1.27 The environmental lead impact studies on the quality of water often measure the level of chemical toxicants by the LC50, the concentration lethal to 50% of the organisms of a particular species under a given set of conditions and specified time period. Two common toxicants are Methyl Parathion and Baytex. LC50 measurements on water samples for each of these toxicants are as follows:

Methyl 2.8, 3.1, 4.7, 5.2, 5.2, 5.3, parathion (MP) 5.7, 5.7, 6.6, 7.1, 8.9, 9.0 Baytex (B) 0.9, 1.2, 1.3, 1.3, 1.4, 1.5, 1.6, 1.6, 1.7, 1.9, 2.4, 3.4