Pros and cons I enjoyed the article “Will LEDs lead to a greener world? Maybe,” in the GreenLight section of the magazine (November 2010, p. 27). I was enlightened by the concept that even though LEDs are more energy-efficient than current lighting technology, their use could increase to a level where there is no net gain in overall energy efficiency on a large scale. Not to imply that the positives don’t outweigh the negatives, I just wanted to point out another potentially negative consequence of large-scale LED usage: the environmental impact of LED materials. Recently, Chemical & Engineering News published an article that discusses research on this issue. Titled “LEDs Not So Green After All,” it can be found on C&EN’s website: http://pubs.acs.org/cen/news/88/i51/8851news8.html. It is very interesting – and perhaps even more important – to consider both the positives and negatives of new technologies. Ryan Pensack, graduate student Chemistry Department Penn State University