Turn the Lights Off When You Stay

Two outbreaks of eye injury were recently reported by the CDC: one following a cheerleading competition and another among players and spectators at a basketball game. The outbreaks occurred in different locations in Philadelphia almost exactly 2 years apart. But they did share one key thing in common – broken lights.

The condition was eventually identified as photokeratitis. This injury brings on symptoms of burning eyes, tearing, redness, and the sensation that something is stuck in the eye, like an object that shouldn't be there. Only, in photokeratitis the cause in not a particle but rather overexposure to waves of ultraviolet light. In the first outbreak, which occurred in 2011 and affected more than 200 people, the ultraviolet exposure was far from obvious at first blush (http://www.ncbi.nlm.nih.gov/pubmed/?term=photokeratitis+philadelphia). In fact, a mass toxic chemical exposure was initially suspected. The Hazardous Material Unit of the Fire Department and the Department of Public Health of Philadelphia were called in. Tests for industrial chemicals, radioactive materials, and hazardous gases were negative. They even performed wipe tests for tear-gas residues, all to no avail. Then, finally, someone noticed a broken “metal halide” light bulb overhead in the gymnasium where the event had taken place. The magnitude of the outbreak was driven in part by the fact that the convocation had been something of a cheerleader mini-marathon, lasting 9 hours (those sitting over two hours in the bleachers were at the greatest risk of injury). The broken light bulb in the later 2013 outbreak was more quickly identified as the culprit by the Department of Public Health, informed through their previous experience two years before (once burned, twice shy, as they say).

Those of us not well versed in the National Electric Code, in particular its 2005 amended subsection 410.4(E) “Luminaires in Indoor Sports, Mixed-Use, and All-Purpose Facilities,” may lack familiarity with the potentially dangerous problem of metal halide lights. These are a subset of electric lights known as high intensity discharge (HID) instruments. Halide HIDs represent a technological fulfillment of the quest for ever-brighter even-purer light by moving forward from mercury filled bulbs by adding to the internal mix iodide or bromide (both are halides that define this class of bulb). Unfortunately, such a fine light comes at the cost of UV co-production. Too much ultraviolet causes burns: photokeratitis to eyes, old- fashioned sunburn to the skin; longer term risk includes skin cancer, depending on the extent and duration of exposure.

The clever engineers who brought us these halide HID bulbs were aware that their UV had to be blocked. For that reason, all such bulbs have a second, outer shell that filters out the dangerous light waves. That is, as long as that outer shell remains intact. Which it wasn’t, in either of the two Philadelphia gyms. Nor was this a bizarre and unpredictable event, a perfect storm of over-bright light in the bleachers. All it takes is a ball thrown or kicked too high in the wrong direction.

The Philadelphia story was by no means the first HID misadventure reported. Three separate outbreaks occurred in Tennessee in 2003, one involving a large fundraising banquet held in a community center gymnasium, another among a group of wrestlers in a three-day competition at a high school gym, and a third affecting volley-ball players in yet another facility (http://www.ncbi.nlm.nih.gov/pubmed/15066878). In Oregon, HID lightning struck twice, once in 2000 and again in 2005 (http://www.mikeholt.com/mojonewsarchive/Safety-HTML/HTML/State-to-Warn-About-Halide-Light-Dangers~20050314.php). In 2004, more than two dozen teachers who attended a back-to-school meeting at the McNaughton High School gymnasium in Moosomin, Saskatchewan experienced eye and face burns from exactly the same broken-bulk scenario (http://www.mikeholt.com/mojonewsarchive/USEI-HTML/HTML/Teachers-Burned-by-UV-Light~20040928.php)

So why not simply develop a technologic fix, for example, a bulb that turns off automatically if its outer shell is damaged? That fix is already in: it’s called a “Type T” HID halide bulb. The Type T bulbs “self-extinguish” after only a few minutes once the protective bulb is broken. “Type R” bulbs, in contrast, keep going and going. In each and every one of the UV over-exposure outbreaks, Type R bulbs were inappropriately in use.

Because radiation emitting devices are regulated by the Food and Drug Administration (FDA) it turns out that they are the ones who have the last word on preventing any further mishaps. Back in 2014, here is what the FDA recommended (http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/AlertsandNotices/ucm116540.htm):

“To prevent these incidents from recurring, FDA recommends the following in schools and other indoor, all-purpose facilities where the light bulbs may be broken:

•replacement of open or wire grid fixtures with enclosed fixtures, or

•replacement of non-self extinguishing “R” type high intensity metal halide and mercury vapor light bulbs used in open or wire grid fixtures with self-extinguishing “T” type light bulbs.”

Since this is only a non-binding recommendation, the FDA also has another piece of sage advice – if by chance you do notice that your HID is broken (the FDA puts in bold CAPS) - TURN OFF THE LIGHT IMMEDIATELY.