A practical ultraviolet inspection light for the detection of rodent urine contamination: the Blak-Ray UVL-26P.

It's rather amazing how much money we go through trying to find the ideal field accessory. I don't think that we are the only sanitarians with drawers full of flashlights, pocket thermometers, and various other objets du travail that looked good in the ads but turned out to be tools from the devil's workshop. Among the more notable and costly castoffs are several ultraviolet lamps that were sorely underpowered or horribly impractical.

We mean to set this one straight. First, however, a little personal history - in the form of a slightly embarrassing confession - is in order. From our apprenticeship into the sanitarian profession, we knew that mammalian urine fluoresces when illuminated with ultraviolet light. Armed with battery-powered UV lamps, we boldly scanned bags, sacks, and boxes in areas that were virtually knee-deep with rodent feces and saw absolutely nothing! We blamed it on our eyesight and a host of other technical maladies, and kept trying with similar outcomes. It finally dawned on us that the battery-powered units might be significantly underpowered, and the areas in which we were working were too bright for us to detect the fluorescence. We finally managed to overcome both conditions using a 120-volt unit. Soon we realized that our inspections were limited by the availability of accessible electrical outlets (which are few and far between in warehouses) and the length of the power cord attached to the UV unit.

We finally found a battery-operated UV lamp that is powerful enough to work well under most warehouse lighting conditions: the Blak-Ray[R] 26P Series Rechargeable Ultraviolet Lamp, manufactured by UVP, Inc.* The 26P Series of ultraviolet lamps offers a powerful 6/12-watt lamp that comes with long- or short-wave UV or a combination of both. For our work, we've chosen the UVL model, which has two long-wave 365-nanometer wavelength) UV self-filtering tubes. This model allows you to use one or two tubes at a time. Not only is the unit ideal for detecting rodent urine on foods, but we also have found it invaluable when working with fluorescein dye to identify sources of contamination from malfunctioning subsurface sewage disposal systems. The long-wave UV light, or "black light," when used in conjunction with a UV reflective oil, powder, or paste, is also an excellent teaching tool for demonstrating the adequacy of handwashing. Other uses of the lamp include detecting environmental molds and ringworm fungus infections. As a plus, this portable lamp is an ideal aid for the antique hobbyist in finding modern repairs on valued ceramics, glassware, and pottery, as well as for the philatelist in identifying tagged stamps.

The UVL-26P lamp is powered by a built-in lead acid battery that must be charged periodically. The unit can be recharged from two sources: a standard wall outlet (this source uses the wall outlet plug that is integral to the unit) or in a car (with an optional automobile outlet adapter plug). When the battery is fully charged, the intensity is fairly steady for at least 5 hours, whether one or two tubes are used. Although the lamp weighs in at a hefty 4 pounds, it is nicely designed for portability with a comfortable handle and carrying strap.

Protective eye wear is not necessary when you are using the longwave UVL-26P lamp. Remember, it's the short-wave (254-nanometer wavelength) UV that causes sunburn and eye irritation. So, at $205, the UVL-26P lamp is well worth the price.

When using the unit to detect urine contamination, place the lamp within a few inches of the suspected food. If the ambient lighting is too bright for contrasting fluorescence, you can provide the necessary shadow by making a simple view box using a cardboard carton and a pocket knife.

Confirming Test

Although mammalian urine stains exhibit strong fluorescence, this examination is not selective - many materials fluoresce under UV light. To confirm the presence of urine contamination, a test strip impregnated with phosphate-buffered urease and Bromthymol Blue is required. These test strips can detect as little as 0.005 milliliter of urine. Of the positive results for urine contamination obtained by sanitarians with these strips, the overwhelming majority have been confirmed by alternative exact chemical analytical methods. Unfortunately, we are unable to find any vendor who currently carries these strips. At one time, the LaMotto Chemical Products Company sold them as part of an excellent Field Unit for Inspection of Food Stuffs kit, but they discontinued the kit in 1992. We even contacted Warner-Chilcott, who manufactured the Urograph[R] strips, and were informed that they no longer make them. Because these strips are so valuable to our profession, we would appreciate hearing from anyone who knows of a source. Please write to us in care of the Journal.