Some of the materials used in the cosmetics industry have been found possibly hazardous to human health in different research.
Since they appear in low concentration or are in contact with the body for short periods of time they are defined as safe, yet it is possible to see people who react strongly and seriously to these materials, even at low concentration and short exposure time.
different substances will affect different people differently
Variance among different people in the population is the main explanation for different individual responses. Since the scientific world is based on numerics that are consistently remeasurable , the population is treated as individuals having the same reaction to each substance or topic.
Thus, the definitions for what is problematic and what is not are true for only a part of the population.
A good example for the concealment of variance, we find in one of the main measurements for toxicity in medicine- The LD50 Lethal Dose. This is a central measurement in the field of hazardous materials. This number is the base for defining what is dangerous to humans, allowed exposure time and concentration.
What is the LD50 and how is it calculated?
A population of mice is taken and administered the toxic substance in growing amounts according to their body weight, until 50% of the mouse population dies. This amount is defined as the substances‘ LD50.
Of course, some of the mice died at a much lower exposure-concentration, perhaps less than 10% of the LD50. In other words, different subjects can react differently to the same substance. The LD50 is a statistical representative number, and in the end, each person will respond differently (For a more detailed account, see 1).
A personal experience of mine demonstrates this very well
While working in a chemistry lab we worked with certain paints for a few hours a week, in regularly examined and approved fume hoods. The chance of getting sick in any way was unlikely. Indeed, we never had any problems with any of the employees working with these paints. A new employee arrived and developed harsh skin problems on her hands, within a few months. After a thorough investigation on our part, the paints were found to be responsible for the skin irritation- even though the employee was exposed to immeasurably lower concentration than any standard. Once she stopped working with these paints, her skin problems were gone.
Similarly, different substances will affect different people differently. Some of the population will have no response, some will respond tolerably, and others yet might respond harshly- even though a clear cause cannot be seen.
Each one of us is different. We each respond differently to different materials. A part of the population might be negatively influenced by using substances found in cosmetic and other products, even if they are defined, as of today, as entirely safe.
Written by: Ido Mashal (BA biology, B.Sc. Chemical Engineering, M.Sc. Material Engineering (Technion, Haifa, Israel))