Toxicology is the science that studies the harmful effects of chemicals on humans and other animals. Traditionally, toxicology has used animal testing with high doses to work out when chemicals are safe. However, concerns over the treatment of animals and environmental impacts mean that alternatives are needed.

In the 1990s, a framework called “green chemistry” aimed to improve chemical practices in industry. Some of its principles have been adapted to make toxicology more ethical and sustainable. This paper describes a framework called “green toxicology” with four pillars:

1. Alternative test methods: Reduce, refine, and replace animal testing. Make testing data more relevant for humans, cheaper, and faster.
2. Precautionary principle: Act quickly when there’s a threat of harm. Commonly, chemicals are only deemed unsafe after there’s concrete evidence of damage.
3. Lifetime impacts: Look at the impacts of the chemical beyond its intended use (e.g., manufacture and disposal). Understand its holistic impacts on ecosystems and communities, not just human health.
4. Prevention over reaction: Incorporate safety earlier in chemical design. Build frameworks to find less toxic alternatives to existing chemicals before evidence of harm exists.

Starting in the 2010s, there have been governmental, industrial, and non-governmental organization-led programs to try to put these pillars into practice. The focus on full life cycles of chemicals means that green toxicology aligns well with environmental and development priorities, like the European Green Deal, U.S. Green New Deal, and United Nations Sustainable Development Goals.

Alternatives To Animal Testing

Animal testing often uses high doses of chemicals. Due to differences in how the bodies of humans and nonhuman animals work, this data might not be relevant for human health. Also, animal testing can be expensive, slow, and, because it’s increasingly seen as unethical, unpopular. In 2010, the European Union (E.U.) committed to ending animal testing in research as soon as scientifically possible. There are several alternatives to animal testing in use now.

High-throughput cell-based assays use cultured cells and robotics to quickly test the effects of many different concentrations of a chemical. Scientists prepare artificially grown cells which are placed in trays containing many small compartments. A robotic arm then places different amounts of the chemical in each compartment and the effects are recorded after some time has passed. It’s possible to do this faster and more accurately than with human labor.

Computational toxicology uses techniques from computer science and engineering to work out the effects of chemicals in different ways. For example, scientists can build models of human tissues and organs that enable them to predict how a chemical might affect the body. Rapid progress in artificial intelligence (AI) is already producing different methods that are replacing animals. AI models are able to draw conclusions about toxicity from very large databases, such as existing test data of similar chemicals or library collections of written scientific studies outside of toxicology. Some AI models are also able to learn from existing data to produce designs of new chemicals that meet safety requirements.

Although computer technology is very useful, the behavior of liquids (like blood) in organs is very complicated and can’t be modeled easily. Human cells can be artificially grown in structures that have fluids pushed through them, mimicking real organs. These organs-on-chips can be used to check the short- and long-term effects of chemicals on human tissues. Organs-on-chips can be combined with each other and with computers to model the whole human body on a small scale. This can be done quickly for different doses and produces data that’s more relevant than tests on animals.

Challenges To Green Toxicology

Despite recent technological progress, there are barriers to change. Institutional inertia means that it’s easier for companies and governments to keep doing things in the same ways. The costs involved in changing equipment and retraining staff make shifting away from animal testing undesirable. It’s especially hard for smaller organizations with fewer resources. Also, many jurisdictions still have legal requirements for new chemicals to be tested on animals before they’re approved. To convince lawmakers that they’re safe, alternative methods often require a lot of data before they can be used as alternatives.

A more unexpected challenge comes from environmental groups. Often, non-governmental organizations that are concerned about damage to ecosystems will lobby governments to do more animal testing. For instance, the World Wildlife Fund convinced the Environmental Protection Agency in the U.S. to require additional animal testing to screen for hormonal effects on wild animals. As noted in this paper, the resulting conflicts between environmental and animal advocates can end up setting both groups back.

Takeaways

It’s important for advocates of animal-free testing to be acquainted with green toxicology and the barriers that exist to disrupting the status quo of chemical screening. Advocates should be aware of legal requirements for animal testing that prevent individual organizations from using alternatives. Also, the costs of new equipment and training can make the transition difficult even when the alternatives are better. Advocates should emphasize the human benefits of non-animal methods: they can be more relevant to humans, faster, and cheaper. Finally, animal advocacy can cause conflict with environmental groups who see animal testing as important for preventing damage to ecosystems. Green toxicology connects improved environmental outcomes with replacing animal testing. Non-animal alternatives can provide more relevant longer-term data and reduce waste in production. Ultimately, finding common ground will help advocates promote change for animals and the world.