1. World Health Organization, http://www.who.int/en/
2. U.S. Environmental Protection Agency, http://www.epa.gov/
3. European Parliament, http://www.europarl.europa.eu/portal/en
4. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry, http://www.atsdr.cdc.gov/
5. U.S. Department of Labor, Occupational Safety & Health Administration, https://www.osha.gov/