{"thcode":2,"term":{"code":1181,"name":"toxic trace element contamination","parent":769,"scope":"Introduction into the environment of elements (such as arsenic, cadmium, lead, and mercury) which have a deleterious effect on living organisms when found naturally in only minor amounts (concentrations less than 1.0 milligram per liter) in water or sediment."},"uf":[],"bt":[{"code":769,"name":"contamination and pollution","parent":1174,"scope":"Introduction of harmful substances into the environment by human action or natural processes."},{"code":1174,"name":"topics","parent":1,"scope":"Themes, subjects, and concerns for which USGS information resources are relevant."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[{"code":720,"name":"mercury contamination","parent":1181,"scope":"Biological disturbances caused by mercury compounds that have entered the environment."}],"rt":[{"code":320,"name":"ecotoxicology","parent":650,"scope":"Scientific study of causes, dispersal, and effects of contaminants on the environment."},{"code":345,"name":"environmental health (human)","parent":533,"scope":"Effects of the environment on human health."}]}