencing of the human genome and birth of functional genomics, the explosive growth of computer power and computational biology, and high-speed robot automation of cell-based (in vitro) screening systems, to name a few, has sparked a quiet revolution in biology. Together, these innovations have produced new tools and ways of thinking that can help uncover exactly how chemicals and drugs disrupt normal processes in the human body at the level of cells and molecules. From there, scientists can use computers to interpret and integrate this information with data from human and population-level studies. The resulting predictions regarding human safety and risk are potentially more relevant to people in the real world than animal tests.

But that’s just the beginning. The wider field of human health research could benefit from a similar shift in paradigm. Many disease areas have seen little or no progress despite decades of animal research. Some 300 million people currently suffer from asthma, yet only two types of treatment have become available in the last 50 years. More than a thousand potential drugs for stroke have been tested in animals, but only one of these has proved effective in patients. And it’s the same story with many other major human illnesses. A large-scale re-investment in human-based (not mouse or dog or monkey) research aimed at understanding how disruptions of normal human biological functions at the levels of genes, proteins and cell and tissue interactions lead to illness in our species could advance the effective treatment or prevention of many key health-related societal challenges of our time.

Modern non-animal techniques are already reducing and superseding experiments on animals, and in European Union, the “3Rs” principle of replacement, reduction and refinement of animal experiments is a legal requirement. In most other parts of the world there is currently no such legal imperative, leaving scientists free to use animals even where non-animal approaches are available.

If animal testing is so unreliable, why does it continue?

Despite this growing evidence that it is time for a change, effecting that change within a scientific community that has relied for decades on animal models as the “default method” for testing and research takes time and perseverance. Old habits die hard, and globally there is still a lack of knowledge of and expertise in cutting-edge non-animal techniques.

But with HSI’s help, change is happening. We are leading efforts globally to encourage scientists, companies and policy-makers to transition away from animal use in favour of 21st century methods. Our work brings together experts from around the globe to share knowledge and best practice, improving the quality of research by replacing animals in the laboratory.

Are animal experiments needed for medical progress?

It is often argued that because animal experiments have been used for centuries, and medical progress has been made in that time, animal experiments must be necessary. But this is missing the point. History is full of examples of flawed or basic practices and ideas that were once considered state-of-the-art, only to be superseded years later by something far more sophisticated and successful. In the early 1900’s, the Wright brothers’ invention of the airplane was truly innovative for its time, but more than a century later, technology has advanced so much that when compared to the modern jumbo jet those early flying machines seem quaint and even absurd. Those early ideas are part of aviation history, but no-one would seriously argue that they represent the cutting-edge of design or human achievement. So it is with laboratory research. Animal experiments are part of medical history, but history is where they belong. Compared to today’s potential to understand the basis of human disease at cellular and molecular levels, experimenting on live animals seems positively primitive. So if we want better quality medical research, safer more effective pharmaceuticals and cures to human diseases, we need to turn the page in the history books and embrace the new chapter—21st century science.

Independent scientific reviews demonstrate that research using animals correlates very poorly to real human patients. In fact, the data show that animal studies fail to predict real human outcomes in 50 to 99.7 percent of cases. This is mainly because other species seldom naturally suffer from the same diseases as found in humans. Animal experiments rely on often uniquely human conditions being artificially induced in non-human species. While on a superficial level they may share similar symptoms, fundamental differences in genetics, physiology and biochemistry can result in wildly different reactions to both the illness and potential treatments. For some areas of disease research, overreliance on animal models may well have delayed medical progress rather than advanced it. By contrast, many non-animal replacement methods such as cell-based studies, silicon chip biosensors, and computational systems biology models, can provide faster and more human-relevant answers to medical and chemical safety questions that animal experiments cannot match.

“The claim that animal experimentation is essential to medical development is not supported by proper, scientific evidence but by opinion and anecdote. Systematic reviews of its effectiveness don’t support the claims made on its behalf” (Pandora Pound et al. British Medical Journal 328, 514-7, 2004).

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Imagine a syringe being forced down your throat to inject a chemical into your stomach, or being restrained and forced to breathe sickening vapours for hours. That’s the cruel reality of animal testing for millions of mice, rabbits, dogs and other animals worldwide.

We’re giving the beauty industry a cruelty-free makeover with a wave of animal testing bans supported by hundreds of companies and millions of caring consumers worldwide.

We all dream of the day when cancer is cured and AIDS is eradicated, but is the continued use of mice, monkeys and other animals as experimental “models” of human disease actually holding us back from realizing the promise of 21st century science?

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Ethical care for research animals

WHY ANIMAL RESEARCH?

The use of animals in some forms of biomedical research remains essential to the discovery of the causes, diagnoses, and treatment of disease and suffering in humans and in animals., stanford shares the public's concern for laboratory research animals..

Many people have questions about animal testing ethics and the animal testing debate. We take our responsibility for the ethical treatment of animals in medical research very seriously. At Stanford, we emphasize that the humane care of laboratory animals is essential, both ethically and scientifically.  Poor animal care is not good science. If animals are not well-treated, the science and knowledge they produce is not trustworthy and cannot be replicated, an important hallmark of the scientific method .

There are several reasons why the use of animals is critical for biomedical research: 

••  Animals are biologically very similar to humans. In fact, mice share more than 98% DNA with us!

••  Animals are susceptible to many of the same health problems as humans – cancer, diabetes, heart disease, etc.

••  With a shorter life cycle than humans, animal models can be studied throughout their whole life span and across several generations, a critical element in understanding how a disease processes and how it interacts with a whole, living biological system.

The ethics of animal experimentation

Nothing so far has been discovered that can be a substitute for the complex functions of a living, breathing, whole-organ system with pulmonary and circulatory structures like those in humans. Until such a discovery, animals must continue to play a critical role in helping researchers test potential new drugs and medical treatments for effectiveness and safety, and in identifying any undesired or dangerous side effects, such as infertility, birth defects, liver damage, toxicity, or cancer-causing potential.

U.S. federal laws require that non-human animal research occur to show the safety and efficacy of new treatments before any human research will be allowed to be conducted.  Not only do we humans benefit from this research and testing, but hundreds of drugs and treatments developed for human use are now routinely used in veterinary clinics as well, helping animals live longer, healthier lives.

It is important to stress that 95% of all animals necessary for biomedical research in the United States are rodents – rats and mice especially bred for laboratory use – and that animals are only one part of the larger process of biomedical research.

Our researchers are strong supporters of animal welfare and view their work with animals in biomedical research as a privilege.

Stanford researchers are obligated to ensure the well-being of all animals in their care..

Stanford researchers are obligated to ensure the well-being of animals in their care, in strict adherence to the highest standards, and in accordance with federal and state laws, regulatory guidelines, and humane principles. They are also obligated to continuously update their animal-care practices based on the newest information and findings in the fields of laboratory animal care and husbandry.  

Researchers requesting use of animal models at Stanford must have their research proposals reviewed by a federally mandated committee that includes two independent community members.  It is only with this committee’s approval that research can begin. We at Stanford are dedicated to refining, reducing, and replacing animals in research whenever possible, and to using alternative methods (cell and tissue cultures, computer simulations, etc.) instead of or before animal studies are ever conducted.

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There are many outreach and advocacy organizations in the field of biomedical research.

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What are the benefits of using animals in research? Stanford researchers have made many important human and animal life-saving discoveries through their work. 

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Why We Still Test on Animals, Explained

A fraught regulatory environment and human stubbornness help explain the roadblocks.

Explainer • Research • Science

Words by Marlena Williams

In a bustling laboratory at the Harvard Stem Cell Institute, hundreds of scientists are busy creating self-organizing, three-dimensional tissue cultures known as organoids out of stem cells. These tiny cell cultures, ranging in size from the width of a hair to five millimeters, are capable of replicating the complexity of real human organs. In practical terms, scientists can — and already are — replicating human kidneys, brains, lungs, intestines, stomachs and livers. The technology offers us a huge opportunity to shift the way we test drugs, foods and cosmetic products. Scaled up, organoids could also eliminate the need to use animals in research and testing . By replicating the complexity and specificity of human organs, organoids offer an accurate, cost-effective and humane alternative to using animal models, so why aren’t we using them?

Organoids aren’t the only promising alternative on the horizon. From organs-on-chips — 3D devices that look and function like human organs — to highly sophisticated computer modeling systems , there are more alternatives to animal testing today than ever before.

And yet laboratory animals remain the dominant means by which we test products, with more than 115 million animals tested annually , to develop new drugs and study both human and animal diseases. While animal testing has certainly helped to usher in many life-saving medical and scientific advancements over the years — including the discovery of penicillin and the development of the polio vaccine — it comes with its own unique set of limitations and concerns.

Animals respond differently to drugs and stimuli than humans, especially when confined in the highly artificial and stressful environment of a lab, and testing on animals often creates unreliable and hard-to-replicate results. About 90 percent of drugs fail once they reach the human clinical trial stage. There are a variety of reasons why this happens, researchers say, including the fact that medicines function differently in the cells of one of the most common lab animals, mice , as compared to humans.

Animal testing is also expensive. The estimated dollar costs to bring a drug to market could be as much as $1 billion, give or take, to more than $2 billion in total, and for cancer drugs, can take more than a decade to hit the market .

So why are we still using laboratory animals, especially when so many other promising alternatives exist? This remains an incredibly fraught and complicated question, one that has divided scientists, animal advocates and even most Americans , for centuries.

Animal Testing: An Overview

There is no one definitive type of animal testing . Animals are tested on in a wide variety of ways, in a wide variety of settings, for a wide variety of reasons.

Scientific and medical researchers use animals to develop new drugs and vaccines, study biological systems and to advance new surgical procedures and treatment methods. Many commercial industries use laboratory animals to test the safety of their cosmetics, household cleaners, food additives, pesticides, chemicals and other potentially harmful substances, either by conducting the tests themselves or by contracting with third party companies.

Laboratory animals are also used in the classroom , in the military and even in outer space .

While there is no definitive number of how many animals are used in total in research and testing, it is estimated that more than 50 million laboratory animals are used in the United States each year. Rats and mice make up 85-95% of animal research subjects here, but dogs, monkeys, rabbits, guinea pigs, fish and birds are also widely used across many industries.

Until the 1960s, there were no federal laws regulating animal research or setting standards for laboratory animal welfare. With no federal oversight, the animal testing world was a sort of wild west , where researchers obtained their animal subjects from questionable sources — like unlicensed dealers and overcrowded animal shelters — and held them in often deplorable facilities, conducting a variety of cruel and unnecessary experiments and procedures on them without anesthesia or other pain management interventions.

The Animal Welfare Act was passed in 1966, largely in response to a disturbing story of a Dalmatian named Pepper who was stolen from her family home in Pennsylvania by an unscrupulous dealer and sold to a hospital in New York, where she was experimented on, killed and then incinerated. Pepper’s story — along with a sensational Life magazine article on dog dealers titled “ Concentration Camps for Dogs ” — spurred the welfare act’s passage and ushered in long overdue welfare protections for laboratory animals, including minimum standards for humane care, a registration system for testing facilities and a clear ban on the use of stolen animals in experiments.

A strategy known as the 3 R’s —  short for Replacement, Reduction, and Refinement — quickly became the guiding principles for humane animal experimentation in the twentieth century, and remain so to this day. The idea is to reduce the number of animals used in testing and improve animal welfare conditions as much as possible.

The Animal Welfare Act — amended in 1985 to make research facilities more accountable — and the Health Research Extension Act that followed were designed to minimize the pain and stress experienced by laboratory animals, not to completely eliminate their use or explore non-animal alternatives.

Legal scholar and animal ethicist Paul Locke argues that the “keys to the laboratory” remain firmly in the hands of researchers . These scientists have little oversight and only have to report the most egregious failures and abuses to federal authorities. What’s more, any researchers who want to treat animals more humanely are often hamstrung by institutional practice, career pressures and a general culture that views animal testing as a “necessary evil.”

Proponents of animal testing often argue that animal models are justified because the benefits to humans outweigh concerns about animal suffering. But as more testing alternatives emerge, the reasons for sticking with animals begin to dwindle. At this point, there are countless technological advancements that could make both human and animal subjects unnecessary.

But despite the promise of these non-animal models, many institutions and researchers cling to the status quo —in part out of a resistance to change, but also a lack of real investment in proven alternatives and political tensions within competing movements.

“The American Chamber of Horrors”

In 1933, one woman died and more than a dozen others were blinded after using a permanent mascara and eyebrow dye called Lash Lure , which contained an untested chemical derived from coal tar called p-phenylenediamine. Lash Lure caused painful blisters, abscesses and ulcers in and around the eyes of its unsuspecting consumers, some of whom were photographed and featured in a display at the 1933 Chicago World Fair that one journalist referred to as “ The American Chamber of Horrors .”

Just a few years later, 107 people, mostly children, died after ingesting the anti-bacterial drug Elixir Sulfanilamide , which contained a sweet-tasting ingredient also found in antifreeze.

The public outcry following the Lash Lure and Elixir Sulfanilamide tragedies prompted Congress to pass the Food, Drug and Cosmetic Act in 1938, the first law in the country to regulate the steadily growing pharmaceutical and cosmetics industries. The FDCA required cosmetics manufacturers to submit evidence of a product’s safety and effectiveness before marketing it to the general public. Animal testing quickly became the default way for cosmetics companies to ensure the safety of their products and to potentially avoid criminal liability for placing a harmful product on the market. Though the original FDCA didn’t require animal testing for cosmetics like it did for drugs, the agency still highly encouraged companies to test their products on animals.

One of the most common cosmetics testing methods involved “acute ocular toxicity,” or Draize, tests , named after the FDA scientist who invented the method in the 1940s. These tests involved restraining a conscious, unanesthetized rabbit and applying the chemical or product directly to its eyes. The substance was left on the eyeball for a set period of time, and the animal was then monitored for up to 14 days for signs of redness, swelling, hemorrhaging or irritation.

Draize tests remained the gold standard for FDCA compliance until a highly visible campaign, led by activist Henry Spira, drew attention to the tests in the 1980s. Spira ran an ad in the New York Times showing a blind laboratory bunny beneath the headline, “How many rabbits does Revlon blind for beauty’s sake?” The ad and resulting campaign brought increased attention to the cruelty of animal testing and prompted many brands to start searching for alternatives.

But cosmetics testing remains common , even in the 21st century. When companies choose to develop or use new ingredients in their products, they may still decide to conduct tests on animals to assess the safety of the product. No one wants to be responsible for another Lash Lure tragedy. Such tests, however, are now completely unnecessary: the FDCA does not explicitly require animal testing for cosmetics — only clearly demonstrated safety — and there are already thousands of ingredients available that have proven histories of safe and effective use.

By far the biggest factor keeping companies from going fully cruelty-free is China, which long required all cosmetics that entered its borders to be tested on animals. Though China has recently amended its regulations to exempt some imported products from mandatory testing, the country still requires animal testing for many popular cosmetics. Beauty companies that want to sell into the massive Chinese market–which accounted for a whopping $88 billion dollar sales in 2021 alone—must allow their products to be tested on animals.

While many cosmetics companies have decided to maintain their cruelty-free status and not sell or market their products in China, some of the biggest beauty companies like Revlon and L’Oreal, which in turn own dozens of other smaller beauty companies, do sell there. Though these companies will often adamantly deny using animal testing, they often do allow animal testing when required by law , likely meaning in China.

But the law elsewhere in the world is rapidly changing. The European Union banned cosmetics testing in 2013 , and dozens of other countries, including Mexico, Canada, Australia and India, quickly followed suit. Though there is currently no federal law in the United States banning cosmetics testing outright, twelve U.S states prohibit the sale of products tested on animals within their borders.

Unlikely Allies and Foes

Voters and consumers are understandably horrified by the idea of rubbing hairspray or perfume into the eyes of helpless white rabbits just so we can defrizz our hair or smell a little better. But making political and social progress on other forms of animal testing is a far more difficult task. When it comes to toxicity testing , progress towards alternative methods has long been delayed by an often surprising web of conflicts between environmentalists, animal advocates, government agencies and polluting corporations.

Take, for example, the case of the Environmental Protection Agency. In September 2019, Andrew Wheeler, the head of the EPA under Donald Trump, announced that the agency would reduce animal toxicity tests by 30 percent by 2025 and stop these experiments altogether by 2035.

Under the Toxic Substances Control Act , the EPA is empowered to conduct and oversee a massive amount of animal testing — involving anywhere from 20,000 to 100,000 animals annually —in order to determine the effects of certain chemicals or pollutants on fertility, development, genetics and overall health. These tests often involve pumping chemicals straight into an animal’s stomach or forcing animals to inhale potentially lethal chemicals in a gas chamber.

The Food, Drug and Cosmetics Act further authorizes the EPA to regulate pesticides . When registering a new pesticide, the EPA requires companies to perform a 90-day oral toxicity study on both rodent and non-rodent species — typically cats and dogs —as part of its human health risk assessment. A 2019 undercover investigation by the Humane Society of the United States revealed dozens of beagles being force-fed varying doses of pesticides at a Dow AgroSciences facility in order to test their toxicity as required by the EPA.

But Wheeler’s decision to roll back animal testing requirements was immediately criticized by people within the environmental movement, who accused the administrator of bowing to pressure from the powerful chemical industry . Chemical giants like Dow and DuPont tend to balk at such testing because it is both time-consuming and expensive.

While Wheeler maintained that his decision was based out of his love for animals, it wasn’t a logical jump to assume that the Trump administration was favoring polluting industries over the health of American citizens and the environment. Major environmental groups like the National Resources Defense Counsel have since come out in support of animal toxicity tests .

These debates show the political thorniness of the toxicity testing debate, which pits environmental groups against the agency tasked with protecting the environment, and aligns animal advocates with the conservatives and big businesses they often oppose.

While animal toxicity tests may prevent potentially dangerous chemicals from harming people, other animals and the environment, these tests are less fool-proof than the agency’s reliance on them might suggest. One study found oral toxicity testing on dogs to be an unnecessary step , and another showed that rodent models accurately predicted human toxicity in only 43 percent of cases. Lethal dose tests, whereby animals are forced to swallow large amounts of chemicals to determine the amount that causes death, are considered impractical, as most humans are exposed to these harmful substances at far slower rates and in far smaller doses.

The National Academy of the Sciences has been urging a shift away from animal testing since 2007. Thanks to a grant from the EPA, scientists at Johns Hopkins have been working to develop lab grown “mini-brains” that may enable researchers to study neurotoxic effects without the need for animal subjects. Even simple changes, like improving the searchability of the EPA’s current testing data , could dramatically reduce the need to test chemicals and pesticides on animals.

But in another twist, it now seems that under the Biden administration, the EPA has scrapped its plans to eliminate animal testing , instead opting for the vague goal of reducing reliance on animal models and researching viable alternatives.

New non-animal models will require rigorous regulatory approval before they are accepted, and even proponents of these alternatives think they are still a long way off from becoming the norm. A potent mix of government inertia, political volatility and public skepticism towards new methods may favor the status quo over more humane and effective alternatives.

Cures vs. Creatures

The toxicity debates look tame compared to the contentious, often ugly debates that have been raging between animal advocates and the medical and scientific community since at least the 19th century.

Professor Paul Locke calls this the “cures vs. creatures” dilemma. On the one hand, there is deep societal respect and need for the doctors and scientists who rely on animal models to better understand human biology, cure horrible diseases and prevent future harms.

But on the other hand, there is an equally strong societal force that believes animals are sentient creatures deserving of protections and rights. Animal advocates find something deeply hypocritical about a research model that uses animal subjects because of their similarity to humans while refusing to acknowledge that these creatures are capable of many of the same emotions and sensations as us.

“To avoid seeing this double treatment as a problem, and thus to avoid ethical reflection on it, requires an extraordinary level of self-deception, rationalization, and selective blindness,” writes scientist John Gluck in his book, Voracious Science and Vulnerable Animals . “It requires [researchers] to objectify experimental animals, categorically excluding them from the class of beings requiring full ethical considerations.”

Both sides of the “cures vs. creatures” dilemma deploy rousing narratives and imagery to prove the nobility of their cause. Animal activists can shock and horrify with nightmarish stories about the thousands of dogs , cats , monkeys and rodents who suffer in labs, while doctors and researchers can comfort and inspire with stories of the life-saving medical advancements that have benefited from animal testing, from the cure for smallpox to the COVID-19 vaccine . But these competing narratives can help to keep the animal testing debate polarized and forestall any effective progress towards widely available non-animal alternatives that could both eliminate animal suffering and offer more accurate, reliable and cost-effective results.

Scholars and animal advocates like Paul Locke believe that animal models will be needed as medical and scientific tools until enough money is pumped into the system to support and vet non-animal alternatives. While technologies like organoids, organs-on-chips and computer simulations show great promise for future advancements, there has not been enough institutional interest or investment in these alternatives to make a meaningful difference in transforming the current system.

In 2023, President Biden signed into law an amendment to the FDCA removing the requirement that pharmaceutical companies test their drugs on animals before moving on to human clinical trials. Testing is no longer required, but it may still be encouraged by the agency if they believe it is useful or necessary. Last year’s federal budget also included $5 million dollars for a new FDA program designed to develop and encourage non-animal testing methods.

But $5 million dollars is a mere drop in the bucket of the FDA’s massive $8.4 billion federal budget and is hardly enough to support the large-scale institutional shift that will be necessary to replace animal testing with non-animal alternatives. If the National Institute of Health invested just 1 percent of its whopping $48 billion dollar budget in exploring non-animal alternatives, for example, we could make significant progress towards shifting away from animal testing, at least when it comes to scientific and medical research.

The Bottom Line

Laboratory animals receive certain minimal welfare protections under the law, but they continue to be used by the millions for research testing for a wide range of industries — from food to fashion to biomedical research — despite the alternatives.

For researchers to shift to using these new methods, we may just need to, as scientist John Gluck writes , “rethink and re-form the entire framework of beliefs that underlies our relationship with nonhuman species.” But that kind of rethinking will require a serious national conversation about the place of animals in society, and how they should be treated and perceived, in the laboratory and beyond.

Independent Journalism Needs You

Marlena Williams is a writer from Portland, Oregon. She is the author of the essay collection Night Mother: A Personal and Cultural History of the Exorcist.

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• Future Perfect

Animal testing, explained

Is anything really “cruelty-free”?

by Celia Ford

It’s nearly impossible to go a day without benefitting from the suffering of animals. The ingredients in your toiletries and makeup; your medicine, vaccines, and implants; your cleaning supplies; the chemicals that helped grow your food — most of it was, at some point, tested on animals.

For centuries, the biological sciences have relied on animal testing. To figure out how a machine works, you need to disassemble it and check out its component parts. Understanding the living body, one of nature’s most complex and beautiful machines, is no different. Taking apart and fiddling with a toaster doesn’t hurt anyone, but dismantling a biological system certainly does.

Many scientists believe that experimenting on living animals is a necessary means of solving problems that affect both humans and animals. But these experiments often involve animals experiencing distress, whether from the side effects of an experimental drug, an intentionally inflicted illness, or simply their confined living situation. Some lucky lab animals get to spend their retirement in sanctuaries once they’re no longer needed. Most of the time, the animal dies, either as a direct consequence of the experiment or from euthanasia.

More often than not, animal research happens behind closed, locked, unmarked doors. That lack of transparency makes it difficult to know what to think about animal testing, and public opinion is tellingly divided. A 2018 Pew Research Center survey found that 47 percent of people in the US support the use of animals in scientific research, and 52 percent oppose it. Unlike climate change or reproductive health , where the parties are highly polarized, animal testing is one of few science-related policy issues where the attitudes of Republicans and Democrats are pretty similar: Both parties are split roughly 50-50.

Experimenting on animals places two seemingly good things — medical innovation and animal welfare — at odds. Even those who support animal research generally hold nuanced, conflicted beliefs about it, and questions about the nature and extent of animal testing are still hotly debated.

Inside this story

• What animal testing actually does
• Who is looking out for the welfare of animals
• The truth behind labels like “cruelty-free”
• The future of animal-free testing

Brands frequently mislead consumers about animal testing involving their products with vague labeling, and alternative research methods aren’t as broadly applicable as some activist organizations imply . Meanwhile, research facilities often ban employees from sharing photos of lab animals without institutional approval and rarely let the media observe experiments for themselves.

After spending six years as a neuroscience PhD student working in a lab with monkeys, I left academia with the impression that animal testing is neither as well-managed or justified as regulators claim, nor as malicious as others fear. Government agencies are starting to direct funding toward finding alternatives to animal testing, but the use of animals is deeply embedded in biological sciences.

A world without lab animals may be possible, but we don’t live in it yet. Here’s what’s actually going on.

What is animal testing?

Before humans invented microscopes, universities, or even paper, we were using animals for medical research. Over two millennia ago , ancient Greek philosopher Aristotle dissected dozens of animal species to better understand their anatomy and argued that studying their bodies could teach us a lot about our own biology. Over four centuries later, Galen of Pergamon , one of the most pivotal characters in Western medical history, performed public surgeries on animals ( especially monkeys ) for science, providing a spectacle that attracted curious audiences.

Today, animal experimentation is widespread and conducted far from the public eye. It falls under two broad, semi-overlapping umbrellas: biomedical research (which aims to understand, prevent, and treat diseases, as well as uncover fundamental information about how bodies work) and toxicology , or testing the effects of chemicals (including everything from toothpaste and makeup to pesticides) on living things.

Humans generally don’t want to be proverbial guinea pigs for new medicines or consumer products. We’d rather know that things are safe before we put them anywhere near our bodies. Companies, whether they deal in cosmetics or pharmaceuticals, also don’t want to be liable for poisoning their customers.

People can participate in experiments that might harm them, but historically, at best, such projects have been difficult to administer . At worst, they have involved illegal human experimentation that cast a long, dark shadow over the field of medical research.

The Tuskegee syphilis study , for example, put hundreds of poor Black men with untreated syphilis through decades of invasive tests in exchange for hot meals and basic medical treatment, just to see how the disease would progress if left untreated. Effective treatments became available during the study, but researchers withheld them. Once the experiment’s scandalous history was publicly disclosed in 1972 , the US government formalized basic ethical guidelines for human research and required Institutional Review Boards (IRBs) to approve studies on humans.

Today, many questions — like What is the lethal dose of this new drug? and Does this new surgical technique actually work? — can’t ethically be asked regarding humans without first being tested on a nonhuman subject.

For a long time, animals were the only alternative to humans available. To figure out the lethal dose of a new drug, scientists can give increasingly large amounts of it to mice and see what it takes to kill them. To test whether a brain implant actually relieves Parkinson’s symptoms, scientists do brain surgery on monkeys . Without computational models or cell cultures sophisticated enough to mimic the complicated interactions between organs, the options have historically been to use animals as a proxy or to drop or scale back your planned research.

We can only guess how many animals are being used in scientific experiments worldwide. The United States Department of Agriculture (USDA) publishes official reports on animal research every year, but they only include animals protected by the Animal Welfare Act (AWA), the federal law setting basic standards for the treatment and housing of certain farm animals and lab animals. The law covers dogs, cats, monkeys, guinea pigs, hamsters, pigs, rabbits, and sheep. In 2019, about 800,000 animals protected by AWA were used in research — 930,000, if you add those that lived in labs but were never included in a study.

Notably, the AWA doesn’t apply to mice and rats, which several studies estimate account for somewhere between 93 and 99 percent of all lab animals in the US. The AWA also excludes invertebrates like flies, worms, fish, and cephalopods like octopuses, whose intelligence makes them intriguing neuroscience subjects. The EU, which counts all vertebrates used in experiments, tallied about 10.6 million animals used in 2017. It’s harder to pin down a number in the US. Depending on who you ask , there might be 10 million rodents subjected to scientific experiments annually, or there might be 111 million. (Either way, it’s more than three times the number of rats in New York City.)

Rodents make appealing animal models for many scientists because they’re smart enough to learn simple tasks but are still socially regarded as pests; those who kill rats for a living don’t face the same kind of backlash as someone who, say, boasts about shooting a puppy . Nearly all mouse genes share functions with human genes, so at a basic level, their biology resembles ours. Mice only live for a year or two, enabling scientists to study things like chronic disease progression without waiting an entire human lifespan. And scientists can genetically alter mice in countless ways, knocking out or adding DNA to express diseases or make certain cell types glow under a microscope.

In some cases, a research question requires invasively studying a full, living biological system, but the gap between mice and humans is too wide. The USDA reported that 68,257 monkeys were used in 2019 to study subjects like SARS-CoV-2 , Parkinson’s disease , and HIV , where physiological and cognitive similarity to humans was a priority. Those primates were mostly macaques and marmosets; the use of chimpanzees (our closest ape relative) is now banned in many countries , including the US .

But monkey research may not be viable much longer. While hundreds of monkey experiments are being funded by the NIH , there aren’t enough long-tailed macaques to go around. In a desperate attempt to keep up with skyrocketing demand, thousands of wild-caught monkeys are illegally imported to US research institutions from countries like Cambodia. Two years ago, the long-tailed macaque was listed as endangered for the first time. PETA petitioned the US government to protect the species under the Endangered Species Act , which could end their use in research altogether, but the request has yet to be approved. Most people are uncomfortable with the idea of experimenting on an animal so similar to us, including some of the scientists who do it. However, many scientists and policymakers agree that we still don’t have non-animal alternatives that can answer tough research questions involving interactions between organs. Researchers worry that the looming primate shortage in the US — engendered by transportation restrictions and therapeutic testing requirements and exacerbated by pandemic-era demands — will limit our ability to respond to public health emergencies.

Monkeys are traditionally recognized as the only nonhuman animals that react to drugs with human-specific targets, meaning that in some cases, their body’s reactions could uniquely predict whether a drug will be safe and effective for humans. During the first years of the Covid-19 pandemic, monkeys were considered so crucial to SARS-CoV-2 research that when the rhesus macaque supply dried up, scientists didn’t turn to cell cultures or computer models — they just looked for different monkeys .

You might not agree that this research justifies the nonconsensual use of highly intelligent animals; many don’t, for both ethical and scientific reasons. But it’s happening, and if you’ve been vaccinated or take medications, you’ve likely benefited from it.

Who’s looking out for the welfare of lab animals?

The regulatory framework surrounding animal research is a tangled web of acronyms, committees, and working groups. Since the Animal Welfare Act was passed in 1966, the USDA has been in charge of enforcing it through inspections and annual reports.

In theory, researchers have to justify the use of animals in their work. To conduct an animal experiment, scientists in the US go through a review process with their Institutional Animal Care and Use Committee (IACUC), which decides whether animals are “necessary” and whether steps are being taken to minimize their pain.

IACUCs are mostly comprised of researchers who experiment on animals and the veterinarians who help them, strongly biasing committees toward approving animal experiments. In the US and elsewhere, scientists are subtly incentivized to use animals, even when they aren’t actually necessary. Academic journals tend to preferentially publish work with animal methods , and academic careers hinge on accumulating publications . These norms seep into the labs where animal experiments are performed. New animal researchers often receive explicit instructions on how to steer clear of animal rights activists, according to several researchers I spoke with while working as a neuroscientist (as well as my own experience).

This can make holding institutions accountable for animal welfare violations challenging. While researchers are required to report information about animals in their facilities, like what medical procedures they’ve received and when they’ve been fed, they are told to keep these reports “ minimal, but complete .” In other words: Avoid including photos, videos, or graphic descriptions that could enrage activists or entice the media.

There also isn’t a clear legal definition for “animal cruelty” in research settings beyond violations of the basic standards outlined by the Animal Welfare Act. This leaves some room for interpretation about what is acceptable and what would constitute illegal treatment. The EU’s Directive 2010/63/EU , its equivalent of the Animal Welfare Act, emphasizes that animals should only be used if there are no other options and if the potential benefits of the research outweigh the animals’ suffering.

This cost-benefit analysis is subjective. For example, a team of immunologists studying cancer in mice would probably say that the potential public health benefits of their work justify harming mice. A team of science policy experts at PETA would say that mice aren’t ours to use and that these experiments often don’t translate to human trials, anyway .

To bridge this ethical divide, research universities and private companies in the UK have signed a Concordat on Openness on Animal Research , pledging to proactively and transparently inform the public about their treatment of lab animals. In the decade since its launch, nine other countries have followed suit. It’s likely not a coincidence that these countries generally have the tightest restrictions on animal use. However, an independent review found that Concordat signatories in the UK are still struggling to be transparent about their animal research practices in the face of potential disapproval.

On top of the slow pace for necessary regulation, stigma obscures the true nature of what happens in these labs. In the late 2000s, the most extreme opponents of animal testing used violence to try to end the practice, sending poisoned razors and death threats to lab heads and, in at least one case, firebombing a neurobiologist’s car . But rather than encourage scientists to reconsider their methods, attacks like these cemented a culture of silence. While physical violence is not representative of activism against animal testing today — which usually centers around investigations , government advocacy , and direct care for animals and has shifted to become more inclusive — the threat of retaliation still haunts animal researchers , some of whom are encouraged by their institutions to hide their connections to animal testing from the public.

Scientists “don’t want to feel like they’re bad people,” said neuroscientist and author Garet Lahvis, who has written about primate research for Vox.

What if I want to avoid animal testing altogether? What does “cruelty-free” mean?

After learning about what lab animals go through, some people will want to find ways to avoid the products of animal testing. This is much easier said than done, however.

Animal testing is pervasive in health care. Many treatments we take for granted today, like anesthesia , flu shots , and allergy medications , went through preclinical trials in animals before reaching us. They are also valuable to your health, so please keep taking your medicine if you need it. We have more power to avoid animal testing elsewhere. Animal testing requirements are generally looser to nonexistent for cosmetics, cleaning supplies, and other household chemicals, so it’s possible to buy “cruelty-free” makeup or laundry detergent.

The legal distinction between “cosmetics” and “drugs” is blurry, though. Essentially, drugs claim to affect the body’s structure or function in some way, while cosmetics are things you apply to your body to change your appearance (like lipstick) or clean yourself (like deodorant — but not soap, which is neither a cosmetic nor a drug, but its own special category ). Many products we might think of as cosmetics are, in fact, also drugs, like anti-dandruff shampoo, tinted moisturizer with sunscreen, and other cosmetics that claim to treat some ailment. In the US, all of these items had to be tested on animals until the FDA Modernization Act 2.0 took effect in 2023 .

Cruelty-free claims used on product labels are often misleading, and differences in regulation across countries add to the confusion.

For years, the EU , Canada, Mexico, and 16 other countries (including South Korea, for the skincare girlies ) have had legislation in place banning animal testing for cosmetics or their ingredients (although last year, the UK changed their policy to allow testing for makeup ingredients again). But testing on final products or their ingredients has never been banned in the US. Even if a company doesn’t test its final product on animals, it may still run animal tests on raw ingredients. And even if those raw ingredients aren’t currently being tested on animals, they probably were when they were first introduced.

The US government doesn’t have a legal definition for the terms “cruelty-free” or “not tested on animals.” A product labeled “cruelty-free” likely earned voluntary certification from a private organization like Leaping Bunny or PETA’s Beauty Without Bunnies program by pledging to end animal testing at all stages of product development. The definition of “cruelty-free” isn’t standardized across animal protection groups, but earning a “bunny label” generally means that a brand attested to never conducting tests on animals during a product’s development.

Despite pressure from advocates and consumers, many US companies don’t bother with these pledges on animal testing. As of this year, approximately 310 brands globally still test their beauty and household cleaning products on animals. And some actively say they don’t test on animals at all but still sell their products to countries like China, which, until recently, required that all cosmetics (even imported ones) be tested on animals . Most certification programs exclude brands and products sold in China for this very reason.

To make it easier for US companies to sell truly cruelty-free products in China, US regulators and animal welfare advocates have been lobbying their Chinese counterparts for years to change their approach to animal testing for consumer products. Twenty years ago, Thomas Hartung, a toxicologist at the Johns Hopkins Center for Alternatives to Animal Testing, spoke with the National Medical Products Administration (China’s FDA) about regulating animal testing of chemicals and told me “it was like we were coming from Mars.”

In response to yearslong campaigns by organizations like PETA and the Institute for In Vitro Sciences, China recently lifted this requirement . It is now possible to buy Chinese cosmetics that weren’t tested on animals — kind of.

As of January 2021, China no longer requires pre-market or post-market animal testing for cosmetics, meaning that companies from the US and elsewhere can sell things like eyeliner or nail polish in China while still maintaining “cruelty-free” status. But certain “special cosmetics,” like sunscreen, teeth whiteners, and hair dye, or products made for children, are all still required to undergo animal testing. And if a product uses a raw ingredient that isn’t already approved in China, foreign companies have to either reformulate or get that ingredient approved, which requires more animal testing. So, it’s possible to sell US-made “cruelty-free” products in China, but it requires sifting through a confusing and ever-evolving swamp of documentation requirements.

We have made imperfect progress toward a world of cruelty-free cosmetics. While the number of animals used for cosmetic testing in the US has dropped by 90 percent since the 1980s, 44 of the largest 50 cosmetic brands in the world still are not cruelty-free . And without a consensus agreement on what “cruelty-free” actually means, consumers are left to guess which bunny labels are genuine and which are false advertising.

Since many brands can just slap on cruelty-free claims while still sending products abroad to animal testing labs, for now, if you want to avoid animal testing, Leaping Bunny and Beauty Without Bunnies are your best bets. These certifications consider post-market animal testing in other countries as part of their standards.

Alternative methods are (slowly) coming

In some places, like the UK, strict restrictions on animal research and a commitment to transparency have considerably improved lab conditions in recent decades. Companies like Neuralink , however, continue to perform high-risk, ethically dubious experiments hidden from the public eye.

While new alternative methods are under development, animal testing remains necessary in at least some circumstances. Tight regulation — and buy-in from scientists — will be key to minimizing harm in the meantime.

Nicole Kleinstreuer, acting director of the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) , told me that improving the current state of animal testing hinges on researchers gathering “the courage to admit that we can substantially improve upon how we’ve been doing things historically.”

Until relatively recently, alternatives to animal testing in many areas of science were very limited. But in the past decade, bioengineering and computer science have advanced rapidly. New tools like AI, organoids (balls of stem cells that grow into organ tissue), and CRISPR have made replacing animals, at least in certain experiments, more attainable.

For chemical testing, good animal-free research methods have been around for decades — long before most scientists considered using them. Even when well-validated animal alternatives exist, researchers can be slow to adopt them . Hartung, a toxicologist, said, “I turned 60 last year. The methods they’re using were introduced when I was in kindergarten.”

In 2007, the National Academies of Sciences, Engineering, and Medicine , a nonprofit that produces independent policy guidance for the US, laid out a strategy for researchers to move away from using animals in toxicity testing and to develop faster, more human-relevant models to take their place. Today, a number of working groups, both within the US and collaborating internationally, are still trying to put this principle into practice.

As the largest single public funder of biomedical research in the world, the National Institutes of Health (NIH) is uniquely positioned to influence animal testing. In 2023, the NIH spent an estimated $19 billion on US-based projects involving animals, according to Citizens for Alternatives to Animal Research and Experimentation. Between 2011 and 2021, they spent $2.2 billion on projects based in other countries — where oversight boils down to trusting self-generated, non-validated reports from foreign institutions.

Kleinstreuer said that changing the current state of animal research “really necessitates a sea change, and a dramatic investment on the part of funders, particularly the NIH.”

The people in charge of the money have the power to redistribute it and could choose to spend more of it on projects that don’t use animals and less on those that do. That’s the easy part. “It’s kind of the lowest-hanging fruit, and the easiest ask,” said Emily Trunnell , director of Science Advancement and Outreach at PETA. “Even people who are in support of animal testing are on board with the funding of different methods as well.”

NICEATM, led by Kleinstreuer, is doing the in-the-weeds work of figuring out how we’d know whether a replacement method is good enough to substitute for animal experiments. Earlier this year, the NIH also approved the Complement Animal Research in Experimentation (Complement-ARIE) Program , which will set up technology development centers for researchers to make better human-based models.

Non-animal methods can already outperform certain animal tests. Back in 2018, Hartung’s research group created algorithms mapping the relationships between 10,000 known chemical compounds. With this model and lots of data, they predicted the toxicity of 89 percent of the 48,000 toxic chemicals more accurately than animal tests could and for much less money — without endangering any living creatures. Since then, Hartung said things have only become better. But AI-driven research methods are still limited by what real-world data has already been collected. “When you have no data,” he said, “nothing is possible.”

In some cases, using animals is simply bad science. There are some questions “that absolutely necessitate a human cell-based approach,” Kleinstreuer said. “You can’t look at the efficacy of a drug whose target is not expressed in animals by using animal models,” she added. Certain cancer drugs target protein receptors that only exist in humans, and gene therapies often aim to rewrite human-specific DNA sequences. One emerging option: take a sample of human cells, reprogram them to behave like whatever cells you want them to be, and test your drug on the resulting tissue sample.

These tools offer exciting opportunities to personalize medicine to individual patients, but it’s still tough to extrapolate results from a small mass of lab-grown cells in a tightly controlled environment to a human body and the complex interactions of its organ systems. Cancer and embryonic development are incredibly complex biological processes, involving lots of different interconnected body parts that evolve over time. Without that capability, Kleinstreuer said it’s harder to argue that a substance is actually safe and ready to clear for human use.

Change happens one retirement at a time

As it stands, alternatives to animal tests are not being used as widely as they should be, especially in cosmetics. But if we want to study things like deep brain stimulation or run safety tests on new cancer drugs , animal tests are all we have.

While we are stuck with animal experiments, we can try to limit them and make them more humane. Lahvis believes that we should have extremely strict criteria for what animal experiments are funded. Strategically allocating grant funding could not only save millions of lives, but also inspire better science.

Convincing animal researchers to replace animals with other methods is still a huge challenge. Hartung joked that in academia, change happens “one retirement at a time.” Unfortunately, “it’s often been one graveyard at a time,” as retired scientists continue to serve as reviewers who help choose what new projects get funded and published.

The further along a scientist is in their career, the more challenging it becomes to pivot. Because scientists are pushed to maintain a constant level of productivity, Trunnell said, someone who builds their whole lab around their current use of animal models has no incentive to change, unless they have a strong desire to do so. Changing tactics could mean putting their job on the line.

“We’re highly leveraged by the system to keep doing what we’ve always done,” Lahvis agreed. And, Hartung said, turning against a tried-and-true method would require a scientist invalidating their existing body of work or at least acknowledging that it was either unethical, ineffective, or inefficient. Using past observations to inform future experiments is at the core of the scientific method, but, Hartung said, “We’re not trained to be very self-critical.”

That said, a growing number of scientists support the development of non-animal methods, even as they continue to work with animals themselves. People want new tools, whether for the sake of animal welfare or simply because it would make for better science. We might just have to wait another generation.

• Animal Welfare

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