I just wanted to foward this on. Anyone know where we could get a hard copy of this article and how to obtain it. I found it very informative. This was originally sent through another forum. When I thought I was giving my veileds a lot of uva and uvb I was really giving them nothing.





I wanted to share this information from an article that appeared in

the Bulletin of the Chicago Herpetological Society (Vol. 40, Number

1, Jan. 05). The article is fairly long (7 pages 2 additional

pages of graphs) and I don't want to violate copyright laws by

scanning and posting it, but I'll try very hard to give you a decent

summary. It's pretty technical, so I'll try my best. I found this

article to be very interesting. I am posting this to both the AIML

and the UVB_Meter_Owners group, so my apologies if you see this

twice.



Deena

********************

Article Title: UV-lamps for Terrariums: Their Spectral

Characteristics and Efficiency in Promoting Vitamin D3 Synthesis by

UVB Irradiation

Author: Jukka Lindgren

Originally published by the Herpetological Society of Finland

[Herpetomania 13(3-4), 2004]



Abstract: Sufficient irradiation within a narrow sub-band of the UVB

range is a prerequisite for the photosynthesis of vitamin D3 in

skin. Although radiation below wavelength of 300 nm promotes

photosynthesis of vitamin D3, radiation above 300 nm destroys

vitamin D3 that has been already synthesized in skin tissue or

nutritionally obtained. Furthermore, skin temperature has a

significant effect on the pace of vitamin D3 synthesis. In a

terrarium, the required UVB-radiation has to be artificially

produced with dedicated lamps. In the study, the characteristics of

light produced by fourteen different models of UV and full spectrum

lamps specifically designed for terrarium use were measured over a

range of 250-800 nm. As a reference, the spectrum of natural

sunlight was also measured when the sun was at its highest point of

elevation in the southern sky of Finland. The proportion of

radiation energy that takes part in the photosynthesis of vitamin D3

was determined and the D3 Yield Index was calculated. Significant

differences as large as a thousandfold were found in the D3 Yield

Indices. The resulting conclusion is that UVB radiation as a

percent of the total radiation figure does not necessarily give a

true indication of a lamp's capability to maintain cutaneous

production of vitamin D3.





Explanation of study:

1) Fourteen lamps of various makes and models were obtained for the

study. The lamps included the following: a new Reptisun 5.0 14W

(ZooMed), a 10-month old Reptisun 5.0 15W, Reptistar 30W (Sylvania),

Reptilight 36W(Narva), Repti Glo 40W, Life-Glo 40W, and Exo-Terra

Repti-Glo 40W 2.0, 5.0 and 8.0 - all by Rolf C. Hagan Corp., ESU

Reptile Super UV Daylight 40 W, ESU Reptile Desert 7% UV 40W, Active

UVHeat 100W (Wild Inside), True-Light 36W and True-light Daylight

6000 15 W ("Manufactured for AD-Lux Oy". Other "full-spectrum"

bulbs not designed for UV output were also included, but I won't

list them here.



2) Measurements were taken of UVA, UVB and UVC emitted by each

lamp. "Measurements were made by Suomen Aurinkosimulaattori

Oy/Solar Simulator Finland Ltd. The spectroradiometer used for all

measurements was IL700A Research Radiometer, by International Light

Inc."



3) UVB irradiance was divided into two categories - what the author

calls UVB-1 and UVB-2. UVB-1 values represent UVB emitted in the

wavelengths range that mainly contributes to vitamin D3

photosynthesis (280-304nm) while UVB-2 values represent UVB emitted

in the wavelengths that may potential destroy vitamin D3 (305-319

nm). The author explains that "the ability of a lamp to efficiently

produce vitamin D3 can be evaluated by comparing values in table 3

[UVB-1 and UVB-2 values]. The higher the irradiance of UVB-2 is in

comparison to UVB-1, the higher the probability that UVB-2 radiation

will start destroying cutaneous vitamin D3."



4) The D3 Yield Index for each bulb was calculated. The author

explains D3 Yield Index: "The basis for the calculation of the D3

Yield Index was the action spectrum of 7-DHC to pre-D3 conversion in

human skin. The index was calculated in the 252-313 nm range by

weighing the irradiance at each wavelength in accordance with the

action spectrum. The effective irradiances thus obtained were

summed over this range, and this value was finally adjusted to the

reference by a suitable multiplication factor, resulting in the

final D3 Yield Index."



He continues, "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

the novice keeper; they indicate with an unambiguous value the

efficience of a lamp to promote photosynthesis of vitamin D3 and by

that, indirectly ensure sufficient level of calcium metabolism."



Results:

Here are some of the data on the lamps. To shorten the amount of

typing I have to do and the amount of reading you have to do, I'll

just include the lamps most commonly purchased and discussed by

hobbyists.



New Reptisun 5.0

UVB-1: 2.057

UVB-2: 8.232

D3 Yield Index (YI): 439.3

UVB%: 6.8



Used Reptisun 5.0

UVB-1: 1.717

UVB-2: 6.663

D3 YI: 367.7

UVB%: 6.6



Reptilight

UVB-1: 1.302

UVB-2: 5.825

D3 YI: 283.7

UVB%: 4.4



Exo-Terra 8.0

UVB-1: 0.780

UVB-2: 6.914

D3 YI: 190.2

UVB%: 4.2



Active UV Heat

UVB-1: 0.815

UVB-2: 14.647

D3 YI: 165.3

UVB%: 1.2



ESU Reptile Desert 7.0

UVB-1: 0.000

UVB-2: 0.443

D3 YI: 0.5

UVB%: 0.3



Conclusions:

The author states: "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 14W

unit, while other units in the study have a nominal power of 30-

40W. 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.



The second best lamp, a Zoo Med Reptisun unit that had been used for

10 months, does not show remarkable weakening of UVB radiation.

While examining the full spectrum, it can be seen that the

irradiance of the lamp as dropped constantly through the whole

spectrum. This means that the UVB radiation of a lamp does not

cease abruptly, as is sometimes suggested, but seems to get

gradually weaker along with the visible light. On this basis a

recommendation to replace the UV lamp twice a year due to alleged

fading of UVB radiation is at least to some extent unwarranted. The

conclusion is of course based only on one individual lamp;

differences due to manufacturing tolerances, etc. are entirely

possible.



The next best lamp, Narva Reptilight, is also very efficient in

promoting vitamin D3 synthesis with a D3 Yield Index of 284.

Additionally, its spectrum is exceptionally beneficial; radiation at

315-335 nm range which potentially destroys vitamin D3 is very low.



Next comes a group of four lamps (Exo-Terra Repti Glo 8.0, Active

UVHeat, Reptistar and Exo-Terra Repti-Glo 5.0), the results for

which are rather equal. Their D3 Yield Indices are already less

than half of that of the best product. In this group, the case of

Sylvania Reptistar is interesting. Even though its irradiance in

UVB range is the third highest of all tested units, its D3 Yield

Index is only modest. Its spectrum curve starts to rise only at

about 300 nm; therefore, the main proportion of its radiation is

concentrated in the UVB-2 and UVA ranges, in which strong

irradiation is known to be detrimental to the production of D3.



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 14W 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....



The Reptile Desert 7% UVB, manufactured by Energy Savers Unlimited

(ESU) turned out to be a disappointment. Despite its name, the unit

only produces 0.3% UVB radiation and its D3 Yield Index is only 0.5."

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