Perchlorate Notes
The widespread interest in the perchlorate ion as a potential risk to ground and surface water environments has generated considerable discussion in the past five years. However, the nuances of perchlorate chemistry require that great care be taken to ensure that technical guidelines and policy decisions are based on scientific data that are both sound and comprehensive. Some brief examples illustrate this point.

In the article on measuring perchlorates in biota (December 2001), you include Bruce Logan’s accurate insight that the health impact of perchlorate at low doses is unresolved. This can be developed further by relating perchlorate exposure ranges to human health effects. Taking therapeutic exposure (usually considered 500–1000 mg/day of perchlorate) as unity, the relative perchlorate exposure levels conform roughly to the following:

• Therapeutic 1
• Pharmacological 0.001–0.1
• Occupational 0.0005–0.05
• Environmental 0.00001–0.00025

In other words, typical environmental exposure (5 to 100 parts per billion) is approximately 10,000 times lower than some levels currently being used in therapeutic treatment of thyroid condition. Still, the application of these figures to the process of risk assessment cannot be expected to resolve all the health issues relating to perchlorate exposure.

Public discourse also suffers from careless use of words. We have seen a major newspaper headline refer to perchlorate as a “water toxin”, an assertion with no basis in fact. The lead paragraph of your recent article described contamination that stemmed from the use of “perchlorate . . . as an ingredient in some fertilizers.” The issue of perchlorate in fertilizers was thoroughly addressed by Urbansky et al. (EPA-600-R01-049, report issued in 2001). While the rare natural occurrence of perchlorate in Chilean saltpeter deposits can be confirmed, perchlorate is not an ingredient in fertilizer formulations and is not presently recognized as a contaminant in agricultural runoff water in the United States.

Three additional publications are recommended to Today’s Chemist at Work readers interested in a broader understanding of the character and chemistries of perchlorates:

• Perchlorate in the Environment; Urbansky, E., Ed.; Environmental Science Research, Kluwer Academic/Plenum Publishers: New York, 2000; Vol. 57.
• Perchloric Acid and Perchlorates, 2nd ed.; Schilt, A. A., Ed.; to be published by GFS Chemicals, in press 2002.
• Long, J. R., Perchlorate Safety: Reconciling Inorganic and Organic Guidelines. Chem. Health Saf. 2002, 9 (3).

Our concern is that the various media (scientific and other) have access to and carefully apply sufficient, accurate information so that the interested public can be properly informed. Your effort in support of these guidelines is greatly appreciated.

The Knead for Speed
I was amused to read “The Knead for Speed” in the Feb. 2002 issue. This article shows the difference between the way a chemist and an engineer approach a problem. An engineer is process-oriented and thinks first of changing the process. A chemist looks at the ingredients and researches before doing an experiment. Research would have indicated that the gluten level of flour and the total protein level influence the rise of bread. So a chemist would have had the gluten level as a variable (add gluten to regular flour) and would have seen the effect without any additional experiments.

I see this all the time at work. I am a chemist by heart (and training, but also have an MBA), but work primarily scaling up materials to commercialize them. It’s good to have at least one chemist involved in this type of work—someone who is more curious about what’s going on in the box rather than just the inputs and outputs of the “black box”. Knowledge of the chemistry of a process helps improve the chance of designing a more efficient experiment. I have done some home experiments on bread rise (but using a small Hobart mixer with dough hook) and have also found that the total liquid level of the dough, salt level, and temperature are significant variables for bread rise. Testing the yeast in warm water with some sugar dissolved in it (to see how alive it is) avoids disappointments with old or ineffective yeast.

Also, now that I know more about the effects of saturated fat (butter) and hydrogenated trans-fatty acids (margarine), I use olive oil and some flax seed meal in my bread.

My daughter, who teaches chemistry, brought me your article. As a weekend bread baker, using only the four basic ingredients of water, flour, yeast, and salt, kneading by hand and baking in an oven, I enjoyed your trials and tribulations and your unexpected results. Using a bread machine, you have great control of the immediate environment. Talking to bread bakers, I am told that they have no clue how the next batch will come out and they blame it on all the ingredients and the air temperature and humidity. Bread baking, they say, is still as much art as science. You also have to train your testers by exposing them to a variety of breads. Lastly, not unlike your children, my 5-year-old granddaughter insists on helping in the kneading process because, like your children, she loves raw dough.

Keep experimenting, it is therapeutic.