For anyone who's unfamiliar with this, and is curious, Greenpeace has a Guide to Greener Electronics.
[Greenpeace rep Casey Harrel] said in a Kotaku interview, that Nintendo (as Kotaku writes, "barely even attempt to submit, or make available, the information Greenpeace require to make accurate judgements." According to Casey (I think; Kotaku suddenly uses the name Corey): "Nintendo consistently scores the poorest on our Guide to Greener Electronics primarily because they donâ(TM)t submit, nor have any publicly available information, on over half the criteria that we use to assess company performance on the Guide."
In other words, Nintendo's "worst environmental record" is the equivalent of a database null. It's not "the worst", it's "unknown".
For the information Nintendo does put out, Greenpeace's rep does note, "those that they do have answers for, are quite poor."
In a response, Nintendo says, "We would like to assure customers that we take our environmental responsibilities seriously and are rigorous in our commitment to comply with all relevant laws relating to environmental and product safety, including avoiding the use of dangerous substances in our manufacturing processes and ensuring the safe disposal and recycling of materials."
Whether one loves or hates a company, it's a bit difficult to fault their abysmal environmental record just because they didn't fill out a third party company's survey.
Disclaimer: I'm a rational Nintendo fanboy. I love their products, but I can criticize Nintendo and their products as well.