I just read one of the best articles I've seen so far on UV lighting, funded by the Herpetological Society of Finland, and Hagen. Hagen Repti Glo and Life-Glo bulbs where included in the study but the results said they "cannot be recommended for use as UV lamps with a purpose to promote vitamin D3 photosynthesis in skin". It was published in Herpetomania (Herpetological Society of Finland).
The specific article is:
Lindgren, Jukka. 2004. UV-lamps for terrariums: Their spectral characteristics and efficiency in promoting vitamin D3 synthesis by UVB irradiation. Herpetomania. 13(3-4):13-20.
Its around 10 pages long, gives a nice description of the processes involved with natural vitamin D3 syntheses and compares 14 different bulbs. Unfortunately, the new compact lights and many of the Mercury Vapor bulbs are not evaluated. The one Mercury Vapor bulb evaluated was the Active UVHeat bulb which didn't perform as well as the regular linear fluorescent Zoo Med ReptiSun 5.0!
The study explains how comparing the whole UVB range from bulb to bulb, like we see many people doing in the US using less sophisticated UVB tools, is misleading because part of the UVB range helps skin create D3 and another part of the UVB spectrum destroys D3 in skin.
The approach used in this study is very good. The article mentions several ways to improve upon itself.
I was disappointed to see the UV Heat bulb do poorly because I currently use three types of mercury vapor bulbs in addition to ReptiSun 5.0 bulbs on my tortoises. It doesn't mean untested mercury vapor bulb types will do poorly, it just uncovers the need for a similar study to be done on them.
Quotes of particular interest from the article include:
"Vitamin D3 production takes place mainly in the wavelength range 295-300 nm, while the UVB range is generally specified 280-320 nm. This difference is significant especially at the top of the range, where vitamin D3 production ceases, but photodestruction by longer wavelength radiation still continues. This makes the use of UVB irradiance figure by itself a poor indicator of the effectiveness of the incident light in photosynthesising vitamin D3 in animal skin.
Use of the D3 Yield Index as a basis for evaluation of UV lamps gives a possibility to compare very different types of lamps with consistent criteria. The D3 Yield Index turns the attributes of a spectrum curve, that are otherwise difficult to compare, into an easily manageable and understandable form even for a novice keeper; they indicate with an unambiguous value the efficiency of a lamp to promote photosynthesis of vitamin D3 and by that, indirectly ensure sufficient level of calcium metabolism."
"Another sample that attracts attention in this group is Active UVHeat. The spectrum of this lamp is almost a pure line. In the wavelengths where radiation exists, it is very strong. In other areas radiation is at the same level as for the 14 W ReptiSun unit. There is only one single peak in the UVB-1 range, at 302-304 nm - this establishes the D3 Yield Index of this lamp at a reasonable level. However, its spectrum has another peak, over 10 times higher, at 313 nm and beyond that generally rather high irradiance values which may contribute to photodestruction of existing vitamin D3 in skin."
"Of all the lamps measured, the best contributor to vitamin D3 photosynthesis in skin is Zoo Med ReptiSun, with a D3 Yield Index of 439. This result can be considered especially noteworthy for the fact that the lamp in question is only a 14 W unit, while other units in the study have a nominal power of 30-40 W. The spectrum of ReptiSun begins very low in the UVB range and the spectrum curve rises steeply. In the most sensitive wavelength for vitamin D3 synthesis, 295 nm, for example, the radiation of ReptiSun is already 1.8 times stronger than that of the next best lamp."
Sources for getting this article include:
1. Herpetomania
2. The Chicago Herp Society plans to republish this article for the US audience next year in their bulletin, (www.chicagoherp.org).
Hope you find this useful,
jbly
25% Finnish
Tortoise Keeper
Ed
