About: http://webisa.webdatacommons.org/129430620

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Clean, in this case, means environmentally clean, i.e. free from contaminants, including corrosive, combustible, noxious, zootoxic, reactive, or radioactive materials.
http://www.w3.org/ns/prov#wasQuotedFrom	straightdope.com