It is no secret, that whichever aspect of this sport you subscribe to, there is much that is not environmentally stable.
The electricity generated by coal fired power plants which runs some of our lifts, to the plastic in old skis in our landfills, to the petrochemicals in our ski wax, and on to the jet travel to the mountains, and the urban sprawl around our big ski areas.
The nordic racing community at this moment, is having an intense debate about the use of complex fluro-carbon wax ingredients. (For instance, the Williams College Carnival races this week, are all non-fluro wax events.)
Please read this review from Wild Snow of one such backcountry wax product.