It's a very low rate of increase, and while it may be statistically significant given the right statistical massage, I don't think I would hang my reputation on that p-value. This research group has come under fire for their numbers before, both from Congress and I believe from NIH. This is just one of hundreds of similar studies on environmental effects, and I don't want to say that these people are in the profession of making mountains over molehills, but I have not read anything about the authors or their institution which has given me any confidence in their result.