Which sunscreens are chemical-free?
Category: Chemistry Published: March 25, 2013
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Associate Professor of Physics at West Texas A&M University
All sunscreens contain chemicals. Everything in the universe that contains atoms is by definition a chemical or a mixture of chemicals. Water is a chemical. Salt, gold, and oxygen are also chemicals. The only physical entities that are not chemicals are unbound fundamental particles, which are known as "radiation". Radiation includes light (streams of photons), cathode rays (streams of electrons), beta rays (streams of positrons or electrons), neutron radiation (streams of neutrons), and cosmic rays (streams of protons). Aside from radiation and non-physical entities such as love and hate, everything else in the universe is a chemical or a collection of chemicals. Even a sunscreen that contains just pure water is not chemical-free because water is a chemical. A consumer product that advertises itself as "chemical-free" is categorically lying (unless the bottle contains pure radiation, which is unlikely because radiation is notoriously hard to trap in a bottle without quickly destroying it).
In popular culture, the word "chemical" is often used as shorthand for "dangerous chemical" or "man-made chemical". But labeling a chemical as dangerous is highly subjective and misleading. Few people would call water a dangerous chemical, and yet water can kill you if you drink too much. Jennete Killpack knows this all too well. Jennete is serving time in prison for killing her daughter by forcing her to drink too much water. Many people would consider hydrochloric acid a dangerous chemical, and yet the human stomach naturally produces hydrochloric acid for beneficial purposes. What makes a chemical dangerous is its concentration, and not just its reactivity.
Similarly, the phrase "man-made chemical" is subjective and misleading. A pure sample of sodium chloride (NaCl) extracted from a salt mine and a pure sample of sodium chloride fabricated in the lab are exactly identical in every way. Atoms don't have memories or birthmarks. Pure NaCl behaves and reacts in exactly the same way no matter where it came from. The label "man-made" is therefore meaningless when applied to chemicals that are also found in nature. Perhaps when people say "man-made chemical", they mean "impure chemical". If that is their implication, they have it exactly backwards. Chemicals created in the lab tend to be more pure than the same chemicals found in nature. That is one of the driving motivations for processing chemicals in a lab. Refined table salt, such as you purchase at the grocery store, is far cleaner and purer than salt shoveled right out of a salt mine.
Let us return to the original question and rephrase it as, "which sunscreens are the healthiest?". The answer is: which ever ones successfully block ultraviolet sunlight and at the same time have the lowest concentration of overly reactive chemicals such as PABA. To get a more specific answer than that, you would have to analyze every sunscreen ever produced, its ingredients, the reactivity of its ingredients, and the concentration of its ingredients. Such a project lies beyond my resources. If you are curious, the FDA does just that very thing.