Letter: Toxic substances, synergism, and drinking-water.
D001151:Arsenic / Q000633:toxicity; D002104:Cadmium / Q000633:toxicity; D004357:Drug Synergism; D007854:Lead / Q000633:toxicity; D008628:Mercury / Q000633:toxicity; D014877:Water Pollution, Chemical; D014881:Water Supply
D002104:Cadmium; D007854:Lead; D008628:Mercury; D001151:Arsenic