The phrase “vaccines are safe and effective” suggests that the use of small amounts of toxic ingredients in vaccines such as aluminum, mercury, formaldehyde, polysorbate 80, and other substances have been tested for safety and proven to be safe when injected, ingested or otherwise introduced into the human body. While federal regulatory agencies state that these substances have individually passed standardized safety testing, there are legitimate questions and concerns about the methodology used in standard toxicity testing to arrive at conclusions about safety.

Understanding the basics of chemical safety testing methods is the first step to understanding how the toxicity of a substance is measured using standard toxicity testing procedures.