Melissa Kaplan's
Herp Care Collection
Last updated January 1, 2014

Mercury Vapor Heat & UV Lamps

Are they suitable or safe for typical home use?

Melissa Kaplan, 1998, 2002


Several years ago, "Dragonlites", a mercury vapor product, made their appearance on the WWW. They were discussed at that time on the Iguanas Mailing List (IML). As so often happens with discussions getting farther into the physics and biology of UV than most listmembers care about, I started a separate "Dragonlites" list for the the few of us who wanted to pursue the discussion of these lights, a list which included the developer/manufacturer of this product. The questions raised by the Dragonlites list members went unanswered and eventually the list was canceled due lack of postings.

Less than a year later, Dragonlites appeared under a new name (ActiveUV) and website ( with no reference made to its previous name or site. The new site contains less information than their old site. In my discussion below, I will indicate which came from their old site, and what comes from their new site.

The claims made for the product, however, are the same as were made for the product under its previous incarnation: that they are a safe alternative product to use in place of the separate UVB-producing fluorescents and heat sources (lights, ceramic heating elements, other infrared devices) that have long been in use by herp keepers.

In support of the developer's claim for his product's suitability and use for home herp keepers, a list of zoos and other institutions keeping herps using this product were listed and testimonials given. For me, that presents a problem: zoos are not people's bedrooms, dens, living rooms, kitchens, classrooms, or other places herp hobbyists keep their reptile and amphibian pets.

What follows is essentially a post I sent to rec.pets.herp when the subject came up in August 1999. It has subsequently come up several times on the IML and other lists I am on, so I have modified it somewhat from is original format to present it here on my site rather than repeatedly posting it when the subject comes up.

There are now other mercury vapor lamps marketed to herp keepers, including Zoo Med's PowerSun UV and Nature Zone's High Noon.

While there are many zoo keepers who are very knowledgeable about the dietary and environmental needs of herps, not all are equally so. I have had too many experiences with those who were not, such as the reptile keeper at a Northern California zoo who insisted I was feeding my green iguana animal protein because "green iguanas need animal protein and he wouldn't have grown so big if you weren't." Then there was the "We feed our green iguanas mice" sign that the National Zoo had posted for years until enough knowledgeable iguana keepers complained. Another zoo I know of had appointed as curator of reptiles someone whose specialty was mammology, not herpetology. So, testimonials by zoo keepers or curates, or lists of zoos, in and of themselves are not enough to sway me unless I know the zoo keeper in question and how his or her animals are actually kept.

While many zoos have small exhibit and off-exhibit enclosures for their reptiles and amphibians, many have very large, high ceilinged enclosures. While that 6 ft. tall iguana enclosure in your living room or bedroom may seem very high to you, it isn't the the 8-12 ft high ceiling that a truly large enclosure has. If using these lights means you have to wear safety goggles when working in your iguana's enclosure, why should I consider the product safe for my iguana?

I. Quantity of UV Produced
The main selling points seem to be

1. Existing products don't produce as much UVA or UVB as the sun;

2. Reptiles need more UVB than existing products can provide in order to produce sufficient levels of UVB and more UVA to encourage more normal behaviors; and

3. Ease of use, with a single product producing both heat and ultraviolet radiation, instead of having to use two separate products.

The third point is dispensed with easily enough: there is no doubt that being able to use a single product is preferable to using two separate pieces of equipment. There is the saving of space in the enclosure or area itself, having to have only one fixture instead of both an incandescent and a fluorescent fixture (or multiples of them, for those who use incandescents or infrared lighting products to provide night time heat, and those who prefer to use two or more UVB-producing fluorescents instead of one). This is probably the most seductive feature of any product claiming to be "full spectrum." As we have found throughout the years, most of these products are not "full spectrum", as they do not emit UVB or appreciable amounts of UVA. Some are not even producing the full visible spectrum, being "color corrected" to alter the appearance of the colors visible to your eye when you use them. So, yes, a combination heat/UV product is a great idea and would be a great use to many, if not most, herpers, at least for daytime use.

Myth of Sun Exposure
There is theme that plays throughout herp postings whenever the subject of UV wavelengths comes up. The variations are all centered around "the sun produces more UVB and UVA than do the UV-producing fluorescents made for reptiles." Another popular refrain is "the UVB-producing fluorescents do not produce as much UVB as the sun does at the equator at noon." Both of these statements and variations on them are correct, as far as they go. What is missing is the basic understanding that:

a. It is not noon at the equator all day long; and

b. Diurnal animals, including reptiles and amphibians, do not spend all of the daylight hours fully exposed to the sun.

Ergo, not only is the amount of UV that hits the exposed earth, water, branches and tops of leaves during the hours from sun up to one minute before noon, and from one minute past noon to sun down, less than the amount of UV that hits the exposed earth, water, branches and tops of leaves at the equator at noon, even if it was the same, the reptiles and amphibians aren't out it in anyway.

During the heat of summer, many diurnal herps actually become crepuscular to escape the unrelenting heat of the day. Depending on where they live, they may retreat to the cool of rocky crevices, underground burrows, beneath fallen logs, mounds of detritus, or retreat into the shade provided by branches and rocky outcroppings. There they remain for much of the day, emerging only to boost their core body temperature as needed to maintain their digestive and other systems functioning at optimum capacity, or staying put until the air temperatures have cooled off a bit. At that time, some come out for a last bit of basking, while others begin the days hunting for prey, or continue their search for prey that was interrupted when the temperatures climbed in the morning.

In lands of almost perpetual summer (the lands laying on the equator and several degrees of latitude north and south of it, considered to be tropical and neo-tropical), the only real seasonal difference is between the wet and dry seasons. Whether it is raining incessantly, or dry as a desert, the temperatures remain remarkably even, always in the low to mid 80s during the daytime hours. Just as the temperature is pretty much the same, so too is the amount of UV hitting the exposed earth, water, branches and tops of leaves during the year. There will be some minor fluctuations, as the sun passes through more or atmosphere as the earth's natural rotation and tilt creates the summers and winters of the northern and southern hemispheres, but by and large, in the tropics, things are pretty much the same, temperatures and UV-wise, day in and day out.

So, to bring us back to the two main "buy this product because" points:

1. Existing products don't produce as much UVA or UVB as the sun.

So what? What matters is not how much UV the sun produces or how much the fluorescent products produce, but rather, does any of the fluorescent products produce enough UVB and UVA to promote formation of essential amounts of vitamin D3 and encourage normal feeding, breeding and other behaviors?

2. Reptiles need more UVB than existing products can provide in order to produce sufficient levels of UVB and more UVA to encourage more normal behaviors.

Wrong. Some of the UVB-producing fluorescents that have been sold sold in North America and Europe for years do indeed promote the formation of essential amounts of D3 and promote normal behavior (insofar as "normal" will ever apply to what are essentially wild animals kept in captivity). Examples include the Duro-test Vita-Lite and Zoo Med's Iguana Light and Reptisun.

So, both the ActiveUV and some of the UVB-producing fluorescents produce UVB suitable for herps. The ActiveUV produces heat as well. Is that enough reason to race out and replace all your fluorescents and incandescents with this product?

II. If some is good, is more better?
In the wild, reptiles and amphibians spend much of their day in shade, either hiding away burrows, crevices or other deeply shaded places, or in the dappled to moderate to heavy afforded by positioning themselves at various places in leafy bushes, shrubs or trees. In the wet forests from where so many of our herps come, little direct sun actually penetrates down to the ground. Terrestrial species have to move around finding places where the shafts of sun penetrate all the way through the 100-150 ft. tall trees and four plant growth layers. Arboreal species who may spend most of their time living in the second and third levels of the forest, move around to find branches in the path of shafts of sunlight penetrating through the first (top, uppermost) layer, or climb to the top to bask on the top of the canopy for a while, moving back down into shady areas when their core temperatures start to exceed comfort levels. All this, if you will, a punctuated thermal gradient.

Contrast that with the typical captive environment. For terrestrial, saxicolous, and fossorial herps, the thermal gradient provided for them is typically horizontal, with heat placed at one end of the width of the tank. The gradient is formed along the horizontal, with the temperature getting naturally lower (cooler) the farther away from the heated end. Depending on the type and depth of substrate used, and whether an overhead heat source is used along or in conjunction with a undertank heat source, the substrate below the surface of the substrate may or may not be warmed enough to form a small vertical thermal gradient. Typically, a hiding place of some sort (box, half log, bark slab) is provided at one place along the gradient, or the herp burrows under the substrate or shelters under live or artificial plant.

In enclosures set up for arboreal lizards, the heat is typically clustered in the the upper end of one side of the enclosure. Depending on what other types of heating equipment is used and where it is placed, the thermal gradient will extend both along the horizontal and vertical. Typically, no hiding place is provided, or if one is, it is placed at one spot in the gradient. Unlike in the wild, where different degrees of shade are available and used all during the daylight hours, in captivity these reptiles are kept with little to no shade. They are therefore subjected to their heat and UV lighting all during the daylight hours rather than their wild counterparts, who spend a significant part of their day in shade.

What does this mean in terms of a mercury vapor like ActiveUV that puts out higher amounts of UV than the UV-producing fluorescents that have been used - and used successfully when installed properly - for years? That's a good question, and one that the manufacturer has not answered. Effects of increased exposure of herps to UV may include effects similar to those in humans...and let us not forget that the destruction of the ozone layer and subsequently higher levels of global UV have been theorize by many scientists to be the cause or one of the causes of the worldwide decline in amphibian populations.

Left to their own devices and given UVB, including the levels of UVB made available by properly installed Vita-Lite, Iguana Light and Reptisun fluorescents, green iguanas make the amount of D3 they need to metabolize calcium. They can tolerate surprisingly high levels of D3, levels that could cause problems in other species and types of animals. That does not mean that they would be any less susceptible to adverse effects of prolonged exposure to higher levels of UV, such as those produced by mercury vapor products (which are not new in the realm of lighting and heating products).

Reptile scales are covered by a thin layer of skin, and on many species, each scale is separated by a thin rim of skin. Amphibians have no scales. While chelonians are mostly bony shell, their heads, legs and tails, shoulder and thigh areas, are all covered with skin. Along with there being no long-term studies on the effects of forced prolonged exposure to higher levels of UV on reptile and amphibian skin, there is similarly no research on prolonged high levels of exposure to their eyes, stress levels (as measured by corticosterone levels) or anything else. This lack of research troubles me in so far as the manufacturer claims the product is just as safe as the lower-output fluorescent products that have been used for years.

The other thing that troubles me is some of the testimonials. All claim that their reptiles are doing better with the ActiveUV light, but there is no clear discussion of what their set up was before using this product. In at least one case, it sounds like the owner of desert lizards wasn't using any UV product at all or regularly prior to his installing the ActiveUV. Is it unreasonable to wonder whether, if these people and others reporting a positive response to the use of this product, are actually getting the same response they would have had they properly installed and used a UV-producing fluorescent and heat source providing the necessary thermal gradients their species require?

The answer is most likely "yes", they would have gotten the same results had they had their reptiles set up properly to begin with. One zoo, discussed on the discontinued "Dragonlites" list, reported a beneficial response to this product. Upon closely questioning what their set up was like before they used this product, it was quite clear that they were using the UV-producing fluorescent in such a way as to guarantee that their lizards would get the least amount of UVB possible from it, thus it was no surprise that the lizard kept that way developed MBD and failed to thrive.

III. Testimonials and Other Statements
On their old site, they had the following statements and testimonials:

"A female crocodile monitor (Varanus salvador) had no Ultraviolet (UV) light source or dietary vitamin D3 supplementation for several years. The animal was exposed to a 300-watt flood Active UV Heat bulb for four months at a ceiling high distance (2.0 to 2.2 meters)."

Here is another example where the reptile was kept with no UV for years. Of course she did better once they gave her a UV source! Would she have done any better had they installed UVB-producing fluorescents? They do not mention what the enclosure temperature was before installing the ActiveUV, so we cannot tell if it was too low prior to the installation of the ActiveUV. If so, then presumably any heat source that effectively increased the heat to the temperatures required by this species have yielded beneficial results.

Two meters x 3.281 inches = 6.56 ft; 2.2 m x 3.281 = 7.21 ft. This is taller than most enclosures used to house reptiles in homes and classrooms.

James Ball, of the York Serpentarium, writes, in his article, A Comparison of the UV-B Irradiance of Low-Intensity, Full-Spectrum Lamps With Natural Sunlight, "Natural sunlight has a much higher UV-B irradiance than most commercial sources of low-intensity, full-spectrum lamps. The maximum UV-B irradiance near the equator (solar elevation angle < 25 deg.) under clear, sunny skies, is about 250 µW/cm². " Now, remember:reptiles thermoregulate by going in and out of shade...wherein they are getting less than 250 µW/cm² at noon, and less than 250 µW/cm² during the rest of the daylight hours.

Their old website gave the following figures for their 100 watt unit:

1.6 the amount of equatorial UVA at 4 ft away
2.25 the amount of equatorial UVA at 3 ft away
6.8 the amount of equatorial UVA at 2 ft away
18.0 the amount of equatorial UVA at 1 ft away

0.12 the amount of equatorial UVB at 4 ft away
0.16 the amount of equatorial UVB at 3 ft away
0.40 the amount of equatorial UVB at 2 ft away
1.28 the amount of equatorial UVB at 1 ft away

They now state that their "Active UV Heat" produces, "at every distance":

100 watt flood @ 12" 50 µW/cm²
160 watt flood @ 18" 55 µW/cm²
275 watt flood @ 24" 66 µW/cm²
100 watt spot @ 30" 70 µW/cm²
160 watt spot @ 48" 100 µW/cm²

If the µW/cm² is supposedly the same "at any distance", why do they specify distances and why is the amount different? And, if the amount put out by a properly installed UVB-producing fluorescent is sufficient for promoting effective levels of D3, and adequate levels of UVA to promote appropriate breeding, feeding and other behavior, why is this product's output better? If the UVB is sufficient to produce the amount of D3 the species needs, they cannot use more D3 than they have calcium and phosphorous; in fact, excessive levels of D3 may lead to bone porosity and other health problems. Without longitudinal tests comparing ActiveUV with UVB-producing fluorescents (which also produce UVA), statements claiming they are better just because some people's animals improved under them are anecdotal and cannot be substantiated without knowing details of how the animals supposedly benefiting from them were kept before and without testing these same animals under identical conditions but with the heat and UV provided by other types of heat sources as required to provide the thermal gradients the species require, and properly installed and utilized UV-producing fluorescents.

I'd want to see this research for a wide range of lizards and chelonians typically kept as pets in captivity - no Komodo dragons, please, with lights placed 4-7 ft away ("In one other zoo both a water monitor (Varanus salvador) and Komodo dragon (Varanus komodoensis) have been documented with normal to fairly high levels of vitamin D3 with use of the Active UV Heat lamp at distances of 4-7 feet away." ) I would also like to know the long-term effects on bone density of "fairly high levels of D3" on pet lizards who generally don't weigh in at 400+ lbs. [Quoted text is from their old website.]

Some other quotes from their website on certain points:

"Consistently there has been a need in reptile exhibit lighting for a bulb that could project ultraviolet for some distance (many fluorescent UV-B lights project over an effective distance of only 12-18 inches)."

"Avoid staring directly into or working under a [n ActiveUV] bulb in use." [emphasis mine]

"If possible, turn lamps off while working close (3 feet or less) for extended periods of time." [emphasis mine]

Time for mini-goggles for reptiles? What does someone do who shares his or her bedroom or main living area with the reptile outfitted with an ActiveUV? Wear protective eyegear when they spend any time in the same room? Turn of the ActiveUV while the kids are doing their homework, or the parent has the book club over for their weekly meeting? What are parents who have young kids who like to sit and watch the nice lizard for long periods of time to do?

What's the point of having a UV/heat light if you have to keep turning it off if you are spending more than a few minutes near it? Just how long are those "extended periods" anyway?

"Always place bulbs in or above reptile enclosures in such a way that the animal always has the option to move out of the direct beam of light." [emphasis mine]

Define "direct." Exactly how far away from the light does the reptile need to be to be safe...and why does he need this? To thermoregulate? That would be accomplished by having a proper thermal gradient set up. Or does it have to do with the high levels of UV produced by these units? If the animal requires shielding by moving away, and humans need to turn it off when near it for any length of time, how are these safe to use in a home or classroom setting?

"Thermal burns should be avoided by placing 100 watt lamps no closer than 18 inches... "

This is the maximum distance from the reptile that a UVB-producing fluorescent needs to be placed. If it is placed closer, from 8-18 inches, as is recommended for optimal access to the UV produced, fluorescents are still too cool to burn the reptile. The output is low enough to not pose a safety hazard to the humans sharing the room or working in the enclosure, yet high enough to promote adequate D3 formation and behavior, low enough to not post a health threat. So, again, I have to wonder about the claims that the ActiveUV product is better.

"...and 160 watt lamps at a distance of 2.5 to 3 feet away from the reptile. 300-watt lamps should be used at a distance of 3-8 feet away from reptiles."

This might work in a large enough room, unfrequented by humans, in which iguanas free-roam. How many of you have such a space? What about other reptiles?

IV. Some Final Questions That Remain Unanswered...
The following issues and questions are ones I have raised which remain unaddressed and unanswered:

The reports on the efficacy of this product are related to their use with zoo animals in zoo settings, not small species of lizards and chelonians typically kept as pets, nor is there any indication that any testing was done on pet species in settings reflecting the typical home environment. If any actual testing of pet species in home settings have been done, why not add them to the website and other marketing literature since the product is being targeted to the home herp keeper, not just zoos and other large animal research facilities?

Testimonials from people who may not have been keeping their reptiles properly to begin with do not justify the use of any product, though they do underscore the necessity for knowing what a species' heating, lighting, and photoperiod requirements are to begin with and to ensure they are provided from the start. A corollary, if you will, is that if you do not provide what the species requires, and then you do, you will see changes consistent with meeting their needs. The provision of their needs should not be confused with the use of a particular product. In other words, if you give a bottle of Evian water to someone who is dehydrated, is it the Evian that causes the physiological changes that happen when a dehydrated organism begins to have its hydration needs met, or would any water, in sufficient amounts and of sufficient cleanliness and purity, do the same job as the Evian?

I have asked repeatedly through the years, as high-output UVB-fluorescent manufacturers made claims that their product was better than the lower-output Vita-Lite, where is the research documenting that more is better if less does the job of promoting healthy bone density and systemic functioning? The same question applies to the ActiveUV, again, assuming that the herp keeper already had heating and UV equipment properly installed and maintained.

Until these questions are adequately addressed, I personally will pass on using these products in favor of ones I know are safe and effective.

November 15, 2000 Update
It came to my attention that my name had come up in conjunction with a discussion of this product on the Pogona email discussion list. What follows is my response and request to the moderators that it be posted to that list:

It has come to my attention that my name has come up a few times on Pogona in conjunction with the ActiveUV product. Would you pass the following along to your list?

>>As we tell people all the time, ultraviolet rays do not penetrate through glass. The only risk would be from directly looking at the bulb.

ActiveUV lamps have a glass cover, behind which is the mercury vapor tube. This is an essential safety feature of all mercury vapor lamps. If UV were not penetrating the glass of the ActiveUV lamps, then these products would be useless in terms of providing UV to your reptiles. Mercury vapor lamps used for other applications have glass that does not permit the passage of much UV, making them useless in terms of using them in applications where UV is desired. This is the same glass-difference that makes the made-for-reptiles UVB-producing fluorescents suitable for providing UVB, while household/commercial fluorescents are not.

>>My herp vet tried to contact Melissa Kaplan to offer to let her try one but she did not respond.

I don't recall receiving any such communication from a vet. David Krughoff, author of "Anna, My Green Friend," wrote me, stating he had absolutely no association with ActiveUV (which is clearly not true, based on the ActiveUV site), as did the developer of the light. No vet. I was threatened with litigation by a vet who did not like my expressing my views on the product on the 'net. This vet turned out to be the wife of the product developer, though she did not state this in her communications to me or to Jeff Barrington at

>>One last comment. Melissa Kaplan argues that if Reptisun 5.0 bulbs have been enough for all these years, then why do we need more uv? She raises the concern about exposing our reptiles to too much uv exposure. Why are people talking about using Reptisun 5.0 in addition to a uvheat bulb to be sure they're getting enough?

First, I want to ensure people realize that I am not the one recommending the use of a UVB-producing fluorescent along with an ActiveUV lamp.

As for the "if Reptisun 5.0 bulbs have been enough for all these years, then why do we need more uv?", that is correct. If your body can only use N amount of something, giving it N x 2 doesn't make your body better or enable it to use it better. The same goes with UVB. If iguanas only need N amount to manufacture the previtamin D they need to ensure calcium metabolism and all the other things D is used for, and they are able to make enough previtamin D using one of the recommended UVB-producing fluorescents, then doubling or tripling their UVB exposure by using a mercury vapor product isn't going to make them better; while it may cause more D to be formed in their body, up to a certain point, that's just wasted energy to make it and get rid of it as they will only metabolize as much calcium as they need. More is not necessarily better. For more information on this, I recommend reading Anne Marsden's articles, UV and D3: An Endocrinologist's View and Sunlight and Reptile UVB Tubes: The Value of UVB Exposure

>>It is unfortunate that someone as highly respected and knowledgeable as Melissa Kaplan has given the bulbs such bad press without ever having tried them.

I've never sprayed my mite-infested reptiles with organophophates either. Does that make me unqualified to have an opinion, based on the available literature on the toxicity and long-term effects of even brief OP exposure?

This, of course, is beside the fact that I already have an autoimmune disease and know that UVR exposure exacerbates it. I don't often go out in the sun; when I do I wear long pants and sleeves and slather sunscreen on my skin (which, as you will see from some of the research, just protects against aging and some cancers, but not against immune factors). Am I supposed to do this inside the house as well? What if I don't and these mercury vapor lights indeed have the potential for adverse human health effects I think they may have? And even if I do keep covered up and keep the sunscreen on, since sunscreen does not protect the body from the harmful effects on the immune system that UVR causes, I'm still at risk. Remember, I'm talking about someone who already has autoimmune disease - and there are a lot of us out there. And what about those who don't yet realize they have an autoimmune disease?

Zookeepers are getting less exposure than pet keepers are because zookeepers don't spend all day in the animals' enclosures. Each keeper has a "string" assigned to him/her. The string includes several animal exhibits which much be cleaned, the animals checked over, fed, and other maintenance tasks that must be performed daily - outside of the exhibit (and exposure to the Active UV bulb). Contrast this with the product used in the home environment, where humans and animals spend far more time, and in closer proximity, to the product than zookeepers do. These lights have just been on the market for home use for maybe 2 years. Tanning lamps, tanning and lighting fluorescents, and a variety of mercury vapor lamps for industrial and home use (as for aquariums - which are shielded so that they do not emit enough UVB for reptile use) have been around for decades and health effects have been seen in clinical practice (as by Nancy's eye doctor) as well as heavily researched in the lab. As far as I know, there have been no such tests on human health effects of the ActiveUV product and they have not been in use widely enough or long enough for any clinical patterns to emerge if, in fact, they can pose a health hazard to humans.

My point here, in case anyone missed it, is that there simply is not enough research to convince me these are safe for humans. That doesn't mean they aren't safe, but for those of us concerned with reducing, rather than increasing, health risks, it is simply a risk I am not going to take at this time. I must say that I rather resent people who have not done the research and who are not aware of the potential for health risks who impugn me for not putting my own already precarious health at further risk.

I have been unable at this point to find information that would enable me to compare apples-to-apples. The ActiveUV output data is expressed in microwatts; so far, I've not been able to find data on safe or harmful human exposure levels expressed in microwatts. It's something I'm looking into, but isn't a high priority for me at this point. Perhaps someone else would like to pursue this?

What I have found is data on the hazards of mercury vapor lamps and UVR (ultraviolet radiation) in general. That information has been around for years, and that is why I have always spoken out against the use of mercury vapor and metal halide lamps. In that respect, I'm not "picking" on ActiveUV, just the technology (mercury vapor). I've linked some abstracts and an FDA article excerpt to some new pages. I'll add to them as time permits.

There is research documenting that, given a choice of a cold, bright area and a warm, dark area, lizards whose inner clock tells them that it is time to warm up will go sit in the cold, bright area rather than the dark, warm one. It is well known that the UVB-producing fluorescents do not produce the bright white light that incandescents (or mercury vapor) lamps produce. Thus, it is best to use a bright white incandescent lamp for daytime heat, rather than, say an incandescent used for nighttime heating or a ceramic heating element, when using a UVB-producing fluorescent tube. This provides the bright light stimulus needed to attract the lizard to the basking area, over which the UVB-producing fluorescent is situated. Desert species, such as bearded dragons, may well be 'programmed' to respond to brighter light than are arboreal species who have greater shade and lower thermal tolerances than desert species, and so we see the "improvement" cited by bearded owners.

A study into whether the improvement perceived by bearded dragon and other reptile owners when they install the ActiveUV is due to the ActiveUV itself, or due to the brighter light it emits, would be interesting and far more useful than a list of zoos who use the product and testimonials about how good the animals are doing when the product is used.

I would also suggest that anyone using any mercury vapor lamp product in their home or workplace read the safety tips in the excerpt from the article by the FDA; it is in the Mercury Vapor Lamp article at my site. Speaking of which, perhaps those who have bought the ActiveUV product could tell us whether they have the safety labels required by the FDA on them?

November 21, 2000 Update
Someone who bought an Active UV bulb sent me the warning printed on the package. As one can see, the FDA warnings are absent.

WARNINGS.....This product omits ultraviolet rays. Do not look or allow others to look directly into light. Do not use as a reading light or tanning light. Turn off the lamp if working closer than minimum distance requirements for an extended period of time. Cannot be used on a dimmer or thermostat. If turned off / on again, it will not relight for at least one minute.

Using Active UVHeat Bulbs....Position and point the lamp at one end of the cage, provide some shade, and always allow the animal to retreat from underneath the light.

September 28, 2001 Update
Zoo Med and T-Rex have both come out with mercury vapor products to compete with the Active UVHeat product. My comments for all mercury vapor products marketed for reptiles is the same as those above.

In closing...
Yes, I know that anything is toxic in large enough quantities. What too many people aren't getting is that we are having increasing problems predicting what is safe and what isn't any more.

We are living in an increasingly toxic environment, with cancers and autoimmune diseases on the rise. In less than 100 years, we have thrown so many chemicals into our air, water, soil, and food that no one can determine what effects the interactions of all these chemicals with each other, let alone on humans. Despite the fact that the Environmental Protection Agency and its predecessors have been around for decades, they have spent more of their time protecting the business environment, not the people. (If you missed Trade Secrets, I suggest at least reading the transcript. Some other good reads: The Toxic Cloud (Michael H. Brown, 1987) and Chemical Exposures: Low Levels and High Stakes (icholas Ashford and Claudia S. Miller, 1998). You will find the former and more resources in the bibliography of my paper, The Effects Of Environmental Pollutants On North American Temperate Forests..

Cancers, cataracts, and autoimmune diseases start long before they are detected or diagnosed. When just eating, drinking and breathing the air is risky, why knowingly add to the onslaught by using a product that is not necessary and may in fact harmful to you and your family?



lives in trees


active at dawn and dusk


active during the day


burrows underground or under vegetation


metabolic bone disease, an umbrella term for the various disorders leading to the loss of bone density


rock and rocky-crevice dwellers


lives on or at ground level

thermal gradient

range of temperatures needed to enable a reptile to regulate its internal (core) body temperature; each species has its own thermal requirements for daytime and night time


ultraviolet radiation












Additional terms may be found in the Glossary of Herp and Related Terms

In addition to the lighting and heating articles linked to my Captivity page, the references in my Iguana Bibliography, the articles referred to in my other UV/mercury vapor pages, and other research on MV-associated health problems, I also used the following:

 Norman Javier Flores E., Usos de la iguana verde en La Biophera Rio Platano, La Moskitia, Honduras



Related Articles
More on Mercury Vapor...
Journal Abstracts: Mercury Vapor
National Toxicology Program Lists UV Radiation as "Known Human Carcinogen"
Gene-Environment Interactions in the Development of Skin Cancer

Environmental Protection Agency
Safe Mercury Management Program

California Dept of Toxic Substance Control
Mercury-containing lamps are now subject to toxic waste disposal guidelines effective Feb 2004 (see pages 12, 21, 34-47)

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