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by Ken Goldstein, Ph.D.
>We recently looked at the subject of cosmetics in cleanrooms. It appears that people are once again asking if it is acceptable to wear these substances inside contamination-sensitive areas. The short answer suggested was a definite “no.”
The sole exception to this rule was moisturizing lotions for those people with dry flaking skin. The implication here was that while lotions were a potential contaminant, the significant numbers of skin flakes were more likely to pose a serious contamination risk than the lotion used to minimize them. The reasoning behind the rule of “no cosmetics” was given as the first rule of contamination control: never bring anything into the cleanroom unless it really and truly needs to be there (as defined by process and product requirements). Because cosmetics do not pass this first critical test, they should be excluded from the cleanroom. Always.
Recall also that we briefly mentioned the list of possible contaminants found in cosmetics: iron (Fe), aluminum (Al), titanium (Ti), magnesium (Mg), potassium (K), sulfur (S) and carbon (C). In the microelectronics world (semiconductors, integrated circuits, storage media and devices, flat panel displays, etc.) these are all capable of harming both quality and reliability levels. Aerospace products are similarly susceptible to contamination. When considering pharmaceutical products, these contaminants are suspect because they commonly slough off people with the potential for carrying bacteria and other bio-burden with them.
The history of this subject is interesting as much as for what is not there as for what is.
During the early 1980s, just a few significant studies told us all we needed to know about contamination, cosmetics and human debris. Since then, this has been essentially a closed topic.
The early studies were sufficiently alarming that the practice of wearing cosmetics in cleanrooms was simply banned. And short of refuting the early research, additional studies were unlikely to be worth the time and cost.
The seminal research was reported in “Cosmetics in Clean Rooms” by Phillips, Auser, Meikel, Baldwin and Washington and published in the proceedings of the Institute of Environmental Sciences, 1984 (p. 317-323). At the time, the researchers were working for IBM's disk drive division in San Jose, CA.
First, note that the term “clean room” was written as two separate words in the title and throughout the article, standard terminology at the time. As described in the paper, “This study was made to determine if the use of cosmetics by clean room personnel would add contamination to the clean room environment and/or to the product.”
It was suggested that these particles might be “transferred by air currents or by touch.” First the researchers divided the cosmetics into classes representing the most commonly used items: lipstick, blush, powder, eye shadow and mascara. Then, using a professional cosmetologist to assist them, the researchers determined the approximate average amount of cosmetic applied in a single facial application. Finally, they looked at the transfer rates of these materials from the faces of the test subjects to contamination-sensitive target areas. Recall that previous to this study, no one had looked at this.
The results were startling. First, using SEM/EDX, they identified 15 separate elements in the cosmetics. These included sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, bismuth, potassium, calcium, titanium, manganese, iron, barium and zinc.
Just scanning the list of ingredients on the packages yielded 48 different compound chemicals. With the assistance of the cosmetologist, the researchers found that the average number of particles (0.5 micrometers and larger) contained in a typical facial application ranged from a low of 82,000,000 for eye shadow to a high of 3,000,000,000 for mascara. The total particle count was 5,100,000,000 per application.
The particle transfer data was similarly alarming. The air current test was done at velocities of 0.25 to 0.3 m/s, well under the typical figures found in most unidirectional flow cleanrooms. The only good news was that lipstick and mascara showed no transfer by air currents. Unfortunately, the blush, powder and eye shadow all transferred moderate to heavy amounts of the cosmetics.
The transfer by touch test involved a subject's cheekbone being touched by another individual, wearing freshly gloved hands, very lightly in order to transfer the least number of particles. According to the researchers:
“The touch was barely felt by the individual wearing the cosmetics and in no case was the surface of the skin visibly depressed.
This 'touch' is considerably lighter than that used to relieve an irritation.” After this face-to-glove transfer, the glove was used to pick up a contamination-sensitive manufactured part at a specific location. This specific location was then subjected to SEM/EDX analysis. The results here ranged from bad to worse. The eye shadow transferred moderately heavy amounts using the touch test. The lipstick, blush, powder and mascara all transferred very heavy amounts.
Summarizing, the cosmetics all contained significant numbers of particles per facial application. These numbers ranged from the tens of millions to the billions. The blush, powder and eye shadow transferred moderate to heavy amounts via low velocity air currents.
All of the cosmetics transferred heavy amounts using an extremely light touch. The authors concluded: “Cosmetic products contain large numbers of particles which are of the size associated with …defects. The particles can easily be transferred by air currents and touch. In fact, individuals who use cosmetic products have been shown to shed particle materials associated with the cosmetic products. The individuals therefore pose a threat to the 'clean room environment' which is necessary for the production of efficient electronic products.” Finally, note that while the researchers were involved specifically in microelectronics, the particle transfer rates established would be valid for any contamination-sensitive industry and product.
With all of this as background, the no-cosmetics rule is easy to understand. But if we take a long-term look at the future of cleanroom technologies, we may arrive at some surprising conclusions that contradict everything I have suggested until now. Stay tuned and keep an open mind.
Dr. Ken Goldstein is a principal with Cleanroom Consultants Inc. (Scottsdale, AZ) and is an expert in planning and designing cleanrooms and ultrahigh purity systems. He has been associated with the cleanrooms industry for 20 years, and is a senior member of the IEST. He is active in WG-012 (Cleanroom Design) and WG-028 (Minienvironments).