[1] Kings Coll London, Dept Geog, Bush House,North East Wing,30 Aldwych, London WC2B 4BG, England
[2] Natl Univ Singapore, Dept Geog, 1 Arts Link, Singapore 117570, Singapore
[3] Kings Coll London, Dept Global Hlth & Social Med, Bush House,North East Wing,40 Aldwych, London WC2B 4BG, England
[4] Harvard Univ, Harvard TH Chan Sch Publ Hlth, 677 Huntington Ave, Boston, MA 02115 USA