Challenge list is taking forever for UCI to publish....
So here are some National federation entry lists:
GB (About 650 total)
http://www.britishcycling.org.uk/events/details/77095/UCI-2012-BMX-World-Championships?awc=3405_1337256297_3af558132eb7d1009d77595a646ef2a2NZ (few world plates in there):
Challenge class:
5-6 years boys: Wyatt Stevens-McNab (Rotorua), Lucas Bhimy (North Harbour), Seth Stylianou (North Harbour).
5- 7 years girls: Caitlin Flavell (Rotorua).
7 yrs boys: Tipene Bishop (Kapiti).
8 yrs girls: Lucy Macready (North Harbour).
8 yrs boys: James Whyte (Mountain Raiders), Lachlan Stevens-McNab (Rotorua), Regan Elliott (Rotorua)
9 yrs boys: Rico Bearman (Waitakere), Boston Caldwell (North Harbour).
10 yrs boys: Zach Paterson (Rotorua), Tasman Wakelin (Nelson), Ryan Martin (Te Awamutu),.
11 yrs girls: Zoe Macready (North Harbour).
12 yrs girls: Brooke Fevre (Hawera).
12 yrs boys: Liam Goodwin (Kaiapoi).
13 yrs boys: Maynard Peel (Sunset Coast), Jayden Fleming (Papakura).
14 yrs boys: Joshua Smith (Te Awamutu).
14 yrs girls: Rebecca Petch (Te Awamutu), Zoe Fleming (Papakura).
15 yrs girls: Tahlia Hansen (Rangiora), Abigail Fox (Gisborne).
15 yrs boys: Liam Perry (Kapiti), Max Macready (North Harbour), Codi Merito (Te Awamutu).
16 yrs girls: Melissa Were (Hawera), Hannah Sarten (New Plymouth).
16 yrs boys: Cameron Petch (Te Awamutu), Cody Elliott (Rotorua), Donald Ross (Whangarei), Ryan Berney (North Harbour).
17 yrs plus girls: Nicole Sarten (New Plymouth),
17-24 yrs men: Avon Peel (Sunset Coast).
30 plus men: Mike Reader (Hawera), Scott Hazlewood (North Harbour),.
Masters men: Ben Rafferty (Dunedin).
Cruiser class:
13-14 boys: Joshua Smith (Te Awamutu), Maynard Peel (Sunset Coast).
15-16 boys: Cameron Petch (Te Awamutu), Donald Ross (Whangarei), Ryan Berney (North Harbour), Max Macready (North Harbour), Codi Merito (Te Awamutu).
16 & under girls: Rebecca Petch (Te Awamutu), Abigail Fox (Gisborne).
17-24 women: Nicole Sarten (New Plymouth).
30-34 men: Mike Reader (Hawera),.
35-39 men: Taky Stylianou (North Harbour).
40-44 men: Scott Hazlewood (North Harbour).
45 plus men: Alf Amor (Rotorua), Michael Batterton (North Harbour).