Non-essential metals are defined as metals that have no biological activity - an easy way to determine if a metal is non-essential is compare it to the metals present in a quality daily vitamin. If the name doesn't appear on the ingredient list in a vitamin, it likely has no biological activity and instead will have
toxic effects. Most non-essential metals are present in skin care products as various salts, such as aluminum silicate, oxide, hydroxide or stearate.
Non-essential metal exposure has long been associated with development of various diseases. How these metals may cause disease is related to pro-oxidative behavior, which results in many forms of cellular damage, and each metal's capacity to replace essential metals in enzymes and other cellular structures, resulting in abnormal functionality.
Here are a few non-essentail metals often present in sunscreens:
Aluminum - oxidative stress, also associated with Alzhemiers and other cognitive disabilities, often present as the silicate, hydroxide, oxide or stearate, among others.
Titanium - oxidative stress, free radical damage, present as titanium dioxide
Other heavy metals as contaminants - zinc and titanium are both derived from ores that commonly have additional non-essential metals such as lead, antimony, silver and gold. Unless a very high purity mineral sunscreen is used, these contaminants will also end up in the product and on your skin.
Conversely, Green Screen exclusively uses ultra high purity zinc oxide as its sunscreen active ingredient. Zinc is an essential metal and necessary for health.