Nonanimal Testing Methods
Building a picture of a chemical’s potential risks to human health or the environment involves an assessment of all descriptive and toxicologic information that is already available, in combination with a number of different scientific techniques, and is often called an Integrated Testing Strategy.
New testing often starts with in silico methods and high-throughput screening to find patterns of activity that can then be followed up with targeted testing using cell or tissue models. Large groups of untested chemicals can also be assessed in this way.
In Silico Methods
Computers can help us learn quite a bit about chemicals and their health effects. Automated decisions trees can be built using knowledge of hundreds of chemicals and predict how likely it is that a new chemical will cause a certain kind of toxicity, such as developmental toxicity, for example.
- Chemicals made up of similar structure fragments can be grouped together and compared, allowing toxicologists to “read across” from a chemical with data to one without. And healthy virtual cells or even entire organs can be created and then used to simulate what might happen when exposed to a particular chemical.
High-Throughput Screening can perform many different tests—maximizing cell types, or amounts or mixtures of chemicals—very quickly:
- These assays usually test chemical activity at the molecular level—whether a chemical binds to DNA or activates the estrogen receptor, for example.
- The “Tox21” consortium uses an ultra-high-speed robot capable of testing thousands of different chemicals for potential toxicity every day. In fact, it can test more chemicals in a single day than have been tested in the past 20 to 30 years using animals.
Fully automated, “this robotic system provides unparalleled speed, reliability and high-quality reproducible data,” according to the National Institutes of Health. Click here to learn more and to watch the robot in action!
Cellular Models for avoiding animal tests
Laboratories can grow two- or three-dimensional models made up of one or many kinds of human cells, which are then used to test chemicals for toxicity. For example, a few human skin cells can be grown into skin tissue which is very useful for assessing the potential skin irritation potential of a chemical. This can be done with a wide variety of cell types.
“Human-on-a-chip” models are created by seeding a small amount of cells onto a tiny silicon chip; often several chips with different types of cells are linked together, allowing scientists to see how the mini “organs” react together and communicate with one another.
Some systems add mechanical force, which can be important for cell function. For example, the “lung-on-a-chip” created by the Harvard University’s Wyss Institute is stretched rhythmically to mimic the motion of the lung as a person breathes in and out.
Isolated organs as an alternative to animal tests
Ethically-sourced human organs can be used in experiments; for example, it is common to test potential asthma triggers or therapies with isolated tracheas.
The assessment of a chemical or ingredient without animals can take advantage of any or all of these methods, depending on the type of chemical and what it might be used for.