Lesson 6 Toxic Organic Chemicals

These well written chapters in Baird deal with the chemistry of various organic chemicals in the environment. As such, you should review your organic chemistry before beginning the study of this chapter. If you have not had any previous instruction in organic chemistry, you are strongly urged to study and complete the exercises contained in the Appendix of Baird.

The subject material of this chapter is the structure and properties of various organic molecules of environmental interest along with some introductory concepts in toxicology. The first addendum to the chapter deals with the subject of bioconcentration factors. I point out the differing relationships relating BCFs and K_ow factors for different types of fish.

The next set of supplemental notes deals with photochemical processes that degrade organic chemicals.

The next set of notes deals the degradation of organic chemicals by water, largely through hydrolysis reactions.

As the instructor of a course (Ch 374) that deals with risk assessment, I feel compelled to expand upon the few remarks by Baird about risk assessment and toxicology. I begin by pointing to various measures of risk, in particular premature death and a second measure which is more economically based, YPLL. I quote the widely accepted number for the “value” of a human life, 10⁶$. This is, of course, not the “value” of a human life, but the amount of money society is generally willing to spend to save a human life. My notes on toxicology begin by discussing the ways that toxic chemicals enter the human body. I offer a somewhat expanded discussion of dose-response issues, introducing the terms “potentcy factor” and “chronic daily input CDI”. Finally I offer some professional assessments of the cancer risks posed by various environmental insults and their relative importance.