Open defecation, for example, is dangerous for several reasons.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/nigeria-experts-worried-nigeria-may-overtake-india-number-one-open-defecation
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/all-africa
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/africa
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nigeria
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sanitation
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/open-defecation
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/who
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/unicef