[1] Univ Alberta, Sch Publ Hlth, ECHA, 11405 87 Ave NW, Edmonton, AB T6G 1C9, Canada
[2] Mem Univ, Labrador Inst, Sch Arctic & Subarct Studies, 219 Hamilton River Rd,Stn B,POB 490, Happy Valley Goose Bay, NF A0P 1E0, Canada
[3] Univ Autonoma Yucatan, Unidad Ciencias Soci, Calle 61 X 66 525, Merida, Yucatan, Mexico