You can see a further break down of Nokia's score in this PDF. It suggests Nokia has more work to do in the area of recycling and using recycled plastics in its phone. Sony Ericsson is also weak in the recylcing area, but scores very well in the chemicals criteria section. Samsung has good all round scores, but this its score includes contributions from its more all of its consumer electronics products.
"First launched in August 2006 and now in its 9th edition, the Guide ranks the leaders of the mobile phone, computer, TV and games console markets according to their policies and practices on toxic chemicals, recycling and energy."