UV-A Radiation and its consequences on the human brain

May 2010

Throughout our long careers, we have given numerous training courses to Level 2 and Level 3 PT people. Our policy is to give what we think is valuable information, not only to have people get their exam, but also to have them better understand safety rules, viewing conditions requirements, etc.

For instance, we explain how spray cans are designed, the difference between liquefied gases and compressed gases, why they are not interchangeable, why liquefied gases are flammable, why they must be used for non-aqueous wet developers, etc. This is not only a technical information useful for their job, but also an information useful for the day-to-day life.

UV radiation is divided in three areas, respectively UV-A (315 nm-380/400 nm), UV-B (280 nm-315 nm) and UV-C (100 nm-280 nm). The shorter the wavelength, the more energetic the photon.

We explain that UV-C radiation is used to sterilize the air in surgery rooms, in antibiotics manufacturing areas, to sterilize water. It is used in chemical analysis to make many molecules/crystals fluoresce.

UV-B radiation is used to initialize some chemical reactions (to make them begin), used also for medical applications against skin diseases such as psoriasis. Skin reacts against UV-B by darkening (suntan): in the middle-dermis, some specific cells called melanocytes produce a dark dye, melanine. These melanocytes, when irradiated by UV-B, produce far more melamine; this dye then migrates to the skin surface and, within 3/4 days, suntan is visible.

UV-A radiation is also used in chemical industry to initialize chemical reactions. Its main use is to make chemicals fluoresce: either for special effects in entertainment industry (the so-called "black-light") or in Non Destructive Testing applications or for criminal investigation. The colour coming from fluorescence due to UV-A or to UV-C is not the same (the excited electrons are not the same). A similar application is found in biology/biochemistry for analysis, for detection of some areas on genes in the cells, etc.

In NDT applications, fluorescent penetrants, fluorescent magnetic particles, fluorescent liquids for leak detection are by far the most widely used. If in the right viewing conditions, an inspector's eyes may detect incredibly small quantities of dye. Sensitivity of fluorescent methods is tremendous.

One of the most interesting parts of our job is ... to hear incredible assertions, sometimes coming from information distorted when it goes from one person to an other one, then to a third one, and so on, back to you! The "word of mouth" which has helped the Homo Sapiens Sapiens to store innumerable experiences, bits of information, sometimes also helps to broadcast rumours or wrong information.

The following stories, once again, are ABSOLUTELY TRUE.

Along the years, several hundreds of Level 2 and Level 3 trainees for Penetrant Testing were given obviously good information -- as they were getting this information from us!!

Among the topics, UV radiation and the safety rules attached are a concern. We give clues to understand how UV, and especially UV-A may harm eyes and skin, not only of PT or MT operators, but also of everyone when in a ski resort in winter/spring, or in mountain or on the beach in Summer. We ask the trainees to let users know they shall wear UV-A blocking goggles, they shall wear long-sleeved clothes and gloves when in the inspection booth.

We draw attention of the audience to a specific body area.

In the booths, quite often operators are experienced men: that means they have long years of expertise. Therefore, they are in their late '40s/beginning '50s. Hence, as they are men, due to male hormones, hair on top of their heads may be scarce. When very powerful UV-A sources are used they are set overhead to illuminate a large area. That means the thin skin on top of the head is exposed to high irradiance levels for long hours. We then recommend to wear a cap, just to prevent any harm.

You could imagine our surprise when we were told that in some companies the information was that "UV-A makes people bald"!! It is now more than 30,000/50,000 years our species lives outside, in plain sun (when the weather is nice!), except for the very last centuries!! (We live more and more INSIDE: homes, malls, metro, cars, trains: the best example being MONTREAL in Quebec, Canada, where one can live the entire year without going out in the street!). So if there was any UV-A's effect detrimental to the hair thickness on men's heads, we may assume we would have noticed!

Once again, word of mouth has sometimes laughable consequences, far from what we could anticipate!

If it will make you feel better you will be happy to learn that no relationship has ever been established between baldness and exposure to UV-A!

We have been also very surprised some 25 years ago when we heard of an amazing demand by people working in UV-A booths: they stubbornly refused to work in the booths unless protected by lead apron from their belly down to the knees ... because "UV radiation makes people infertile"!

In fact, the information we gave to some people was relayed in their companies, "adapted" because badly understood, "translated" into frightening words!

That is why since this time we are very careful about the ability of the audience to really understand what we say!