Close inspection of this brand-new CFL, like others found at the hardware store where this photo was taken, reveals many small defects in the phosphor coating.
Compact fluorescent lamps (CFLs) use a fraction of the energy of incandescent bulbs, but a new study finds that minor damage makes their UV emissions dangerously high at close range.
Researchers at Stony Brook University in New York sought to follow up on European research that had found prolonged exposure at close range (less than 20 cm, or about 8 inches) could approach workplace-safety UV limits and worsen pre-existing skin conditions. Miriam Rafailovich, Ph.D., led the Stony Brook study, published in Photochemistry and Photobiology, to determine what effect CFLs might have on healthy tissue. Using various manufacturers’ bulbs purchased from locations around Long Island, the researchers exposed Petri dishes of two types of skin cells to light from a desk lamp: keratinocytes, the outermost layer of skin, and dermal fibroblasts, the underlying connective tissue. Cells of both types stopped growing and changed shape under close-range exposure.
All of the CFLs in the study had some UV emissions, but some were much higher than others. In investigating the source of the difference, the researchers found that the signature twisted shape that allows CFLs to fit into spaces designed for incandescent bulbs also makes them vulnerable. All fluorescent lamps, from long, straight tubes to compact curls, are coated with phosphor and filled with mercury vapor that, when excited by electricity, produces UV rays. This is absorbed by the phosphor and transformed into visible light. However, the small diameter and curlicue shape of CFL tubes creates places where the brittle phosphor coating is vulnerable to falling away, allowing UV rays to leak out.
Rafailovich told EBN, “It’s not clear when it chips—after it’s made, or in the transport and handling at the point of sale or distribution. But the fact is that most (nearly all) bulbs we examined, regardless of brand or store, had defects and UV emissions.” (There are currently no durability standards that cover the lamps’ phosphor coatings.) According to Rafailovich, use of the average damaged bulb at a range of about one foot is “the equivalent of sunbathing at the equator” in terms of UVA, which oxidizes skin cells and penetrates deep into skin.
The CFLs were also found to emit significant amounts of DNA-damaging UVC, which is not common in sun exposure because it is largely scattered by air before reaching Earth’s surface. The lack of space for scattering makes close-range CFL use potentially more damaging than sunbathing. The researchers note that typical use of CFLs in ceiling fixtures should not pose a significant risk, but desk lamps should use encapsulated, “double envelope” CFLs—or utilize other technologies such as LEDs or next-generation incandescent bulbs, neither of which creates UV emissions. While the U.S. Department of Energy has encouraged the switch to CFLs through its Energy Star program, the results of this study could hasten adoption of newer technologies.
The chips in the coating were often visible to the naked eye, Rafailovich told EBN, giving consumers an indication that a bulb should be replaced or at least not used at close range. However, the disposal of a bulb designed to last for nine years greatly reduces the life-cycle benefits of switching to CFLs, especially as they contain small quantities of mercury.