Boxing officially ranked 75th most dangerous sport
http://www.guardian.co.uk/sport/2009/nov/15/boxing-popularity-schools-clubs
But she said boxing's safety record had improved and it was now ranked 75th by the Royal Society for the Prevention of Accidents on its list of the most dangerous sports, behind rollerblading, gymnastics and horse riding.
Also according to this boxing isn't even one of the top worries for brain trauma, though they do give it special mention for no particular reason.
http://www.aans.org/Patient%20Information/Conditions%20and%20Treatments/Sports-Related%20Head%20Injury.aspx
Cycling: 85,389
Football: 46,948
Baseball and Softball: 38,394
Basketball: 34,692
Water Sports (Diving, Scuba Diving, Surfing, Swimming, Water Polo, Water Skiing, Water Tubing): 28,716
Powered Recreational Vehicles (ATVs, Dune Buggies, Go-Carts, Mini bikes, Off-road): 26,606
Soccer: 24,184
Skateboards/Scooters: 23,114
Fitness/Exercise/Health Club: 18,012
Winter Sports (Skiing, Sledding, Snowboarding, Snowmobiling): 16,948
Horseback Riding: 14,466
Gymnastics/Dance/Cheerleading: 10,223
Golf: 10,035
Hockey: 8,145
Other Ball Sports and Balls, Unspecified: 6,883
Trampolines: 5,919
Rugby/Lacrosse: 5,794
Roller and Inline Skating: 3,320
Ice Skating: 4,608