Related by context. Frequent words. (Click for all words.) 68 hexavalent chromium 64 arsenic 62 selenium 61 radium 59 manganese 57 fluoride 57 contaminant 57 sulfate 56 benzene 56 contaminants 55 perchlorate 55 Chromium 54 mercury 54 nitrate 54 ppb 53 cadmium 53 carcinogen 53 chloride 53 nitrates 53 magnesium 52 trace amounts 52 strontium 52 toxic chemicals 51 PFOA 51 tritium 51 dioxins 51 PCBs 51 toxicity 50 iodine 50 phosphorus 50 beryllium 50 toxins 50 Cadmium 50 carcinogenic 49 hydrogen sulfide 49 dioxin 49 groundwater contamination 49 Arsenic 49 particulates 49 carcinogens 49 phthalates 48 TCE 48 volatile organic compounds 48 atrazine 47 harmful chemicals 47 Fluoride 47 particulate 47 toxic substances 47 pollutants 47 toxin 47 silica 47 VOCs 47 phosphorous 47 chlorine 46 Iodine 46 contamination 46 sludge 46 acrylamide 46 solvents 46 boron 46 cesium 46 contaminated groundwater 46 radioactive iodine 46 sodium 46 calcium 46 radon 46 naturally occurring 46 neurotoxin 45 particulate matter 45 toxic 45 toxics 45 pollutant 45 C8 45 concentrations 45 chemicals 45 formaldehyde 45 sulfur dioxide 45 hazardous chemicals 45 ppm 45 sulfur 44 groundwater 44 fatty acid 44 nitrogen 44 zinc 44 coliform bacteria 44 radioactive 44 pH 44 oxides 44 additive 43 cobalt 43 Sodium 43 fatty acids 43 radioactivity 43 PBDEs 43 alkaline 43 chemical 43 coal tar 43 melamine 43 contaminated 43 phosphate 43 EPA