Modern methods of illumination use less energy and reduce environmental risks
If you break a mercury thermometer, blobs of silver liquid scatter. This chemical element—atomic number 80 and the symbol Hg—looks harmless, but it’s not. The U.S. Environmental Protection Agency warns that high exposure can damage your brain, heart, kidneys, lungs, and immune system. From bald eagles to the Florida panther, methylmercury can alter an animal’s behavior, reduce its reproduction, retard development, and even cause death. Beyond broken thermometers, people can be exposed to mercury from improperly disposed of metal-halide bulbs, which are used in many illumination systems for microscopy. But, you can get the mercury out of your microscopy—all while saving energy and getting the same, if not better, results.
A metal-halide bulb produces light when an arc of electricity goes through a gas, which contains mercury and metal halides. Alternatives include light-emitting diodes (LEDs) and light-pipe technology from Lumencor (Beaverton, OR), which uses a proprietary technology that includes solid-state luminescent materials. Both of these forms of illumination include no mercury.
The question is: Should you make the switch in your lab?
Analyzing the outcome
Most scientists would agree that putting less mercury in the environment is good and that reducing the risk of being exposed to mercury is good, but are we absolutely sure that the other imaging options are more environmentally friendly than, for example, a metal-halide bulb?
To address that question—at least in part—Claire Brown, director of the Advanced BioImaging Facility (ABIF) at McGill University (Montreal, Quebec, Canada), hired an engineering student to compare metal halide- and LED-based imaging systems. To make the comparisons as balanced as possible, the study used systems from one company that makes both kinds of lighting.
Both systems include many similar parts, and the main environmental difference comes from the light source. “The LED lasts about 20,000 hours, and the metal-halide bulb lasts about 2000,” Brown explains. That means that at least 10 metal-halide bulbs need to be manufactured and disposed of to reach the same lifetime as one LED-based source. So far, Brown’s lab has never even used an LED source until it burned out.
Moreover, the LED is only turned on when being used. “With metal-halide, you have to warm it up for 20 to 30 minutes, so it is often turned on in the morning and turned off at the end of day,” Brown notes. “So, it is left on for 8 to 12 hours.”
Encouraging adoption
Persuading biologists to convert to nonmercury lamps often requires an organized effort. At Northwestern University (Evanston, IL), assistant vice president for research Philip Hockberger and his colleagues promoted an LED microscopy initiative. To make it more affordable for scientists to switch to LEDs for microscopy, the Northwestern team searched for a commercial partner, and it selected Nikon Instruments.
When I ask Hockberger why they chose Nikon, he quickly said, “Customer service.” Plus, Nikon offered the same discounts as anyone else, including a local distributor for LED-based microscopy illumination.
In one year, that initiative spurred the conversion of about 100 out of 500 microscopy light sources at Northwestern to LEDs. The financial incentive created by the partnership with Nikon made a big difference.
“If a scientist was buying a new system, we highly recommended LEDs,” Hockberger says. “For LED replacement, though, most researchers were not compelled to make the switch. In the short term, it’s still cheaper to replace the mercury lamp rather than convert to the LED solution. In the long term, I expect they will all make the change.”
Counting photons
Beyond the environmental benefits of getting rid of mercury in microscopy, LED sources can even improve results. “Unlike mercury or metal-halide bulbs, solid-state illuminators are better suited to quantitative imaging,” says Allison Paradise, executive director of My Green Lab (Los Gatos, CA). “They are much more stable.”
Other kinds of light sources become less intense over time, starting almost from the moment a bulb is used. “Metal-halide bulbs do remain stable for a short period of time,” Paradise explains, “but in order to quantify experiments using metal-halide bulbs, it’s important to quantify how the light intensity degrades over time.”
Despite the opportunities with solid-state lighting, microscopists could make better use of some. “The idea of quantitation in lighting is still relatively underserved,” explains Claudia Jaffe, co-founder and executive vice president of business development at Lumencor. “People don’t think of lighting the way they do reagents, which they routinely measure.”
As microscopy relies increasingly on fluorophores and measuring the resulting signals, quantifying the light applied to a sample can be even more useful. “You’d like to meter how many photons you deliver to a sample to eliminate variance, which has traditionally been caused by pretty noisy lamps with bulbs that decay over time,” Jaffe says. Some of the new methods of lighting for microscopy, though, provide new capabilities. “Our lighting is so stable that you can provide a dose of a known number of photons,” she says.
Over time, more scientists will remove mercury from microscopy. At My Green Lab, says Paradise, “being mercury-free is part of our Green Lab Certification.” She adds, “We’ve helped core facilities write grants and obtain funding for large-scale conversions.”
Similarly, Lumencor runs free lighting giveaways every Earth Day, and other supportive events. Efforts like those from Northwestern University, Lumencor, and My Green Lab will help scientists light up samples for microscopy with greener and more powerful light sources.