The main purposes of this class are to:

1. Revisit the recreational water sampling exercise in light of a study conducted for the same purpose.
2. Provide a quick introduction to toxicokinetics.
3. Learn about the relationship between biological half-life and sampling duration.

To prepare for this class:

A. Let the instructors what Project Group you are in, and whether you will work on the occupational or environmental scenario.

B. Read the following article, consider its contents in light of your Working Group activity last week, and think about the following questions to discuss in class:

• Reicherts JD, Emerson CW. Monitoring bathing beach water quality using composite sampling. Environ Monit Assess. 2010;168(1-4):33-43 (download).
  • There are two sets of compliance standards indicated in the paper, each with two times frames. What are these time frames? What are the diseases that the standards are meant to protect against? Which time frame is more likely to accomplish this and why?
  • There are several sources of spatial and temporal variability described in this paper. Where or when is there likely to be more variability? What does this suggest should be the emphasis for compliance sampling?
  • This paper suggests both worst case and routine sampling. Please note examples of each.
  • Is there anything these authors failed to consider, based on your conversations last week?

C. Download the following class notes to be prepared for our discussion in class. You may want to print them to take notes about our conversations.

• Toxicokinetics Notes

D. Review the following classic article in preparation for an in-class exercise with your Working Group. You may find that it helps to focus on Figure 1 and the tables, rather than the equations. This paper is a hard slog, but understanding its key messages is critical to the practice of hygiene.

• Rappaport SM. Smoothing of exposure variability at the receptor: Implications for health standards. Annals of Occupational Hygiene 1985:29:201-214 (download).

E. Look up the current exposure limits (occupational and/or environmental) for the substances listed in the table below. Note the agency whose limit you are reporting. Does the sampling duration associated with the exposure limit make sense in context of the Rappaport paper? Why or why not?

F. What are the typical sampling durations of the following types of samplers:

• filter sampler (e.g., PVC, glass fibre, cellulose ester filters)
• sorbent tube sampler (e.g., charcoal tube, silica gel tube)
• Alpha-Trak (radon)
• direct-reading instrument (e.g., PhotoVac, Miniram, Miran, 4-gas analyzer)

Do they make sense given the types of agents they sample?

G. In the following book, European Union recommendations for the interval between occupational exposure measurements are outlined. Why do you think the sampling intervals are the length specified?

• Boleij JSM, Buringh E, Heederik D, Kromhout H. Occupational Hygiene of Chemical and Biological Agents. Amsterdam: Elsevier, 1995.