1. Environmental Biology for Engineers and Scientists D.A. Vaccari, P.F. Strom, and J.E. Alleman © John Wiley & Sons, 2005 Chapter 19 – Dose-Response Relationships Chapter 21 – Toxicity of Specific Substances

2. Figure 19-1. Hypothetical dose-response relationship for (a)a substance required at low dosages, and (b)a nonessential substance. Homeostasis Reversible damage Irreversible damage Death Exposure concentration for fixed time Toxic response a b C1C1 C2C2

3. Figure 19-2. (a) Sigmoidal logarithmic- dose-response relationship. (b) Normal tolerance distribution of mortality frequency. Dose-response curve Percent mortality Log dose Slope of response Toxicity distribution (a) (b)

4. Figure 19-3. Dose-response curve for a carcinogen and extrapolation to low dosages by linear and multistage models.

5. Figure 19-4. (a) Linear relationship for toxicity (the inverse of LD 50 ); (b) Effect of mixture fraction ( ) directly on LD 50. LD 50 mix 1 / LD 50 mix

6. Figure 19-5. A hypothetical time-toxicity curve. Time (hrs) LD 50 (mg/L) dtdt

7. Figure 21-1. Structures of some organochlorine pesticides.

8. Figure 21-1. More structures of some organochlorine pesticides.

9. Figure 21-2. Structures of some unchlorinated pesticides.

10. Figure 21-2. More structures of some unchlorinated pesticides.

11. Figure 21-3. Effect of thiophosphorus pesticides on ammonia oxidation by estuarine nitrifiers. [Originally from Jones, RD, Hood NA: The effects of organophosphorus pesticides on estuarine ammonia oxidizers. Can J Microbiol 26:1296-1299, 1980.]

12. Figure 21-4. The Uranium-238 decay series.

13. Figure 21-5. Relation between forward mutation rate per locus per rad and the DNA content per haploid genome. Line is regression through zero. Point for man estimated from DNA content. Redrawn from data of Abrahamson, S., Bener, M.A., Conger, A.D., and Wolff, S. (1973). Uniformity of radiation-induced mutation rates among different species. Nature 245, 460.] DNA per haploid genome Log of specific locus mutations per locus per rad